HMManual

Hydromax

Windows Version 16

User Manual

© Formation Design Systems Pty Ltd 1984 - 2011

iii

License and Copyright

Hydromax Program

© 1985-2011 Formation Design Systems Pty Ltd

Hydromax is copyrighted and all rights are reserved. The license for use is granted to the

purchaser by Formation Design Systems as a single user license and does not permit the

program to be used on more than one machine at one time. Copying of the program to

other media is permitted for back-up purposes as long as all copies remain in the

possession of the purchaser.

Hydromax User Manual

© 2011 Formation Design Systems Pty Ltd

All rights reserved. No part of this publication may be reproduced, transmitted,

transcribed, stored in a retrieval system, or translated into any language in any form or

by any means, without the written permission of Formation Design Systems. Formation

Design Systems reserves the right to revise this publication from time to time and to

make changes to the contents without obligation to notify any person or organization of

such changes.

DISCLAIMER OF WARRANTY

Neither Formation Design Systems, nor the author of this program and documentation

are liable or responsible to the purchaser or user for loss or damage caused, or alleged to

be caused, directly or indirectly by the software and its attendant documentation,

including (but not limited to) interruption on service, loss of business, or anticipatory

profits. No Formation Design Systems‟ distributor, agent, or employee is authorized to

make any modification, extension, or addition to this warranty.

Contents

v

Contents

License and Copyright ...................................................................................................... iii Contents .............................................................................................................................. v About this Manual .............................................................................................................. 1 Chapter 1 Introduction ........................................................................................................ 3

Input Model .............................................................................................................. 3 Analysis Types ......................................................................................................... 4 Analysis Settings ...................................................................................................... 4 Environment Options ............................................................................................... 4 Stability Criteria ....................................................................................................... 5 Output....................................................................................................................... 5

Chapter 2 Quickstart ........................................................................................................... 7 Upright Hydrostatics Quickstart .............................................................................. 7 Large Angle Stability Quickstart ............................................................................. 8 Equilibrium Condition Quickstart ............................................................................ 9 Specified Condition Quickstart .............................................................................. 10 KN Values Quickstart ............................................................................................ 10 Limiting KG Quickstart ......................................................................................... 11 Floodable Length Quickstart .................................................................................. 12 Longitudinal Strength Quickstart ........................................................................... 13 Tank Calibrations Quickstart ................................................................................. 13 MARPOL oil outflow Quickstart ........................................................................... 14 Probabilistic Damage Quickstart ............................................................................ 15

Chapter 3 Using Hydromax .............................................................................................. 16 Getting Started ....................................................................................................... 16

Installing Hydromax .................................................................................... 16 Starting Hydromax ....................................................................................... 16

Hydromax Model ................................................................................................... 17 Preparing a Design in Maxsurf .................................................................... 18 Opening a New Design ................................................................................ 21 Opening an Existing Hydromax Design File ............................................... 22 Effect of Zero Point change ......................................................................... 24 Updating the Hydromax Model ................................................................... 26 Hydromax Sections Forming ....................................................................... 27 Checking the Hydromax model ................................................................... 30 Setting Initial Conditions ............................................................................. 34 Working with Loadcases.............................................................................. 38 Modelling Compartments ............................................................................ 51 Tank sections ............................................................................................... 61 Forming Compartments ............................................................................... 62 Compartment Types ..................................................................................... 68 Sounding Pipes ............................................................................................ 69 Damage Case Definition .............................................................................. 71 Key Points (e.g. Down Flooding Points) ..................................................... 74 Margin Line Points ...................................................................................... 76 Modulus Points and Allowable Shears and Moments ................................. 76 Floodable Length Bulkheads ....................................................................... 77 Stability Criteria ........................................................................................... 77

Analysis Types ....................................................................................................... 77 Upright Hydrostatics .................................................................................... 78 Large Angle Stability ................................................................................... 80 Equilibrium Analysis ................................................................................... 87

Contents

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Specified Conditions .................................................................................... 90 KN Values Analysis ..................................................................................... 92 Limiting KG ................................................................................................. 95 Limiting KG for damage conditions with initially loaded tanks.................. 98 Floodable Length ....................................................................................... 102 Longitudinal Strength ................................................................................ 105 Tank Calibrations ....................................................................................... 107 MARPOL Oil Outflow .............................................................................. 112 Probabilistic Damage ................................................................................. 115 Starting and Stopping Analyses ................................................................. 137 Batch Analysis ........................................................................................... 138

Analysis Settings .................................................................................................. 141 Heel ............................................................................................................ 141 Trim ........................................................................................................... 142 Draft ........................................................................................................... 144 Displacement ............................................................................................. 145 Specified Conditions .................................................................................. 145 Permeability ............................................................................................... 145 Tolerances .................................................................................................. 146

Analysis Environment Options ............................................................................ 147 Fluids Analysis Methods ........................................................................... 148 Density of Fluids ........................................................................................ 150 Waveform .................................................................................................. 152 Grounding .................................................................................................. 153 Stability Criteria ......................................................................................... 154 Damage ...................................................................................................... 154

Analysis Output .................................................................................................... 155 Reporting ................................................................................................... 155 Copying & Printing .................................................................................... 157 Select View from Analysis Data ................................................................ 159 Saving the Hydromax Design .................................................................... 159 Exporting ................................................................................................... 160

Chapter 4 Stability Criteria ............................................................................................. 163 Criteria Concepts .................................................................................................. 163

Criteria List Overview ............................................................................... 163 Types of criteria ......................................................................................... 166

Criteria Procedures ............................................................................................... 167 Starting the Criteria dialog ......................................................................... 167 Resizing the Criteria dialog ....................................................................... 168 Working with Criteria ................................................................................ 168 Editing Criteria .......................................................................................... 170 Working with Criteria Libraries ................................................................. 172

Criteria Results ..................................................................................................... 174 Criteria Results Table ................................................................................ 174 Report and Batch Processing ..................................................................... 176

Nomenclature ....................................................................................................... 176 Definitions of GZ curve features ............................................................... 176 Glossary ..................................................................................................... 179

Chapter 5 Hydromax Reference ..................................................................................... 181 Windows .............................................................................................................. 181

Assembly View and Property Sheet .......................................................... 181 View Window ............................................................................................ 181 Loadcase Window ...................................................................................... 183

Contents

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Damage Window ....................................................................................... 183 Input Window ............................................................................................ 184 Results Window ......................................................................................... 185 Graph Window ........................................................................................... 188 Report Window .......................................................................................... 191

Toolbars ............................................................................................................... 194 File Toolbar................................................................................................ 194 Edit Toolbar ............................................................................................... 194 View Toolbar ............................................................................................. 194 Analysis Toolbar ........................................................................................ 195 Window Toolbar ........................................................................................ 195 Design Grid Toolbar .................................................................................. 195 Visibility Toolbar ....................................................................................... 195 Edge VIsibility Toolbar ............................................................................. 196 Render Toolbar .......................................................................................... 196 Report Toolbar ........................................................................................... 196 View (extended) Toolbar ........................................................................... 196 Design Grid Toolbar .................................................................................. 196 Extra Buttons ToolbarToolbar ................................................................... 196

Menus ................................................................................................................... 197 File Menu ................................................................................................... 197 Edit Menu .................................................................................................. 200 View Menu ................................................................................................ 202 Case Menu ................................................................................................. 204 Analysis Menu ........................................................................................... 204 Display Menu ............................................................................................. 207 Data Menu.................................................................................................. 211 Window Menu ........................................................................................... 212 Help Menu ................................................................................................. 212

Appendix A: Calculation of Form Parameters ............................................................... 214 Definition and calculation of form parameters .................................................... 214

Measurement Reference Frames ................................................................ 214 Nomenclature ............................................................................................. 216 Coefficient parameters ............................................................................... 216 Length ........................................................................................................ 217 Beam .......................................................................................................... 218 Draft ........................................................................................................... 219 Midship and Max Area Sections ................................................................ 220 Block Coefficient ....................................................................................... 221 Section Area Coefficient ............................................................................ 221 Prismatic Coefficient ................................................................................. 221 Waterplane Area Coefficient ..................................................................... 222 LCG and LCB ............................................................................................ 222 Trim angle .................................................................................................. 223 Maximum deck inclination ........................................................................ 223 Immersion .................................................................................................. 223 MTc or MTi ............................................................................................... 223 RM at 1 deg................................................................................................ 224

Potential for errors in hydrostatic calculations ..................................................... 224 Integration of wetted surface area .............................................................. 224

Appendix B: Criteria file format .................................................................................... 226 Appendix C: Criteria Help.............................................................................................. 228

Parent Calculations............................................................................................... 228

Contents

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Selecting a calculation in a criterion .......................................................... 228 Angle calculators ....................................................................................... 228 GM calculators ........................................................................................... 229

Parent Heeling Arms ............................................................................................ 232 Heeling Arm Definition ............................................................................. 232 Parent Heeling Moments ........................................................................... 240

Parent Stability Criteria ........................................................................................ 242 Criteria at Equilibrium ............................................................................... 242 GZ Curve Criteria (non-heeling arm) ........................................................ 243 Heeling arm criteria (xRef) ........................................................................ 260 Heeling arm criteria ................................................................................... 264 Multiple heeling arm criteria ..................................................................... 275 Heeling arm, combined criteria .................................................................. 281 Derived heeling arm criteria ...................................................................... 285 Other combined criteria ............................................................................. 290 Specific stand alone heeling arm criteria ................................................... 291 Stand alone heeling arm criteria ................................................................ 291 Stand alone heeling arm combined criteria ................................................ 292

Appendix D: Specific Criteria ........................................................................................ 295 Dynamic stability criteria ..................................................................................... 295

Capsizing moment ..................................................................................... 295 Heeling arms for specific criteria - Note on unit conversion ............................... 297

IMO Code on Intact Stability A.749(18) amended to MSC.75(69) ........... 297 IMO HSC Code MSC.36(63) .................................................................... 299 USL code (Australia) ................................................................................. 301 ISO 12217-1:2002(E) ................................................................................ 302 ISO 12217: Small craft – stability and buoyancy assessment and

categorisation. ............................................................................................ 304 Appendix E: Reference Tables ....................................................................................... 307

File Extension Reference Table ........................................................................... 307 Analysis settings reference table .......................................................................... 308

Appendix F: Quality Assurance ..................................................................................... 309 Quality Assurance ................................................................................................ 309

Quality Principles ...................................................................................... 309 Structured Programming ............................................................................ 309 Verification of Algorithms ......................................................................... 309 Testing of Implementation ......................................................................... 312 Testing of Upgrades ................................................................................... 312 Beta Testing ............................................................................................... 312 Version Control .......................................................................................... 312 But we're not Perfect .................................................................................. 312

Index ............................................................................................................................... 313

About this Manual

Page 1

About this Manual

This manual describes how to use Hydromax to perform hydrostatic and stability

analyses on your Maxsurf design.

Chapter 1 Introduction

Contains a description of Hydromax functionality and its interface to Maxsurf

Chapter 2 Quickstart

Gives a quick walk through the analysis tools available in Hydromax.

Chapter 3 Using Hydromax

Explains how to use Hydromax' powerful floatation and hydrostatic analysis routines to

best advantage.

Chapter 4 Stability Criteria

Gives details of the stability criteria that may be evaluated with Hydromax.

Chapter 5 Hydromax Reference

Gives details of Hydromax' windows and each of Hydromax' menu commands.

If you are unfamiliar with Microsoft Windows® interface, please read the owner's

manual supplied with your computer. This will introduce you to commonly used terms

and the basic techniques for using any computer program.


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Hydromax is a hydrostatics, stability and longitudinal strength program specifically

designed to work with Maxsurf. Hydromax adds extra information to the Maxsurf

surface model. This includes: compartments and key points such as downflooding points

and margin line.

Hydromax‟ analysis tools enable a wide range of hydrostatic and stability characteristics

to be determined for your Maxsurf design. A number of environmental setting options

and modifiers add further analysis capabilities to Hydromax.

Hydromax is designed in a logical manner, which makes it easy to use. The following

steps are followed when performing an analysis:

Input model

Analysis type selection

Analysis settings

Environment options

Criteria specification and selection

Run analysis

Output

Hydromax operates in the same graphical environment as Maxsurf; the model can be

displayed using hull contour lines, rendering or transparent rendering. This allows visual

checking of compartments and shows the orientation of the vessel during analysis.

Input Model

Maxsurf design files may be opened directly into Hydromax, eliminating the need for

time-consuming digitising of drawings or hand typing of offsets. This direct transfer

preserves the three-dimensional accuracy of the Maxsurf model.

Tanks can be defined and calibrated for capacity, centre of gravity and free surface

moment. Tanks and compartments can be flooded for the purpose of calculating the

effects of damage.

A number of loadcases can be created. The loadcase allows static weights and tank-

fillings to be specified and calculates the corresponding weights and centres of gravity as

well as the total weight and centre of gravity of the vessel under the specified loading

condition. Loadgroups may also be created and cross referenced into loadcases.

Other input consists of: tank sounding pipes; key points, such as downflooding points,

immersion and embarkation points; margin lines and section modulus.


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Analysis Types

Hydromax contains the following analysis tools:

Upright hydrostatics

Large angle stability

Equilibrium analysis

Specified Condition analysis

KN values and cross curves of stability

Limiting KG analysis

Floodable Length analysis

Longitudinal Strength analysis

Tank Calibrations

MARPOL oil outflow

Probabilistic damage (Hydromax Ultimate only)

Although common analysis settings are used where possible, different analyses may

require different settings. For example: the upright hydrostatics analysis simply requires

a range of drafts; whereas the longitudinal strength analysis requires a detailed load

distribution. The analysis settings for each analysis type are explained in detail in the

analysis synopsis below.

Analysis Settings

The analysis settings describe the condition of the vessel to be tested. For example, a

range of drafts in the case of upright hydrostatics, or a range of heel angles for a large

angle stability analysis.

The following analysis settings are available:

Heel

Trim

Draft

Displacement

Permeability

Specified condition

The analysis settings are specified prior to running the analysis. Settings that are not

relevant to the selected analysis type are greyed out in the Analysis menu.

Environment Options

Environmental options are modifiers that may be applied to the model or its environment

that will affect the results of the all the hydrostatic analysis types.


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Depending on the analysis being performed, different environmental options may be

applied to the Hydromax:

Type of Fluid Simulation

Density (of fluids)

Wave form

Grounding

Intact and Damage condition

Stability Criteria

Hydromax has the capability to calculate compliance with a wide range of stability

criteria. These criteria are either derived from the properties of the stability curve

calculated from a Large Angle Stability analysis or from the vessel‟s orientation and

stability properties calculated from an Equilibrium analysis. Limiting KG and Floodable

length analyses also use stability criteria.

Hydromax has an extensive range of stability criteria to determine compliance with a

wide range of international stability regulations. In addition, Hydromax has a generic set

of parent criteria from which virtually any stability criterion can be customized.

Output

Views of the hull are shown for each stage of the analysis, complete with immersed

sectional areas and actual waterlines. The centres of flotation, gravity and buoyancy are

also displayed. Heeled and trimmed hullforms and water plane shapes may be printed.

Results are stored and may be reviewed at any time, either in tabular form, or as graphs

of the various parameters across the full range of calculation. All results are accumulated

in the Report window (which can be saved, copied and printed), or output directly to a

Word document.

The criteria checks are summarised in tables listing the status (pass/fail) of each criterion

as well as the margin. The criterion settings and intermediate calculation data may also

be displayed if required.

For a brief overview of the different analysis that Hydromax has available, continue

reading Chapter 2 Quickstart.


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Chapter 2 Quickstart

This chapter will briefly describe each analysis type and its output. For each analysis

type, a list of the required settings as well as the available environment options is given.

Hydromax contains the following analysis types

Upright Hydrostatics

Large Angle Stability

Equilibrium Condition

Specified Condition

KN Values

Limiting KG

Floodable Length

Longitudinal Strength

Tank Calibrations

MARPOL Oil Outflow

Probabilistic Damage

Each analysis has different settings that may be applied

Heel

Trim

Draft

Displacement

Specified condition

Permeability

Loadcase

Tank and compartment definition

Hydromax offers different environment options that may be applied to the analyses

Fluid Densities

Treatment of fluids in tanks: fluid simulation or corrected VCG

Wave form

Grounding

Damage

Hydromax offers an extensive range of stability criteria that are applicable to

equilibrium, large angle stability, limiting KG and Floodable length analysis.

The Analysis types section describes each of the analysis types, settings and environment

options in more detail.

Upright Hydrostatics Quickstart

For Upright Hydrostatics, heel is fixed at zero heel, trim is fixed at a user defined value

and draft is varied in fixed steps. Displacement and centre of buoyancy and other

hydrostatic data are calculated during the analysis.


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Upright hydrostatics requirements

Range of drafts to be analysed

VCG (for calculation of some stability characteristics such as GMt and GMl only)

Trim

Upright hydrostatic options

Fluid Densities

Wave form

Damage

Compartment definition (in case of damage)

The results are tabulated and graphs of the hydrostatic data, curves of form and sectional

area at each draft are available.

For more detailed information please see: Upright Hydrostatics on page 78.

Large Angle Stability Quickstart

For the analysis of Large Angle Stability, displacement and centre of gravity are

specified in the loadcase. A range of heel angles are specified and Hydromax calculates

the righting lever and other hydrostatic data at each of these heel angles by balancing the

loadcase displacement against the hull buoyancy and, if the model is free-to-trim, the

centre of gravity against the centre of buoyancy such that the trimming moment is zero.

Large angle stability requirements

Range of heel angles to be analysed

Trim (fixed or free)

Loadcase or loadgroup

Tank definition in the case of tank loads being included in the Loadcase (and/or for

the definition of damage)

Large angle stability options

Fluid Densities


Wave form

Damage


Key points

Margin line and deck edge

Analysis of stability criteria

The key output value is GZ (or righting lever), the horizontal distance between the

centres of gravity and buoyancy. A graph of these values at the various heel angles forms

a GZ curve. Various other information is often overlaid on the GZ curve, including

upright GM, curves for wind heeling and passenger crowding levers and the angle of the

first downflooding point. These additional data depend on which (if any) stability criteria

have been selected.


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A number of other graphs may be selected from the pull-down list in the graph window.

Remember that you can access this data in tabular form by double clicking in the graph

window:

Dynamic stability curve (Area under GZ curve, integrated from upright)

Variations of other hydrostatic and form parameters may be plotted against heel

angle.

Maximum safe steady heel angle

The sectional area curve at each of the heel angles tested may also be displayed.

Note that some of these graphs have parameters that may be adjusted in the Data Format

dialog

If large angle stability criteria have been selected for analysis, these results will also be

reported in the criteria results table and they may lead to additional curves being

displayed on the GZ curve.

Downflooding angles for any key points, margin line and deck edge will also be

computed and tabulated.

For more detailed information please see: Large Angle Stability on page 80.

Equilibrium Condition Quickstart

Equilibrium Analysis uses the Loadcase, to calculate the displacement and the location

of the centre of gravity. Hydromax iterates to find the draft, heel and trim that satisfy

equilibrium and reports the equilibrium hydrostatics and a cross sectional areas curve.

Equilibrium analysis requirements

Loadcase or loadgroup



Compartment definition and damage case (in case of damage)

Equilibrium analysis options

Fluid Densities


Wave form

Grounding

Damage


Key points


Analysis of equilibrium criteria

Equilibrium analysis result table lists the hydrostatic properties of the model. If a wave

form has been specified there will be a number of columns; each column contains the

results for a different position of the vessel in the wave as given by the wave phase

value. The sectional area curve is also calculated, as is the freeboard to any defined key

points, margin line and deck edge. Any equilibrium criteria will also be evaluated and

their results reported.


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For more detailed information please see: Equilibrium Analysis on page 87.

Specified Condition Quickstart

In the specified condition each of the three degrees of freedom, for which the hydrostatic

properties of the model are to be calculated, can be set.

Specified Condition Requirements

Specified Conditions Input Dialog

If fixed trim is specified, you may enter the trim or specify the forward and aft drafts

(these are at the perpendiculars as specified in the Frame of Reference dialog).

Specified Conditions options

Fluid Densities

Wave form

Damage

Tank and Compartment definition (in case of damage)

The output for the specified condition consists of a curve of cross sectional areas and

hydrostatics of the vessel in the specified condition.

For more detailed information please see Specified Conditions on page 90.

KN Values Quickstart

KN values or Cross Curves of Stability are useful for assessing the stability of a vessel if

its VCG is unknown. They may be calculated for a number of displacements before the

height of the centre of gravity is known. The KN data may then be used to obtain the GZ

curve for any centre of gravity height (KG) using the following formula:

GZ = KN - KG * sin(Heel)

where GZ is the righting lever measured transversely between the Centre of Buoyancy

and the Centre of Gravity, and KG is the distance from the baseline to the vessel's

effective Vertical Centre of Gravity.

KN Values Analysis Requirements


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Range of displacements to be analysed



Estimate of VCG (provides more accurate result if free-to-trim)

TCG (if required)

KN Values Analysis Options

Fluid Densities

Wave form

Damage


Output is in the form of a table of KN values and a graph of Cross Curves of Stability.

If the analysis is performed free-to-trim and an estimate of the VCG is known, this may

be specified. The computed KN results will then give a more accurate estimate of GZ for

KG close to the estimated VCG since the effects of VCG on trim have been more

accurately accounted for.

For more detailed information please see KN Values Analysis on page 92.

Limiting KG Quickstart

The Limiting KG analysis may be used to obtain the highest vertical position of the

centre of gravity (maximum KG) for which the selected stability criteria are just passed.

This may be done for a range of vessel displacements. At each of the specified

displacements, Hydromax runs several Large Angle Stability analyses at different KGs.

The selected stability criteria are evaluated; the centre of gravity is increased until one of

the criteria fails.

Limiting KG Analysis Requirements




Stability criteria for which limiting KG is to be found

TCG (if required)

Limiting KG Analysis Options

Fluid Densities

Wave form

Damage


Laodcase (in case of initial loading of damaged tanks)

Key points (if required for criteria)

Margin line and deck edge (if required for criteria)


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A graph of maximum permissible GZ plotted against vessel displacement is produced as

well as tabulated results indicating which stability criteria limited the VCG. If limiting

curves are required for each of the stability criteria individually, this may be done in the

Batch Analysis mode.

A check will be made to ensure that any selected equilibrium criteria are passed,

however at least one large angle stability criterion is required. Only relevant criteria will

be used, i.e. if a damage case is chosen, only damage criteria will be evaluated; if the

intact condition is used, only intact criteria will be evaluated. Some criteria, such as

angle of maximum GZ, are very insensitive to VCG and may prevent the analysis

converging. If the analysis is unable to converge for a certain displacement this will be

noted and the next displacement tried.

For more detailed information see Limiting KG on page 95.

Floodable Length Quickstart

This analysis mode is used to compute the maximum compartment lengths based on

user-specified equilibrium criteria. Floodable Lengths may be computed for a range of

displacements; the LCG may be specified directly or calculated from a specified initial

trim. In addition a range of permeabilities may be specified. The VCG is also required to

ensure accurate balance of the CG against the CB at high angles of trim. As well as the

standard deck edge and margin line immersion criteria (one of which must be specified)

the user can also add criteria for maximum trim angle and minimum required values of

longitudinal and transverse metacentric height.

Floodable Length Analysis Requirements


VCG

Range of permeabilities to be analysed

Trim (free- to- trim to either initial trim or specified LCG)

Floodable length criteria to be tested

Margin line and deck edge (required for criteria)

Floodable Length Analysis Options

Fluid Densities

Wave form


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The output is in the form of tabulated Floodable Lengths for each displacement and

permeability. The data is tabulated for each of the stations as defined in Maxsurf. The

data is also presented graphically.

For more detailed information please see Floodable Length on page 102.

Longitudinal Strength Quickstart

Hydromax calculates the net load from the buoyancy and weight distribution of the

model. That data is then used to calculate the bending moment and shear force on the

vessel.

Longitudinal Strength Analysis Requirements

Loadcase (including distributed loads if required)



Longitudinal Strength Analysis Options

Fluid Densities

Treatment of fluids in tanks: fluid simulation is always used for Longitudinal

Strength analysis

Wave form

Grounding

Damage

Compartment definition and damage case (in case of damage)

Allowable shear and bending moment

The longitudinal strength graph and tables contain all information on weight and

buoyancy distribution, the shear force and bending moment on the vessel. If defined,

graphs of allowable shear and bending moment are superimposed on the graph.

For more detailed information please see Longitudinal Strength on page 105.

Tank Calibrations Quickstart

Tanks can be defined and calibrated for capacity, centre of gravity and free surface

moment (FSM). Fluid densities and tank permeabilities can be varied arbitrarily. Tank

calibrations may be calculated for a range of trim and heel angles. Hydromax uses its

fluid simulation mode to calculate the actual position of the fluids in the tanks, taking

into account the vessel trim and heel; i.e. the position of the fluid in the tank will be

computed so that the fluid surface is parallel with the external seawater surface. Tank

ullages are measured from the top of the sounding pipe to the free surface of the liquid

within the tank along the sounding pipe and in a similar manner, soundings are measured

from the bottom of the sounding pipe to the free surface.

Tank calibrations may be performed for a range of heel and trims. The results for a

single condition are shown in the results table. The condition to be viewed may be

selected from the Results toolbar; Tabulated results may be customised using the Data

Format dialog:


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Tank calibration analysis requirements

Tank definitions

Sounding pipe definition (if required)

Sounding intervals for calibration levels

Trim range

Heel range

Tank calibration analysis options

Fluid Densities

Treatment of fluids in tanks: fluid simulation always selected

Damage: Intact case always selected

What to calibrate (Analysis | Calibration options)

For each tank, a table of capacities, volumes etc. is calculated. These results are

presented in both tabular and graphical forms.

For more detailed information please see Tank Calibrations on page 107.

MARPOL Oil Outflow Quickstart

MARPOL probabilistic oil outflow calculation may be computed according to the

following MARPOL regulations:

Resolution MEPC.141(54), Regulation 12A: Oil fuel tank protection

Resolution MEPC.117(52), Regulation 23: Accidental oil outflow performance

Seltect the Reolution and tanks to be included in the analysis in the MARPOL options

(Analysis menu) dialog. Then in the MARPOL results data table, edit any values as

required; the resulting oil outflows will be calculated automatically. The “Start Analysis”

button will send the tabulated results to the Report.


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For more detailed information please see MARPOL Oil Outflow on page 112

Probabilistic Damage Quickstart

Attained index using probabilistic damage analysis may be computed.

Probabilistic damage analysis requirements

Loadcase definitions

Tank and compartmentation definition

Main probabilistic damage analysis parameters and criteria setup

Subdivision definitions

Heel angle range for GZ curve calculation

Trim

Probabilistic damage analysis options


Wave form

Key points


For more detailed information please see the Probabilistic Damage section on page 115.


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This chapter describes

Getting Started

Hydromax Model

Analysis Types

Analysis Settings

Analysis Environment Options

Analysis Output

Getting Started

This section contains everything you need to do to start using Hydromax

Installing Hydromax

Starting Hydromax

Installing Hydromax

Install Hydromax by inserting the CD and running the Setup program, then follow the

instructions on screen.

Note:

Before installing any program from the Maxsurf suite for the first time,

please read the purchase letter (also referred to as installation manual).

Starting Hydromax

After installation, Hydromax should be accessible through the Start Menu. Simply select

Hydromax from the Maxsurf menu item under Programs in the Start menu.

Windows Registry

Certain preferences used by Hydromax are stored in the Windows registry. It is possible

for this data to become corrupted, or you may simply want to revert back to the default

configuration. To clear the Hydromax preferences, start the program with the Shift key

depressed. You will be asked if you wish to clear the preferences, click OK, doing this

will reset all the preferences.

The following preferences are stored in the registry:


Page 17

Colour and line thickness settings of contours and background

Fonts

Window size and location

Size of resizing dialogs (alternatively, these may be reset by holding down the shift

key when activating them)

Density of fluids

Heel angles for large angle stability, KN and Limiting KG analyses

Permeabilities for floodable length analysis

Location of files

Units for data input and results output

Convergence tolerance (Error values)

Maximum number of loadcases

Reporting preferences

Note:

The default density for the fluid labelled "Sea Water" is stored in the

windows registry. All hydrostatic calculations use this. Check the density of

seawater after resetting your preferences.

It is recommended to save your customized densities with your project

using the File | Save Densities As command.

Hydromax Model

This section describes how to open a Maxsurf model in Hydromax and provides some

important information to ensure that your model is correctly interpreted by Hydromax.

Preparing a Design in Maxsurf

Opening a New Design

Opening an Existing Hydromax Design File

Updating the Hydromax Model

Hydromax Sections Forming

Checking the Hydromax model

After checking the Hydromax model, the next step is to check the Hydromax settings

and initial analysis conditions.

Setting Initial Conditions

Depending on the analysis performed, you may need to set up the following additional

model data:


Page 18

Working with Loadcases

Modelling Compartments

Forming Compartments

Compartment Types

Damage Case Definition

Sounding Pipes

Key Points (e.g. Down Flooding Points)

Margin Line Points

Modulus Points and Allowable Shears and Moments

Stability Criteria

Preparing a Design in Maxsurf

There are several important checks that must be carried out in Maxsurf before opening a

design in Hydromax:

Setting the Zero Point

Setting the Frame of Reference

Surface Use

Skin Thickness

Outside Arrows

Trimming

Coherence of the Maxsurf surface model

Setting the Zero Point

Ensure that the zero point is correctly setup in Maxsurf. A consistent zero point and

frame of reference should be used for the model throughout the Maxsurf suite. In

Hydromax you have the option of displaying longitudinal measurements such as LCB or

LCF from the model zero point or amidships.

Setting the Frame of Reference

It is vital that the Frame of Reference is correctly setup in Maxsurf before attempting to

analyse the model in Hydromax. The Frame of reference should not be changed in

Hydromax. The frame of reference defines the fore and aft perpendiculars, the baseline

and the datum waterline; midships is automatically defined midway between the

perpendiculars. By convention, in the profile and plan views, the vessel‟s bow is on the

right.

The perpendiculars define the longitudinal positions of the vessel‟s draft marks and

cannot be coincident. The base line is the datum from which the drafts and KG are

measured.

The frame of reference cannot be changed in Hydromax. However it is possible to

specify upto nine additional locations at which the drafts should be reported. This is done

through the Data | Draft Marks dialog.


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Note: Draft and Trim specification

It should be remembered that the drafts specified for an analysis are the

drafts at the perpendiculars (or amidships) and the trim specified (and

reported) is the difference between the draft at the AP and draft at the FP.

Surface Use

In Maxsurf you can choose between two types of surface use

Hull

Hull surfaces are used to define the watertight envelope of the hull.

Internal structure

Internal structure surfaces are used for all other surfaces (any surfaces which do

not make up the watertight envelope) and also surfaces which are to be used in

Hydromax to define the boundaries of tanks and compartments that have complex

shapes.

The following table describes the difference between each surface use in Hydromax:

Included: Hull Shell Internal

Structure

Hydrostatic sections

Selection of tank/compartment

boundaries

Skin thickness applied to the surface

Verify that all surfaces that are to be used as tank/compartment boundaries are defined as

Internal Structure. If a surface is defined as internal structure, it is not included as part of

the hull shell by Hydromax, i.e. internal surfaces will be ignored in the forming of

hydrostatic sections.

Skin Thickness

If skin thickness is to be used in hydrostatic calculations, ensure that the thickness and

projection direction have been specified for the hull shell surfaces. Thickness can be

specified differently for each hull surface, resulting in more accurate hydrostatics. To

activate skin thickness in Hydromax ensure that the “Include Skin Thickness” option is

selected when reading the file or calculating the hull sections.

Note

Tank boundaries made from internal structures surfaces do not have skin

thickness. To include skin thickness, the internal structure surface should be

placed to model the inside of the tank if the tank wall has significant

thickness.

Skin thickness for hull surfaces will be treated so that the hull sections go to

the outside of the plate whilst any tanks are trimmed to the inside of the

plate.


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Outside Arrows

The surfaces‟ outside arrows define the orientation of the surfaces. Ensure that you have

used the Outside Arrows command from the Maxsurf Display menu to define which

direction points outwards (towards the seawater) for each surface. The surface direction

may be flipped by clicking on the end of the arrow.

Trimming

Ensure that all surfaces are trimmed correctly. At any longitudinal position on the hull,

you should have completely closed transverse sections or sections with at most one

opening (e.g. the deck).

Correct Section with no opening.

Correct section with one opening: this section will be closed across the top.

Also see:

Hydromax Sections Forming on page 27

Checking the Hydromax model on page 30

Coherence of the Maxsurf surface model

Hydromax will generally have no problem correctly interpreting your design as long as

the following requirements for the Maxsurf model are observed:


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Make sure that each surface touches its adjacent surfaces at its edge, preferably by

bonding the edges together

Where surfaces intersect, trim away the excess regions of the surface; e.g. the part

of the keel that is inside the hull and the part of the hull that is inside the keel

Do not have surfaces that cannot be closed in an unambiguous fashion, i.e. a

maximum of one gap in a transverse section through the hull.

Remember that the inner portions of each intersecting contour will be trimmed off

Check surface use; internal structure surfaces are ignored when forming the hull

sections in Hydromax

Note:

For groups internal structure surfaces that will be used to define tank (or

compartment boundaries) the same requirements apply.

Also see:

Checking the Hydromax model on page 30.

Opening a New Design

File opening in Hydromax is window specific, i.e. Hydromax will automatically look for

compartment definition files when you are in a Compartment Definition window and a

loadcase in a Loadcase window.

To open a design for analysis, ensure that the design view window is active, then select

Open Design from the File menu. Choose a Maxsurf design file (.msd).

The following dialog will appear:

Calculate new Sections

Choosing Calculate Sections will calculate the specified number of sections through the

hull. These will then be used for the Hydrostatics calculations.

The meaning of (ignore existing data, if any) is explained in Opening an Existing

Hydromax Design File.

Include Plating Thickness

At this stage, any surface thickness specified in the Maxsurf Surface Properties dialog

may be included.

Use Trimmed Surfaces

If the Maxsurf model has trimmed surfaces, the Use Trimmed Surfaces item should be

ticked.


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Stations

When calculating stations, you may select how many stations should be used. Reducing

the number of stations will speed up the analysis time but reduce the accuracy,

conversely increasing the number of stations will increase the analysis time but lead to

higher accuracy results.

The first option allows you to use the station grid created in Maxsurf. This is extremely

useful for hulls that have features such as keels or bow thrusters that need to be

accurately modelled and may need a locally denser station spacing to do so. It also

allows designs with significant longitudinal discontinuities in their sectional areas to

have stations specified either side of the discontinuity, avoiding any errors inherent in

the integration of evenly spaced stations. For example, if it was known that a design had

a significant discontinuity in its sectional area curve at amidships, by specifying one

station 1mm aft of amidships and one station 1mm forward of amidships this

discontinuity can be modelled very accurately.

The upper limit for the number of stations is 200.

Surface Precision

The Surface Precision options has two functions:

Setting for calculating the hydrostatic sections

Setting used to form new compartments or tanks.

The precision at which the design was saved in Maxsurf is included in the Maxsurf

design file (.msd). Hydromax recognises this precision setting and will and set the

Surface Precision button accordingly.

Note:

Maxsurf surface trimming information may vary for different precisions.

Therefore it is recommended not to change the precision setting when

opening the Maxsurf design file in Hydromax.

Note:

The accuracy of the results depends much more on the number of sections

than the accuracy at which the sections are calculated. Reducing the

precision of the sections can greatly improve performance, usually at

relatively small impact on the accuracy of the hydrostatics.

Opening an Existing Hydromax Design File

After saving the Maxsurf design file for the first time in Hydromax, a “Hydromax

Design file” (.hmd) is created. The Hydromax design file will consist of the hydrostatic

sections and all input data such as loadcases, compartment definition, key points,

sounding pipes etc. Hydromax also allows saving of all input and output files into

individual files.

To open an existing design, there are two options:


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Double click on the .hmd file from any Windows explorer window

Use the Hydromax Open command form the file menu and select the .msd file

An existing Hydromax design consists of a number of files with different file extensions.

When Hydromax opens a .msd file, it will look for a .hmd file with the same name as the

.msd file. For example: when opening OSV.msd, the OSV.hmd file is found. The

Calculate Sections dialog now has the option to read the sections from the file.

Ensure “Read existing data and sections” is selected and click OK.

Hydromax will now open the .hmd file. This contains hydrostatic sections information

and all input information from last time the .hmd file was saved, i.e. compartment

definitions, loadcases, damage cases, key points etc.

Notes:

1) When selecting “Read existing data and sections (do not update geometry)” the

Maxsurf surface information is not recalculated. This means that changes to the

hull shape in the Maxsurf Design file, are not automatically incorporated. You will

load your existing sections, loadcases and compartment definitions etc. See:

Updating the Hydromax Model on page 26 for more information.


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2) Calculate new sections (ignore existing data, if any) means that Hydromax will

recalculate the hull sections and ignore any data stored in the .hmd file. You will

have to reload your individual loadcases and compartment definition files etc after

you have selected this option and pressed OK. Do not choose this option if you

wish to keep the additional Hydromax data and you have not yet saved them as

individual files as if the model is saved in Hydromax the .hmd file will be

overwritten and any existing data lost. For more information on file properties and

extensions in Hydromax, please see: File Extension Reference Table on page 307.

Effect of Zero Point change

The description below relates to what happens in the following situation:

A hull model is generated in Maxsurf

Tank and load etc. data is then created in Hydromax and that data all saved in the

.hmd file (as is done when you chose Save when the drawing window is top most).

The model is closed in Hydromax

The model is opened in Maxsurf and for some reason the location of the zero point

is changed

The model is reopened in Hydromax and the tank and load etc. data is

automatically read from the .hmd file.

Hydromax 13 behaviour

It may sometimes occur that the model zero point location is changed in Maxsurf after

tank, loadcase. Etc. data is defined in Hydromax. In previous versions of Hydromax this

could cause problems because the loadcase and tank data maintained their position

relative to the zero point, where as the key points and margin line remained in the same

position relative to the hull.

The two images from Hydromax 13 show this problem. The first image shows the model

as initially defined in Hydromax with the zero point amidships and at the baseline. In the

second image, the zero point has been moved (in Maxsurf) to the aft-perpendicular and

the DWL. Note that whilst the margin line and key points have remained in their same

locations relative to the hull, the tanks and centre of gravity (from the loadcase) have

remained in their same locations relative to the zero point.

Original location of data as entered in Hydromax before zero point change in Maxsurf.


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Effect of Zero point change in Maxsurf 13.

Hydromax 14 behaviour

To rectify this problem, when loading a .hmd file, Hydromax now detects if the zero

point has been modified in Maxsurf when the model is reopened in Hydromax. Note that

this is only possible with Hydromax models that have been saved from the new version

of Hydromax (because the new version of Hydromax now saves the zero point

independently so that it can check for changes).

Original location of data as entered in Hydromax before zero point change in Maxsurf.

Now, if the zero point has changed, Hydromax will display the following message:

If the zero point is moved in Maxsurf, you will now be prompted.

Selecting “yes” will maintain the position all the Hydromax data relative to the hull;

essentially just the zero point it moved. This of course means that the numerical values

of the various data are changed:


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Click “yes” to maintain position of tanks, loads etc relative to the hull.

Selecting “no” will move all data other than the margin line with the zero point. Thus the

tanks and loads etc. will move relative to the hull, but their numerical values will remain

the same: The example shown is quite extreme, it is more likely that this option would be

selected if it was realised that the zero point for the tank plan were slightly different than

the zero point of the lines plan and a small correction to the zero point was required.

Click “no” to maintain position relative to zero point.

Updating the Hydromax Model

To update the hydrostatic sections to the latest Maxsurf Design File, select “Recalculate

Hull sections” in the analysis menu after reloading the Maxsurf Design File with the

“read existing data and sections from file” option selected. This function can also be

used to include/exclude surface thickness or change the number of sections and to

change use/not use trimmed surfaces without reloading the Maxsurf Design File.

The “Recalculate Hull Sections” command recalculates Hull surfaces as well as Tank

Boundary surfaces (Internal Structure surfaces in Maxsurf). Any tanks and loadcases

will also be updated with this command.


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Note:

Changes to the Maxsurf design are only recalculated after the new Maxsurf

design has been re-loaded into Hydromax. This means that if the model is

simultaneously being edited in Maxsurf and Hydromax, it is necessary to:

1) save and close the model in Hydromax

2) save in Maxsurf

3) open in Hydromax, using “Read existing data and sections” to make sure

the loadcase, compartment definition etc remain part of the Hydromax

design file.

4) use the “Recalculate Hull Sections” from the analysis menu.

Hydromax Sections Forming

Hydromax works by applying trapezoidal integration to data calculated from a series of

cross sections taken through the Maxsurf model surfaces. Hydromax will automatically

form these sections, called “Hydromax sections”, “hydrostatic sections” or just

“sections”. Hydromax deals only with sections that are completely closed, or can be

unambiguously closed. This section outlines the section forming process used in

Hydromax and may be helpful when preparing a Maxsurf design for Hydromax. Whilst

it is always preferable to give Hydromax a completely closed model with no ambiguities,

Hydromax will try to resolve any problems with the model definition in the manner

outlined in the following sections.

Note:

The golden rule is that for any longitudinal position, the section must be

made up of closed, non-intersecting (and non-self-intersecting) contours. In

practice, one opening is acceptable and this will be automatically closed

with a straight line.

Furthermore, contours cannot be contained wholly within another contour.

The same is true for groups of internal surfaces that have been selected to

define a tank boundary.

Where a section consists of an open shell (e.g. a hull surface with no deck), Hydromax

will automatically close the section with a straight line connecting the opening ends.

If, however, the section is made up of two line segments, (e.g. having both a gap at the

centreline as well as an open deck), an ambiguity exists as to how the two line segments

will be connected. This is not an acceptable shape.


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In the example above, if either the top or bottom gap had been closed in Maxsurf the

design would cease to be ambiguous.

Multiple surfaces that are trimmed correctly, bonded together or use compacted control

points will not cause any problems when opened in Hydromax. Hydromax will form a

closed section through multiple surfaces by linking the curve segments together.


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A section through a multihull containing a single closed contour

A section comprising two closed contours

Hydromax will link curve segments together if they are only separated by a small

amount. The user cannot change these tolerances, because there are too many

dependencies in the program.

Where surfaces intersect, Hydromax will make an attempt to remove excess portions of

the curve to form a single continuous contour. However this is not always possible so it

is much better practice to trim the model correctly manually.

Ambiguous Sections (e.g. decks, bulwarks)

A common example of ambiguous sections is a model with multiple decks. Hydromax

will have difficulties distinguishing the intended main deck.

Hydromax closes the outside contour and trims remnants


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The example above has bulwarks; generally these will be treated correctly by Hydromax

and removed, but this depends on the height of the bulwark relative to the rest of the

section. To prevent ambiguities it is recommended to trim the bulwark in Maxsurf. If the

bulwark‟s volume is expected to influence the hydrostatic calculations, the bulwark‟s

volume has to be properly modelled in Maxsurf by modelling both the outside and the

inside of the bulwark.

Checking the Hydromax model

Before starting any analysis you should check whether Hydromax has been able to

correctly interpret your design. The following tools are available to validate the

Hydromax model.

Show Single Hull Section

Checking the Sectional Area Curve

Using Rendering to Check the Model

Note:

Sections that are not formed correctly cause the majority of problems with

Hydromax models. Therefore, checking your sections after opening the

design in Hydromax is strongly recommended. Incorrect sections in the

model will give incorrect results.

These sections should be continuous with no gaps and no unexpected lines.

In particular, look closely at intersections between surfaces to make sure

that Hydromax has interpreted the shape correctly.

Show Single Hull Section

In the body plan view, you can step through the sections one-by-one to verify that they

have been correctly calculated. This is done by selecting Show Single Hull Section in

Body Plan view from the Display menu. You can then click in the inset box to view the

sections, the left and right arrow cursor keys will enable you to step through the sections

one-by-one. This works the same as the Maxsurf body plan window and is an extremely

powerful tool to validate your Hydromax model. For more information see the Maxsurf

manual.


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Checking the Sectional Area Curve

Another way of checking the Hydromax model is to perform a specified condition

analysis at quite deep draft and look carefully at the sectional area curve in the graph

window. If this displays any unexpected spikes or hollows Hydromax may not have

correctly interpreted the hull shape. This is not a foolproof method since it does not

necessarily highlight problems in the non-immersed part of the hull.

This Cross Sectional Area curve indicates there may be a problem with section forming from 12 m to 16 m.

Using Rendering to Check the Model

The model may also be rendered, which makes it easier to see if there are any areas of

the model which have not been properly defined. Select Render from the Display menu

whilst in the perspective view and turn on the sections:


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Note:

In rare instances incorrect rendering may occur. This does not necessarily

mean that the model is incorrect. As long as the sections are formed

correctly, the model is correct.

Further detailed checking of hull and tank/compartment sections

When checking that your model is correct, you are interested in whether the sections are

correct. To do this go to the body plan view in Hydromax and select “Show Single

Section”:


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Then to check that the tanks are OK, leave the view as it is, but turn on the visibility of

all the tanks of interest (if there are few tanks, then you can show all of them, if there are

many it may help to hide some and check a few at a time).

In the single section view, only tank sections near the current hull section are shown:


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Setting Initial Conditions

All Hydromax calculations are performed in the frame of reference of the model.

Hydromax uses the aft perpendicular and forward perpendicular together with the

baseline and the zero point for all calculations and gives the results in the units specified

in the display menu.

Note:

Before you run any analysis using Hydromax, it is important that you set up

the required initial conditions for the design.

Coordinate System

Hydromax uses the Maxsurf coordinate system:

Longitudinal +ve forward -ve aft

Transverse +ve starboard -ve port

Vertical +ve up -ve down

View window View direction


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Body plan From the stern, looking fwd

Plan From above, Port side above the centreline (this

the opposite direction to Maxsurf)

Profile From Starboard, bow to the right.

Frame of Reference and Zero Point

It is essential that a frame of reference be specified. This should be done in Maxsurf and

not in Hydromax. Draft and trim are measured on the forward and aft perpendiculars. If

these are not in the correct positions, some analysis results will be meaningless or may

even fail to complete.

See: Setting the Zero Point and Setting the Frame of Reference on page 18.

Note:

Changing the zero point in Maxsurf will not update the compartment

definition, loadcase and other input values. Changing the zero point after

you have started analysing the model in Hydromax is not recommended.

Draft Marks

Drafts are automatically calculated at the perpendiculars and amidships, should you

require drafts to be calculated at other locations, you may specify upto nine additional

locations at which the drafts should be reported. This is done through the Data | Draft

Marks dialog. Drafts are always measured to the Baseline in the centre plane of the

vessel. Immersed depth measurements are made perpendicualar to the free-surface.

Difference between “Immersed depth” and “Draft” measurements


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User-defined Draft Marks

Note that the Trim is still defined as the difference between the drafts at the

perpendiculars and the Midship draft (used to define the range of immersions for the

Upright Hydrostatics analysis) is the mean of the drafts at the perpendiculars; i.e. neither

of these values has changed and neither are affected by the user-defined draft locations.

Drafts can only be defined when the vessel is rotated to the DWL (Display | Set vessel to

DWL).

User-defined draft locations and new toolbar button

Note: Draft and Trim specification

It should be remembered that the drafts specified for an analysis are the

drafts at the perpendiculars (or amidships) and the trim specified (and

reported) is the difference between the draft at the AP and draft at the FP.

Customising Coefficients

In Hydromax you may choose between the length between perpendiculars and the

waterline length for the calculation of Block, Prismatic and Waterplane Area

Coefficients. You may also select the draft, beam and sectional area to be used for

calculation of these coefficients.

The LCB and LCF can be displayed in the Results windows relative to the specified Zero

Point, Amidships location, Aft Perpendicular, Fwd Perpendicular or from the Aft,

Middle or fwd end of the actual waterline. You can also specify whether you want the

forward (towards the bow) or the aft (towards the stern) to have a positive sign. Finally

you can chose whether you want the LCB and LCF to be displayed as a length or as a

percentage of the waterline or LPP length as specified in the Length for Coefficients.


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Data | Coefficients dialog

Setting Units

The units used may be specified using the Units command. In addition to the length and

weight (mass) units, units for force and speed (used in wind heeling and heeling due to

high-speed turn etc. criteria) and the angular units to be used for areas under GZ curves,

may also be set. The angular units for measuring heel and trim angles are always

degrees. Units may be changed at any time.


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Other Initial Conditions

See:

Fluids Analysis Methods on page 148

Density on page 150

Working with Loadcases

Loadcases define the loading condition of the vessel. Static weights that make up the

vessel lightship are specified here as well as tank filling levels, expressed as either a

percentage of the full tank capacity or as a weight.

Loadcases automatically contain all the tanks defined in the Tank definition. Loadgroups

are special loadcases that contain no tanks. These may be used to define groups of fixed

weights (such as the steel weight or lightship weight) in a single location which may then

be cross-referenced into a loadcase. Any changes to the loadgroup are then automatically

incorporated into any loadcases that reference them.

A loadgroup is included in a loadcase simply by specifying the loadgroup name in the

“Item Name” column.

The loadcase will normally update the column totals automatically as weights or tank

loadings are changed. The exception to this is if tanks have not yet been formed or the

vessel is still rotated from the result of an analysis. If the loadcase does not update, click

on the update Loadcase button and ensure that the hull is at the DWL by selecting “Set

vessel to DWL”:


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The individual loads can be displayed graphically:

Creating a new Loadcase File

To create a load case, switch to the loadcase view by selecting Loadcase from the

Loadcase sub-menu in the Window menu. Then select “New Load Case” from the File

menu or press Ctrl+N. A new load spreadsheet will be displayed in the Loadcase

window. The default loadcase will contain a lightship entry and an entry for each tank

(with a default filling of 50%).


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The tabs in the bottom of the window can be used to skip through the different loadcases

in the design.

Create New Loadcases based on Template

To avoid rework, an existing loadcase may be used as a template when creating a new

loadcase. To do this,

In the loadcase window, select the Loadcase you wish to use as a template

Bring the loadcase you wish to use as a template to the front for example by clicking on the tab on the bottom

select File | New

First, you will be asked for a new Loadcase name after which the following dialog

appears:


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A new loadcase will appear in one of the blank (…) loadcase tabs. If there are no blank

tabs left, you will either have to close an existing loadcase, or add more loadcases using

the Case | Max. Number of Loadcases command.

Note

The template is only used during the creation of the loadcase. Once a

loadcase has been created from a template loadcase, changes made in the

template are NOT automatically changed in the loadcase derived from it.

Naming and Saving a Loadcase

A loadcase can be given any name by saving it to a separate file where the loadcase

filename will be used as the loadcase name and displayed on the tab in the loadcase

window. Alternatively,

Select Edit Loadcase from the Case menu

Changing the name in the Loadcase Properties dialog.

The next time you use the File | Save Loadcase command you will be asked to confirm

the loadcase file name.

Loading a Saved Loadcase

You can load a saved loadcase into your loadcase window by:

Select an empty tab in the loadcase window that you wish to load the

loadcase into

Empty tab.

If there are no empty tabs, you should either increase the maximum number of loadcases

(see below), or close an existing loadcase.

Select File | Open Load Case


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Select the .hml file you wish to open.

Setting the Maximum Number of Loadcases

The maximum number of loadcases (up to twenty-five) that can be loaded in Hydromax

at any one time is set by selecting “Max. Number of Loadcases” from the Case menu.

You may then enter the maximum number of load cases you require.

You must restart Hydromax for this change to take effect. In most cases, you will only

need to set this once to the maximum number of loadcases you are ever likely to use. For

convenience of use, a sensible number is recommended.

Each loadcase can be selected and used for analysis. Each may be saved and loaded

independently, effectively allowing you as many loadcases as you require.

Note:

When loading a design that has more loadcases than the maximum you have

currently set in Hydromax, you will receive a warning and the file will not

be loaded. You must increase the maximum number of allowable loadcases

and restart Hydromax before you can load the design.

Closing a Loadcase

Select the tab of the loadcase you wish to close in the Loadcase window

Select File | Close Load Case

Adding and Deleting Loads

To add an extra load to the loadcase,

Select Add Load from the Edit menu or press Ctrl+A.

A new load will be inserted into the table above the currently selected row. You can

repeat this process for as many loads as you wish.

If you want to remove a load from the table, simply click anywhere in the row you want

to remove, and choose Delete Load from the Edit menu (or highlight the complete row

by clicking the grey cell to the left of the row and press the Delete key). If you wish to

delete several loads simultaneously, click and drag so that all of the loading rows that

you wish to delete are selected, then select Delete Load.

Editing Loads

Click on the cell containing the load name and type in a name for this load, for example

"Lightship", and press the Tab key to go to the next column in the table (or simply click

directly in the cell you wish to edit).

For each item in the list you can specify a quantity. This is used to calculate the total

weight of that item. For example: if the item was “crew” with a weight per unit, you

could specify the quantity and unit weight, and the total weight of crew would be

automatically calculated. The weight of each item should be entered in the next column.


Page 43

The weight must always be positive. If for some reason you wish to have an upward

(negative) load, you can do so by entering a negative quantity – this can be useful if you

want to apply a pure moment to the model by applying equal magnitude, but opposite

sign loads to the vessel in the loadcase.

Tab to the next column and enter the horizontal lever for the item. After you type in this

number, press enter and the total LCG will be automatically re-calculated and displayed

in the bottom row of the table. The CG position will also be shown and updated in the

View windows if Large Angle Stability, Longitudinal Strength or Equilibrium analysis

are selected.

Note:

Levers, as with all other measurements in Hydromax, are measured from

the Zero Point.

Loadcase Sorting

A number of tools are available for controlling the order in which items and tanks occur

in the loadcase. You may move selected items and tanks up and down in the loadcase;

you may also sort selected items by name, fluid type (for tanks) etc.

Insert row | Delete row | Sort rows | Move row(s) up | Move row(s) down

Sort selected columns

After moving loads, subtotals and subsubtotals, you may have to use Analysis | Update

Loadcase ( button) to update the subtotals and subsubtotals. To ensure data

consistency, Hydromax does this automatically prior to running an analysis.

Loadcase Formatting

Hydromax allows you to improve the presentation of the Load Case window by adding

blank, heading or sub-total lines in the table.

Adding Component or Heading Lines

Components or headings can be included in a load case by preceding the text with

a period (.) character.

Adding Blank Lines

A blank line can be added into the load case by placing a dollar ($), apostrophe („)

or full-stop(.) character in the Item Name field.


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Adding Totals or Subtotals

A subtotal can be displayed for several loads within a load case. To do this the

item name field must commence with the word „total‟ or „subtotal‟.

Sub-subtotals

Sub-sub-totals may also be inserted. Sub-subtotals must start with the text

“subsubtotal”.

Grouping Similar Tanks

Use the move items UP or Down commands in the Edit menu to adjust the row

order in the loadcase.

Quantity and Unit mass for sub total rows

If a sub total includes only tanks, then the quantity and unit mass items will be included.

The unit mass is the sum of all the masses of the full tanks and the quantity is the sum of

the masses divided by the sum of the full tank masses. When tanks are grouped by fluid

type this can be useful for calculating the total tank capacity for that fluid type.

Loadcase Colour Formatting

Different colours can be defined for fixed mass items and tanks; alternatively, tanks may

be displayed in the same colour as the fluid they contain (As defined in Analysis | Fluids

dialog).

View | Colours and lines menu when Loadcase window is frontmost

Loadcase format

It is possible to select which columns are displayed in the loadcase window. Use the

Display | Data Format dialog:


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The Relative density and Fluid Type which allow you to override the default tank

densities as defined for each tank in the Compartment Definition window. This can be

useful for vessels such as product carriers which may have cargos of different types of

fluids with different densities.

Moment columns (mass * lever) can be displayed if desired.

Longitudinally Distributed Loads

Distributed loads can be entered in the Loadcase window in the aft limit and forward

limit cells. The aft limit and forward limit columns only appear when Longitudinal

Strength analysis is selected and the distributed loads will only have an effect on the

results in this analysis mode. The “Long. Arm” column defines the longitudinal position

of the centre of the load; the fore and aft limits define the longitudinal extents of the

load.

If the longitudinal arm is changed in the Loadcase window, the forward and aft limits

will be moved by the same amount.

For an evenly distributed load, the centre of gravity should be midway between the

forward and aft limits.


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Evenly distributed loads. Red = green and divided in the centre.

For trapezium shaped distributed loads the centre of gravity is not midway between the

boundaries, but within the middle third 1/3 of the centre.

Trapezium shaped distributed load. Red = Green divided within middle 1/3 of centre.

Note:

Since the load is distributed as a trapezium, the centre of gravity should lie

within the middle third between the forward and aft limits of the load, at

these extrema, the load distribution becomes triangular.

Tanks will be automatically treated as distributed loads for the longitudinal

strength calculations.

Tank Loads

When you create tanks using the compartment definition, they will be automatically

included in the loadcases (but not in Loadgroups which do not contain tanks).


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Tanks have a quantity value, expressed as a percentage of the full capacity and a weight

column. Tank level can be given as either a percentage of full capacity, volume, a

sounding or a weight.

The tank Unit Mass is the tanks mass at 100% filling.

When a tank is changed in the Compartment definition table, question marks may be

shown in the loadcase momentarily while the tank‟s new volumetric properties are being

calculated. To update the loadcase for changes in tank loads, select Update Loadcase

from the Analysis menu or toolbar.

Updating tank values in the loadcase

Irrespective of whether you have updated the values in the Loadcase Condition, the

Loadcase will be automatically updated as the first step of any analysis using the

Loadcase information.

Also see:

Update Loadcase on page 206

Loadcase cross-referencing; Loadgroups

It is possible to cross-reference one loadcase from another. This is useful if you wish to

define a detailed lightship mass distribution but do not want to have it displayed in full in

each loadcase. It also means that this lightship mass distribution would only need to be

defined and edited in one location instead of in each loadcase.

To prevent the problems of recursively including the same loadcase and also prevent

tanks from being included more than once, we have defined the following rules:

A special type of Loadcase called a Loadgroup has been defined.

A Loadgroup does not contain tanks

Only a Loadgroup can be referenced

Only a Loadcase can reference a Loadgroup.

A Loadcase can reference any number of Loadgroups

A Loadgroup is referenced in a Loadcase by typing the name of the Loadgroup to

be referenced in the Item column

You can factor the referenced Loadgroup by changing the value of the Quantity

column in the Loadcase.

Loadgroups may be analysed in the same way as Loadcases – but remember the

tanks are implicitly empty in a Loadgroup.

For the example above this means that the lightship mass distribution would be defined

as a Loadgroup and then this Loadgroup could be referenced in any number of loadcases.

The Loadcase properties dialog (Case menu) is used to define a loadcase as a

Loadgroup:


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This lightship Loadgroup contains the lightship mass distribution along the ship. The

Lightship load group can then be cross-referenced into any loadcase


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The referenced Loadgroup is automatically calculated and the appropriate values

included in the Loadcase:

Note: Loadgroup naming

The cross-referencing of loadgroups in a loadcase is case insensitive.

Loadcase density override

It is now possible to override the default tank fluid densities as defined in the

Compartment definition window. This allows you to load the same tanks with different

fluids in different Loadcases – as might be the case for a product carrier, for instance.

By default use tank defined densities:


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Type in a valid (>0.0) specific gravity and it will override the tank value:

Type in any string that doesn‟t begin with an “L” for the fluid and it will revert back to

the tank value:

Type in some thing that begins with an “L” and it will revert back to the “Private”

density of the loadcase item.


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Free surface correction

If the corrected VCG fluid option has been chosen, the Loadcase will sum the free

surface moments, divide by the total displacement to obtain the VCG correction and

adjust the VCG accordingly to obtain the corrected fluid VCG.

Fluid simulation

If the Fluid simulation option is selected in the analysis menu, no correction

is made to the upright VCG. Instead, at every step of the analysis,

Hydromax calculates the actual position of the fluid in the tanks taking into

account heel and trim, making the tanks‟ free-surface parallel to the sea

surface, thus the actual vessel CG is recalculated accounting exactly for the

static shift of the fluids in slack tanks.

When the corrected VCG method is selected in the analysis menu, it is possible to

choose the type of free surface moment to be applied for each tank in a Hydromax

Loadcase. The options available are

Maximum

Hydromax will use the maximum free surface moment of the tank in upright

condition for all fluid levels.

Actual

Hydromax uses the free surface moment for the current fluid level of the tank in

upright condition.

IMO

Hydromax uses IMO MSC75.(69) Ch 3.3 for the calculation of the free surface

moment. This method approximates the movement of fluid due to heeling and is

based on the fluid shift in a 50% full rectangular, box-shaped-tank. For other

shapes and fillings of tanks it will not correctly approximate the free surface

moment.

User specified

A user specified value is used for all levels and heel angles.

Workshop structure

Workshop can save a Loadgroup that contains the masses of all the structural parts. This

can be loaded into Hydromax and referenced in any Loadcase.

Modelling Compartments

This section will describe in detail how to model different types of tanks and

compartments.

Besides a general explanation on how to model tanks using the compartment definition

table, this section contains a number of important sections that the user should be aware

off when modelling tanks:

Number of Sections in Tanks on page 67

Tank and Compartment Permeability on page 59

Creating a Compartment definition file (.htk)

Select the Compartment Definition table by clicking on the Compartment

Definition tab at the bottom of the Input window.

Select New Compartment Definition from the File menu


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This will give you a new set of compartment definitions with one default tank.

Adding and Deleting Compartments

Before you can start adding compartments, make sure you have created a Compartment

definition file, see above.

Compartments may be added or deleted by

Select Add or Delete Compartment from the Edit menu.

Add will add a tank after the currently selected compartment and Delete will delete the

currently selected compartment(s). The accelerator keys Ctrl+A and the Delete key may

also be used to add and delete entries respectively.

Modelling Box Shape Tanks

Simple tanks and compartments are created by specifying six values that define a box-

shaped boundary for the tank. This box will be called the Boundary Box. The boundary

box is made up of the fore and aft extremities of the tank, the top and bottom, and the

port and starboard limits of the tank. Each value defines one of the six planes of the tank.

The column headings in the Compartment Definition table include terms such as 'F

Bottom, 'A Top', 'F Port' and 'A Starboard'. The 'F' and 'A' abbreviations stand for

Forward and Aft, in other words the two ends of the compartment. You will notice that

aft columns contain the word "ditto". This means that the value is identical at the aft end

of the tank to the forward end, resulting in a parallel tank.

When the “Update Loadcase” command from the Analysis menu is used, or an analysis

started, Hydromax will form the sections that define the tanks and compartments. This is

done by finding the intersection of the tank bounding box and the hull. Thus it is not

necessary to make the tanks fit the hull manually – this is done automatically by

Hydromax.

Box shaped compartments can be formed from the numerical values in the compartment definition table.

See Longitudinal Extents of Boundary Box on page 67 for some recommendations

regarding setting the boundary box.


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Modelling Tapered Tanks

The default is for compartments to have parallel sides. If you wish to define tapered

compartments, it is possible to enter different transverse and vertical values for the

points defining the forward and aft ends of the compartment.

If a different value is entered in one of the “ditto” columns, a tapered tank will result.

Tanks can be tapered or sloped in Plan or Profile views. Hydromax does not have a

mechanism for creating a sloped tank boundary in the Body Plan view.

By changing the “ditto”-input fields, tapered tanks can be formed

Note:

Tapering can be done in Plan and in Profile view. Tapered tanks in Body

Plan view have to be created using a boundary surface. See Modelling

Tanks Using Boundary Surfaces on page 54.

Linked Tanks

Tanks and compartments may be linked. This means that although they are defined as

separate tanks, they act as a single tank with a common free surface. To link tanks,

compartments or non-buoyant volumes, first make them the same type as the parent and

give them the same name. The easiest way to do this is to copy and paste the name from

the Name column of the parent row into the Name column of the linked tank row. They

may then be linked to the parent by typing l or linked in the Type column. Linked tanks

and compartments do not have to be physically linked in space. However, the fluid in a

linked tank or damaged compartment is always assumed to be able to flow freely

between the linked volumes.


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Modelling Tanks Using Boundary Surfaces

Tanks, compartments and non-buoyant volumes may have their boundaries defined by

surfaces as well as being constrained to particular dimensions. This allows for the

modelling of arbitrarily shaped tanks.

Forming tanks using boundary surfaces

The surfaces to be used to define the tank boundaries are selected by clicking in the

Boundary Surfaces column in the middle of the Compartments Definition table. A dialog

will appear that allows you to select which surfaces form the boundary of the tank. If a

tank uses boundary surfaces, the cell in the Boundary Surfaces column is coloured blue.


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If you wish to use a Maxsurf surface to define a tank or compartment, tick next to the

surface name in the Boundary Surface list. Note that symmetrical surfaces appear twice

as there will be a starboard and a port side copy of the surface. The Starboard surface is

first in the list and the Port surface second. The port surface is also identified with the

suffix (P) after the name.

Note:

Only internal structure surfaces appear in the boundary surfaces list.

Symmetrical surfaces are duplicated, with the port-side surface having “(P)”

appended to the surface name.

After selecting the internal surfaces, it is necessary to type in the extents of

the boundary box. Hydromax will automatically set the “Fore” and “Aft”

limits of the boundary box to just within the longitudinal limits of the

Boundary Surface. This ensures that at least 12 sections are inserted in the

tank.

Also see:

Forming Compartments on page 62


Longitudinal Extents of Boundary Box on page 67

Modelling External Tanks

External tanks may not be modelled in Hydromax. However, it is normally possible to

add "Hull" surfaces in the Maxsurf model, which will enclose the external tanks. The

tanks can then be modelled in Hydromax.

Additional box-shaped hull surfaces used to define deck tanks


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Modelling Non-Buoyant Volumes

Non-buoyant volumes are effectively permanently flooded compartments. These parts of

the hull can normally be modelled using trimmed hull surfaces. However, there are

occasions where it is more convenient to use non-buoyant volumes. In some cases,

where the volume to be flooded forms sections within the hydrostatic section, this is the

only option, e.g. waterjet ducts. The choice whether to use trimmed surfaces or non-

buoyant volumes is primarily determined by the length of the non-buoyant volume

relative to the length of the vessel.

Using trimmed hull surfaces

When the length of the non-buoyant volume, relative to the length of the model, is

large enough; the non-buoyant volume can be calculated accurately from the hull

sections. If possible, trimmed surfaces should be used. The picture below is a good

example of when to use trimmed surfaces.

Propeller tunnels modelled with trimming surfaces

Using tank type: Non-buoyant volume

In some cases using trimmed surfaces is just not possible. For example, when the

sections of the non-buoyant volume are entirely enclosed within the hull sections

(as is the case for a water jet duct) the use of a non-buoyant volume is the only

way in which these features can be modelled.

Water-jet ducts modelled as non-buoyant volumes


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Another occasion when non-buoyant volumes should be used, is when the length

of the compartment relative to the length of the hull is too small to calculate its

volume from the hull sections. A good example of this is a bow thruster on a long

ship. If the vessel is very long, and the thruster duct is of small diameter, there

may not be sufficient sections to model it accurately (even if you use the

maximum of 200 sections for the Hydromax model). In this case you are better off

modelling the thruster duct as internal structure and using these surfaces to define

a non-buoyant volume. For example: in the image below the bow thruster volume

is only calculated with one section.

For more information, see Number of Sections in Tanks on page 67.

Tip: Besides increasing the number of sections through the bow thruster from 1 to 12,

modelling the thruster duct as a non-buoyant volume has the additional advantage of

being able to specify a Tank and Compartment Permeability, and hence also account for

the thruster.

Bow thruster tube modelled as two non-buoyant volumes

Tanks within Compartments

When a tank is defined within a compartment, Hydromax will automatically deduct the

volume of the tank from the compartment volume using a “linked neg. (negative)

compartment”. This is necessary for damage cases where the compartment is flooded

and the volume of the tank should be treated completely separately from the

compartment.

Linked negative compartments are deleted and recreated whenever a tank or

compartment is added, deleted or modified. Negatively linked compartments are

displayed on the bottom of the Compartment Definition table solely for reference

purposes and are not under direct user control. This means that linked negative

compartments cannot be added, deleted or modified.


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Linked negative compartments are named based on both the parent compartment as well

as the tank from which the linked negative compartment was derived. For example a

linked negative compartment might be named “Compartment3 (Stbd Hydr Oil)” to

reflect that it is derived from the intersection of Compartment3 with the Stbd Hydr Oil

tank.

Tanks Overlapping

As mentioned earlier in this manual, only compartments and non buoyant volumes or

tanks can overlap with each other. Tanks or compartments of the same type (eg two

tanks) can not overlap. A tank and a non-buoyant volume are also not allowed to

overlap.

Hydromax will first try to form tank sections and then check whether these sections

overlap tank sections of adjacent tanks. When two conflicting or overlapping tanks or

compartments are detected during the forming process, you will receive an error

message:

Notice that the compartment definition row number of the tank is given in brackets i.e. tank #8 intersects tank #3.

Troubleshooting Overlapping Tanks

Sometimes the reason for the conflict can be quite simple: eg an overlapping boundary

box. However, when you are modelling tanks using boundary surfaces, the surface

boundaries act as a boundary between two adjacent tanks and the bounding box extents

are allowed to overlap. In these cases, it can be quite difficult to see why the tanks

overlap, especially if you have a large number of tanks already defined.

By temporarily deleting all tanks except for the one that does not form, it often becomes

clear why the tank overlaps. In the case of the image above, the tank‟s fwd most section

goes all the way to the CL (probably because the fwd boundary box extent is just fwd of

the boundary surfaces or exactly on the edge of a boundary surface). This causes this

particular tank to “overlap” with surrounding tanks.


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Procedure to Fix Overlapping Tanks:

Save Model

Go into Comp def window

Save comp def

Delete all tanks except for one you wish to investigate

form tanks, inspect tank sections

Try to fix tank definition, eg by selecting additional boundary surfaces

Now that you know how to fix it..

Close comp def file. Do NOT save!!

Open saved Comp def file

Fix compartment.

Save & move on to next compartment.

Tank and Compartment Permeability

Tanks may have two permeabilities; one, which is used when the tank is intact, and the

other when it is damaged. Compartments and non-buoyant volumes have only one

permeability, thought it is listed in both columns. The compartment permeability is

applied when the compartment is flooded in a damage condition and the non-buoyant

volume permeability is applied at all times since it is always flooded.

In the case of damaged tanks and compartments, the permeability fraction is also applied

to the free-surface-moment contribution of that tank or compartment.

Permeability of Compartments

As opposed to tanks, compartments typically have structure (other than plate

stiffeners) and equipment inside. In case of large variations in permeability within

a compartment it is recommended to model separate linked compartments with

separate permeability to increase accuracy.

For example an engine room with engines and auxiliaries at the tanktop could be

divided up in a lower- and an upper engine room compartment. The lower

compartment will have a permeability of, for example, 60% and the upper

compartment a permeability of 95%. Depending on the level of accuracy required,

the engines and equipment could also be modelled individually as empty tanks.

Relative Density of Tank Fluids

Relative Density (Specific Gravity) values can be typed directly into the Relative

Density column of the Compartment Definition table.


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Alternatively the fluid type can be entered into the Fluid Type column, either as the

name or as one of the single letter codes (when entering the name, auto complete is used,

so it is normally only necessary to type the first few letter of the name). If a fluid type is

entered, the relative density value is obtained from the value specified in the Density

dialog. Whenever values are changed in the Density dialog (see Density of Fluids on

page 150), all entries for that fluid in the compartment definition are automatically

updated.

If the tank defines a cargo tank that will carry different liquid cargoes, the default density

specified here in the compartment definition may be overridden in the loadcases.

Tanks and Surface Thickness

If you have specified that Hydromax should include the surface thickness, the tanks,

compartments and non-buoyant volumes will correctly account for the surface thickness

and its projection direction: the tanks will go to the inside of the hull shell.

Note:

Thickness of boundary surfaces are not taken into account, hence you

should design these surfaces to the inside of the tank.

Compartment and Tank Ordering

The tank definition order can be adjusted in a similar way to loads in the loadcase. Select

the rows you wish to use and use the Edit | Move Items Up or Down commands (there is

no provision for sorting tanks alphabetically). Groups of linked tanks and compartments

will be moved together.

Compartment and Tank Visibility

When creating complicated tank plans, it is often useful to check individual tanks. You

can either control the tank visibility through the Assembly window, or if you prefer, you

can use damage cases to quickly change the display to show certain tanks.

Assembly view can be used to show and hide tanks/compartments

Using damage cases, selected tanks may be displayed in the following manner:

Define a damage case

Select only damaged tanks and compartments for display, turn off the

display of intact tanks and compartments.


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Select whether you want to see the tank outline or the tank sections (tanks

sections are preferable when checking that tanks have been formed

correctly since it is these sections which are used to determine the tank

volume and other properties).

Choose the damage case from the Analysis toolbar

Set any of the tanks and compartments you wish to be visible to damaged

in the damage case window.

You can make the damage case window quite small and tile it next to the perspective

view. Use this to quickly turn tanks on and off by changing their damage status.

Using a damage case to quickly change the tank and compartment visibility

Tank sections

When in Tank Calibration mode, tank sections are also displayed in the Bodyplan view

when the “Show single section” option is selected. Only tank sections that lie on or near

the current station are shown – this makes it easier to verify that the tanks have been

formed.


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Forming Compartments

Tanks and compartments are formed automatically by Hydromax (once the tank extents

and any boundary surfaces have been defined) by selecting Recalculate Tanks and

Compartments from the Analysis menu. The formed status of a tank (yes or no) is shown

in the last column of the compartment definition table.

This section describes the internal tank-forming process that Hydromax uses to form

tanks. First a step-by-step outline of the tank forming process is given, followed by the

tank section insertion process. Understanding these processes may assist you in rare

situations where the tank forming does not work as expected.

Step-by-Step Tank Forming Process

As an example, the starboard waterballast tank below will be created using boundary

surfaces.

An example of a port and starboard waterballast tank with a pipe tunnel at the centreline. The water ballast tanks have a margin plate on the side.

Hydromax uses three input items to form the compartment

Boundary surfaces (if defined)

Boundary box

Hydromax Hull sections

Starting position

The starboard tank margin plate is modelled using an Internal Structure surface from

Maxsurf.

Starting point: Hydromax Hull sections with an internal surface and a bounding box

Also see:

Modelling Tanks Using Boundary Surfaces on page 54 and the Maxsurf manual

on internal structure surfaces


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Step 1: Close Internal Structure Surface

Hydromax will close the Internal Structure Surface contour by drawing a straight line between the ends of the opening.

Hydromax uses the same method for forming the tank section from the boundary

surfaces as for forming the hydrostatic sections through the hull. As with the hull

sections, the surfaces selected to form the tank boundary must form closed section

contours at all longitudinal positions through the tank. The area inside the selected

surfaces will define the tank contour.

Make sure that the boundary surfaces:

Form a closed section contour, or

There is no more than one opening – the opening will be closed with a straight line

Note:

Hydromax will close the section contour of the selected boundary surfaces

only. Often a tank is not formed as expected because only one side of the

internal structure surface was selected for example the portside (p).

Another common cause of unexpected results is trimming. If you selected

“use trimmed surfaces” while opening the Maxsurf model, Hydromax will

use the trimmed internal structure surface. Usually the internal structure

surfaces are best to be left untrimmed.

Step 2: Clip to Boundary Surface

Using the closed surface section contour Hydromax can now form a closed compartment

section. The tank or compartment looks like this at this stage:


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Step 3: Clip to Hull

Hydromax will clip the compartment section to the hull.

Step 4: Clip to Boundary Box

Finally the compartment section is clipped to the boundary box. The boundary box is

formed from the numerical input in the Compartment definition table.

More realistic surface-bounded tanks

Whilst the above example shows the principles by which surface-bounded tanks are

formed, it is not really realistic because it would not be possible to define a tank above

the surface-bounded double bottom tanks. In practice additional surfaces would be

required. A more realistic example is shown in the following section.

In this example the vessel has both wing and double bottom tanks with non-rectangular

cross-sections thus requiring them to be defined by boundary surfaces – see blow:


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Sketch of tank cross-sections

Five surfaces have been defined to define the tank boundaries:

Tank Boundary surfaces defined in Maxsurf

The following surfaces need to be selected for the different tanks so that closed sections

are generated (or at most one section)

Hold (C) TankWing, TankWing (P), TankTop, TankTop (P)

Double Bottom (P) TankTop (P), BottomClosure (P), TankBilgePlate (P)

Double Bottom (S) TankTop (S), BottomClosure (S), TankBilgePlate (S)

Wing Ballast (P) TankWing (P), OuterClosure (P), TankBilgePlate (P)

Wing Ballast (S) TankWing (S), OuterClosure (S), TankBilgePlate (S)


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Hydromax tank definition

Surfaces for Hold (C) (top is closed automatically)


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Surfaces for double bottom tanks

Surfaces for wing tanks (top is closed automatically)

Number of Sections in Tanks

The volume of a tank or compartments is calculated by integrating section properties

along the length of the tank. Thus it is important to have a sufficiently large number of

sections to accurately model the tank. Hydromax will normally place twelve sections

between the forward and aft limits defining the tank. If this results in a section spacing

greater than the spacing for the hull spacing, additional sections will be inserted into the

tank so that the tank section spacing match the hull section spacing.

Also see

Longitudinal Extents of Boundary Box on page 67

Longitudinal Extents of Boundary Box

For tanks near the ship‟s extremities it is good practise to set the “Fore” and “Aft” limits

in the compartment table to just inside the hull surface (say 1mm). In most cases, this

will be done automatically by Hydromax. The following example illustrates why:


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If the boundary box is set like this:

The number of hull sections is dependent on the section spacing in the model.

But if the boundary box is set just inside the forward limit of the bulbous bow:

To recap – Near the ship‟s extremities, the longitudinal extents should not be set to

extreme values, they should be set to just inside the extents of the hull surfaces to ensure

that at least 12 sections are used to calculate the tank volumes.

For internal structure surfaces that are used as boundary surface, Hydromax will

automatically set the “Fore” and “Aft” limits of the boundary box to just within the

longitudinal limits of the boundary surface. This ensures that at least 12 sections are

inserted in the tank.

Note that transversely and vertically there are no such restrictions.

Also see


Forming Compartments on page 62

Compartment Types

Five compartment types can be created using the Compartment Definition table - tanks,

linked tanks, compartments, linked compartments and non-buoyant volumes.


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Tanks

Will be included in the tank calibration output and are automatically added to the

loadcase.

Linked Tanks

Will have their volume added to the parent tank with the same tank name. They do

not have a separate entry in the loadcase. In addition, if a tank is damaged, any

tank that it is linked to will also be regarded as damaged. Tanks need not be

adjoining to be linked, they can be remote from one another. In this case the tank

linking simulates tanks with cross connections.

Compartments

Are only used to specify compartmentation for damage. They are not included in

the tank calibration output and will not be added to the loadcase.

Linked Compartments

Work in the same way as linked tanks. This allows you to damage a complex

compartment configuration by linking compartments together and damaging the

parent compartment.

Non-Buoyant Volumes

Are only used to specify compartments of the vessel which are permanently

flooded up to the static waterline. They are ideal for defining water-jet ducts,

moon pools, etc. and essentially behave as damaged compartments. They are not

included in the tank calibration output and will not be added to the loadcase.

To change the type of a tank, type the first character of the tank type (t, c or n) in the

Type column of the Compartment Definition table and then press Enter. This will

automatically set the tank/compartment to the correct type.

Sounding Pipes

Hydromax allows sounding pipes to be defined for each tank. One sounding pipe per

tank is permitted and up to nine vertices per sounding pipe, allowing inclined, bent or

curved sounding pipes to be modelled.

Hydromax creates a default sounding pipe when the tank is formed (either by running an

analysis, or using one of the following commands: Analysis | Recalculate Tanks and

Compartments; or Analysis | Update Loadcase. The default sounding pipe is placed at

the longitudinal and transverse position of the lowest point of the tank. If the lowest

point of the tank is shared between several locations (e.g. the bottom of the tank is flat

either longitudinally or transversely) the default sounding pipe location is placed at the

aft-most low point and as close to the centreline as possible. The top of the sounding

pipe is taken to be level with the highest point of the tank and the default sounding pipe

is assumed to be straight and vertical. Automatically created sounding pipes will be

recalculated if the tank geometry changes. However, once the sounding pipe has been

edited manually, any changes to the sounding pipe due to tank geometry changes will

also have to be made manually.

Edit Sounding Pipes

To customise a sounding pipe, you need to use the Sounding Pipes table in the Input

window, shown below.


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You can activate this window by selecting from the Windows | Input | Sounding Pipes

menu, by clicking on the tabs at the bottom of the Input window, or by clicking on the

icon in the window toolbar.

To add vertices to create a bent sounding pipe, make the sounding pipe type User

Defined, then click on the first row of a particular sounding pipe and choose Edit | Add

or use the Ctrl+A key combination. A new row will be added to the sounding pipe and

the longitudinal position, offset and height of the vertex can be edited. Unwanted

vertices can be deleted by clicking on the relevant row in the table and selecting Edit |

Delete or by hitting the Delete key. Note that each successive vertex in a sounding pipe

must be no higher than the previous vertex i.e. it is not acceptable to have S-bends in the

sounding pipes.

Calibration Increment

Hydromax allows user definable increments (or: intervals) for tank soundings. This is

done by specifying a numerical value for the increment for each tank in the Calibration

Spacing column of the Sounding Pipes Input window.

Type the value of the desired calibration increment in the Calibration

Spacing cell for the tank calibration you wish to modify.

If no increment is entered, Hydromax uses its default value based on a reasonable

division of the depth of the tank. In this case the Sounding Pipes table will display

“Auto” in the Calibration Increment column for the tank.


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Note

Increments are measured along the sounding pipe, not along the vertical

axis of the tank. If the sounding pipe is inclined or if it has multiple angles,

soundings will step evenly along the inclined length of the sounding pipe.

Damage Case Definition

In all but the floodable length and tank calibration analysis modes, Hydromax is capable

of including the effects of user-defined damage. Hydromax allows the user to set up a

number of damage cases. Volumes that are permanently flooded should be defined as

non-buoyant volumes.

Adding a Damage Case

To add a damage case, make the Damage window active and select Add Damage Case

from the Case menu. You may specify a name for the Damage Case in the dialog. Each

new damage case will have a column in the Damage Window and a tick may be placed

to indicate which tanks and compartments are damaged for that particular Damage Case.

The new damage case is added after the currently selected damage case column, to insert

a damage case immediately after the intact case, select the intact case column. Several

damage cases may be added in one go by selecting a number of columns.

Deleting a Damage Case

To delete damage cases, simply select the columns to be deleted in the Damage Window

and select Delete Damage Case from the Case menu. Note that it is not possible to delete

the intact case.

Renaming a Damage Case

The name of the current damage case may be changed by selecting Edit Damage Case

when the damage case window is active, the current damage case is selected from the

Analysis toolbar – see below.


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Selecting a Damage Case

The current damage case is selected from the Analysis toolbar.

The Loadcase and View windows will reflect the damage defined in the current damage

case. To perform analyses for the intact vessel, select Intact as the current damage case.

Any subsequent analyses will take into account the damaged compartments. Note that

carrying out a Tank Calibration analysis will force the intact case to be selected. This is

also the case for the Floodable Length analysis which effectively sets up its own

longitudinal extent of damage.

When tanks have been damaged, their weights and levers are no longer displayed in the

Loadcase window and the word „Damage‟ is displayed in the quantity column. This is

because Hydromax uses the “Lost buoyancy” method rather than “Added mass”.

Note:

Hydromax uses the “Lost buoyancy” method rather than “Added mass”.

Flooding is considered to be instantaneous up to sea level. Any tank fluids

are treated as having been completely replaced by seawater up to the

equilibrium waterline.

Hydromax assumes that all compartment definition has been done after the

tanks have been defined. If you have linked tanks or compartments or added

tanks within compartments after the definition of a damage case, you should

toggle the damage status of the damaged tanks. This is simply done by

copying all the damage case data to a spread sheet, turning off all damage in

all the damage cases (use the fill down command) and then pasting back in

the original data from where it was stored in the spreadsheet.

Displaying Damage Cases

When a damage case is selected, all damaged tanks and compartments will be displayed

in damaged tank or damaged compartment colour respectively. These colours can be

specified in the View | Colours and lines menu.

In the Loadcase Window damaged tanks are displayed with the label 'Damaged' in the

Quantity column, and all values set to zero.


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The Loadcase Window displays damaged tanks and excludes them from any calculations.

Extent of Damage Cases

The damaged compartments can automatically be set by using the Case | Extent of

damage command. Select the column of the damage case you wish to specify the extent

of damage for and choose Extent of Damage from the case menu:


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Defining the damaged compartments by specify the extent of damage.

Specify the extent of the damage – any tanks or compartments that lie partially or wholly

within the extent of damage will be automatically flagged as damaged:

Automatically generated damage case from using Extent of Damage command.

Key Points (e.g. Down Flooding Points)

Key points such as downflooding points and hatch openings can be defined in Hydromax

using the Key Points window. The points may be displayed in the Design View window

and will be displayed in different colours depending on whether or not they are

immersed. Immersed key points will be displayed in the same colour as flooded tanks or

compartments.

Key points may be placed asymmetrically, a positive offset is to starboard and a negative

offset is to port. Vessels which have symmetrical key points on starboard and port sides

must have both key points added to the table.

There are several types of Key Points:

Down Flooding points

Potential Down flooding points

Embarkation points

Immersion Points

Only downflooding points are used in determining the downflooding angle, which is

used in criteria evaluation. The other types of points have their freeboard measured but

are not used for the evaluation of the downflooding angle and are for information only.

Adding Key Points

To start adding downflooding points go to the Key Points table, select New Key Points

from the File menu. You will be given a default point. To add additional key points to

the table, choose Add from the Edit menu or press Ctrl+A. A new point will be inserted

below the currently selected row in the table.

Deleting Key Points

To delete a Key point, click anywhere in the row of the point to be deleted and select

Delete. To delete more than one point at a time, click and drag over the rows you want

deleted.


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Select Delete from the Edit menu, and the selected rows will be deleted.

Editing Key Points

Key points are defined by entering a name, a longitudinal position, a transverse offset

from the centreline, and a height. Click in any cell and enter the name or value you

require. All points are entered relative to the zero point.

The type of Key Point may be selected from the combo-box in the Type column of the

Down Flooding Points table in the Input window:

Links to Tanks or Compartments

Downflooding points may be linked to tanks or compartments. Select the tank or

compartment from the combo-box in the Linked to column of the Down Flooding Points

table in the Input window:

Downflooding points that are linked to tanks or compartments, which are damaged in the

currently selected damage case, will be ignored when computing the downflooding

angle. These downflooding points will appear italicised and an asterisk (*) is postfixed to

the downflooding point‟s name in the DF Angles table of the Results window:


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The downflooding angles for each of the points are displayed in the results window. The

downflooding angles are computed during a large angle stability analysis; the freeboards

after an Equilibrium or Specified Condition analysis. Immersed points are highlighted in

red in the Freeboard column. In addition to the Key Points results, immersion angles or

freeboards (depending on the analysis) are also given for the margin line and deck edge.

In the Name column the longitudinal position where immersion first takes place (or the

lowest freeboard) is given.

Note:

Linking a downflooding point to a tank does not mean that Hydromax will

consider a tank damaged when the downflooding point is submerged. This

form of automatic flooding is not supported in Hydromax yet.

Margin Line Points

The margin line is used in a number of the criteria. Hydromax automatically calculates

the position of the margin line 76mm below the deck edge when the hull is first read in.

If necessary, the points on the margin line may be edited manually in the Margin Line

Points window (the deck edge is automatically updated so that it is kept 76mm above the

margin line).

It is only necessary to modify the height value of the margin line points. Once this has

been done for all the points that need to be changed, selecting Snap Margin Line to Hull

in the Analysis menu will project all of the points horizontally onto the hull surface,

ensuring that the margin line follows the hull shape precisely. Asymmetric margin lines

and deck edges are not supported.

Points may be added or deleted as required using the procedure described in Adding Key

Points and Deleting Key Points on page 74.

Modulus Points and Allowable Shears and Moments

The Modulus window can be used to enter maximum allowable shear forces and bending

moments for each section. One or more points can be entered in this window. Allowable

shear force and/or bending moment can be specified at each point. The modulus value is

not currently used as deflections are not calculated.


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To start a table of allowable shear forces and bending moments, bring the Modulus table

to the front and choose New Modulus Points from the File menu with the Modulus

window frontmost. The allowable values can be saved and recalled as text files by using

Open and Save from the File menu. New allowable values can be inserted by selecting

Add from the Edit menu and entering a longitudinal position as well as an allowable

shear and/or moment.

Points may be added or deleted as required using the procedure described for the key

points.

These allowable values are displayed as lines on the longitudinal strength graph.

Floodable Length Bulkheads

Bulkheads entered in the Input window are used for Floodable Length analysis in order

to optionally plot the compartment lengths in the floodable length graph for easy

verification that the critical compartment lengths are not exceeded.

The Bulkheads are automatically sorted by longitudinal position. For more information

see Floodable Length on page 102.

Stability Criteria

Stability criteria may be evaluated after a Large Angle Stability analysis and after an

Equilibrium analysis. Stability criteria are required to perform a limiting KG and

Floodable Length analysis. Please refer to Chapter 4 Stability Criteria starting at page

163 for information on defining and selecting criteria.

Analysis Types

After specifying the input values and checking the Hydromax model, the analysis can be

performed. In this section the different analysis types available in Hydromax will be

described.

The following analysis types are available in Hydromax:



Equilibrium Analysis

Specified Conditions

KN Values Analysis

Limiting KG

Floodable Length


Tank Calibrations

MARPOL Oil Outflow


Also, some general information is given on:


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Starting and Stopping Analyses

Batch Analysis

The required analysis settings and environment options will be discussed separately and

in more detail in the next two sections of this chapter.

Following each analysis, one or more graphs may be shown – select the graph to be

displayed from the pull-down menu in the Graph window. The Data Format dialog can

be used to specify what is displayed in some graphs and tables; the available options

depends on the current results table or graph:

Data format dialog for Upright hydrostatics table and graph


Upright hydrostatics lets you determine the hydrostatic parameters of the hull at a range

of drafts, at zero or other fixed trim.

Choosing Upright Hydrostatics

Select Upright Hydrostatics from the Analysis Type option in the Analysis menu or

toolbar.

Upright Hydrostatic Analysis Settings

The following analysis settings apply for Upright Hydrostatic Analysis:

Draft from the Analysis menu, specify range of drafts for analysis

Trim from the Analysis menu, you may specify a fixed trim for all drafts

A range of drafts for upright hydrostatic calculations can be specified using the Drafts

command from the Analysis menu.


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Initial and final drafts can be entered, together with the number of drafts to be used. The

Vertical Centre of Gravity is also required for the calculation of GM etc (if the vessel is

trimmed, the LCG also affects these measurements).

When a design is first opened, the initial draft defaults to the draft at the DWL in

Maxsurf. Similarly the VCG defaults to the height of the DWL.

Upright Hydrostatics Environment Options

The following environments can be applied to the upright hydrostatics analysis:

Density from the Analysis menu

Wave Form (if any)

Damage (or Intact) from the Analysis toolbar

Upright Hydrostatic Results


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The curves of form are shown on a separate graph and the sectional area may be show

for any of the drafts: see Select View from Analysis Data on page 159.


Large angle stability lets you determine the hydrostatic parameters of the hull at a range

of heel angles either with or without trim or free-to-trim.

Choosing Large Angle Stability

Select Large Angle Stability from the Analysis menu or toolbar.

Large Angle Stability Settings

The following analysis settings apply for Large Angle Stability Analysis:

Displacement and Centre of Gravity using the Loadcase window

Heel from the Analysis menu, select range for analysis

Trim (fixed or free) from the Analysis menu

If criteria are being evaluated, the heel range and heel angle steps should be chosen

accordingly, to ensure accurate evaluation of the criteria.


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Note

You can select positive heel direction (port or starboard). However, you can

enter negative values and test full 360 degrees of stability if you wish. Some

criteria require calculations of GZ at negative heel. The criteria are only

evaluated on the side of the graph that corresponds to positive heel angles.

For example: when using a -180 to 180 heel range, the results may be two

angles of vanishing stability, the one that would be reported in the criteria

would be the one with a positive heel angle (even if the one at negative heel

occurred at an angle closer to zero).

Also see: Heel on page 141 in the Analysis Settings section.

Large Angle Stability Environment Options

The following environments can be applied to the large angle stability analysis:

Fluid simulation of tank fluids centre of gravity

Density

Wave Form (if any)


Stability Criteria

Large Angle Stability Results

Large Angle Stability Analysis results are:

Hydrostatic data table for each angle of heel

GZ curve

Dynamic stability (GZ area) curve

Graph of hydrostatic parameters against heel angle

Graph of max. safe steady heel angle

Stability Criteria evaluation

Downflooding angles to key points, deck edge and margin line

Curve of areas at each heel angle


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Dynamic stability Graph A graph of the GZ area integrated from upright may be plotted, features such as

downflooding angle are also included on the graph.

Curve of Areas Shows the curve of areas for the currently selected heel angle (use Display | Select

view from data to chose the heel angle from the GZ results table).

Large Angle stability Graph; Curves of Form;

Shows the variation of hydrodynamic properties with heel angle.

Graph of maximum safe steady heeling angles for sailing vessels

These calculations are derived from the value of GZ at a critical heel angle, for

example the angle of downflooding or angle of deck edge immersion.

Once a GZ curve has been calculated, you can display the maximum safe heeling

angle curves by selecting the graph type in the pull-down menu.


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The parameters for the calculation can be modified in the Display | Data Format

dialog (this graph must be selected in the topmost window):


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Analysis options for the calculation of Maximum steady heel angles (Display | Data Format).

The first part of the dialog is almost exactly the same as the “Angle of equilibrium

- derived wind heeling arm” criterion. This allows you to specify the critical

condition that should not be exceeded due to a gust or squall. MCA require

downflooding but you can include additional criteria if desired. You can also

change the shape of the heeling arm curve and the gust ratio.

In the lower-left, you can specify the squall wind speeds (you can add any

number) The default gives three wind speeds of 30, 45 and 60kts. Finally you can

adjust the axis limits. This is because normally you will have computed a GZ

curve for a wider heel range than you would wish to display in this graph – it is

uncommon to sail a vessel with a steady heel angle of greater than 40 degrees.

It can often be useful to duplicate this criterion in the GZ criteria that are

evaluated. This will give you the same result as for the gust limiting line.


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The same safe angle of heel to prevent downflooding in the event of a gust (16.5 deg) is found.

To obtain smooth curves, the GZ curve should be calculated at small intervals of

heel, especially at the lower heel angles – typically steps of 1degree. Under some

circumstances, it may not be possible to evaluate the curves, the most common

reason for this is that the GZ curve has not been calculated up to a sufficiently

high angle of heel and downflooding angle cannot be found.

Full details of the calculations can be found in:


Page 86

Sailing Yacht Design: Practice. ed. Claughton, Wellicome and Shenoi. Adison

Wesley Longman 1998. ISBN 0-582-36857-X

STABILITY INFORMATION BOOKLET available from the MCA.

www.mcga.gov.uk

Stability Criteria Evaluation

The criteria results are displayed in the Criteria tab in the results window. For

more information on how to customize the display of the criteria results, please

refer to the Results Window on page 185 in the reference section.

Important:

For important information on varying displacement while evaluating

criteria, see: Important note: heeling arm criteria dependent on displacement

on page 240.

Downflooding Angle

After a Large Angle Stability analysis, the Key Points Data table lists the

downflooding angles of the margin line, deck edge and defined Key Points. In

addition, the first downflooding point is marked on the large angle stability graph.

Only the positive downflooding angles are displayed, hence if there is any

asymmetry, the large angle stability analysis should be carried out heeling both to

starboard and to port. For the margin line and deck edge the longitudinal position

at which immersion first occurred is provided.

Downflooding points that are linked to tanks or compartments that are damaged in

the currently selected damage case, will be ignored when computing the

downflooding angle. These downflooding points will appear italicised, and an

asterisk (*) is postfixed to the downflooding point‟s name in the Key Point Data

table of the Results window.

Emergence angles of the key points is also calculated – this is where they cross the

waterline in an upward direction to become dry; as opposed to the immersion

angle which is when the cross the waterline in a downward direction, becoming

wet.

A downflooding angle of zero degrees indicates that the key point is immersed at

zero degrees of heel.

Also see:

Select View from Analysis Data on page 159.


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Equilibrium Analysis

Equilibrium analysis lets you determine the draft, heel and trim of the hull as a result of

the loads applied in the table in the Loadcase window. The analysis can be carried out in

flat water or in a waveform.

Choosing Equilibrium Analysis

Select Equilibrium from the Analysis Type option in the Analysis menu.

Equilibrium Analysis Settings


Also see:

Setting the Frame of Reference on page 18

Equilibrium Analysis Environment Options

The following environments can be applied to the Equilibrium analysis:

Fluid simulation of tank fluid centre of gravity

Density

Wave Form (if any)


Grounding (if any)

Criteria

Equilibrium Results

Equilibrium Results are:

Hydrostatic data

Freeboard of key points, deck edge and margin line

Criteria evaluation

Wave phase animation

Curve of areas


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Hydrostatic data

Height/freeboard above free surface

The freeboard of each Key Point is also calculated. The freeboard is for the vessel

condition currently displayed in the Design view and is recalculated after each

Equilibrium and Specified Conditions analysis. The freeboard calculated is the

vertical distance of the Key Point above the local free surface; hence the local free

surface height if a waveform is selected will be taken into account.

Freeboard of key points.

Negative freeboards, i.e. where the Key Points are immersed are displayed in red.

The longitudinal positions at which the minimum freeboard for the margin line

and deck edge occurred are also specified.

Stability Criteria Evaluation

The criteria results are displayed in the Criteria tab in the results window.


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Equilibrium Animation in Waves

If performed in conjunction with analysis in waves, the Equilibrium analysis will

automatically phase-step the waveform through a complete wavelength. This gives

ten columns of results, one for each position of the wave crest. If necessary the

results of this phase stepping can be animated giving a simple, quasi-static

simulation of the hull motion in waves (Display | Animate).

Note:

This simulation only includes static behaviour at each wave phase, and does

not cover dynamic or inertial forces. This can be done using Seakeeper.

Equilibrium Concept

The definition of equilibrium is “Position or state where object will remain if

undisturbed”. You can distinguish equilibrium into two types:

Stable, when disturbed the object will return to its equilibrium position

Unstable, when disturbed the object will not return to its equilibrium position

With ships, an unstable equilibrium can exist when the KG > KM, i.e. the centre of

gravity is above the metacentre (negative GMt). In real world a ship in unstable

equilibrium will roll from the upright unstable equilibrium position to a position of stable

equilibrium and assume an “angle of loll”. Since Hydromax starts the equilibrium

analysis in upright position, it has no way of determining whether the equilibrium is

stable or unstable. This means that unstable equilibrium may be found instead of the

stable equilibrium. Therefore it is recommend to check the value of GMt yourself after

doing an equilibrium analysis or perform a Large Angle Stability analysis and look at the

slope of the GZ curve through the equilibrium heel angle.

Stable equilibrium Unstable equilibrium


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Unstable equilibrium

Stable equilibrium

”Angle of loll”

The graph above shows the results of a Large Angle Stability analysis for a vessel with

negative initial GMt. In practice this vessel would have a loll angle of approximately 25

degrees. If an equilibrium analysis is performed for this vessel with the transverse arm

set to zero, Hydromax will find the unstable equilibrium position with zero degrees of

heel.

In practice, it is desirable to find the stable equilibrium position. To do this, first ensure

that the tolerances (Edit | Preferences) are set as sensitive as possible. This will ensure

that the smallest possible heeling moment is required to find stable equilibrium position.

Then create a very small heeling moment by offsetting one of the weight items in the

loadcase window TCG by just a fraction. The equilibrium analysis will now find the

stable equilibrium position.

Note:

It is good practice to always perform a Large Angle Stability analysis as

well as the equilibrium analysis to check if the vessel is in stable or unstable

equilibrium. This is most likely to occur if the VCG is too high and the

vessel has negative GM when upright. The problem can be overcome by

offsetting the weight of the vessel transversely by a small amount.


Specified Condition analysis lets you determine the hydrostatic parameters of the vessel

by specifying the heel, trim and immersion. Heel can be specified by either the angle of

heel or the TCG and VCG. Trim can be specified by the actual trim measurement, or the

LCG and VCG. Immersion can be specified by either the displacement or the draft.

Choosing Specified Conditions

Select Specified Conditions from the Analysis Type option in the Analysis menu or

toolbar.


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Specified Conditions Settings

The settings required for Specified Condition analysis are:

Specified Conditions from the Analysis menu

Three Sets of variables are provided, labelled Heel, Trim and Immersion. One choice

must be made from each of these groups. Hydromax will then solve for the vessel

hydrostatics at the conditions specified.

Values from the current loading condition can be inserted into the Centre of Gravity and

Displacement fields by clicking on the Get Loadcase Values button.

Also see:

Setting the Frame of Reference on page 18

Specified Conditions on page 145 in the Analysis Settings section.

Note:

If the fluid simulation has been turned on in a previous analysis mode, then

the VCG obtained from the loadcase will not include the free surface

correction; the “Get Loadcase Values” button will return exactly the

displacement and CG as displayed in the current loadcase window.

The specified condition analysis itself ignores tank fillings and does no

correction to VCG.

Specified Conditions Environment Options

The following environments can be applied to the Specified Condition analysis:

Density

Wave Form (if any)


Specified Conditions Results

The specified conditions results are the same as equilibrium analysis results except that

criteria are not evaluated, i.e. hydrostatic data and key points freeboard are calculated.


Page 92

KN Values Analysis

KN Values Analysis allows you to determine the hydrostatic properties of the hull at a

range of heel angles and displacements to produce the cross curves of stability diagram.

Choosing KN Values Analysis

Select KN Values from the Analysis Type option in the Analysis menu or toolbar.

KN Values Analysis Settings

The analysis settings required for KN Values analysis are:

Heel from the Analysis menu, select range for analysis


Displacement from the Analysis menu, select range for analysis and specify

estimate of VCG if known

The heel angles used may differ from those used in the Large Angle Stability and

Limiting KG analyses. To set the range of angles, select Heel from the Analysis menu.

A range of displacements for KN calculations can be specified using the Displacement

command from the Analysis menu. Initial and final displacements can be entered,

together with the number of displacements required.

Displacement range dialog


Page 93

Trim dialog

The VCG can also be entered (specified from the vertical zero datum). Traditionally, KN

calculations are calculated assuming the VCG at the baseline (K). However if the

analysis is being calculated free-to-trim and an estimate of the VCG is known, the

accuracy of the KN calculations (for VCGs in the vicinity of the estimated VCG) may be

improved by calculating the GZ curve using the estimated VCG position – this will

reduce the error in the trim balance due to the vertical separation of CG and CB because

this vertical separation is specified more accurately than simply assuming the VCG at the

baseline.

If a VCG estimate is specified, the KN values are still presented in the normal manner

with the KN values calculated as follows:

KN(φ) = GZ(φ) + KG_estimated sin(φ)

For information on Trim settings for KN Analysis, see: Trim on page 142

Also see

KN Value Concepts on page 94

KN Values Analysis Environment Options

Density

Wave Form (if any)



Page 94

KN Values Analysis Results

KN curves calualated at each heel angle

Immersion angles calculated at each displacement

KN Value Concepts

The righting lever, GZ, may be calculated from the KN cross curves of stability (at the

desired displacement) for any specified KG using the following equation: .

GZ = KN - KG sin(φ)


Page 95

Note: KN values can also be referred to as “Cross curves of stability”.

Limiting KG

Limiting KG analysis allows you to analyse the hull at a range of displacements to

determine the highest value of KG that satisfies the selected stability criteria. GZ curves

are calculated for various KG values. After each cycle, the selected criteria are evaluated

to determine whether the CG may be raised or must be lowered.

When comparing the results of a limiting KG analysis to that of a Large Angle Stability

analysis, it is essential that the same heel angle intervals are used and that the free-to-

trim options and CG are the same. Some criteria, notably angle of maximum GZ, are

extremely sensitive to the heel angle intervals that have been chosen.

Choosing Limiting KG

Select Limiting KG from the Analysis Type option in the Analysis menu or toolbar.

Limiting KG Settings

The initial conditions required for Limiting KG analysis are:

Displacement from the Analysis menu, select range for analysis

Heel from the Analysis menu, select range for calculation of GZ curves


The range of displacements to be used is set in the same way as they are set in the KN

analysis.

The heel angles used may differ from those used in the Large Angle Stability and KN

analyses. To set the range of angles, select Heel from the Analysis menu. See Large

Angle Stability on page 80 for further details.

For information on Trim settings for Limiting KG Analysis, see: Trim on page 142

KK

B

M

B’

NN

G

Z


Page 96

Note:

Since Limiting KG can be quite a time consuming analysis, you may wish

to use a smaller number of heel angles than for the Large Angle Stability

calculations. (However this will cause some loss of accuracy.)

Limiting KG calculations will be significantly faster if the trim is fixed.

Limiting KG Environment Options

Density

Wave Form (if any)


Criteria

Limiting KG Results

Limiting KG analysis results are

Limiting KG values, for each displacement and the limiting criterion.

Limiting KG vs displacement graph

The Limiting KG value is measured from the baseline, which is not necessarily the same

as the zero point. As well as the limiting KG, the minimum GM, draft amidships, trim

and centre of gravity are given in the results table.

The Limiting KG analysis also checks that any selected equilibrium based criteria are

passed at each VCG that it tries. However, you must still have at least one Large Angle

Stability criterion selected.

Criteria are only evaluated on the positive side of the GZ curve, so if there is any form of

asymmetry, it may be necessary to run the analysis heeling the vessel to both starboard

and port (this can be done automatically in the Batch Analysis).


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After a Limiting KG analysis has completed, the results in the Criteria results table

display “Not Analysed”, this is because they do not necessarily refer to the final KG and

would be misleading. If you require the limiting KG for each criterion individually or

wish to perform a Large Angle Stability and Equilibrium analysis at each of the

displacements and the corresponding limiting KG, this can be done in the Batch

Analysis.

Some criteria may depend on the vessel displacement and or vessel‟s VCG. Where these

values are explicit in the criterion‟s definition in Hydromax, the correct values of

displacement and VCG will be used in the evaluation of these criteria. However,

problems can arise if the criterion is only available in its generic form – most commonly

heeling arm criteria where the heeling arm is specified simply as a lever and not as a

moment. In this case, since the heeling arm is not related to the vessel displacement in its

definition within Hydromax, the heeling arm will remain constant for all displacements

(where it is perhaps desired that the heeling arm should vary with displacement. For

example in the case where the heeling moment, rather than the heeling arm is constant).

Important:

For important information on varying displacement while evaluating criteria

see Important note: heeling arm criteria dependent on displacement on page

240.

Also see:

Convergence Error on page 146 in the Analysis Settings section.

Limiting KG Concepts

Hydromax will iterate to a KG value that just passes all criteria you have specified in the

criteria dialog. Hydromax will start with a set start KG value (e.g. 1 meter), run a large

angle stability analysis and check the selected criteria. If any of the criteria fail,

Hydromax will lower the KG and try again. If the criteria pass, Hydromax will raise the

KG value and try to make the criteria fail. Hydromax will continue doing this until the

limiting KG value has been iterated to within 0.1mm. If this tolerance is not achieved in

a certain number of iterations, Hydromax will move on to the next displacement.


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When performing a Limiting KG analysis, Hydromax will evaluate any equilibrium-

based criteria that are selected for testing and act accordingly. However, at least one GZ-

based criterion must also be selected. This is because to perform a sensible search,

Hydromax must have at least one criterion that will improve by reducing the VCG;

Hydromax assumes that raising the VCG will make criteria more likely to fail and that

reducing the VCG will make the criteria more likely to pass. This is not necessarily the

case for equilibrium-based criteria such as freeboard requirements or for GZ-based

criteria such as Angle of maximum GZ; if only these types of criteria are selected,

Hydromax may have difficulty in finding a true limiting KG and specify convergence

errors.

Limiting KG for damage conditions with initially loaded tanks

The set up of the Limiting KG analysis parameters has been modified to facilitate setting

up the required TCG when calculating the Limiting KG for a damaged vessel where

liquid cargo tanks initially carrying cargo or ballast water are damaged.

Hydromax assumes that damaged tanks lose all liquid cargo or ballast that they may

have been carrying and their buoyancy is lost from the vessel – analysis is done by the

lost buoyancy method rather than the added mass method.

For Limiting KG calculations for a damaged vessel where some of the damaged tanks

were initially non-empty, it is often required to specify a required TCG. This is because

under most circumstances, the intact vessel is upright (zero heel). The tanks would

generally provide a transverse moment that must be balanced by the mass of the vessel,

which must therefore be offset. Note that we are only concerned about the tanks that will

be damaged and that initially contain cargo or ballast; this is because when they are

damaged the ballast or cargo is assumed to be totally lost from the vessel. (Although

seawater enters these damaged areas, this is not seen as an additional mass because

damage is computed by the lost buoyancy method.)

Two methods of specifying the required TCG are possible. The second method was

available in older versions of Hydromax and it is the first method that provides the

additional functionality:

1. Current loadcase specifies initial loading of damaged tanks: This means that the

currently selected Loadcase will be used to define the volume of cargo or ballast

in tanks before damage is applied. If this method is selected Hydromax will look

at the mass and CG of cargo or ballast in tanks which will be damaged during

the analysis. This is used to compute required TCG. Note that all results and

input data will be assumed to be for the intact vessel. That is the specified

displacement will be that of the intact vessel and that the resulting LCG, TCG

and KG will also be for the intact vessel. If the vessel has an off-centre intact

TCG, this can be specified below (if the vessel is symmetrical and initially

upright, this should be zero).

2. The second option is for the used to specify the required TCG directly. This

functionality has been in Hydromax for many years. In this case, however the

specified displacement and CG corresponds to that of the intact vessel with

damaged tanks empty. i.e. the mass and CG of the intact vessel after deducting

the masses of cargo or ballast in any tanks that will be damaged.

Example calculations

It is probably simplest to explain this functionality by means of an example.


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The following sample calculations demonstrate how the new Limiting KG options may

be used. A vessel with a port-side tank that are initially full will have this tank damaged.

We wish to find the maximum VCG that the intact vessel may have in order to pass the

selected stability criteria.

Initial tank loadings

First we need to define how much cargo is in the tanks that will be damaged. This is

done by defining a loadcase and switching to the intact mode to specify the tank filling

levels. Here we have specified that the tank is 80% full before the damage is applied.

Use a loadcase to specify the initial quantities of fluids in tanks

Setting the Displacements

Secondly we need to define the displacement range we wish to calculate the Limiting

KG for. This is done in the Displacements dialog:

Displacement dialog

Setting the Trim options

We now need to specify the trim options we wish to use. In this case we shall use free to

trim, but with an initial vessel trim of 0.25m by the stern. Importantly we shall also

specify that the current loadcase should be used to determine the required TCG and

because the vessel is symmetrical, the specified TCG is zero:


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Trim and TCG specification

Running the Analysis

We now need to select the damage case to be evaluated, the stability criteria that need to

be passed and a suitable range of heel angles to be computed to evaluate the criteria. We

also need to determine which way we should heel the vessel and in doubt should try

heeling the vessel in both directions to see which will give the worst result. In this case

large port-side tanks are to be damaged; these are filled significantly above the waterline

so loss of ballast from these tanks will cause a list to Starboard, so the analysis should be

done in this direction.

Results from Limiting KG analysis

Limiting KG results

Validation of results

The results can be validated by completing a Large Angle Stability analysis with the

specified displacement and CG. It must be remembered that these are KG results not

VCG so when checking the VCG must be calculated. In this case the baseline (K) is at –

356.845mm


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Model baseline

Computed VCG values

We can now set up a loadcase for one of the displacements. Remember that these are the

intact vessel displacement and CG:

Loadcase to check calculated Limiting KG

When the analysis is run, it can be seen that (as expected) the stability criterion is passed

with a very small margin.


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Criterion is passed with a small margin

Floodable Length

The Floodable Length analysis allows you to calculate the longitudinal distribution of

maximum length of compartments that can be flooded with the vessel still passing

specified equilibrium criteria. The results are presented as the maximum length of

compartment plotted (or tabulated) against the longitudinal position of the

compartment‟s centre. Traditionally the criterion of margin line immersion is used to

compute the Floodable Length curve. The Floodable Length may be computed for a

range of displacements and compartment permeabilities.

Choosing Floodable Length

Select Floodable Length from the Analysis Type option in the Analysis

menu or toolbar.

Floodable Length Analysis Settings

The initial conditions required for Floodable Length analysis are:

Trim (free-to-trim, either initial trim or specified LCG)

Displacement, select range and specify VCG

Permeability, select range

Bulkhead location (if applicable)

1. The analysis is always carried out free-to-trim, but the centre of gravity can

either be specified directly in the Trim dialog or it is computed from the

specified initial trim. For information on Trim settings for Floodable Length

Analysis, see: Trim on page 142.

The range of displacements to be used is set in the same way as they are set in the KN

and Limiting KG analyses. The VCG must also be specified since the Floodable length

analysis is very sensitive to accurate trim calculations. This means that the vertical

separation of CG and CB is accounted for in the trim balance.

The permeability dialog is used to specify the permeabilities to be used for the Floodable

Length analysis; the permeability is applied over the entire length of the vessel and is

also applied to the free-surface when calculating the reduction of waterplane area and

inertia.


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This permeability is unrelated to the permeability when defining compartments and is

only used for floodable length calculations.

Floodable Length Environment Options

Density

Wave Form (if any)

Damage: no damage case may be selected as this is automatically defined by the

analysis. The Intact condition is automatically selected and the Damage toolbar is

disabled

Criteria from the Analysis menu, select which criteria should be evaluated

Criteria must be specified from the analysis menu. These are used to compute the

Floodable Lengths.

Note that internally, Hydromax will treat the vessel sinking or the trim exceeding +/-89º

as a criterion failure.

Floodable Length results

The results of the analysis are given in tabulated format at the stations defined in the

Maxsurf Design Grid as well as graphical format. The tabulated data is linearly

interpolated from the graphical data. (The raw graph data can be accessed by double

clicking the graph.)

There are several graph plot options available in the Data | Data format dialog (when the

floodable length graph is topmost). The vessel profile (centreline buttock) may also be

displayed. All compartment standards up to the maximum specified will be plotted.


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Floodable lengths graph options:

Fix the y-axis so that it is the same scale as the x-axis.

Plot the different compartment standards up to a specified maximum value.

Vessel profile (shown in light grey)

Floodable Length Bulkheads locations are specified in a table in the Input window.

The graph updates in real time as you adjust the bulkhead locations so once you

have calculated the floodable lengths, you can quickly adjust the bulkhead

locations so that the vessel meets the required compartment standard.

If the analysis is unable to find a condition where the vessel passes the selected criteria,

the following dialog will be displayed. The vessel sinking or the criteria failing in the

intact condition could cause this.

Floodable Length Concepts

The analysis is performed by defining a flooded compartment, with the centre of the

compartment at a section under investigation. The length of this flooded compartment is

increased section-by-section until one of the criteria is failed. The compartment is then

moved progressively forward along the vessel. This process may be visualised by turning

on the display of the Hydromax sections.


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Note: Speed versus Accuracy

The analysis will be both considerably more accurate and slower with a

larger number of sections in the Hydromax model; it is recommended that a

minimum of 100 sections be used for most situations.

The speed of the analysis can be increased quite considerably by increasing

the allowable tolerances in the Edit | Preferences dialog.


Longitudinal Strength lets you determine the bending moments and shear forces created

in the hull due to the loads applied in the Loadcase window. The analysis can be carried

out in flat water or in a specified waveform.

Choosing Longitudinal Strength

Select Longitudinal Strength from the Analysis Type option in the Analysis menu or

toolbar.

Longitudinal Strength Settings

The initial conditions required for Longitudinal Strength analysis are:


Distributed loads using the Loadcase window

When the Longitudinal Strength analysis mode is selected, two extra columns appear in

the Loadcase window. These are used to specify the longitudinal extents of the load. A

trapezium shaped distributed load is derived from the centre and fore and aft extents of

the load. See the Loadcase Longitudinally Distributed Loads section on page 45 for more

details.

Longitudinal Strength Environment Options

Density

Wave Form (if any)


Grounding (if any)

Criteria, allowable shears and moments from Input window


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Note that Hydromax will always use the fluid simulation method when performing a

longitudinal strength analysis. For more information on how Hydromax can take fluids

in tanks into account see Fluids Analysis Methods on page 148.

Longitudinal Strength Results

The output from the longitudinal strength calculations is a graph of mass, buoyancy,

damage and non-buoyant volumes and grounding loads. From these, the net load, shear

force and bending moment along the length of the hull are computed. If defined,

allowable shear forces and bending moments are overlayed on the graph.

Downward acting masses, such as normal masses in the loadcase or lost buoyancy due to

damage, are given positive values. Upward acting forces such as buoyancy and

grounding reactions are given negative values.

Name of Curve Description

Mass Vessel mass / unit length

Buoyancy Buoyancy distribution / unit length = immersed cross sectional

area * density. Damaged tanks and compartments reduce the

buoyancy.

Grounding Grounding reaction

Damage/NBV Loas buoyancy due to damaged tanks and compartments and

Non-Byoyant Volumes (NBV)

Net Load Mass + Buoyancy + Grounding + Damage (and NBV)

Shear Shear Force =

x

AftSt

dxx)(NetLoad


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Moment Bending Moment =

x

AftSt

dxx)(ShearForce

Allowable shear

and moment

Allowable shear and bending moments as specified in the input

Modulus table.

This data is also displayed in the “Long. Strength” tab in the Results window. You can

display this table by choosing Longitudinal Strength from the Results sub-menu under

the Window menu; alternatively double-clicking in the graph will give you all the data as

plotted.

Note

Make sure you have defined sections in your model in Maxsurf. Without

this, the longitudinal strength table will be empty.

Note:

For the purposes of strength calculations, any point loads in the loadcase

will be applied as a load evenly distributed 100mm either side of the

position of the load.

Tanks are taken into account as distributed loads as well based on their

mass distribution that is calculated from the tank sections.

Tank Calibrations

Tank Calibration allows you to determine the properties of the tanks you have defined in

the Compartment window, at a range of capacities.

Choosing Tank Calibrations

Select Tank Calibrations from the Analysis Type option in the Analysis menu or toolbar.

Tank Calibration Input

Tank definitions and boundaries

Permeability

Fluid type

The above data are specified in the Compartment and Sounding Pipes definition tables.

Also see:


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Relative Density of Tank Fluids on page 59

Tank Calibration Settings

Trim range, angle or trim measurement

Heel angle range

Which items to be calibrated: Analysis | Calibration options dialog

Analysis | Calibration options dialog: Compartments and Non-buoyant volumes may be calibrated if desired

Tank Calibration Environment Options

Calibration intervals – see Sounding Pipes

Tank Calibration Results

If a range of heel (and / or trim) angles have been defined, you may select which are

displayed in the results table and graph using the Results toolbar. If Compartments or

Non-buoyant volumes have also been calibrated, they are shown in grey.

You may chose which columns are displayed using the Data Format dialog:


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In the Window | Graphs menu each tank can be selected for display in the Graph

window. For more information see Chapter 5 Hydromax Reference.

Tank calibration calculations

A number of data are calculated for the tanks. These include the tank inertias about their

centre of gravity, the wetted surface area of the tank and the free-surface area.


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The wetted surface area of the tank includes only that part of the tank that is wet by the

fluid in it at the corresponding sounding level, the top of the tank is only included when

the tank is pressed-full.

The inertias are in fact “volume inertias” in that they are not multiplied by the density of

the fluid in the tank. The following notation is used:

x longitudinal-axis

y transverse-axis

z vertical axis

Calculation of tank inertias, where M and dm indicate an integration over the volume of fluid in the tank.

Sounding pipes and tank calibration results

If the vessel is trimmed, there are ranges of tank volumes that will show the same

sounding/ullage. (The same effect can occur if the sounding pipe does not reach the

lowest or highest point in the tank – remember that this can change as the vessel trims,

which is effectively what is happening in the figures below). These points occur when

the tank is near empty or near full, see below (increasing the trim, will exacerbate this

phenomenon):

Figure a Zero trim

Figure b Trim by bow, near-

empty tank

Figure c Trim by bow, near-full

tank

Figure a shows a sounding pipe that extends the whole height of the tank, with the

vessel at zero trim. Here all tank filling levels will have a valid sounding.

Figure b shows the vessel with (bow down) trim and a small amount of fluid in the tank.

Here there will be a range of tank filling levels which all show zero sounding.


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Figure c shows the vessel with the same trim, but with the tank nearly full. Here there

will be a range of tank filling levels that all show maximum sounding.

These effects will be noted in the tank calibration results if they are extreme enough

since Hydromax always adds calibrations at 1%, 97.9%, 98% and 100% full; if the 1%

level does not intersect the sounding pipe, the sounding will be given as zero. Similarly

if the 97.9%, 98% and 100% full levels do not intersect the sounding pipe, the maximum

sounding will be displayed, see below. In the results out lined in red, there are four

results which all have a sounding of 1.0m but different capacities – the fluid levels are all

above the top of the sounding pipe. In the blue results, the last two results are below the

bottom of the sounding pipe, giving soundings of 0.0m but different capacities (the last

but one calibration point is the fluid remaining in the tank when the sounding is 0.0m).

Tank calibrations for severely trimmed vessels; sounding pipe does not cover full range of tank capacities. The

profile view of the tank in the trimmed vessel is shown on the right; the sounding pipe is in the middle of the tank and extends from the bottom to the top of the tank.

In a similar way, if the sounding pipe extends above or below the maximum and

minimum fluid levels, you will get readings which have the same capacity but different

soundings.

Sounding intervals

The sounding intervals for the calibration table may be:

Automatic,

User defined

Fredyn – {0%, 0.1%, 5%, 10%, … , 85%, 90%, 95%, 99.9%, 100%}

Max. only – {100%}

In automatic mode the increments along the sounding pipe are chosen depending on the

height of the tank to give approximately 20 soundings. Alternatively you may specify a

precise sounding step (this is the step along the sounding pipe, not the vertical step of the

tank level). Finally a “Fredyn” sounding list may be generated, this gives intervals of

{0%, 0.1%, 5%, 10%, … , 85%, 90%, 95%, 99.9%, 100%} of the full capacity of the

tank. To specify the interval, type “A”, “F”, “Max” or a numerical value in the

“Calibration Spacing” column of the Sounding Pipe definition table.


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Note: Backward compatibility with earlier versions of Hydromax

If the model is saved with Fredyn calibration intervals and is loaded into an

earlier version of Hydromax, you must change the calibration intervals to

Automatic or a positive value otherwise Hydromax will crash during the

tank calibration analysis.

Fredyn calibration intervals

The tank calibrations normally follow regular length intervals along the sounding pipe. A

common sounding pipe is used for “Fredyn tanks”, this sounding pipe starts at the vessel

zero point and projects vertically upwards; all soundings for “Fredyn tanks” use this

common sounding pipe.

Fredyn sounding pipe

The tank calibration intervals required by Fredyn are (as a percentage of full capacity)

{0.1, 5.0, 10.0, …, 90.0, 95.0, 99.9}. To use these intervals, type “Fredyn” in the

Calibration Spacing column of the Sounding Pipes Definition table:

Specification of Fredyn calibration intervals

Note that Compartments and non-buoyant volumes are always calibrated at the

calibration intervals required by Fredyn. If only the 100% full values are required “Max”

may be specified for the calibratin spacing.

MARPOL Oil Outflow

MARPOL probabilistic oil outflow calculation may be computed according to the

following MARPOL regulations:

Resolution MEPC.141(54), Regulation 12A: Oil fuel tank protection

Resolution MEPC.117(52), Regulation 23: Accidental oil outflow performance

Define the tanks in the Compartment definition window then choose the MARPOL

analysis mode. Seltect the Reolution and tanks to be included in the analysis in the

MARPOL options (Analysis menu) dialog (see below).

MARPOL Options dialog (Analysis menu)

The MARPOL options dialog allows the user to select the tanks that should be included

in the analysis for both MARPOL Regulations.


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Tank selection for the MARPOL analysis

The list of selected tanks is different for both Regulations since Regulation 12A is for

fuel tanks and Regulation 23 applies to cargo tanks. Further each tank has the option for

being included in the computation for outflow due to side- and bottom-damage. When

you select a Regulation with the radio buttons, the corresponding list of selected tanks

will be displayed in the grid.

MARPOL Tank measurements

If the “Update all tank measurements” check-box is ticked, then Hydromax will attempt

to measure the required tank parameters (over-writing any that have previously been

manually edited).

Due to the nature of some of the measurements, it is not possible to guarantee that

Hydromax will be 100% accurate in interpreting the measurements as defined in the

MARPOL documents, for this reason the user should carefully review the values

generated by Hydromax.

MARPOL Results and additional Input

Because the calculations of the MARPOL analysis are very quick they are done in real-

time as input data is edited by the user. For this reason the data input and results are

combined in one table. The table is in the MARPOL tab of the Results window:


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MARPOL calculations: Results Window

The table is split into three parts: main Hull parameters, oil outflow due to Side damage

and finally oil outflow due to Bottom damage. Parameters that can be edited are shown

in black; those which cannot are shown in grey.

Main Hull Parameters

Different parameters are shown depending on the Regulation being used. Regulation 23

calculates the nominal oil density as the deadweight divided by the total tank capacity;

the deadweight is computed as the difference in displacements between the deepest

loadline draft and the lightship draft (or may be specified directly). For Regulation 12A,

the nominal fuel oil density is specified by the user, the default being 1000kg/m3.

Furthermore the inert gas overpressure may be specified for Regulation 23.

The deepest loadline draft is taken as the DWL draft; the lightship draft is used to

calculate the deadweight for Regulation 23 and the partial draft, which affects bottom-

damage outflow in Regulation 12A.

If a parameter is modified, it is possible to revert back to the Hydromax calculated value

or default by typing „H‟ or double clicking:

Reverting back to default/calculated parameter values

For full definitions of the parameters, please refer to the relevant IMO instruments.


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Main hull parameters required for each Regulation

Tank Parameters

Calculations are shown further down; listing first side-damage tanks, then bottom-

damage tanks. The user-editable tank parameters are the main dimensions which affect

the probability of damage. These should be carefully checked since these can be difficult

for Hydromax to automatically measure in some cases. For tanks which are to be

considered for both side- and bottom- damage, these values are linked so it is only

necessary to edit them in one location.

Note: Hydromax will overwrite user-edited tank parameters!

Remember that any data that you change manually will be overwritten by

Hydromax if the “Update all tank measurements” option is ticked in the

MARPOL options dialog.

It is advisable to copy any manually edited data to a spreadsheet or text file

if you only want to update the measurements of some tanks.

For full definitions of the parameters, please refer to the relevant IMO instruments

Saving

With the MARPOL sheet active, the MARPOL data may be saved; it is also saved in the

main .hmd file when the design is saved.


IMO Probabilistic damage

Hydromax support for Probabilistic damage according to both IMO MSC.216(82) and

IMO MSC.19(58) . MSC.216(82) can be applied to both dry cargo and passenger ships

whilst MSC.19(58) is applicable to dry cargo vessels only.


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Probabilistic damage – Principles

Essentially the probabilistic damage analysis performs a number of large angle stability

analyses and uses the IMO criterion to determine an s-factor that depends on certain

parameters of the GZ curve. The GZ curves are calculated for a large number of different

damage conditions and several load cases. For each condition, a p-factor can be

calculated. The vessel‟s attained subdivision index is the sum of the products of the p-

factors with their corresponding s-factors. The attained subdivision index can then be

compared with a required subdivision index to see if the vessel achieves a sufficiently

high degree of safety.

Flow through – Typical Use-case

The following section shows how the probabilistic damage analysis might typically be

used.

Maxsurf model is loaded as normal

User defines (first selecting File | New to open the Probabilistic damage data table)

other ship data required for the probabilistic damage analysis in the Damage

window | Global table.

User defines the damage zones they wish to consider in the Damage window |

Zones table

Once 2 and 3 have been completed, the p-factors Damage window | p Factors table

are automatically calculated and displayed as the zone data is modified. It is useful

to have this interaction because if the p Factor is too large for a particular zone,

the user may decide to refine the zone arrangement.

User defines the bulkheads and deck values for single and groups of adjacent

zones.

When the Zones have been defined the user can then define which tanks are

damaged in each zone in the Damage window | Zone damage table. A first pass at

this can be automatically generated using the Case | Extent of damage command.

The user can then perform the probabilistic damage analysis. Hydromax runs a

large angle stability analysis for each combination of loadcase and damage and

collates the results to calculate the attained index. This is then compared with the

required index.

During the analysis each GZ curve and details on the evaluation of the s-factor may be

saved in a log file. The same log file is used for each analysis so it is important to either

change the name or copy the file at the end of the analysis if the results are to be kept.

The log file parameters may be specified in the Edit | Preferences dialog:


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Probabilistic damage result logging options (Edit | Preferences)

Finding the probabilistic damage input sheets.

The probabilistic damage input sheets are in the damage window after the normal

damage condition sheet.


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A Probabilistic Damage toolbar button is available in the Windows toolbar which will

take the user back to the last used probabilistic damage input table:

Probabilistic damage – Saving input parameters

The probabilistic damage data is saved in the .hmd file. However this is new to version

14.1 and if the file were read into an earlier version of Hydromax and saved, these data

would be lost. For this reason it is also possible to save the probabilistic damage data as

a separate file (in a similar way to the other Hydromax input data). To load or save the

probabilistic damage data as a separate file, ensure that one of the probabilistic damage

data sheets in the Damage window is on top.

Bring one of the probabilistic damage tables to the front to enable File menu items

Probabilistic damage – Inputs

In this section we shall look at the input parameters required for the probabilistic damage

analysis.

Settings for Probabilistic damage GZ curve calculation

Since the analysis essentially consists of a large number of GZ curve calculations, most

of the settings that are applicable to the Large Angle Stability analysis are also

applicable to the Probabilistic Damage Analysis.

Chose the Probabilistic Damage analysis mode from the pull-down or Analysis menu:


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Selecting Probabilistic Damage anlysis mode

Once you have selected the probabilistic damage analysis mode, you can define the heel

angle range and trim settings to be used as well as any environmental parameters such as

waveform (as well as the fluid analysis method to be used).

During probabilistic damage analysis, it is possible to check the vessel heeling to both

port and starboard. This is useful if the tanks contain ballast or cargo and it is uncertain

in which direction the vessel will list when damaged (or indeed the vessel may list to

different directions depending on the loadcase and damage). Hydromax will calculate the

GZ curve in both directions and, if the criteria can be evaluated in both directions, the

lowest s-factor will be taken. If the criteria can only be evaluated in one direction, then

this value for the s-factor will be taken.

It is recommended to evaluate at least one negative heel angle and the direction of heel

should correspond to the side of the vessel that is being damaged (see below):


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Heel angle specification (as per Large Angle Stability)

Use either fixed trim or free to trim to loadcase.

s-factor calculation

The s-factors are calculated by stability criteria. The Probailistic damage analysis has its

own set of criteria (though the same parent criteria are also available in the large angle

stability analysis criteria). When the analysis mode has been set to Proababilistic

Damage, you will see the criteria that are used for this analysis. The number of parent

criteria is reduced to only those which can calculate the s-factor. Also some “Default”

criteria are supplied, you can add or modify these should you so desire. When running

the analysis, Hydromax will look at the probabilistic criteria that have been selected and

warn you if there are any problems.


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Probabilistic Damage Criteria Manager with Parent and Default criteria

The following rules should be observed when defining the probabilistic damage criteria:

As with the normal criteria manager, changes made to the parent (bold) criteria are

not saved. If you need to modify any of the criteria you should make your own

copies of the parent criteria

A set of Default criteria are provided – these can be modified and changes will be

saved.

Only one criterion should be selected and it should correspond to the IMO

Resolution being used. (Strictly, you may have up to one of each MSC.216(82) or

MSC.19(58) criteria selected and Hydromax will automatically use the appropriate

one – according to the selected Resolution in the Global sheet – but for clarity, it is

probably best practive to just have a single criterion selected.)

The criteria should always be selected for Damage analysis.

Hydromax will automatically update some of the criteria parameters according to

corresponding parameters in the probabilistic damage setup. However it is still

good practice to review criteria parameters before starting the analysis. This is

particularly true for the MSC.216(82) Resolution where the vessel type and heeling

moments must be defined correctly.

The criteria window can be closed with either of the close buttons.

For further information on how the s-factors are calculated and the different parameters,

please refer to the Criteria Help section for the appropriate criteria (and heeling arms).

Main parameters and calculation of required subdivision index

The other parameters required for the probabilistic damage analysis are defined in the

last four tables in the Damage window:


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Additional tables in the Damage window define the remaining Probabilistic damage input data

Depending on the selected IMO Resolution, different rows and columns will be

displayed in the tables; both MSC.216(82) and MSC.19(58) are provided, A.265 VIII is

not included.

Tool tips have been added to provide a more detailed explanation of the input parameters

and also the options available.

Tool tips for Global data sheet

Global table

This table is used to define the main parameters for the probabilistic damage anlysis as

well as provide some intermediate calculations. Input data are shown in black whilst

results are shown in grey. Depending on the Resolution and vessel type, some rows may

be hidden.


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Global table – MSC.216(82) Dry Cargo vessel and Passenger vessel


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Global table – MSC.19(58) Dry Cargo

Row Description

Resolution --

MSC.216(82) or

MSC.19(58)

IMO Resolution to be used.

Deepest subdivision

draft (summer

loadline) Loadcase

Name of loadcase that defines the vessel at the deepest

subdivision draft.

Partial subdivision

draft Loadcase

Name of loadcase that defines the vessel at the partial

subdivision draft.

Light service draft

Loadcase

Name of loadcase that defines the vessel at the light subdivision

draft.

not required for MSC.19(58).

Type -- Cargo or

Passenger

Vessle type.

not required for MSC.19(58).

Lifeboat capacity

N_1

Number of persons for whom lifeboats are provided.

required for MSC.216(82), pax. Vessel only.

Permitted max. num.

of persons in excess

of N_1: N_2

Number of persons inclusing officers and crew that the vessel is

permitted to carry in excess of N_1.

required for MSC.216(82), pax. Vessel only.

max. moulded

breadth at or below

deepest subdivision

draft: B

Parameter not currently used.

max. number of

adjacent zones to

consider

Specifies the upper limit of the number of adjacent zones that

should be damaged. If you wish to limit the analysis by p-factor

only, then specify the number of zones here (see min p-factor

below).

min. p-Factor of

damage to consider

Specifies the minimum p-factor for which an analysis should be

performed. The maximum a condition can contribute to the


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attained index is the p-factor. If the the p-factor is very small the

contribution to the attained index will be negligible and there is

little point in carrying out the analysis. Conditions whose p-

factor is below this minimum will not be evaluated; this can

speed up the analysis. If you wish the analysis to be purely

limited by the number of adjacent zones (see above) then specify

a small negative value. This will ensure that conditions with zero

p-factor will still be evaluated.

max. trim angle to

consider

If the vessel trim exceeds this value, then the s-factor will be

taken as zero (irrespective of the GZ curve). This can speed up

the analysis.

Limit vertical extent

of damage?

If desired the vertical extent of damage (when automatically

generating the zone damage) can be limited.

max. vertical extent

of damage

If desired the vertical extent of damage (when automatically

generating the zone damage) can be limited.

Damaged side --

Starboard or Port

Specifies which side of the vessel will be damaged (when

automatically generating the zone damage). The extent of

damage is assumed to go all the way to the centreline but you

may specify which side of the vessel is damaged. The heel

direction in the Heel setup should correspond to the side of the

vessel being damaged.

Zone 1 located at

bow or stern?

It is normal to begin the Zone numbering at the stern, but the

option to start from the bow is also allowed in Hydromax

Longitudinal Zone definition

The next table (Zones) allows for the definition of the longitudinal damage zones. Fore

and aft extents of the zone boundaries are input by the user and the length and centre of

the zone is automatically calculated; the boundaries of adjacent zones are automatically

updated if required, as are the zone names. The subdivision length is taken as the limits

of the length defined by the zones. As for other similar tables, use Edit | Add or Delete

(or Ctrl+A or Del key, with a number of complete rows selected) to add or delete zones.

Damage zones defined by fwd and aft boundaries

Zones may be shown in the drawing views (this display option is only available in

Probabilistic Damage analysis mode):


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Probabilistic damage zones (stbd. side damage) shown in pink.

P-Factors

From the damage zone calculations, the probability of damaging a longitudinal zone or

group of adjacent zones is calculated as well as the cumulative probability. The columns

displayed depends on the choice of Resolution: MSC.216(82) or MSC.19(58) made in

the Global table.

All combinations of adjacent zones are calculated at this point. A subtotal for the p-

factor for a given number of adjacent zones is given as well as a cumulative to total for

all the p-factors. This will help the user to determine the maximum number of adjacent

zones that should be analysed. In practice, it probably makes more sense to limit the

analysis by specifying a desired minimum p-factor rather than a number of adjacent

zones. This can easily be done by specifying the maximum number of adjacent zones as

the number of zones defined. The last column shows whether a particular condition will

be tested (if the p-factor is sufficiently large and the maximum number of adjacent zones

is not exceeded).


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p-factor calculations for individual and groups of zones

Sub zones due to transverse and vertical subdivision

As well as the main longitudinal subdivision, it is also possible to define sub-zones due

to longitudinal bulkheads (transverse subdivision) and decks (vertical subdivision).

Transverse sub-zone definition and R-Factors

Transverse sub-zone definition allows the user to limit the damage penetration to a

certain distance into the vessel towards the centerline, measured from the side-shell. I

have followed IMO notation by specifying the penetration depth from the side-shell

(rather than specifying the offset from the centerline). A column is provided for the user

to specify the side-shell offset (from the centerline) and this is used only to draw the

transverse extents of the damage zone, the inner limit being at a distance side-shell offset

minus b from the centreline. The side-shell offset value defaults to the maximum half-

beam of the vessel.

The r-factors are then calculated for each of the b-values that have been defined. Note

that there is one extra r-factor than the number of bulkheads – this represents the

probability of damaging to the centerline. The sum of all r-factors should be unity (a

check is provided).

The b-values are defined not only for each individual zone, but also for groups of

adjacent zones. This is because where the side-shell or bulkhead is not parallel to the

centerline, there is a special way of calculating the b-value and this needs to be done for

each set of adjacent zones. If no b-values are specified, the zone will be damaged up to

(but not across) the centreline.


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Longitudinal bulkhead definition and corresponding r-factors


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Visualisation of zones and sub-zones: sub-zones shown dashed; selected zone shown in bold.

The currently selected zone or sub-zone is shown in bold as well as any damage for that

zone. This can also be seen in rendered view to quite effectively visualize the damage.

Clicking in a zone or sub-zone in the table highlights the zone graphically


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Vertical sub-zone definition and V-Factors

Similarly decks may be defined to create vertical subdivision of the zones. The

corresponding v-factors are calculated, but these also depend on the draft of the vessel.

Thus we introduce the concept of the currently selected Loadcase for the displayed v-

factors. The loadcase for v-factor calculations is selected by clicking on the desired

loadcase in the Global table. Note that during the full probabilistic damage analysis, the

v-factors will be automatically recalculated for the loadcase under consideration.

Loadcase for v-factor calculations is selected by clicking on the desired loadcase in the Global table.


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Deck definition and corresponding v-factors


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Zone damage

The zone damage sheet specifies which tanks are damaged for a given zone. From this

Hydromax can work out what should be damaged for any combination of adjacent

damaged zones.

Definition of whats damaged in each zone

Once the zones are defined the user can select the Case | Extent of damage command and

this will automatically generate the zone damage according to which tanks lie within the

zone boundaries. Once the automatic damage is defined, this can be modified by the user

should this prove to be necessary (or it can be defined from scratch by the user). The

“Zone damage” tab of the Damage window must be on top to enable this command.

Automatic definition of damage for each zone

Additionally the user may automatically generate damage cases for the Zone damage

that has been defined damage configurations within the maximum number of adjacent

zones range and above the minimum p-factor will be added. This stage is not required

for the probabilistic analysis, but has been added for convenience should the user wish to

manually run large angle stability analyses for the same damage cases.

The Damage window must be on top for this command to work. Damage cases will be

added up to the maximum number of adjacent zones specified in the Global tab, if the p-

factor exceeds the minimum values specified (again in the Global tab).


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Automatic creation of damage cases using the damage defined for each zone

Visualization of zone damage

When in Probabilistic damage analysis mode the damaged tanks and compartments

displayed are not those of the current damage case, but those of the currently selected

zone. The zone is selected by clicking in the corresponding column of the Zone Damage

table.


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Zone damage visualisation

Probabilistic damage permeabilities

It is possible to define different permeabilities to be used for tanks and compartments for

the different load conditions – as required for “cargo compartments” in MSC.216(82)

Regulation 7-3.2:

MSC.216(82) Regulation 7-3.2

Thess values are defined in the Permeabilities table in the Probabilistic Damage window.

By default, the permeabilities are the same as the damage permeabilities given in the

Compartment Definition table, but these can be overridden (for the probabilistic damage

analysis only) for each draft if desired. When you generate new probabilistic damage

data, the permeability values are copied from the Compartment definition, but they are

not updated if they are then changed in the Compartment definition window.


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In the log file, the permeability used for any damaged tanks is shown:

Probabilistic damage – Analysis

Once the analysis parameter data has been defined, it is worth checking that the heel

direction (Analysis | Heel) is correct and also check that the s-factor calculation

parameters are corerect (Analysis | Criteria)

Pre-run checks

When trying to run the probabilistic damage analysis, Hydromax will make several

checks to see if the analysis parameters have been correctly set up. These are not

exhaustive tests but should pick up critical errors.

The following checks are made:


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That loadcases that have been specified exist

That the vessel type is correct in the criteria (if MSC.216(82) is being used)

That the correct s-factor criterion has been selected. Note that only one criterion

may be selected. If Hydromax finds no criteria selected but a suitable one is

available (but unselected) then it will prompt the user to use this one:

Analysis

Large angle stability analyses are computed for each combination of loadcase and zone

damage up to either the specified maximum number of adjacent zones or the minimum

specified p-factor. Basic data pertinent to calculation of the s-factor is also presented as

well as a total Attained subdivision index at the bottom of the table. The required index

is also shown as well as pass/fail status. Should the vessel sink, excessive trim occur or

the large angle stability analysis fail to converge, this is reported and the s-factor given

as zero.


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Probabilistic analysis results

Probabilistic damage – Future developments

The probabilistic damage analysis is still under development and new features will be

added in subsequent versions of Hydromax.

Starting and Stopping Analyses

To start the analysis, choose Start Analysis from the Analysis menu or toolbar.

Hydromax will step through the parameter ranges specified, floating the hull to

equilibrium conditions where required. Hydromax will redraw the contents of the

windows to display the current hull position for each iteration.

Calculations may be interrupted at any time by selecting Stop Analysis from the

Analysis menu or toolbar.

If you have stopped the analysis, you can resume calculation by selecting Resume

Analysis from the Analysis Menu or toolbar.

There may be a slight time delay on all of these operations while the current cycle is

finished.

You can also switch application by clicking in the window of any background program.

Hydromax will continue to calculate in the background although its speed will be

reduced. The drawing of the vessel at each step of the analysis can be quite time

consuming. If you are not interested in seeing the progress of the analysis, switch to a

table window and maximise it to speed up the analysis. Should the analysis take longer

than about 45 seconds, Hydromax will flash and beep to indicate that the analysis has

been completed.

The start, pause and resume functions are also available in the Analysis toolbar:

Probabilistic damage Log file

All the intermediate results, including all the GZ results and criteria evaluation for each

loadcase / damage case combination are logged during the analysis. The logfile location

is specified in the Preferences dialog:


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Probabilistic Damage analysis logging

Batch Analysis

Batch Analysis Concepts

Hydromax has basic batch processing capability. With a single command, Hydromax

will run Large Angle Stability and Equilibrium analyses for all combinations of load and

damage cases. Further, Limiting KG and KN calculations can be made for each damage

condition. There are other options which allow the analysis to be performed heeling to

both port and starboard. For the Limiting KG analysis you may also check the Limiting

KG for each criterion individually. You may also choose to perform a Large Angle

Stability and Equilibrium analysis at the final VCG.

The aim of the batch processing function is to:


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Provide the user with a simple and consistent way of carrying out Large Angle

Stability and Equilibrium analyses on a large number of load and damage cases.

Facilitate time consuming Limiting KG analyses, especially where results for all

individual criteria are required.

Enable Limiting KG and KN analyses to be performed automatically for all damage

cases.

Facilitate testing with heel to port and starboard for vessels with asymmetric

loading and/or damage conditions (or hulls).

Facilitate export of the data from Hydromax and import into MS Excel for post

processing and report generation.

Provide all relevant results and the data required to be able to reproduce the runs,

i.e.: analysis parameters, file name etc.

Before you can perform a Batch Analysis it is recommended that you run a number of

Analyses manually to check whether the Model has been defined correctly and all

Analysis Settings and Environment conditions have been set correctly.

Batch Analysis – Procedures

Once the loadcases, damage cases, key points, criteria and analysis parameters for the

required analyses have been set up, the Batch Analysis is started

Analysis | Start Batch Analysis


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Batch analysis runs all combination of loadcases and damage cases.

Tip: Under most operating systems, minimising Hydromax can reduce the time required

to perform the calculations. This is because time consuming redrawing of the design

windows, graphs and tables is avoided.

Batch Analysis Settings

Analysis parameters such as trim, heel angles etc. are set in the normal way for each

analysis type included in the Batch analysis. For example, if you want the Large Angle

Stability to use a fixed trim of 0.5 m:

first select the Large Angle Stability analysis type from the analysis menu

set the trim to Fixed trim and 0.5 m

then select Analysis | Batch Analysis

Batch Analysis Environment Options (Criteria)

Any Analysis Environment Options specified prior to a Batch Analysis will be used

during the Batch Analysis. Any criteria that have been set are evaluated at the end of

each analysis and the results of these are also output to the text file.

Important:

For important information on varying displacement while evaluating

criteria, see Important note: heeling arm criteria dependent on displacement

on page 240.

Batch Analysis Results

Before analysis starts, you will be prompted to enter the name and location of the file

where Hydromax will write the results of the batch analysis. Once the analysis is

complete, this tab delimited text file may be imported directly into MS Excel for further

processing.

Because the analyses are simply carried out one after the other, it is not possible to go

back to the results for a specific analysis from within Hydromax; only the results of the

final analysis will be stored in Hydromax.

At the bottom of the dialog is a check box which allows users to select whether the

results of a batch analysis should go to the Report window in Hydromax as well as the

batch analysis text file. When the option for Sending the results to Word is selected in

the Edit | Preferences dialog, the batch analysis will automatically create a Word

document.

Warning:

Sending the results to the Report can slow down analysis considerably and

also consume considerable system resources. For large batch analysis, it is

advisable not to include the results in the report. The report is stored in

memory and if you have insufficient memory, it is possible that your

computer will become very slow to respond and under some circumstances

with certain operating systems even cause Hydromax to crash.

Also see: Reporting on page 155.


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Analysis Settings

In the previous sections opening and preparing a model in Hydromax was discussed

together with descriptions of the different Analysis types. This section will describe the

following analysis settings:

Heel

Trim

Draft

Displacement


Permeability

Hydromax will allow specification of only those analysis settings that apply to the

currently selected analysis type.

In hydrostatic analysis, there are three degrees of freedom: Trim, Heel and Draft.

Hydromax matches the trim, heel and draft with the vessel‟s mass and centre of gravity

or visa versa. This way the volume of the displaced hull matches the required mass and

the centres of gravity and buoyancy lie one above the other in a vertical line. For

example: it can match a specified heel, trim and draft by varying the displacement and

centre of gravity; or it can match a specified displacement and centre of gravity by

varying the heel, trim and draft. Combinations of both are also possible. The following

table is a very simplified representation of the degrees of freedom and their weight

counterpart:

Degree of Freedom Weight

1 Draft Displacement

2 Trim Longitudinal Centre of Gravity (LCG)

3 Heel Transverse Centre of Gravity (TCG)

In fact it is a rather more complicated situation than that suggested by the table above,

because vertical centre of gravity is also important and also because most of the

variables are coupled.

The various analysis types and settings can be thought of as setting one variable in each

pair to a fixed value and deriving the others from the analysis.

For example: the Upright Hydrostatics analysis consists of fixing heel and trim and

stepping through a series of fixed drafts. In this case the LCB and TCB (and therefore

the required LCG and TCG) are calculated from the underwater hullshape at each draft.

For an equilibrium analysis all degrees of freedom are derived from the centre of gravity

and Displacement. In the Specified Condition Analysis any combination of the variable

pairs may be specified.

Heel

The Heel dialog from the analysis menu is used to specify the range of heel angles to be

used for Large Angle Stability, KN and Limiting KG analyses. Heel angles between -

180 and +180 may be specified. The heel steps must be positive. If only one set of

steps is required, simply put 0 in the other steps.


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If there is any asymmetry in the vessel due to either: hull shape, key points, loading,

damage, etc., and there is any doubt as to which will be the worst heel direction, then the

analysis should be carried out for both heel to starboard and heel to port to find the most

pessimistic condition.

If all the heel angle intervals are 10 deg or less, Hydromax will fit a cubic spline to the

GZ curve and use this to interpolate for values between the tested heel angles. If any step

is greater than 10 deg, Hydromax will not do any curve fitting and linear interpolation

will be used.

Note:

For the angle of equilibrium to be found (when analysing criteria), it is

essential that the GZ curve crosses the GZ=0 axis with positive slope. It is

possible that the GZ at zero heel may be very slightly positive (due to

asymmetry or rounding error) for this reason, it is advisable to test at least

one negative heel angle, at say -5 degrees, to ensure that the equilibrium

angle is identified.

It is good practise to start the heel range at an angle of approximately -30°.

This is to allow roll back angle criteria to be evaluated correctly.

Note:

The heel angles to be used are specified independently for each analysis

mode. This can be a source of apparent differences in the results from the

different analyses.

Trim

For most analyses you may specify whether the vessel is free-to-trim or has fixed trim.

Select Trim in the Analysis menu to bring up the Trim dialog.

Trim may be specified for Upright Hydrostatics, Large Angle Stability, KN Analysis

Limiting KG, Floodable Length and Tank Calibrations. (For the Specified Condition

analysis, the trim may be specified in the Specified Conditions dialog.) Equilibrium and

Longitudinal Strength analyses always use a free trimming (and free heeling) analysis so

that there is no trimming (or heeling) moment applied to the vessel at the final

equilibrium.


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Essentially there are three options for trim:

1. Fixed trim – the analysis is carried out at a fixed, specified initial trim. This

applies to all analyses that carry out a large angle stability-type analysis (Large

Angle Stability, Limiting KG, KN, Probabilistic Damage) as well as Upright

Hydrostatics and Tank Calibrations

2. Free to trim to loadcase – the analysis trims the vessel to the CG specified in the

loadcase. This option is available for all analyses that have a loadcase: Large

Angle Stability, Equilibrium, Longitudinal Strength, Probabilistic Damage.

3. Free to trim to specified CG – this is again free-to-trim but the CG is specified in

the dialog. This is for when a range of displacements is used for the analysis:

Limiting KG, KN, Floodable Length. In this case, all three components of the

CG need to be know. This it is possible to specify the LCG either directly or so

that the upright, intact vessel floats at a specified trim. The TCG and VCG are

specified directly. In the case of the Limiting KG analysis, the VCG is being

found by the analysis, so cannot be specified. For the Floodable Length analysis,

heel is not considered thus TCG cannot be specified.

Specification of different trim options is dependent on the type of analysis currently selected.

Fixed trim

(KN and Limiting KG analyses only).

The analysis is carried out with the specified fixed trim; the vessel is not free-to-

trim as it heels. Although considerably faster, this analysis will tend to over-

estimate ship stability properties such as GZ.

Free-to-trim using a specified initial trim value

Using this method, for each displacement, the LCB of the intact vessel at the

specified trim and zero heel is computed. The LCG is calculated using this value

and the VCG. Calculations at each heel angle of the large angle stability analysis

are then done free-to-trim using the derived LCG and VCG. Thus, for each

displacement, the upright, intact vessel trim will be the same, but the LCG will be

different.


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Free-to-trim to a specified LCG value

With this method, a specified constant LCG is maintained for each displacement.

This LCG is then used to compute the free-to-trim vessel orientation at each heel

angle as the large angle stability analysis is performed. Thus, for each

displacement, the LCG will be the same, but the upright vessel trim will be

different.

VCG for trim balance

The VCG, measured from the vertical zero datum (not necessarily KG), may be

specified.

For KN analysis, the VCG will only have an effect if the analysis is free-to-trim. It

will be used to determine the LCG if an initial trim value is specified. It will also

be used to improve the accuracy of the KN results.

For Floodable Length calculations, which are always calculated free-to-trim, the

VCG will be used to calculate the LCG if an initial trim value is specified. Also,

because the analysis is very sensitive to trim, the VCG is needed to provide an

accurate balance of the trimming moment. (As the trim angle increases the

longitudinal movement of the centre of gravity due to its vertical position becomes

more important.)

In the case of the Limiting KG analysis, the actual VCG is used and the VCG

input field will state “not applicable”.

TCG value

The TCG option allows you to specify an off-centreline centre of gravity for

Limiting KG and KN calculations. This is especially useful when evaluating the

Limiting KG of a damaged vessel that had cargo or ballast in tanks which are

subsequently damaged. The TCG can be either specified directly or calculated

from the tank loadings defined in the current loadcase.

Current Loadcase specifies initial loading of damaged tanks (los mass during analysis)

Finally, for the Limiting KG analysis, there is an option to automatically adjust the

displacement and LCG of the vessel so that liquid cargo of damaged tanks is removed

from the model. This is for consistency with the lost buoyancy analysis method: the

buoyancy contribution of damaged tanks is removed from the model, so to be consistent,

any liquid cargo should also be removed from the model.

Draft

The draft dialog is used to specify the range of drafts to be used for the Upright

hydrostatics analysis.


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The VCG specified in the draft dialog is used for the calculation of upright stability

characteristics such as GMt only, and is specified in terms of KG – i.e. from the

baseline, which is not necessarily the vertical zero datum.

Displacement

The displacement dialog is used to specify the range of displacements to be used for the

KN, Limiting KG and Floodable Length calculations.


The specified conditions analysis setting is only available for the specified condition

analysis.

See Specified Conditions on page 90.

Permeability

The Permeabilities are set in a table in the Permeability dialog. Use the Add and Delete

buttons to add or delete rows from the table. The permeabilities may be sorted by double

clicking on the permeability column heading. The last set of permeabilities used will be

recalled from the registry when Hydromax is started.

The Permeability dialog is used to specify the permeabilities to be used for the Floodable

Length analysis; the permeability is applied over the entire length of the vessel.

This permeability is unrelated to compartment, tank or non-buoyant volume permeability

and is only used for floodable length calculations.

Individual Permeability of Tanks and Compartments

The individual permeability of each compartment (or tank) is specified in the

Compartment definition table. The compartment, tank and non-buoyant volume

permeabilities are used when calculating the effects of damage, and/or calculating the

weights of fluids in tanks in the loadcase.


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Also see:

Modelling Compartments on page 51

Tolerances

In the Edit | Preferences dialog, calculation tolerances can be set. This defines the

tolerances that Hydromax uses to determine when to finish iteration during


Equilibrium analysis

Specified conditions

KN calculations

Floodable Length


Ideal tolerances can range between 0.00001% and 0.1% (1 gram in 10 tonnes of

displacement). Acceptable tolerances can range from 0.001% to 1.0%. Acceptable

tolerances should always be greater than Ideal tolerances.

Convergence Error

Hydromax will attempt to solve most analysis to within the ideal tolerance. If this is not

achieved within a certain number of iterations, but the acceptable error has been

achieved, Hydromax will continue. If convergence to within the acceptable error has not

been achieved, Hydromax will display a warning.

One of the most common causes of non-convergence is if the specified displacement

exceeds the volume of the completely submerged vessel and it sinks. Also convergence

may be poor if the trim angle approaches 90 . If Hydromax thinks that it is likely that

the model has sunk (waterplane area is zero at the current condition) the following dialog

will be displayed. The specified displacement and the actual displacement at the current

iteration are provided for information.

Note

This warning is not displayed during batch analysis, instead the warning is

written in the batch file.

The warning is also not shown when accessing Hydromax from a VBA

macro using the Automation interface


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If there is a convergence problem, which appears not to be due to sinking, then the

following dialog will be displayed.

This problem can sometimes occur if the specified displacement is extremely small and

the vessel has a large flat bottom, producing a highly non-linear waterplane area vs. draft

plot. Other causes of non-convergence can be non-linear moment to trim vs. trim angle

curve or moment to heel vs. heel angle curve.

Note:

There are occasions when convergence will not necessarily occur within the

maximum allowable number of iterations. If Hydromax fails to converge it

will give you a warning, but will allow you the option of continuing the

search. If you choose to continue, Hydromax will search for the equilibrium

position indefinitely. If the search is unsuccessful after a reasonable period

of time, you can interrupt Hydromax by pausing the analysis.

The analysis will also fail to converge if the trim becomes excessive. All analyses other

than Floodable Length will fail if the trim exceeds +/-45º; in the case of the Floodable

Length analysis, this limit is increased to +/-89º.

Analysis Environment Options

The analysis can be performed in different environments; this section describes the

analysis environment options available in Hydromax in more detail:


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Fluids Analysis Methods

Density

Waveform

Grounding

Stability Criteria

Damage

Fluids Analysis Methods

Hydromax allows you to specify two different ways of simulating any fluids contained in

tanks or compartments. Selecting Fluids in the Analysis menu opens the Fluids Analysis

dialog.

It is possible to specify the range of filling levels for which free surface moments should

be applied in the loadcase. This functionality is accessed through the Analysis | Fluids

dialog:

Fluid Analysis dialog

If the corrected the VCG method is used, the FSM is applied if the filling level is within

the exclusive range specified; i.e. if the filling level is less than or equal to the lower

limit or the filling level is greater than or equal to the upper limit, the free surface

moment will be zero. The upper limit is clearly stated by IMO as 98%, but the code

provides some flexibility in interpretation for the lower limit. You may set different

limits for each of the different free surface moment types other than “User Specified”.

(see IMO IS Code)

3.3.2 Free surface effects should be considered whenever the filling level in

a tank is less than 98% of full condition. Free surface effects need not be

considered where a tank is nominally full ,i.e. filling level is 98% or above.

3.3.10 The usual remainder of liquids in empty tanks need not be taken

into account in calculating the corrections, provided that the total of

such residual liquids does not constitute a significant free surface effect.

In addition it is possible to ignore the free surface moment if the VCG correction for a

single tank, due to the free surface moment is less than a specified amount. This requires

that a nominal minimum displacement be specified. This is applicable to the “IMO” free

surface moment type only. (see IMO IS Code)


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3.3.9 Small tanks which satisfy the following condition using the values of

"k" corresponding to an angle of inclination of 30°, need not be included in

the correction:

m01.0/ minfsM

where fsM is the free surface moment of the tank in question and min is

the ship displacement at the minimum mean service draft of the ship without

cargo, with 10% stores and minimum water ballast, if required.

Note: Tank Calibration results

In the tank calibration results the free-surface moment based on the

transverse second moment of area of the tank waterplane is given for all

filling levels. This is because the actual free surface moment to be used to

determine the VCG in a loadcase depends on the method being used and

also the heel angle in question (in the case of the IMO correction).

Note: Calculation of GM

GM values always use the centre of gravity corrected for free surface

moments even if the “simulate fluid” option has been chosen. Note that the

upright free surface moments as shown in the loadcase are used, not those

from the actual second moment of area of the inclined tank waterplane.

Note

Most documented stability criteria assume that the corrected VCG method

has been used. Although the computational potential is available, authorities

have not adopted this more accurate calculation of the shift in centre of

gravity due to fluid movement.

Fluid analysis method: Use corrected VCG

Tank capacities and free surface moments are calculated for the upright hull (zero trim

and zero heel). The effective rise in VCG due to the tanks' free surface is calculated by

summing the free surface moment of all the tanks and dividing by the total vessel

displacement (the free surface moment to be applied is specified in the loadcase).

This method should be used when compiling a stability booklet for a design, as it

corresponds with the traditional approach used by naval architects and classification

societies worldwide. It is reasonably accurate at low angles of heel and trim.

In this case, the loading window will include a column for free surface moment and cells

for corrected fluid VCG. These values are automatically calculated from the maximum

free surface moments of the tanks, calculated in the upright condition. There are several

FSM types available. For more information, see Working with Loadcases on page 38.


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Fluid analysis method: Simulate fluid movement

This method is a faithful simulation of the static movement of the centre of gravity of the

fluid in each tank. Every tank is rotated to the heel and trim angle being analysed.

Hydromax iterates to find the fluid level for the rotated tank at the specified capacity.

The new centre of gravity is calculated for each tank and used in the analysis. The new

LCG, VCG and TCG are calculated for the whole design and used in the calculation of

GZ, KG, and GM.

This approach is used when the stability of a vessel is being investigated and the closest

possible simulation of the hull's behaviour is required. It is particularly useful at high

angles of heel or trim, or with tanks whose heeled water plane area may be significantly

different from the upright case (i.e. tall narrow tanks, or wide shallow tanks). The

penalty of using this approach is that the calculation time is longer, however the results

are significantly more accurate.

When fluid simulation method is selected, free surface moments and corrected fluid VCG are normally not displayed in the loadcase.

When selected, fluid simulation is used for analyses that use a loadcase, i.e. Large Angle

Stability, Equilibrium Condition and Longitudinal Strength (the Longitudinal Strength

analysis always uses fluid simulation). When fluid simulation is used in one of these

analyses, the actual fluid level in the tank, filled to the volume specified in the loadcase,

will be displayed in the View window. Otherwise the complete tank will be shown.

Density of Fluids

Where necessary, the density of sea water (the fluid in which the vessel is floating) and

fluids commonly carried on board can be adjusted using the Density dialog.

Density using the current units, or non-dimensional relative density (specific gravity),

may be specified. Alternatively, density may be specified using Barrels as the unit of

volume. Conversions are performed automatically. Specific gravity is calculated relative

to a fluid having a density of 1000.0 kg/m3.


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By assigning a code to the fluid you can easily apply the fluid type in the Compartment

Definitions table. Tanks that have been specified as containing one of these fluids will be

updated automatically when the density of the fluid is changed in the Density dialog.

Tank calibrations results and loading conditions will also be updated.

Note

The vessel's hydrostatics are always calculated assuming the vessel is

floating in the fluid labelled "Sea Water". This is the first fluid in the list

printed in bold font. If the vessel is to float in a different fluid, it is

necessary to change the density of this fluid. Note that only the custom

fluids may have their names changed. Thus, if you wanted to carry out an

analysis for a vessel in fresh water, you would change the density of "Sea

Water" to 1000.0 kg/m3.

Saving and Loading Densities

Densities listed in the Density table can be saved and loaded using the File menu.

The densities file may be edited manually if desired. There is one row for each of the 18

fluid types. The four columns, each separated by a tab character. These are fluid name,

fluid code, specific gravity, colour respectively (the colour is in hexadecimal for the red,

green, blue components and are probably much more easily edited in the Density dialog.

The name and code for the first entry, Sea Water, cannot be changed (any changes made

will be ignored). All other entries may be edited (the same restrictions area applied as

when editing through the Density dialog).

Sea Water S 1.0250 6D00FF00FF00 Water Ballast B 1.0250 6D006D00FF00 Fresh Water W 1.0000 FF005F005F00 Diesel D 0.8400 FF005B00FF00 Fuel Oil F 0.9443 6D00FF006D00 Lube Oil L 0.9200 7F007F007F00 ANS Crude C 0.8883 3F003F003F00 Gasoline leaded G 0.7499 FF0000007F00


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Unlead. Gas. U 0.7499 FF007F007F00 JFA J 0.8203 7F007F00FF00 MTBE M 0.7471 F600FA00C900 Gasoil GO 0.8524 FF00FF007F00 Slops SL 0.9130 FF006F00FF00 Custom 1 C1 1.0000 D6000300D600 Custom 2 C2 1.0000 D600D6000300 Custom 3 C3 1.0000 0300D600D600 Custom 4 C4 1.0000 D60003000300 Custom 5 C5 1.0000 DF00DF00DF00

If you make an error, you can always reset the densities to their default values in the

Densities dialog.

Also see:

Windows Registry on page 16

Waveform

Hydromax is capable of analysing hydrostatics and stability in arbitrary waveforms as

well as for a level water plane. To specify a waveform, select the Waveform command

from the Analysis menu:

The water plane can be specified as flat, or as a sinusoidal or trochoidal waveform. If a

waveform is specified, the wavelength, wave height and phase offset can be specified.

The wavelength defaults to the waterline length of the hull at the DWL. If the

wavelength is modified the wave height defaults to a value in metres of:

Wave height [m] = 0.607 √ Wavelength [m]

This is the metric equivalent of the US Naval standard wave height:

Wave height [ft] = 1.1 √ Wavelength [ft]

For short waves of wavelength less than 64m, the waveheight reduces linearly with

wavelength given by the formula:

Wave height = 0.075875 Wavelength


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Once a wavelength has been set, the wave height may be modified.

The phase offset governs the position of the wave crest aft of the forward end of the

DWL, as a proportion of the wavelength. The phase offset varies between 0 and 1, both

of which correspond to a wave crest at the forward end of the DWL.

For example, a phase offset of 0.5, with a wavelength equal to the waterline length, will

give a single wave crest at amidships.

Grounding

Grounding is an additional analysis environment option for the Equilibrium or

Longitudinal Strength analysis. It is possible to specify grounding on one or two points

of variable length. The Equilibrium analysis will determine whether the hull is grounded

or free floating and will trim the hull accordingly. Damage can be specified concurrently

with grounding.

If the vessel touches one or both grounding points, this will be reflected in the results:

The displacement column will show the total grounding reaction force in brackets;

the sum of the buoyancy and the grounding reactions equals the loadcase

displacement.

The effective centre of gravity will be modified by the grounding reactions – a

mass is effectively being removed from the vessel; this will bring the effective

centres of gravity and the centre of buoyancy in line vertically. The value of KG,

GMt and GMl are all calculated to the effective centre of gravity. Remember that

KG is measured in the upright vessel reference frame (normal to the baseline);

whilst GMt and GMl are the actual vertical separation of the metacentres above

the centre of gravity in the trimmed reference frame normal to the sea surface.


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Note:

Grounding points are considered to span the transverse extents of the hull

and therefore constrain the heel to zero. The length of the grounding points

is only used when considering the load distribution for Longitudinal

Strength analysis and not to determine the pivot point. The vessel is

considered to pivot at the centre of the grounding point.

When two grounding points are entered, the first point (edit boxes on the

left) must refer to the forward grounding point; the second grounding point

is the aft grounding point.

Note: Fixed zero heel during grounding analysis

The equilibrium analysis will only consider the longitudinal balance of

moments, i.e. the vessel will not be balanced in heel and the vessel will

remain upright (zero heel) even if the transverse metacentric height is less

than zero.

Stability Criteria

Stability criteria may be seen as the “environment of authorities” that the ship will be

deployed in.

For more information see Chapter 4 Stability Criteria starting at page 163.

Damage

You can specify whether the model is to be analysed in intact or damaged condition

using the Analysis Toolbar.

Also see:

Damage Case Definition on page 71


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Analysis Output

Hydromax will produce the following output data:

Hydromax model visualisation

Result data tables per analysis

Graphs per analysis

Report

o Report window

o Streamed directly to a Word document

o Report Templates

In this section:

Reporting

Copying

Select View from Analysis Data

Saving the Hydromax Design

Exporting

Reporting

Hydromax has several options to do your reporting:

Batch Analysis text file and/or streaming to Report window

Automatically generate a report in the Report Window for each analysis run

Automatically Streaming results to Word

Manually copy and paste tables and graphs from the Results Window and Graph

Window

The most efficient method depends on the number of loadcases and damage cases you

have to analyse and the output you require.

Form small number of loadcases and damage cases you can do a manual copy and paste

of the results into a report. This then allows you to validate the results at the same time.

For large numbers of cases, it is recommended to use batch analysis. Batch Analysis

results saved as text files do not include graphs. Select the option to send the results to

the report window if you require Graphs. Additionally, if the option to Stream the report

to Word has been selected in the Edit | Preferences dialog a word document is

automatically generated after a Batch Analysis.

Streaming results to Word

It is possible to stream the Analysis results directly to Word. To do this:

Edit | Preferences

Select the option to Send the Report to Word

This will send the Report document to Word instead of to the Report window. After you

have run an analysis a Word document is created and opened automatically. This also

applies to Batch Analysis.


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Report Templates

Hydromax offers the ability to customise reports through a Report Template. This

feature is only available when sending reports to Microsoft Word.

With report templates, instead of just dumping the results of each analysis into a Word

document, it is possible to use template keywords to specify where in the document the

analysis results go and where each element of the output (such as graph, tables, etc) is

placed.

This gives you much greater control over how the analysis results are output than with

the normal Send Report to Word option and allows you to customise your own report

template document.

To turn on Report Templating you need to select it in the Preferences dialog box.

Simply tick the box „Use Word Templating‟. Please note that Send Report to Word

must be enabled before you can enable this option. See the dialog box below as an

example:

The Word Template File specified should be in .dot or .dotx/dotm (for Word 2007)

format and will be used when creating any future reports. You can use one of the sample

templates provided, or you can build your own template.

Two Report Templates have been included to get you started:

StabilityBooklet.dot


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This is an example of a complete Stability Booklet template – this document is the

default Word Template file for new users and is recommend for users wanting to

quickly create a Stability Booklet. Users can start with StabilityBootlet.dot and then

use it customise their own report template.

HMReportTemplate.dot

This document is a good starting point for creating your own customised template. It

contains an introduction to how templates are created and configured. It also includes

all of the basic analysis blocks and variables to get you started.

Both of these templates contain macros and toolbar items to make life easier when you

design your own template. These allow you to easily add and remove the analysis

keyword blocks.

Note:

To edit a report template in Microsoft Word you will need to start Microsoft

Word and then open the template directly using the File menu. Simply

double-clicking on a template document opens up a new document based on

the template (which is not what you want).

The location of these report templates varies depending on which operating system you

are using.

On Windows XP/Server 2003 the default location for the report templates is:

C:\Program Files\Maxsurf 14\Report Templates\

On Windows Vista, due to new security changes we‟ve had to move this to an alternative

location that every user has write access to – so you can find it at:

C:\Users\Public\Documents\Maxsurf\Maxsurf14\Report Templates\

Tips:

See:

Copying Tables on page 158 for tips on how to include the table header in a copy

paste to for example Excel

Graph Formatting on page 190 for tips on how to format your graph prior to

copying to another application.

Data Format on page 207 for tips on how to specify what should be displayed and

customise how to display tables (vertical or horizontal).

Copying & Printing

A range of options for transferring data from Hydromax to other programs such as

spreadsheets and word processors is provided through copy and paste functions. This

data transfer works both ways: e.g. copying and pasting data to and from Excel

spreadsheets allows you to use the full spreadsheet capabilities of Excel on your

Hydromax model.

Copying Hull Views

Pictures of the hull in the View windows may be copied to the Clipboard using the Copy

command from the Edit menu. The image copied is as per the image displayed in the

Hydromax view window.


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These pictures can then be pasted into other applications or the Hydromax Report

window.

To copy a simple bitmap image of the view at the current resolution, use Ctrl+I;

additionally, a bitmap of the current image may be saved by pressing Ctrl+Shift+I

Copying Tables

Tables may be copied to the clipboard. Simply select a cell, row, column, range of cells

or the whole table and then choose the Copy command or Ctrl+C.

The data copied from the table will be placed on the clipboard and can then be pasted

into a spreadsheet or word processor for further work.

Note:

Copying data from the table with the Shift key depressed, will also copy the

column headings.

Printing

Each of the windows in Hydromax may be printed. Simply bring the window you wish

to print to the front and choose Print from the File menu. Views of the hull in the View

window may be printed to scale as in Maxsurf.

Prior to printing you may wish to set up the paper size and orientation by using the Page

Setup command from the File menu.

Print Preview

The page to be printed is initially displayed in print preview mode. To print the page

click the Print button, otherwise click the Cancel button.

The printing may be forced to be black and white. Choose the Colours button and select

the options required. Note that the print preview is not refreshed after these changes, but

the selection will be reflected in the printout.

The titles may be edited by clicking the Titles button.

Graph Printing to Scale

When printing the graph, it is possible to ensure that the graph is plotted to a sensible

scale so that measurements can be made directly from the graph. To do this, hold the

shift key down when selecting the print command for the graph. You will be asked if you

want to print the graph to scale or to fill the page:

The scale used will depend on the length units that are currently selected. If these are

metric, then the graph will be plotted so that the grid lines are at one of the following

intervals (If the current length units are imperial then similar intervals will be used, but

they will be inches instead of cm.): 1.0cm, 2.0cm, 2.5cm, 5.0cm.


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Exporting a Bitmap Image

You may also export a bitmap of the rendered perspective view with the File | Export |

Bitmap Image command.

Select View from Analysis Data

For most analyses, each step from the analysis can be visualised when the analysis has

completed. For example: the angle of downflooding can be visualised by returning to the

Stability table in the results window, selecting the column at the required heel angle and

select “Select View From Data” in the Display menu.

In the View window the hull will be displayed in the selected position. This can also be

done for Upright Hydrostatics and the different wave phase calculations for an

Equilibrium analysis in a waveform.

The Select View from Data can also be used to display the Curve of Areas graph for

each intermediate analysis stage, see Graph type on page 189.

Saving the Hydromax Design

Hydromax design data may be saved

Saving in a Hydromax Design File

Saving Input Files separately

Saving in a Hydromax Design File

To save the design in one file, ensure that the View window is topmost and select Save

from the File menu. The Hydromax data is saved in a .hmd file with the same name as

the design.

Saving Input Files separately

In addition to saving all the data together, the data in the individual tables such as

loadcases, damage cases, compartment definition, key points etc., may also be saved

separately.

For more information on file properties and extensions in Hydromax, please see:

File Extension Reference Table on page 307.

Note

Although all Hydromax model data is saved in the .hmd file automatically

every time you press Save from any of the design windows, it is

recommended to also save the Hydromax input files separately. This gives

the option of loading common data into different design files. E.g. for

comparing the characteristics of vessels which have only minor differences

in hull shape and identical tank layouts and loadcases.


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Saving Loadcases to a File

Once you have set up a loading spreadsheet, you can save it in a file on disk. This

allows the same loading spreadsheet to be recalled at any time for use with the

same design or with any other hull.

To save the loadcase table, ensure the Loadcase window is topmost on the screen

and choose Save Load Case from the File Menu. Selecting this option saves all the

loads displayed in the current tab in the Loadcase window.

Saving Damage Cases to a File

Bring the Damage window to the front and select Save Damage Cases or Save

Damage Cases As from the file menu.

Saving Compartment Definitions to a File

To save a compartment definition to a file, bring the Input window to the front and

choose the compartment definition table; select Save Compartment Definition

from the File menu. You will be asked to name the file and select where it is to be

saved.

Saving Input Window Tables

To save a input window table to a file, bring the Input window to the front and

choose the required input table; select Save from the File menu. You will be asked

to name the file and select where it is to be saved.

Saving Results to a File

Once you have performed an analysis, the data generated may be saved as a text file.

This allows for further calculations to be done in a spreadsheet or for formatting to be

done in Word, Excel or other programs.

To save the data, ensure the Results window is topmost on the screen and choose the

table containing the data you wish to save. Select Save or Save As from the File Menu.

Selecting this option saves all the data currently displayed in the Results window. The

Results files are saved as tab delimited text, meaning that they can be read directly into

spreadsheets such as Excel with values being placed in individual spreadsheet cells.

Exporting

The data export function in Hydromax is similar to Maxsurf. Some Hydromax-specific

export features are described below.


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Data export dialog in Hydromax.

DXF export

Contains all lines displayed in the active design window as closed poly-lines. In

addition, each tank, compartment and non-buoyant volume is exported on a

separate layer. This export function is particularly useful to export tank

arrangement drawings.

Note:

The layer name is the same as the compartment name, so it is important to

have unique compartment names.

For more information on data export of DXF and IGES, please see the “Output of Data”

section in the Maxsurf manual.

Exporting the Model to Hydromax Version 8.0

After Hydromax version 8, a major change to the Hydromax file structure was made.

Hydromax models created in versions greater than version 8.0 can be exported using the

File | Export menu so that it is compatible with Hydromax version 8.0. All key points

will become downflooding points in the version 8 file and any tank sounding pipe

information will be lost.

http://www.fdsfiles.com/webmanuals/maxsurf/msmanual.htm#output_of_data


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This chapter describes how stability criteria are used in Hydromax. Stability criteria are

evaluated for Large Angle Stability, Equilibrium and Limiting KG calculations. A fixed

sub-set of criteria is used for the Floodable length analysis and these criteria are accessed

in their own, simplified dialog.

The following sections will be discussed:

Criteria Concepts, an overview of what capabilities Hydromax offers with regards

to stability criteria.

Criteria Procedures, explanation how to work with the Hydromax criteria dialog to

create your own custom set of criteria.

Criteria Results, criteria evaluation results

Nomenclature, explanation of terms and definitions

See also:

Appendix B: Criteria file format

Appendix C: Criteria Help

Appendix D: Specific Criteria

Criteria Concepts

Hydromax includes a wide range of template criteria (or: parent criteria) as well as pre-

defined custom criteria such as IMO, HSC, DNV, ISO and more. Hydromax uses a

single dialog to control all the stability criteria. This makes it quick and easy to set which

criteria should be included for analysis and to change criteria parameters. It is also

possible for users to create their own custom sets of criteria. Users may save, import and

edit their criteria sets. These custom criteria files may be easily transferred via email.

Criteria may be identified as intact or damage criteria (or both). This ensures that the

correct criteria are evaluated and displayed during normal and batch analysis. Although

all criteria are displayed in the criteria table, only criteria that are applicable are added to

the report; i.e.: if the intact case is being computed, only the criteria that are selected for

evaluation during an intact analysis will be evaluated and added to the report, similarly

for the damage cases.

Criteria results are added to the Report after a Large Angle Stability or Equilibrium

analysis. However, only the applicable criteria are added to the report (although all are

displayed in the Results table); i.e. after an Equilibrium analysis only those criteria that

are evaluated from Equilibrium data are added, and after a Large Angle Stability analysis

only GZ based criteria are added to the report.

Help information relating to the use and parameters of each criterion is displayed in the

lower right hand corner of the dialog.

Criteria List Overview

Hydromax includes a wide range of criteria. These criteria are listed using in a tree

control on the left-hand side of the criteria dialog. This section describes how this list of

criteria can be divided up in to Parent heeling arms, Parent criteria, predefined custom

criteria and user created custom criteria. This section also explains how all criteria can be

divided up into two different criteria types: equilibrium and GZ curve based.


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The criteria tree list

Parent Calculations

This folder contains calculations that are required for certain criteria parameters,

for example, the roll-back angle required for the IMO IS code Severe wind and

rolling (weather) criterion.

These calculations may be referenced in certain criteria.

Parent calculations in Hydromax Criteria dialog

Parent Heeling Arms

In most cases a ship is subject to specific heeling moments. Those heeling moment

are then used in a number of different criteria. The Hydromax criteria list contains

Parent Heeling Arms that can be copied into a custom criteria folder and then

cross-referenced into the stability criteria.


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The advantage of using cross-referenced Heeling Arms is that a heeling arm is

now defined (and edited) in only one place. This ensures that all criteria which use

a specific heeling arm use exactly the same heeling arm. Another benefit is that,

since the heeling arm is defined in one place, it is only displayed once in the GZ

graph and not duplicated for each criterion that uses it. Furthermore some newer

heeling arm criteria are only available for cross-referenced heeling arms and a

greater variety of heeling arm definitions are available through cross-referencing.

Parent Criteria

The Parent Criteria group contains all the parent criteria types that are available in

Hydromax. Each parent criterion allows you to perform a specific calculation;

these are the fundamental criteria from which criteria for specific codes are

derived.

Parent criteria are special in that you cannot rename, delete or add criteria to the

Parent Criteria group. Also the parent criteria settings cannot be saved, they will

always revert to their default values when Hydromax is restarted. This is because

the parent criteria are intended for use as templates from which you can derive

your own custom criteria. This is done by dragging the required parent criteria in

to the “My custom criteria” group or any other group you create.

To distinguish the Parent criteria from your derived criteria, they are displayed in

bold text in the Criteria list.

Predefined Custom Criteria

A number of criteria files containing criteria for specific codes are supplied with

Hydromax. These may be found in the “HMSpecificCriteria” folder. This folder

can be found in the Maxsurf root directory: c:\program files\Maxsurf.

Most specific criteria are locked; those that are not locked require your ship design

data to be input.

Also see

Working with Criteria Libraries on page 172

Appendix D: Specific Criteriaon page 291.

Custom Criteria

You can create your own set of criteria in the tree as well. This is explained in the

section on Working with Criteria on page 168.


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Types of criteria

There are two fundamental types of criteria:

Equilibrium criteria

Equilibrium criteria are evaluated after an Equilibrium analysis and refer only to

the condition of the vessel in its equilibrium state For example: margin line

immersion tests, freeboard measurements, trim angle, metacentric height, etc. This

type of criterion is also used by the Floodable Length analysis. Equilibrium

criteria can be recognised by the icon.

Criteria derived from measurements of the GZ curve.

These are calculated after a Large Angle Stability analysis and during a Limiting

KG analysis. For example, area under GZ curve between specified limits, angle of

maximum GZ, etc. These criteria are often referred to as Large Angle Stability

(LAS) or GZ criteria.

Note that there is some cross-over between the criteria types, notably angle of

equilibrium heel. This can be measured from the GZ curve by looking for an up-crossing

of the GZ=0 axis. The equilibrium heel angle is also a fundamental output of the

Equilibrium analysis. The same also applies for GMt. For this reason, in some criteria

sets some criteria are included twice, once in the form of an Equilibrium criterion and

again as a Large Angle Stability criterion.

For a criterion to be used in the search for maximum VCG in the Limiting KG analysis,

it must be a LAS criterion. This is because it is only this type of criteria that is more

likely to pass as VCG is reduced. A check is also made to ensure that any selected

Equilibrium criteria are passed, but they cannot be included directly in the search

algorithm.

You will notice that different icons are used to differentiate between different types of

criteria. These icons are derived from the parent criterion type. The different types of

criteria and their icons are described below:

Folder icon, create separate folders to store related criteria. All folders must

have unique names (even if the parent folders have different names).

Equilibrium criterion. These criteria are evaluated only after an equilibrium

analysis has been performed.

GZ criterion. These criteria make measurements from the GZ curved obtained

from a Large Angle Stability analysis.

GZ area criterion

GZ criterion with heeling arm

GZ area criterion with heeling arm

GZ criterion with several heeling arms and their combinations

GZ area criterion with several heeling arms and their combinations

Combined GZ criterion. These criteria perform several individual tests on the

GZ curve. e.g. STIX.

Combined GZ heeling arm criterion. These criteria perform several individual

tests on the GZ curve including a heeling arm. e.g. Weather criterion.

See next: Criteria Procedures


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Criteria Procedures

This section describes how to work with the stability criteria dialog.

Starting the Criteria dialog

Resizing the Criteria dialog

Working with Criteria

Editing Criteria

Working with Criteria Libraries

Starting the Criteria dialog

The criteria dialog allows you to select which criteria are selected for inclusion in the

analysis and change their parameters. To bring up the Criteria dialog, select Criteria from

the Analysis menu:

or use the Criteria button, , in the analysis toolbar:


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The criteria dialog is shown below:

Note:

The Floodable Length analysis uses its own set of criteria. The criteria

command will bring up the Floodable Length Criteria dialog when the

Floodable Length analysis is selected.

Resizing the Criteria dialog

The dialog may be resized and a vertical and horizontal slider can be used to resize the

width of the Criteria List and the height of the Criterion Details areas.

Note that if, in the unlikely event that the dialog items vanish due to resizing the dialog,

the dialog size can be reset by holding down the “Shift” key when you open the dialog.

This behaviour is the same as all other resizing dialogs.

Working with Criteria

In the Concepts section it was explained how the criteria are listed in a tree list. This

section explains how to create and customise your own criteria from the Parent Heeling

Arms and Criteria provided with Hydromax.


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Using the Criteria Tree List

The tree works in much the same way as the file folders in Windows Explorer:

Click on the “+” sign to expand the folder (or double click on it).

Click on the “-” sign to collapse the group (or double click on it).

Click on an item’s name or icon to select it

Once selected, click again on the on the item’s name to edit its name

Some short-cut keys for the tree list:

Tree control smart keys Function

Alt+Keypad * Recursively expands the current group

completely

Right Arrow or Alt+Keypad + Expands the current group

Left Arrow or Alt+ Keypad - Collapses the current group

Up Arrow Move one item up tree

Down Arrow Move one item down tree

Space Include criterion for analysis

Criteria Tree Right-click Context Menu

Several options are available by right-clicking on a criterion or criterion group:

Criterion right-click menu

Include for Analysis:

Toggle whether the criterion (or all criteria within the group) should be evaluated.

Intact:

Toggle whether the criterion (or all criteria within the group) should be evaluated

for intact conditions.

Damage:

Toggle whether the criterion (or all criteria within the group) should be evaluated

for damaged conditions.

Lock:

Toggle whether the criterion (or all criteria within the group) are locked. If a

criterion is locked, this prevents inadvertent editing of its parameters. Locking is

used for criteria belonging to specific codes where the required values are fixed.


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Add Group:

Add a new criterion group.

Cut:

Cut the criterion (or whole criterion group) to the clipboard. This may then be

pasted into another location in the tree.

Copy:

Copy the criterion (or whole criterion group) to the clipboard. This may then be

pasted into another location in the tree.

Paste:

Paste the criterion (or whole criterion group) from the clipboard to the selected

location

Rename:

Renames the criterion or group. This may also be done by selecting the label, then

clicking again in the label.

Delete:

Deletes the criterion or all the criteria and sub-groups within the group.

Defining new Custom Criteria and Groups

New custom criteria sets may be created by first creating a new criterion group and then

dragging the desired criteria into the criterion group. By holding down the Ctrl button a

copy of the criterion being dragged is created (unless it is a parent criterion, in which

case a copy will be made regardless of whether the Ctrl key is held down or not).

Alternatively use the Copy and Paste functions from the right-click context menu (see

above).

It is extremely important to ensure that all criteria groups have unique names. If

duplicate group names exit, then loading the criteria file may cause unexpected results.

As criteria (and new groups) are loaded they are inserted into the first group that is found

with a name that matches the name of the group to which the criterion should belong. If

there are groups with the same name, all criteria that should be in a group of that name

will end up in the first one and none in the second.

Moving Criteria

Criteria may be moved from one group to another by dragging them with the left-mouse-

button or by using the cut and paste functions in the right-click context menu (see

above). Note that if you drag a criterion from the Parent Criteria group a copy will be

made and the original will not be deleted.

Copying criteria

You can use the Criteria Tree Right-click Context Menu to copy and paste criteria.

Alternatively, you can hold down the CTRL-key while moving the criteria you will copy

the criteria.

Selecting the Criteria for Analysis

Criteria may be selected for analysis by ticking the tick box to the left of the criterion.

Other functions are available from a menu activated when the right button is clicked on

your mouse. To select an entire group, right-click on the group and choose Include for

Analysis from the menu.

Editing Criteria

The specific details for a criterion are displayed in the table in the top-right of the dialog:


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Criterion details table

To edit the parameters for a specific criterion, click on the criterion‟s name in the tree

and the criterion‟s parameters will be displayed in the table on the right. Edit the

parameters as required and then select the next criterion to be edited from the tree, or

click the dialog‟s Close button. Please note that the criteria are updated as you change

their data and that there is no “Cancel” function for this dialog. If in doubt, use the File |

Save Criteria command to save a copy of your current criteria selection and data before

making any changes in the Criteria dialog.

The parameters that may be adjusted have a white background; those which cannot be

edited, have a grey background.

The values that are required for passing a criterion are in bold.

Check Boxes in Criteria Properties Section of Criteria Dialog

There is some subtly different behaviour for the check boxes in the dialog depending on

their context. In most cases there will be group of related options used to define a

criterion parameter. For example the limits for an upper integration range or the

individual criteria to be evaluated for a more complex criterion:

In both of these cases the selection is cumulative and none of the selections are mutually

exclusive. However, at least one must be selected.

In other cases, where the items are mutually exclusive, the check boxes act as radio

buttons and only one may be selected. This occurs, for example, with the “Value of GMt

at” criterion:


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Finally a check box can be used to select whether a specific effect should be included,

for example, GZ curve reduction in the wind heeling criteria:

Criterion Pass/Fail Test

There are some subtle differences between the wordings for different criteria. For

example one criterion may state “Shall be greater than…”, whereas another may state

“Shall not be less than…”. Hydromax allows you to make this distinction by selecting

the required comparison from a combo-box in the criterion row of the details table:

Description Symbol Logical test

Shall be greater than > Greater than

Shall not be less than ≥ Greater than or equal to

Shall be less than < Less than

Shall not be greater than ≤ Less than or equal to

Damage and Intact

Criteria may be defined as intact or damage stability criteria (or both). Intact criteria are

only evaluated for the intact case and damage criteria are evaluated when a damage case

has been selected (irrespective of whether there are actually any damaged compartments

or tanks in the damage case). Criteria that are defined for both are always evaluated.

A third option which is not yet implemented is WOD (Water on deck) this checkbox has

no effect.

These options may either be set using the right-click menu or by ticking the appropriate

boxes in the bottom of the dialog:

Intact and Damage tick-boxes.

Working with Criteria Libraries

It is possible to load and save the criteria. The parent criteria, built into Hydromax are

not saved, only the criteria that you create or import will be saved.

Default Criteria Library File

When starting, Hydromax will try to open the default criteria library file called:

“Hydromax Criteria Library.hcr” from the directory in which the Hydromax program

resides. By default this is c:\program files\Maxsurf\ Hydromax Criteria Library.hcr. If

this file cannot be found, you will be prompted to locate a criteria file:

You may select an alternative file or click the Cancel button to proceed and be given the

default criteria, which consists of the Parent criteria and a “My Custom Criteria” group.


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The default criteria library will be automatically updated every time the criteria dialog is

closed. Even if you loaded an alternative file, updates will be saved in the default criteria

library, either overwriting the existing one or creating a new one.

Note

It is good practise to save the criteria file with the project in the project

folder. That way, when at a later stage you need to re-analyse the project, all

criteria are still available. See Saving Criteria below.

Saving Criteria

It is also possible to save the criteria into a new file. This can be useful when you are

defining new custom sets of criteria that you wish to keep separate or when defining

criteria sets for different vessels. Choose Save Criteria As from the File menu. This will

simply export all the custom criteria (parent criteria are not saved) to the specified file.

Further updates will, however, continue to be saved to the default criteria library file that

was opened when Hydromax was first started, so if you want to save any further changes

you will have to resave as described above.

Importing Criteria and Specific Criteria Files

New criteria may be added to your criteria list by importing them – choose Import

Criteria from the File menu. You will then be asked if you wish to keep the existing

criteria:

If you choose “Yes” your existing criteria will be kept, if you choose “No”, all existing

criteria except the parent criteria will be removed and replaced by those in the file you

are opening. The default criteria library will be over-written with the new criteria so if

you wish to keep any custom criteria that you may have added to your default criteria

library, you must save them in a new file first.

Note that when keeping your existing criteria, it is important to ensure that the group

names in the file you are importing are not the same as those that already exist. If this

does occur, the imported criteria will be found in the original groups, not in the new

groups.

A number of criteria containing criteria for specific codes are supplied with Hydromax.

These may be found in the “HMSpecificCriteria” folder.

You can import several criteria files in one go using Shift, or Ctrl select to select

multiple files in the Open Hydromax Criteria dialog.


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Criteria File Format

The criteria are saved in a Hydromax criteria file with the extension .hcr. The file is a

normal PC text file, which may be edited manually so as to generate custom criteria. The

typical format of the file is given in the following file: c:\Program

Files\Maxsurf\\HMCriteriaHelp\CriteriaHelp.html. Editing this file will also allow you

to add your own help text or associate rich text format help files (rtf) files with your

criteria.

Criteria Results

After a Large Angle Stability or Equilibrium analysis, criteria are evaluated and the

results displayed in the Stability Criteria table in the Results window. Criteria can also be

re-evaluated without having to redo the analysis when “Close and Recalculate” is

selected in the criteria dialog. This allows you to edit criteria parameters or selected

criteria and re-evaluate using the existing analysis results. After calculation the relevant

criteria are also added to the Report.

Criteria Results Table

The tested criteria are listed one above the other. Intermediate values are displayed.

Values that could not be calculated, e.g.: angle of vanishing stability, angle of

equilibrium, etc., have n/a in the Actual and/or Value column. This is normally due to an

insufficient range of heel angle having been used.

Results may be displayed in “Verbose” or “Compact” format (see above). The format for

the results table and the report are specified separately. Chose the Display | Data Format

command when the Stability Criteria results are displayed:


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Stability criteria results window: compact format

Stability criteria results window: verbose format


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Report and Batch Processing

As noted earlier, only the relevant criteria results are added to the Report and/or Batch

file. Criteria that are not relevant, i.e. any criteria that have a “not analysed” result, are

not added to the Report (although they are displayed in the Criteria Results table). For

example damage criteria during intact analysis or Equilibrium criteria during a Large

Angle Stability analysis are not added to the report.

Also see

Reporting on page 155

Batch Analysis on page 138

Nomenclature

This section gives a brief description of the various values that are determined by

Hydromax in the evaluation of criteria.

There are two distinct types of criteria:

Equilibrium criteria

Equilibrium criteria are evaluated after an Equilibrium analysis and refer only to

the condition of the vessel in its equilibrium state For example: margin line

immersion tests, freeboard measurements, trim angle, metacentric height, etc. This

type of criterion is also used by the Floodable Length analysis. Equilibrium

criteria can be recognised by the icon.

Criteria derived from measurements of the GZ curve.

These are calculated after a Large Angle Stability analysis and during a Limiting

KG analysis. For example, area under GZ curve between specified limits, angle of

maximum GZ, etc. These criteria are often referred to as Large Angle Stability

(LAS) or GZ criteria.

Note:

The metacentre is always (even for Large Angle Stability criteria) computed

directly from the vessel‟s hydrostatic properties (i.e. water-plane inertia and

immersed volume) at the specified heel angle and not from the slope of the

GZ curve. This gives an accurate result that is not dependent on the heel

angles and intervals tested during the analysis.

Definitions of GZ curve features

Some typical GZ curves are shown below, the third graph shows the GZ curve with a

heeling arm overlayed.


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Typical GZ curve

Unusual GZ curve with double peak


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GZ curve with heeling arm superimposed

GZ Definitions

The table below defines how Hydromax calculates the various features of the GZ curve:

Angle of vanishing

stability

The angle of vanishing stability is the smallest positive

angle where the GZ curve crosses the GZ=0 axis with

negative slope.

Angle of vanishing

stability with

heeling arm curve

The angle of vanishing stability with a given heeling arm

is the smallest positive angle where the GZ curve crosses

the heel arm curve and where the GZ-Heel Arm curve

has negative slope.

Downflooding

angle

The downflooding angle is the smallest positive angle at

which a downflooding point becomes immersed.

Equilibrium angle The equilibrium angle is the angle closest to zero where

the GZ curve crosses the GZ=0 axis with positive slope.

Equilibrium angle

with heeling arm

curve

The equilibrium angle with a given heeling arm is the

angle closest to zero where the GZ curve crosses the heel

arm curve where the GZ-Heel Arm curve has positive

slope.

First peak in GZ

curve

In some cases, the GZ curve may have multiple peaks;

this often occurs if the vessel has a large watertight

cabin. The angle of the first peak is the lowest positive

angle at which a local maximum in the GZ curve occurs.


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GML or GMT Vertical separation of the longitudinal or transverse

metacentre and centre of gravity. The location of the

metacentre is computed from the water-plane inertia, not

the slope of the GZ curve. Note that the centre of gravity

used is the upright centre of gravity corrected by the free

surface moments of partially filled tanks in their upright

condition, rotated to the specified heel (and trim) angle.

GZ Curve The curve of vessel righting arm (GZ) plotted against

vessel heel angle

Heeling arm curve A curve of heeling lever, which is superimposed on the

GZ curve. This is typically used to assess the effects of

external heeling moments, which are applied to the

vessel. These include the effects of wind, passenger

crowding, centripetal effects of tuning, etc. Depending

on the moment that they represent, the heeling arm

curves will have different shapes.

The heeling arms are never allowed to be negative; if the

cos function goes negative, the heeling arm is made zero.

If the heeling arm has a power of cos greater than zero,

the heeling arm is forced to be zero at heel angles greater

than 90° and less than -90°.

Maximum GZ Positive angle at which the value of GZ is a maximum

Maximum GZ

above heeling arm

curve

Positive angle at which the value of (GZ - heel arm) is a

maximum

Glossary

The table below describes some commonly used terms:

Angle of heel measured from upright.

Deck Slope /

maximum slope

The maximum slope of an initially horizontal, flat deck at

the resultant vessel heel and trim. i.e. combined effect of

heel and trim.

Gust Ratio Used for some wind heeling criteria, the Gust Ratio is the

ratio of the magnitude of the gust wind heeling arm to the

steady wind heeling arm.

g = 9.80665ms-2

1998 CODATA recommended value for standard

acceleration of gravity

Roll back angle A negative heel angle change. Often a roll back angle is

measured from some equilibrium position; the resulting

heel angle after the roll back has been applied is more

negative than the original. Commonly used in wind and

weather criteria to account for the action of waves rolling

the vessel into the wind. If a criterion uses a roll back

angle, it is often necessary to calculate the GZ curve for

negative angles of heel.


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This chapter contains brief descriptions of the tools available in Hydromax:

Windows

Toolbars

Menus

Windows

Hydromax uses a range of graphical, tabular, graph and report windows.

View Window

Loadcase Window

Damage Window

Input Window

Results Window

Graph Window

Report Window

Assembly View and Property Sheet

An assembly view has been added to Hydromax, this makes it easier to control the

visibility of individual tanks and surfaces.

The Properties sheet can be used to change tank properties of the tank currently selected

in the Assembly or design View.

View Window

The View window displays the hull, frame of reference, immersed sections of the hull

and any compartments, and the centroids of gravity, buoyancy, and flotation. These

positions are represented by:

c b centre of buoyancy

c g centre of gravity

c f centre of flotation

K location of keel (K) for KN

during KN analysis

You can choose which type of view is displayed by selecting from the Window menu or

the View toolbar.

The Zoom, Shrink, Pan and Home View commands from the View menu may be used

and work in exactly the same way as in Maxsurf. If a Perspective view is shown, you

may also use the Pitch, Roll and Yaw indicators to change the angle of view. Please refer

to the Maxsurf manual if you are unfamiliar with these functions.

You may set the visibility of the various display elements by using the Visibility

command from the Display menu. Two sets of visibility flags are maintained, one is used

for all analyses other than tank calibration and the other is used for when the tank

calibration analysis is selected.


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If a view window is visible when an analysis is being carried out, it will display the hull

shape using the correct heel trim and immersion for the current step of the analysis.

After an analysis, the Select View from Data command in the Display menu may be used

to move the hull to a selected position from the Results window.

The view of the tanks, compartments and non-buoyant volumes can be toggled between

an outline view and a view of the sections.

Perspective view

In the perspective view, the model may be rendered.

The rendered view also enables tanks and compartments to be more easily visualised,

especially when the hull shell is made transparent.

The rendering options are to be found in the Display menu, with further lighting options

in the Render toolbar.

Please refer to the Maxsurf manual for more information on the different rendering

options available in perspective view.


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Note:

Fastest performance will be achieved by reducing the amount of redrawing

that is required from Hydromax. For this reason, it is best to turn off

sections, and especially waterlines, when performing an analysis. You may

then turn them on again after the analysis has completed. For fastest

performance, e.g. when running in Batch mode, minimise the Hydromax

window so that no redrawing occurs.

Loadcase Window

In the Loadcase window a spreadsheet table of all loads and tanks is displayed.

Using the tabs on the bottom of the window allow you to quickly browse through the

different loadcases.

Hydromax allows you to improve the presentation of the Load Case window by adding

blank, heading or sub-total lines in the table. For more information see Working with

Loadcases on page 38.

The columns that are displayed may be selected using the Display | Data Format dialog.

Damage Window

The Damage window is used to specify which tanks and compartments are flooded in

each damage case. There is always an Intact case, which cannot be edited, this is the

default condition. If flooded volumes are required in the intact case they should be

defined as non-buoyant volumes.


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Input Window

The Input window contains tables where the additional Hydromax design data is entered.

The tables in the Input window contain the:

Compartment Definition

Sounding Pipes

Key Points

Margin Line Points

Modulus Points

Bulkhead locations

The input window contains tabs on the bottom that allow you to quickly browse through

the different input tables.

Compartment Definition

This table can be used to define the tanks and compartments in the Hydromax models.

For more information see Modelling Compartments on page 51 in the Analysis Input

section.

Sounding Pipes

This table is used to define the tank sounding pipes and calibration intervals. Default

values are provided but these may be edited if necessary.


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Key Points

There are several types of Key Points:

Down Flooding points

Potential Down flooding points

Embarkation points

Immersion Points

Only downflooding points are used in determining the downflooding angle, which is

used in criteria evaluation.

Margin Line Points

The margin line is used in a number of the criteria. Hydromax automatically calculates

the position of the margin line 76mm below the deck edge when the hull is first read in.

If necessary, the points on the margin line may be edited manually in the Margin Line

Points window (the deck edge is automatically updated so that it is kept 76mm above the

margin line).

Modulus Points

This table is used to define the allowable limits for shear force and bending moment

during the longitudinal strength calculations.

Bulkheads

See Floodable Length Bulkheads on page 77.

Results Window

The Results window contains ten tables, one for each of the different analysis types plus

criteria results and key points results tables. When switching mode, the currently

selected results table will change to reflect the current analysis mode. Note that results

are never invalidated if analysis options are modified – it is up to the user to ensure that

the results are recalculated as necessary.

Setting the Data Format

It is possible to configure Hydromax so that only the results that you wish to see are

displayed. To do this, choose Data Format from the Display menu.


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A dialog similar to the one above will appear. Items that are selected with a tick will be

displayed in the Results window and on any printed output. Items that are not selected

are still calculated during the analysis cycle, but are not displayed. You may change the

display format at any time after the analysis without having to redo the calculations.

The data available for display depends on the analysis.

Data Layout

Most analysis data can be formatted vertically or horizontally to fit better on the screen

or the printed page. For example, with Upright Hydrostatics, the data can be formatted so

that each draft has a column of results, or so that each draft is on a separate row.

To change the format, select Data Format from the Display menu, and select either the

horizontal or vertical layout button.

Key Points Data Result Window

Key points data is calculated for Large Angle Stability, Equilibrium and Specified

condition Analysis. The DF angle column is only visible when the analysis mode is set

to Large Angle Stability and the Freeboard column is only displayed when the analysis

mode is set to Equilibrium or Specified condition.


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Stability Criteria Result Window

If stability criteria are turned on in the analysis menu, they will be evaluated during

Large Angle Stability, Limiting KG and Equilibrium analyses. The results of the criteria

evaluation are presented in this table after Large Angle Stability and Equilibrium

analyses. Criteria results are not displayed in this table after a Limiting KG analysis. The

results may be displayed in compact format:

Alternatively, the results can be displayed in verbose format, where all the intermediate

calculations are shown, by selecting the desired format in the Display | Data format

dialog.


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Graph Window

The Graph window displays graphs, which show the results of the current analysis.

Hydromax will automatically display the graph that displays the result of the current

analysis when you select Graph from the Windows menu or press the toolbar button.

Alternatively you can select a specific graph using the Windows | Graphs menu item.

Only the graphs that are applicable to the current analysis can be displayed.

Graphs can be copied using the Edit | Copy command.

Depending on the analysis mode, different graphs are available.

Upright Hydrostatics Analysis:

Hydrostatics

Curves of Form

Curve of areas – different graph for each draft tested (selected using

Display|Select view from data)

Large angle stability Analysis

Righting Lever (GZ)

Curve of areas – different graph for each heel angle tested (selected using

Display|Select view from data)

Max steady heel angle

Large angle stability (hydrostatic data other than GZ)

Curves of Form

Dynamic stability (GZ area)

Equilibrium Analysis:

Curve of areas

Specified condition Analysis:

Curve of areas

KN Values Analysis:

Cross curves (KN)

Limiting KG Analysis:

Limiting KG

Floodable length Analysis:

Floodable length

Longitudinal strength Analysis:

Longitudinal strength

Curve of areas

Tank Calibration

One graph for each tank

For many graphs you can select what is plotted and other options with the Display | Data

Format dialog.


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Graph type

Hydromax can graph many types of data depending on the type of analysis being

performed. These graphs include Upright Hydrostatics, Curves of Form, Curve of Areas,

Righting Lever (GZ curve), Longitudinal Strength, Floodable Length and Tank

Capacities. These can all be displayed via the Graphs item in the Windows menu.

Tip: You can use the Select View from Analysis Data option (page 159) to see the Curve

of Areas for each heel angle and/or intermediate stage during the analysis.

Interpolating Graph Data

To display an interpolated value from one of the curves, use the mouse to click anywhere

on the curve. The data in the lower left corner of the window will change to display the

curve name and co-ordinates of the mouse on the curve. Click anywhere on the dashed

line and drag it with the mouse; as you move the cursor the interpolated values will be

displayed.

Note:

In case multiple curves are plotted in the same graph you can switch

between the curves by clicking on them. Hydromax will ignore the exact

position you click on the curve to allow reading all related interpolated

values along the black dashed line.

GZ Graph

The GZ value, Area and corresponding heel angle can be measured by using the slider;

the slider data is displayed at the bottom of the Graph window. The area is integrated

from zero heel angle to the location of the graph slider.

Note:

Because the horizontal axis scale is always in degrees, the area is always

given in units of length.degrees and cannot be displayed in units of

length.radians.


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Note

The lower integration limit is always zero (irrespective of the equilibrium

angle). Thus if you require the area between two limits, you must subtract

the area at the lower limit from the area at the higher limit.

Curve fitting for GZ graph

A curve fit will be performed if all the heel angle intervals are less than or equal to 10˚.

If this is the case, a parametric cubic spline is used to fit a smooth curve through the

calculated GZ data at the specified heel angles. This ensures that the fitted line goes

exactly through the calculated GZ points. If you wish to prevent this curve fitting, add a

heel angle interval of greater than 10˚ as the final step. This can sometimes be useful if

you expect a discontinuity in the GZ curve.

Graph data

The graphed data can be obtained by double clicking on the graph. Since the graph data

contains more data points than most tables in the results window, this double click can

be extremely helpful to export the analysis data to for example Excel fro further

processing. Especially in the case of the sectional area curve, where there is no tabular

data available.

Also see: Copying Tables on page 158.

Graph Formatting

When you are in the Graph window you can use the View | Colours and lines dialog to

change the colours of the curves in the graph as well as the background. The View | Font

command allows you to change the text size and font size.

Copying Graphs

You can copy the contents of the Graph window using the Copy command or Ctrl+C.

Note that the picture is placed in the clipboard as a meta-file which can be resized in

Word or Excel.


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Note

When the graph is pasted in Microsoft Word®, the graph can be edited by

right clicking on the graph and selecting “edit picture”.

Report Window

Hydromax contains a Report window. This window is used to create a progressive

summary of the analyses that have been carried out. This report can be edited via Cut,

Copy and Paste; printed, saved to and recalled from a disk file.

Report Window Page Setup

When you are in the Report window, the File | Page setup command allows you to

customise the page orientation and size you wish to use for reporting. This is important

because, inserted tables will be automatically formatted to fit the current page set up.

However, once the tables have been placed into the report, their formatting will not be

changed by changes to the print set up. Hence it is often most convenient to select the

desired report page set up before any analyses have been made. You can for example

choose the landscape Page Setup prior to running an analysis to make the tables fit

better.

Hydromax will split most results tables so they fit the specified page set up. However,

both Loadcase and Criteria results tables will not be split.

Editing a Report

The Report window has it's own toolbar permanently attached to the view, as well as a

ruler showing you tab stops, indentation and margin widths. Underneath all of this you

have your actual editing area.

As the built-in report window only has basic editing and formatting functionality, it is

recommended that the report window be used only to accumulate the results. Once all

the results have been gathered in the report window, these should be saved and opened in

a word processor such as Microsoft Word or Open Office for formatting:

set the results tables up as you want them to appear in the report (the report uses

the same column widths, fonts etc.); do the same for the graph widow;

choose an appropriate paper size for the report (the tables will be split to fit this

paper size, so choosing a wide paper size will prevent all but the widest tables

from being split);

copy and paste the Hydromax report into Microsoft word. Use the Format |

Autoformat function in Word (with the default settings) to set the correct styles for

the different levels of heading in the document, this will facilitate generating a table

of contents and also allows you to re-format the various styles (or import a custom

set of styles using the style organiser in Word).


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The information below is provided for reference, but it is strongly recommended not to

use any of the formatting commands in the Report window. The toolbar has a number of

buttons that allow you to change either the current settings, or the section of text that is

currently highlighted.

The toolbar contains the following items:

Font combo box Use this to change the current font

Font Size combo box Use this to change the current font size

Bold Use this to toggle the Bold style

Italic Use this to toggle the Italic style

Underline Use this to toggle the Underline style

Colour Use this to set Text Colour

Left Justify Use this to set Left Justification

Centre Justify Use this to set Centre Justification

Right Justify Use this to set Right Justification

Bullet Use this to toggle Bullet Points

The Ruler comes in two formats, in metric and in inches - the format you have displayed

on your screen depends on the current Dimension Units you have (use Units in the

Display menu to change this). The format shown below is metric.


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The Ruler allows you to set left, right, centre, and decimal tab stops. The tab stops are

very useful for creating columns and tables. A paragraph can have as many as 20 tab

positions.

The 'left' tab stop indicates where the text following the tab character will start. To create

a left tab stop, click the left mouse button at the specified location on the ruler. The left

tab stop is indicated on the ruler by an arrow with a tail toward the right.

The 'right' tab stop aligns the text at the current tab stop such that the text ends at the tab

marker. To create a right tab stop, click the right mouse button at the specified location

on the ruler. The right tab stop is indicated on the ruler by an arrow with a tail toward the

left.

The 'centre' tab stop centres the text at the current tab position. To create a centre tab

stop, hold the shift key and click the left mouse button at the specified location on the

ruler. The centre tab stop is indicated on the ruler by a straight arrow.

The 'decimal' tab stop aligns the text at the decimal point. To create a decimal tab stop,

hold the shift key and click the right mouse button at the specified location on the ruler.

The decimal tab stop is indicated on the ruler by a dot under a straight arrow.

To move a tab position using the mouse, simply click the left mouse button on the tab

symbol on the ruler. While the mouse button is depressed, drag the tab to the desired

location and release the mouse button.

To clear a tab position, simply click on the desired tab marker and drag it off the ruler.

Normally, a tab command is applicable to every line of the current paragraph. However,

if you highlight a block of text before initiating a tab command, the tab command is then

applicable to all the lines in the highlighted block of text.

Keyboard Support for Reports

In addition to menu support, there are also several useful keystrokes that are available

while editing the report. These are listed below for convenience:

Ctrl+B Toggle Bold on/off

Ctrl+U Toggle Underline on/off

Ctrl+PageUp Position at the top of the report

Ctrl+PageDown Position at the bottom of the report

Ctrl+Enter Insert a page break

Opening and Saving the Report

The report can be saved to a file or read in from a file using the Save and Open Menu

commands with the report window highlighted. This is useful if you wish to append an

analysis to a report that had been calculated at some time in the past. (Load in the old

report, perform the analyses; the new results will be appended to the end of the report

which may then be resaved).


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Pasting images into the report

Sometimes, it is desirable to insert schematic images of the vessel into the report. This is

very easily done, by copying an image from one of the design views and then pasting it

into the report at the desired location. The image copied is as per the image displayed in

the Hydromax view window. Ensure that the colors selected will be easily visible in the

white background of the report view.

Depending on which Microsoft operating system you are using (notably Win98), the

image may not maintain its aspect ratio and may be pasted into the report as a square. To

overcome this problem, paste the image into Microsoft Word first, then copy it from

Word back into the Hydromax report window.

Toolbars

Hydromax has a number of icons arranged in toolbars to speed up access to some

commonly used functions. You can hold your mouse over an icon to reveal a pop-up tip

of what the icon does.

File Toolbar

The File toolbar contains icons that execute the following commands:

New – Open – Save – Cut – Copy – Paste – Print

Edit Toolbar

The Edit toolbar contains icons that execute the following commands:

Add Row - Delete Row | Sort Loadcase Rows – Move Loadcase/Tank Row up – Move

Loadcase/Tank Row Down

View Toolbar

The View toolbar contains icons that execute the following commands:

Zoom – Shrink – Pan – Home View – Rotate – Assembly window.


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The Rotate command is only available in the Perspective window. The Assembly

window is not available in Hydromax.

Analysis Toolbar

The Analysis toolbar contains icons for selecting the current analysis, loadcase and

damage case:

Analysis Type – Current Loadcase – Current Damage Case

The Analysis toolbar also contains icons that execute the following commands:

Criteria (dialog) | Start Analysis – Pause Analysis – Resume Analysis | Update Tank

Values in Loadcase

The “Update Tank Values in Loadcase” is exactly the same as the menu command for

“Recalculate Tanks and Compartments on page 206.

Window Toolbar

Allows quick switching between commonly used windows:

Perspective – Plan – Profile – Body Plan |

Loadcase – Damage Case |

Compartment – Downflooding – Margin Line – Modulus – Bulkheads |

Results for Current Analysis – Criteria Results – Key Point Results |

Graph – Report

Design Grid Toolbar

The Design Grid toolbar contains icons that show or hide various items in the graphical

views

Frame of Reference (always on) | Toggle Design Grid Visibility

Design Grid | Design Grid Labels | Design Grid Tickmarks

Visibility Toolbar

The Visibility toolbar contains icons that show or hide various items in the graphical

views:

Sections – Datum Waterline – Waterlines |

Key Points – Margin Line |

Loadcase mass items |

Tanks – Damaged Tanks – Compartments – Damaged Compart. – Linked Negative

Compartment. – NBV – Tank Names – Tank Fluid Level – Tank Sections – Tank

Outlines |

Probabilistic Damage Zones

* NBV = Non Buoyant Volume


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Edge VIsibility Toolbar

The Visibility toolbar contains icons that show or hide various items in the graphical

views:

Hull Surface Edges – Internal Surface Edges – Feature Edges – Bonded Edges

Render Toolbar

Render – Render transparent – Toggle custom light 1 – Toggle custom light 2 – Toggle

custom light 3 – Toggle custom light 4 – Customise light settings

Report Toolbar

Spool results to report

View (extended) Toolbar

Set Home View – Colour – Font – Preferences – Properties

Design Grid Toolbar

Display Frame of Reference (always on) – Display Design Grid – Show Grid – Show

Labels – Show Ticks

Extra Buttons ToolbarToolbar

Add surface areas to loadcase – Preferences |

Heel – Trim – Draft – Displacement – Displacement – Specified Condition –

Permiability – Fluid simulation – Densities – Waveform – Grounding – Batch Analysis

Data Format – Units – Coefficients – Set to DWL – Set View from Data –Visibility

Dialog – Show Single Section


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This toolbar provides a number of buttons for commonly used commands in case you

should wish to customise your toolbars.

Menus

The following section describes all of the menu commands available in the Hydromax

program.

File Menu

Edit Menu

View Menu

Case Menu

Analysis Menu

Display Menu

Data Menu

Window Menu

Help Menu

File Menu

The File menu contains commands for opening and saving files and printing.

New

Creates a new table for whichever input table is frontmost, e.g: when the Loadcase

Condition is the frontmost window, the New command will create a new loading

condition. When the Compartment Definition table is frontmost, New creates a new

compartment definition.

Open

When no design is open, selecting the Open command will show a dialog box with a list

of available Maxsurf designs. Select the design you wish to open, click the Open button.

The requested design will be read in and its hull shape calculated for use in Hydromax.

If a design is already open, the Open command will open whichever file corresponds to

the frontmost input window.

Close

The Close command will delete the data in the frontmost window. Hydromax will ask

whether you wish to save any changes.

Selecting Close when one of the design view windows is frontmost will close the current

Maxsurf design.

Save

Selecting Save will save the contents of the frontmost window to a file on the disk.

Save As

Selecting Save As performs the same function as save but allows you to specify a new

filename preventing the original file from being overwritten.

Import

Allows import of file types other than Maxsurf design files


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nuShallo

Allows direct import of a nuShallo pan file.

GHS

Allows direct import of a GHS geometry file. A full GHS model file may be

imported directly into Hydromax for analysis. Because the GHS file does not

contain a full, interconneceted, three-dimensional model of the hull, the geometry

is locked: the tank geometry is locked and tanks cannot be added to the model.

The full model including critical points, tanks and sounding pipes are read from

the GHS file. The following limitations currently apply, but will be removed in

subsequent versions:

Hydromax supports only a single buoyant hull part. The buoyant hull part with the

most sections is loaded from the GHS file.

Linked negative tanks are not supported in Hydromax. Any container parts with

elements with negative effectiveness will be read in as tanks. All other cotainers

are read in as tanks.

Sail parts are ignored

Import DXF Background

Enables you to import a DXF file into Hydromax to use as construction lines. The

DXF file will be displayed in the design views.

Import Image Background

Enables you to import an image file (jpg, gif, bmp or png) file into the background

of any of the Hydromax design views.

Export

Selecting Export enables you to export a Hydromax file as a variety of different file

formats such as:

DXF or IGES

DXF exports sections as closed poly-lines. In addition, each tank, compartment

and non-buoyant volume is exported on a separate layer (the layer name being the

same as the compartment name, so it is important to have unique compartment

names).

IGES exports the NURB surface data. See the Maxsurf manual for more

information.

GHS

If you have a Hydrolink license, you may export the Hydromax model to a GHS

geometry file. The hull, tanks and compartments and key points are all exported.

To enable the export command, chose Edit | Activate GHS export.

Hydromax supports only a single buoyant hull part with one byouant component.

The buoyant hull is exported as a single part with a single buoyant component

(Non-buoyant volumes are included in this part as components with negative

effectiveness). It is possible that this might cause problems for some models

where the section through the hull at a certain location contains more than one

closed contour. In subsequent versions of Hydromax we will add the capability to

divide the main buoyant hull into different components.

Hydromax v8.0 file

Also allows users to export Hydromax files that are compatible with earlier

versions of Hydromax.


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Export Bitmap

Allows you to export the rendered image as a bitmap file at the specified

resolution. This command is only available when the Perspective window is

frontmost with rendering turned on.

Fredyn

Hydromax is able to export data suitable for input into Fredyn, exporting

Hydromax calibration results, hull form and compartment definitions into Fredyn

input files. To export use the File|Export|Fredyn… command. The Export will

generate 3 files, all with the name you specify in the “Fredyn Export XML”

dialog. The following files will be generated

.xml: Containing compartment definition

.out: Tank calibration results and compartment definitions

.txt: Mesh file representing the current hull shape.

Before doing the Fredyn export ensure you have specified the desired trim and

heel ranges, and performed a tank calibration, as this information is required for

the export.

Fredyn mesh group definition

When exporting from Hydromax to Fredyn you will be asked to name the .xml file

and also the location to which it should be saved. After assigning the .xml file

name, the following dialog will appear:

“Fredyn group definition” dialog

This dialog is where the user will specify the values for the variables used to

generate the mesh file that defines the geometry of the hull.

The most important part of the procedure is setting up the groups required in the

mesh file. The groups are defined by selecting the surfaces to be measured and

defining a boundary box that defines the limiting extents of the group. Contours

will be formed through the selected surfaces and then trimmed back to the

bounding box.

In the group definition dialog, any number of groups may be added and for each

group. For more information on each of the fields in the table click on the Help

button on the right hand side of the dialog.

Allows you to export the rendered image as a bitmap file at the specified Import Main Criteria

Imports criteria from the selected criteria files. Current criteria may be kept or discarded.


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Save Main Criteria As

Exports the current criteria set to the specified file. It is good practice to save the criteria

library with each project in a project folder.

Note that a branch of the criteria tree may be saved in its own file by right-clicking on

the branch folder in the Criteria dialog tree. The whole library may be saved by right

clicking on the root “Criteria” branch; this is not normally necessary as this is done after

any major changes to the criteria definition.

Import Prob Damage Criteria

As for main criteria but applies to the probabilistic damage criteria.

Save Prob Damage Criteria As

As for main criteria but applies to the probabilistic damage criteria.

Rest Prob Damage Criteria to defaults

Results the probabilistic damage criteria to their default values.

Load Densities

Loads density table data previously saved from Hydromax – can be useful for

synchronising the densities on several computers.

Save Densities As

Saves the Fluid densities table data, see Density of Fluids on page 150.

Page Setup

The Page Setup dialog allows you to change page size and orientation for printing.

Print

The Print command allows you to print the contents of the frontmost window on the

screen.

Exit

Exit will close Hydromax and all the data windows. If you have any data or results,

which have not been saved to disk, Hydromax will ask you if you wish to save them

before quitting.

Edit Menu

The Edit menu contains commands for working with tables.

Undo

Undo may be used with desk accessories, but cannot be used on Hydromax drawing

windows or data windows.

Cut

Cut may be used in the Report window but cannot be used on Hydromax drawing or data

windows.

Copy

The Copy command allows you to copy data from any of the windows, including the

design view, input tables, results tables and graph window.


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Paste

Choose the Paste command to Paste data into the Loadcase window or other input tables,

or the Report window. Paste cannot be used in the View, Graph or Results windows.

Select All

Selects the entire Report.

Fill Down

Copies text in a table down a column like a spreadsheet.

Table

Performs operations on Hydromax's Report window.

Insert New Table

Create a new table in the Report.

Insert Row

Insert a new row into the current table in the Report.

Split Cell

Split the currently selected cell into two separate cells in a table in the Report.

Merge Cells

Merge the selected cells in a table into a single cell in the Report.

Delete Cells

Delete current cell, column or row or a range of cells, columns or rows in the

Report.

Row Positioning

Set Justification for the current table row or an entire table in the Report.

Cell Border

Set Cell Border Width for a single cell or range of cells in the Report.

Cell Shading

Set Cell Shading Percentage for a single cell or a range of cells in the Report.

Show Grid

Toggle table grid lines in the Report.

Add

The Add command is used to add an entry to the input tables (Load, tank, margin line

point etc.).

Delete

The Delete command will delete rows from the input tables. If no rows are selected, the

last row in the window will be deleted, otherwise all selected rows will be deleted.

Sort Items

Sorts the selected rows in the Loadcase window


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Move Items Up

Moves the selected rows up (if possible) in the Loadcase and Compartment definition

tables.

Move Items Down

Moves the selected rows down (if possible) in the Loadcase and Compartment definition

tables.

Add Surface Areas

This command automatically adds the surface areas and centres of gravity of all hull

surfaces into the current loading condition. This is useful for estimating the initial weight

of hull plating.

Activate / Deactivate GHS Export

This command activates the GHS Import command in the File menu if a Hydrolink

License is available. It can also be used to release the Hydrolink license – a restart of

Hydromax will be required for this to take effect.

Preferences

The Hydromax preferences dialog allows you to set your analysis tolerances (or: error

values) and select the option to stream the report to a Microsoft Word document.

Also see:

Tolerances on page 146

Streaming results to Word on page 155.

View Menu

The View menu contains commands for controlling the views in the graphics windows.

Zoom

The Zoom function allows you to examine the contents of the design view windows in

detail by enlarging the selected area to fill the screen.

Shrink

Choosing Shrink will reduce the size of the displayed image in the design view windows

by a factor of two.

Pan

Choosing Pan allows you to move the image around within the View window.

Home View

Choosing Home View will set the image back to its Home View size.

Rotate

Activates the Rotate command, which is a virtual trackball which lets you freely rotate a

design in the Perspective view window.

Set Home View

Choosing Set Home View allows you to set the Home View in the View window. To set

the Home View, use Zoom, Shrink, and Pan to arrange the view, then select Set Home

View from the View menu.


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Colours and lines

The Colours and lines function allows you to set the colour and thickness of the lines,

labels, and graphs.

Remember to always be careful when using colour. It is very easy to get carried away

with bright colours and end up with a garish display that is uncomfortable to work with.

In general it is best to use a neutral background such as mid grey or dull blue and use

lighter or darker shades of a colour rather than fully saturated hues.

From the scrollable list, select the item whose colour you wish to change. The item‟s

current colour will be displayed on the left of the dialog. To change the colour click in

the box and select a new colour from the palette. To Change the thickness select the

thickness from the drop down list.

When Loadcase window is frontmost, Colours for the loadcase items can be set. See

Loadcase Colour Formatting on page 44.

Font

Font command allows you to set the size and style of text.

The text style chosen will affect the display and printing of all text in the Report,

Loadcase, Graph, Curve of Areas, and Results windows.

Toolbar

Allows you to turn the Toolbars on and off.

Status Bar

Allows you to turn the Status Bar on and off at the bottom of the screen.

Assembly

Show or hide the assembly tree view.

Properties

Displays the properties sheet, which may be used to view parameters of selected objects

(such as tanks).


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Full Screen

Maximises screen usage.

Case Menu

Commands associated with the Loadcases and Damage cases

Edit Loadcase

Edit the properties of the current Loadcase (name and whether it is a loadcase or

Loadgroup). Loadcases are created, opened and closed through the file menu. See

Working with Loadcases on page 38.

Add Damage case

Add another damage case

Delete Damage case

Delete the selected damage cases

Edit Damage case

Edit the properties of the selected damage case

Extent of Damage

Automatically finds the breached tanks and compartments due to a cuboid extent of

damage (or in the case of Probabilisitic damage, the zone or sub-zone).

Create cases from Zone Damage

Automatically creates damage cases based on the zones that have been defined for

Probabilistic damage analysis. (This is only required if you want to manually recreate

some or all of the Proabilistic damage analysis conditions; when running Probabilistic

damage analysis, temporary damage conditionas are created automatically.)

Max. number of Loadcases

Specify the number of loadcase tabs – this requires a restart to activate the changes

made.

Analysis Menu

The Analysis menu can be used to change the current analysis mode. It also contains

commands to set the input data and analysis settings and environment options required

for the current analysis.


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Note:

It is good practice when preparing to run analysis to work down the

Analysis menu starting at the top and checking all of the settings and

environment options.

Heel

Selecting Heel allows you to specify the three ranges of heel angles that you wish

Hydromax to step through. Separate ranges are used for Large Angle Stability, KN and

Limiting KG analyses.

Trim

Allows the specification of the trimming mode to be used for the analysis. This can be

fixed trim; free-to-trim to loadcase; free-to-trim specifying initial trim value and free-to-

trim specifying LCG position.

Draft

The range of drafts used for the analysis of upright hydrostatics can be set using this

command. KG for the upright hydrostatics is also specified in this dialog.

Displacement

The range of displacements used for the analysis of KN values, Limiting KG and

Floodable Length can be set using this command. The vertical centre of gravity to be

used for KN and Floodable Length analyses is specified here.

Permeability

The range of permeabilities used for the Floodable Length analysis are set using this

command.

Calibration Options

Specify whether compartments and non-buoyant volumes should also be calibrated.

MARPOL Options

Select MARPOL Regulation and specify which tanks should be incuded in the

MARPOL oil outflow analysis.

Specified Condition

Allows you to specify Heel, Trim, CG, Displacement and Draft for the Specified

Condition analysis.

Fluids

Allows you to specify whether to use Corrected VCG method or Simulate Fluid

Movement method when treating the fluid contained in slack tanks. See Fluids Analysis

Methods on page 148.

Density

This command allows you to set the density of fluids used in the analysis. See Density

on page 150.

Waveform

The Waveform command allows you to perform analysis for a flat waterplane or

sinusoidal or trochoidal waveforms.


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Criteria

The criteria menu item will bring up the criteria dialog. This allows you to specify which

criteria will be checked during the analysis.

See Criteria on page 163.

When the floodable length analysis is selected, the criteria command will bring up a

Floodable Length Criteria dialog with criteria that only apply to floodable length

analysis.

Grounding

Specifies grounding on one or two points of variable length for use with the Equilibrium

and Longitudinal Strength analyses.

Update Loadcase

Checks for changed tanks and makes sure that any tanks and compartments that have not

been formed are correctly calculated. It then updates the loadcase with the correct

capacities and free surface moments for the tanks. Also recalculates totals and sub-

subtotals after a row sorting or moving command.

Also see:

Tank Loads on page 46

Recalculate Tanks and Compartments

Forces all tanks and compartments to be re-formed from their initial definition. This

command also updates the loadcase.

If any of the tank boundaries are made up from boundary surfaces, it is better to use

“Recalculate Hull Sections” after re-opening the Maxsurf model to make sure the latest

internal structure surfaces are being used as well.

Recalculate Hull Sections

Deletes all existing hull, tank and compartment sections and recalculates them from the

hull surface data and compartment definition. This is particularly useful if the underlying

Maxsurf model has been modified, if you wish to recalculate at a different precision, or

if you wish to modify whether skin thickness or trimming options are applied.

Note:

To be able to update the Hydromax model to changes made in Maxsurf see

Updating the Hydromax Model on page 26 for a step-by-step procedure you

can follow.

Snap Margin Line to Hull

Project all of the margin line points horizontally onto the hull surface, ensuring that the

margin line follows the hull shape precisely.

Also see:

Margin Line Points on page 76.

Set Analysis Type

Choose the analysis type you wish to use from the sub-menu.


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Start Analysis

Selecting Start Analysis causes Hydromax to start performing the specified analysis. The

analysis may be halted at any time by choosing Stop Analysis from this menu, also.

Resume Analysis

If you have halted analysis by choosing Stop Analysis, Resume Analysis may be used to

restart the calculation from the point where it was interrupted.

Stop Analysis

This command halts the analysis at the current iteration. Note that the analysis may not

have been completed and in the case of large angle stability, equilibrium condition and

KN values, any data displayed for the final iteration may be incorrect.

Start Batch Analysis

Hydromax will run the selected analyses for all combinations of load and damage cases

using the batch processing command. Results are written to a tab delimited text file as

specified by the user at the start of the analysis.

Spool to Report

Send the results of the analysis to the report upon completion. This should be turned on

before commencing the analysis to ensure that results are added to the report when the

analysis is completed.

Display Menu

The Display menu contains commands for controlling the data, which are displayed in

the graphics and other windows.

Data Format

Data Format allows you to choose which data are tabulated and graphed (Upright

Hydrostatics, Stability, Equilibrium and Specified Condition). A dialog box allows you

to choose from a range of stability variables. See Setting the Data Format on page 185.

Hydrostatic results Data format dialog

Used to select display options for Criteria results:


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Criteria table Data format dialog

Used to select which columns are displayed in the Loadcase window:

Loadcase Data format dialog

When the Max. Safe heeling angle angles graph is shown as a result of a Large Angle

Stability analysis the Data Format dialog may be used to customise the graph layout:


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Max safe heeling angle Data format dialog

May be used to customise the Floodable length graph:

Floodable length Data format dialog

Set Vessel to DWL

Rotates the vessel back to upright and to DWL after an analysis has been completed (or

Select View from Data used). This is required for automatic update of the Loadcase

(note that if you do not rotate back to the DWL, the Loadcase will not update while

editing – only when start another analysis). This is to ensure that tank data in the

Loadacase are for the vessel in the upright condition, not for tanks with the vessel at the

final heel and trim of the last analysis.

Select View from Data

This function may be used to synchronise the display in the Design View window with

one of the sets of data in Results window. The view may be set from any of the results

from Upright Hydrostatics, Large Angle Stability or Equilibrium analyses. Simply

highlight the column or row that corresponds to the condition you wish to view and

select “Select View From Data”; the Design View will change to match the condition in

the selected row or column in the Results window.

Visibility

The visibility of tanks, compartments, labels, hull contours, and other items in the design

view may be set by using this dialog.

Prob damage zones

Toggle the visibility of the probabilistic damage zones.


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Individual Loadcase masses

Toggle the visibility of the individual mass items in the current loadcase.

Background

Controls whether the background DXF construction lines and the background images are

displayed or not. The background may be loaded from an existing DXF file using the

Import function in the File menu. Tools for positioning and scaling the background

image are also here.

The commands in the submenu are only available when a background image or DXF has

been imported. See the Maxsurf manual for more details

Hide DXF

Hides the DXF background.

Show DXF

Shows the DXF background.

Delete DXF background

Deletes the DXF background.

Hide Image

Hides the background image in the current view window.

Show Image

Shows the image in the current view window.

Set Image Zero Point

Sets the image zero point. This command is not available for images in the

perspective window.

Set Image Reference Point

Sets the image reference point..

Delete Image

Deletes the background image in the current view window.

Design Grid

The grid submenu allows you to hide the grid or show the grid with or without station

grid labels. The grid can only be displayed when the vessel is in upright position on its

design waterline. The option to display the grid will be greyed out when the ship is

currently displayed in, for example, a trimmed state at the end of an equilibrium analysis.

Switching analysis type puts the boat back into upright position on its design waterline.

Show Single Hull Section in Body Plan

Selecting the Show Single Hull Section item from the Display menu will change the

display in the Body Plan window to show only one section through the hull, as well as a

control box, similar to the one in Maxsurf, in the top right corner of the window.

The section being displayed can be chosen by clicking on the section indicators at the top

of the control box. Alternatively, the section chosen can be changed by pressing the left

or right cursor keys on your keyboard. This allows you to rapidly step through the hull

sections from bow to stern.

Also see:

Show Single Hull Section on page 30


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Render

When the Perspective window is the current view for the model the Render option may

be toggled on and off to render the surfaces.

Render Transparent

When the Perspective window is the current view for the model the Render Transparent

option may be toggled on and off. Render Transparent makes the hull surfaces of the

model semi transparent so that the rendered tanks and compartments within the model

may be viewed.

Animate

This command is available for any analysis that steps through several steps. For

example, when a waveform has been specified and an equilibrium analysis is selected or

after a Large Angle Stability analysis over a heeling range.

Selecting Animate will animate the stability sequence in the design View window,

through the range of heel angles specified. You may set the initial viewing position in

the Perspective View window using the Pitch, Roll and Yaw indicators. When

Hydromax has finished calculating the frames the sequence may be replayed by moving

the mouse from side to side. Clicking the mouse button will terminate the animation.

If animation is chosen after an Equilibrium Analysis has been performed in waves, the

animation will automatically cycle through the full range of wave phases, giving a

simple visual simulation of the motion of the hull through the wave.

Hold the shift key down while selecting the command to save the animation.

Data Menu

Units

The units used may be specified using the Units command. In addition to the length and

mass units classes, units for speed (used in wind heeling and heeling due to high-speed

turn etc. criteria) and the angular units to be used for areas under GZ curves, may also be

set. The angular units for measuring heel and trim angles are always degrees. See

Setting Units on page 37 for more information.

Coefficients

Allows you to customise how you wish to calculate the coefficients as well as the display

format for the LCB and LCF.

See Customising Coefficients on page 36 for more information.

Design Grid

Access to the Design Grid is intended for information only. You are not expected to

change the Design Grid in Hydromax.

Frame of Reference

Access to the Frame of Reference is intended for information only. You are not expected

to change the Frame of Reference in Hydromax.


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If the position(s) of the Baseline and/or Perpendiculars need to be changed from those

defined in the Maxsurf model, they may be changed using the Frame of Reference

command. It is highly recommended that the correct frame of reference be set in

Maxsurf prior to loading the design into Hydromax. This will ensure that a consistent

frame of reference is used in all the programs. See: Setting the Frame of Reference on

page 18.

Window Menu

For the items in this menu, each represents a Hydromax window. Selecting the item

brings the appropriate window to the front.

Cascade

Displays all the Windows behind the active Windows.

Tile Horizontal

Layout all visible windows across the screen.

Tile Vertical

Layout all visible windows down the screen.

Arrange Icons

Rearranges the icons of any iconised window so that they are collected together at the

bottom of the Maxsurf program window.

View Direction

Select the desired view direction from the sub-menu. The selected design window will

then be brought to the front.

Loadcase

Brings the Loadcase window to the front. The Loadcase window allows you to enter a

series of component weights, together with their longitudinal and vertical distances from

the zero point. These inputs are used to calculate the total Displacement and Centre of

Gravity for Stability, KN and Equilibrium analysis.

Input

Choose from the Input item to bring the desired Input window to the front and display

the Compartment Definition, Key Points, Margin Line Points or Modulus table.

Results

Choose from the Results item to bring the desired Results window to the front and

display the desired table.

Graph

Brings the selected Graph window to the front. The Graph window displays a number of

different graphs, depending on which analysis mode is currently active.

Help Menu

Provides access to Hydromax Help.

Hydromax Help

Invokes Hydromax Help.


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Hydromax Automation Reference

Invokes the Automation Reference help system.

Online Support

Provides access to a wide range of support resources available on the internet.

Check for Updates

Provides access to our website with the most recent version listed.

About Hydromax

Displays information about the current version of Hydromax you are using.

Appendix A

Page 214

Appendix A: Calculation of Form Parameters

This Appendix explains how the calculation of form parameters (CB, CP, AM, etc.) is achieved in

Hydromax, and investigates why differences with other hydrostatics packages may occur.

Definition and calculation of form parameters

Below is a summary of the definitions of basic vessel particulars and form parameters used in

Hydromax.

Measurement Reference Frames

Results in Hydromax are given from the vessel‟s zero point. However, because Hydromax treats

trim exactly (the hull is rotated not sheared when trim occurs), there are two frames of

reference:

Ship or upright frame of reference

The “ship” or “upright” reference frame is that of the upright vessel with zero-trim. Here

the baseline is horizontal and the perpendiculars are vertical. “Longitudinal”

measurements are made parallel to the baseline and “vertical” measurements are

perpendicular to the baseline.

World or trimmed frame of reference

The “world” or “trimmed” reference frame is that of the trimmed vessel. Here the

baseline is no longer horizontal and neither are the perpendiculars vertical.

“Longitudinal” measurements are made parallel to the horizontal, static waterline and

“vertical” measurements are perpendicular to the waterline

Rotated reference frame (red) and measurements in the two reference frames: Measurements in the upright vessel reference frame (green) and trimmed reference frame (blue)

When the vessel is upright (zero trim and zero heel) these axis systems are parallel. However if

the vessel is trimmed or heeled or rotated in both directions simultaneously, these axis systems

are no longer parallel.

Appendix A

Page 215

Ship-Fixed and Earth-Fixed(world) axis systems

The majority of measurements are given in the “ship” frame of reference. These include

longitudinal centres of gravity, floatation and buoyancy (LCG, LCF, LCB); and measurements

from the keel such as KB and KG. Measurements such as BM, GM, that are explicitly vertical,

are measured in the “world” frame of reference, i.e. GM is the true vertical separation of the

metacentre and the centre of gravity with the vessel inclined and are always measured normal to

the water surface.

Thus the metacentre is always vertically (in the earth-fixed axis system) above the centre of

buoyancy by a distance BM = I / vol where I is the second moment of area of the waterplane.

It is for this reason that, in general, KM is not equal to KB+BM (BM is in a different axis

system to KB and KM, and only if the vessel is upright are the axis systems parallel and hence

the equation holds).

Similarly, in generally for the vessel to be in equilibrium, LCG is not equal to LCB – if both

LCB and LCG are measured in the ship-axis system (of course if they are measured in the earth-

fixed axis system then they are the same. This is because if the vessel is trimmed and if the

VCG and VCB are not the same, then there will be a sin(trim angle) term introduced. The same

is true of TCB and TCG if the vessel is heeled.

Appendix A

Page 216

Nomenclature

Amax Maximum immersed cross-sectional area to waterline

under investigation

Ams Immersed cross-sectional area to waterline under

investigation amidships

A Immersed cross-section area: Amax or Ams as selected by

user

AWP Area of waterplane at the waterline under investigation

BOA Overall beam of whole vessel (above and below

waterline)

BWL Maximum waterline beam at design waterline

B Maximum beam of waterline under investigation

b Waterline beam of station under investigation

GM Metacentric height: vertical distance from centre of

gravity to metacentre, measured in the trimmed reference

frame

KB Distance from keel (baseline) to centre of buoyancy,

measured normal to the baseline.

KG Distance from keel (baseline) to centre of gravity,

measured normal to the baseline.

LOA Length overall

LCB Longitudinal Centre of Buoyancy, measured in upright

reference frame, parallel to baseline.

LCF Longitudinal Centre of Floatation, measured in upright


LCG Longitudinal Centre of Gravity, measured in upright


LWL Length of design waterline

LBP Length between perpendiculars

L length of waterline under investigation

T0 Draft from some arbitrary baseline (normally the lowest

point on the design)

T Maximum immersed depth (draft) of hull

t Draft (immersed depth) of station under investigation

Immersed volume of displacement at waterline under

investigation

Coefficient parameters

There are several options for calculating hullform coefficients. These can be modified in the

Data | Coefficients dialog shown below:

Appendix A

Page 217

Length

The datum/design waterline or DWL is a waterline near which the fully loaded design is

intended to float under normal circumstances. The forward perpendicular is normally defined as

the intersection of the DWL with the bow. The after perpendicular is normally defined as the

position of the rudder post, or possibly the transom.

Several lengths may be defined: the LBP is the length between perpendiculars, this may be

different from the length of the DWL (LWL) and in general, will also be different from the

LOA (overall length). In some cases, particularly for resistance prediction purposes, it may be

more appropriate to define an effective length of the underwater body, features such as bulbous

bows and overhangs can make the LBP, LWL and LOA quite different. In addition, for

calculations at drafts other than the DWL, it may be appropriate to use the actual waterline

length at that draft (L).

Some of the more common lengths that may be used to characterise a vessel.

In Hydromax you may choose between the length between perpendiculars and the waterline

length for the calculation of Block, Prismatic and Waterplane Area Coefficients. Select

Coefficients from the Display menu:

Appendix A

Page 218

Beam

It is normal to use the maximum waterline beam for calculation of coefficients, and this may be

of the DWL or the waterline under consideration. However, there may be times when it is

appropriate to use the maximum immersed beam (e.g. submarine, vessel with tumble-home or

blisters). For the calculation of section area coefficients it is normal practice to use the beam and

draft of the section in question.

Vessel with tumble-home

Catamarans and other multihull vessels pose another difficulty. In some cases the overall beam

is of importance, in others, the beam of the individual hulls may be required.

Hydromax uses the total waterline beam of immersed portions of the section for

calculation of block coefficient and other form parameters. For the case of a monohull this

will be the normal waterline beam. For catamarans this will be twice the demihull beam

(remember that the total displaced volume is used and hence the block coefficient is the

same as that of a single demihull). For the section shown below, the beam used would be

the sum of B1, B2 and B3.

Multihull beams

You may choose which beam should be used from the following list:

In the reported hydrostatics, you can select various beams:

Appendix A

Page 219

Calculated beams

The values “Beam extents” are those that measure the beam across the maximum port and

starboard extents of the vessel. For a catamaran this would be from the outside of the port

demihull to the outside of the starboard demihull. For a monhull, this would simply be the

distance from the port side to the starboard side.

The other beam values are calculated by summing the breadth of waterline crossings as

described above. For a monhull without tunnels, this will be the same as the extents value, but

for a multihull, it will be less than the extents value. Hydromax uses these values for computing

coefficients.

Draft

The draft is normally specified from a nominal datum. Normally this datum is the lowest part of

the upright hull. However, for vessels with raked keel lines or yachts, the datum may be

elsewhere. In Hydromax drafts are defined from the datum line. However, there are also

occasions when the immersed depth of the section is a more relevant measure of draft, this is

often the case when form parameters are calculated.

Hydromax uses the depths that stations extend below the waterline for calculation of form

coefficients. Both depths are measured in upright position.

You may select which depth should be used for the calculation of form parameters, including

the option of measuring the draft to the baseline – this gives the option of ignoring appendages

such as fin keels when determining the draft to be used to calculate the form parameter (if the

baseline is defined to the bottom of the canoe body for example). It should be noted that the

section area will, however, include the appendages.:

Appendix A

Page 220

Draft measurements

Draft measurement at heel angle

When the vessel is heeled, the draft is measured through the intersection of the upright

waterline and the centreline, perpendicular to the heeled waterline (see figure below).

Essentially the draft is measured along the heeled and trimmed perpendiculars on the

centreline. It is for this reason that as the heel approaches 90degrees, the draft becomes

very large.

Draft measured along the inclined perpendicular lines

Immersed depth and Draft measurements

The images below show the difference between the draft measurements (which are made

in the inclined centreline plane of the vessel) and the immersed depth measurements

(which are made normal to the free-surface).

Difference between “Immersed depth” and “Draft” measurements

Midship and Max Area Sections

It is current usual practice to define the midship section as midway between the perpendiculars,

however for some vessels it is defined as the midpoint of the DWL. For vessels with no parallel

mid-body, the section with greatest cross-sectional area may also be of particular interest. In

Hydromax, the position midway between the perpendiculars is defined as midships.

Appendix A

Page 221

When computing form coefficients, such as CP and CM, you may select which section area

should be used: Hydromax uses the station with the maximum immersed cross-sectional area at

the waterline under consideration.

Block Coefficient

Principles of Naval Architecture defines the block coefficient as:

"the ratio of the volume of displacement of the moulded form up to any waterline to the volume

of a rectangular prism with length, breadth and depth equal to the length, breadth and mean draft

of the ship at that waterline."

However, the actual definitions of the length, beam and draft used vary between authorities.

Length may be LBP, LWL or some effective length. The beam may be at amidships or the

maximum moulded beam of the waterline; or may be defined according to another standard –

this may be important for hulls with significant tumble-home or blisters below the waterline.

Hydromax uses the length beam and draft as selected in the Coefficients dialog to compute

the block coefficient. The beam used is that obtained by summing the immersed waterline

crossings of the specified section.

TBLCB

Section Area Coefficient

Principles of Naval Architecture defines the midship coefficient as:

"The ratio of the immersed area of the midship station to that of a rectangle of breadth equal to

moulded breadth and depth equal to moulded draft at amidships."

It should be noted that, for sections that have significant tumble-home or blisters below the

waterline, the midship section coefficient can be greater than unity.

In Hydromax midships is midway between the perpendiculars.

The section area coefficient used by Hydromax, is calculated at either the station with

maximum cross-sectional area or the midship section area (as defined in the Coefficients

dialog). The beam and immersed depth of the selected section is used unless the draft to

baseline option has been selected in which case this draft is used.

Options for Section area coefficient

tb

ACM

Prismatic Coefficient

Principles of Naval Architecture defines the prismatic coefficient as:

Appendix A

Page 222

"The ratio between the volume of displacement and a prism whose length equals the length of

the ship and whose cross-section equals the midship section area."

Again the definition of midship section and vessel length depend on the standard being used.

Hydromax uses the selected length and the selected immersed cross-section area Amax or

Ams.

ALCP

Waterplane Area Coefficient

Principles of Naval Architecture defines the waterplane area coefficient as:

"The ratio between the area of the waterplane and the area of a circumscribing rectangle."

Hydromax uses the length and beam as selected.

BL

AC WP

WP

LCG and LCB

Hydromax allows you to fully customise how you want to display the LCB and LCF values. See

Customising Coefficients on page 36 for more information.

The LCG and LCB are calculated in the “ship” or “upright” frame of reference; see

Measurement Reference Frames on page 214. When the vessel is free-to-trim, the LCG and

LCB will be at the same longitudinal position in the global coordinate system, but not in the

frame of reference. Therefore a difference between the LCG and the LCB value will occur when

the vessel is trimmed. This is explained in the figure below:

Effect of vertical separation of CG and CB on LCG and LCB measured in the Ship reference frame

Appendix A

Page 223

Note:

LCG and LCB are calculated in the vessels‟ frame of reference and therefore will

have different longitudinal positions when the vessel is trimmed then for when it is

upright.

This is the same for differences in TCG and TCB values due to heeling.

Trim angle

The trim angle as defined by:

pp

fa

L

TT1tan

where: is the trim angle; Ta , Tf are the aft and forward drafts at the corresponding

perpendiculars and LPP is the length between perpendiculars.

Maximum deck inclination

The inclination angle is a combination of heel and trim angle. Hydromax calculates the steepest

slope of the deck when the ship is trimmed and/or heeled. Deck camber and initial deck slope

are not taken into account.

For example:

The Max deck inclination is the

maximum slope of the deck when

combining the trim and heel angle

of the vessel, assuming the deck

inclination is zero when the vessel is

in upright position.

Immersion

The weight required to sink the model one unit-length below its current waterline. The unit-

length can be either in cm or inch depending on your unit settings.

MTc or MTi

The required moment to make the vessel trim one unit-length. That can be either cm or inch

depending on your unit settings.

Appendix A

Page 224

RM at 1 deg

The righting Moment at 1 degree heel angle, calculated by

)1sin(**GMtDisplRM

Potential for errors in hydrostatic calculations

There are a number of potential sources of error when calculating the hydrostatic properties of

immersed shapes. These mainly occur from the integration method used, and occur in both hand

calculations, and most automatic calculations carried out by computers. Both methods use

numerical integration techniques, which are normally either based on Simpson's rule or the

Trapezium rule. As with all numerical integration schemes, the accuracy increases as the step

size is reduced, hence computer calculations offer an enormous advantage compared with hand

calculations, due to the increased speed and accuracy with which these calculations may be

carried out. With hand calculations, it is normal to use perhaps 21 sections and perhaps 3-5

significant figures; with computer calculations, it is quite feasible to use 200 sections or more

with 10s of significant figures. These effects are noted from comparing the results of different

hydrostatics packages on the same hullform. In general, differences for basic parameters such as

displacement etc. are under 0.5% (note that, in general, agreement of hand calculations to within

2% is considered good). Differences in derived form parameters may show considerable

variation. However, this is primarily due to differences in the definitions used – see discussion

above.

The 0.5% error discrepancy noted above, may be attributed to a number of causes:

Convergence limits when balancing a hull to a specified displacement or centre of gravity.

Different number of integration stations used, and their distribution. Where there are large

changes in shape, such as near the bow and stern, the stations should be more closely

spaced. This can be of particular importance if the waterline intersects the stem profile

between two sections.

Differences in the hull definition, and number of interpolation points used to define each

section. If the surface is exported as DXF poly-lines then the precision used and the

number of straight-line sections used to make up the poly-line are important.

The integration method used: trapezium, Simpson, or higher order methods.

Integration of wetted surface area

At first glance, it may seem that wetted surface area may be calculated by simply integrating the

station girth along the length of the hull, in a similar way that one might integrate the station

cross-sectional area along the length of the hull to obtain the volume. However, this is not the

case, and the wetted surface area can only be accurately found by summing elemental areas over

the complete surface. Further, the error due to integrating girths along the vessel length cannot

be removed simply by increasing the number of integration stations. The only accurate

numerical method is to sum the areas of individual triangles interpolated on the parametric

surface.

The differences are easily shown by considering the surface area of half a sphere. This is given

analytically by: 22 RA , where R is the radius of the circle.

It may be shown that the area obtained by integrating the girth of the sphere along its length is

given by:

2

22' R

A , note that this is with an infinite number of integration steps, and hence the

integration of section girths underestimates by error factor of 27.1/45.0

222

2

R

R, or

approximately 27%.

Appendix A

Page 225

However, for normal ship hulls the differences will be much less, due to the greatly reduced

longitudinal curvature. Surface areas calculated by the 'Calculate Areas' dialog in Maxsurf are

the most accurate, since they are derived from the actual parametric definition of the surface.

Those calculated by Hydromax and most other hydrodynamics packages, which use a number of

vertical stations to define the hull, will be subject to the error described above.

Appendix B

Page 226

Appendix B: Criteria file format

The criteria are saved in a Hydromax criteria file with the extension .hcr. The file is a normal

PC text file, which may be edited manually so as to generate custom criteria. The typical format

of the file is given below:

Please refer to the file C:\Program Files\Maxsurf\HMCriteriaHelp\CriteriaHelp.html for a full

list of all the parameters for all the different criteria types.

Hydromax Criteria File

[units]

LengthUnits = m

MassUnits = tonne

SpeedUnits = kts

AngleUnits = deg

GZAreaGMAngleUnits = deg

[end]

[criterionGroup]

GroupName = Specific Criteria

ParentGroupName = root

[end]

[criterionGroup]

GroupName = My Custom Criteria

ParentGroupName = root

[end]

[criterionGroup]

GroupName = STIX input data

ParentGroupName = Specific Criteria

[end]

[criterion]

Type = CTStdAreaUnderGZBetweenLimits

RuleName = STIX input data

CritName = GZ area to the lesser of downflooding or…

CritInfo = Area under GZ curve between specified heel…

CritInfoFile = HMCriteriaHelp\StixHelp.rtf

Locked = true


TestIntact = true

TestDamage = false

Test = false

Compare = GreaterThan

UseLoHeel = false

UseEquilibrium = true

UseHiHeel = false

UseFirstPeak = false

UseMaxGZ = false

UseFirstDF = true

UseVanishingStab = true

LoHeel = 0.0

HiHeel = 30.0

RequiredValue = 0.000

[end]

Appendix B

Page 227

[criterion]

Type = CTStdAngleOfVanishingStab

RuleName = STIX input data

CritName = Angle of vanishing stability

CritInfo = Calculates the angle of vanishing stability…

CritInfoFile = HMCriteriaHelp\StixHelp.rtf

Locked = true


TestIntact = true

TestDamage = false

Test = false

Compare = GreaterThan

RequiredValue = 0.0

[end]

The file must have “Hydromax Criteria File” in the first row. The first section of the

file is the units section and this specifies the units that are to be used in the file. There are two

angular units:

AngleUnits Specifies the units for angular measurements,

e.g. range of stability

GZAreaGMAngleUnits Specifies the angle units used for area under

GZ graph and for GM.

The criteria then appear after the units section and as many criteria as required may be included.

The common parameters for all criteria are as follows: Type Describes the type of criterion

RuleName Text which specifies the rule to which the

criterion belongs

CritName Text which specifies the criterion‟s name CritInfo Verbose description of the criterion

Locked Whether the criterion may be edited in

Hydromax or not. If Locked is set to true, it is

not possible to edit the criterion‟s parameters

in Hydromax

The other parameters that may be set depend on the criterion type.

Appendix F

Page 228

Appendix C: Criteria Help

In this Appendix all individual Parent Criteria are explained in detail. This information can also

be found in the lower right of the Criteria Dialog in the Criteria Help section.

In this section:

Parent Calculations

Minimum GM Calculators

Parent Heeling Arms

Parent Heeling Moments

Parent Stability Criteria

For all general help on criteria or working with the criteria dialog, see Chapter 4 Stability

Criteria on page 163.

Parent Calculations

Special calculations are provided for some criteria parameters. This allows for complex

calculations to be cross referenced into criteria. Currently this has only been implemented for

the IMO roll-back angle calculation used in the IMO code on Intact Stability, severe wind and

rolling (weather) criterion; and the IMO required GM for vessels carrying grain in bulk. If there

are any other calculations that you would like implemented, please contact

[email protected] with details of the required calculations.

The parent calculations are listed above the parent heeling arms:

Parent calculations in Hydromax Criteria dialog

As with other criteria and heeling arms, you should make a copy of the parent calculation by

dragging it to your custom criteria folder.

Selecting a calculation in a criterion

Using a calculation in a criterion is very similar to using a heel arm:

Define your custom calculation by copying it from the parent list.

In the criterion select the required calculation from the pull down list:

Angle calculators

These calculators produce an angular measurement and may be referenced by the following

criteria: Criteria that currently support roll-back angle calculations

Heeling arm

criteria (xRef)

Ratio of areas type 2 XRefHeelRatioOfAreas2

Combined Combined criteria (ratio of areas XRefHeelGenericWindHeeling

mailto:[email protected]

Appendix B

Page 229

heeling arm

criteria (xRef)

type 2)

Heeling arm

criteria (stand

alone)

Ratio of areas type 2 - general

wind heeling arm

CritHeelRatioOfAreas2

Heeling arm,

combined

criteria (stand

alone)

Combined criteria (ratio of areas

type 2) - general wind heeling arm

CritHeelGenericWindHeeling

Heeling arm,

combined

criteria (stand

alone)

Combined criteria (ratio of areas

type 2) - wind heeling arm

CritHeelWindHeeling

IMO roll-back angle calculator

The IMO roll back angle calculator calculates the roll back angle as per the severe wind and

rolling (weather) criterion as defined in the IMO Code on Intact Stability. The input parameters

may be specified by the user or calculated by Hydromax for the vessel in the upright condition

for the current loadcase. The block coefficient is calculated with the current user settings for

length and beam (not necessarily the waterline beam which another parameter required for the

calculation). The method used for the k-factor can be one of three options: “Round bilge: k =

1.0”, “Sharp bilge: k = 0.7” or “Tabulated value for k” – these are auto completed so you only

need to type the first letter.

This calculation follows the function defined in the Intact Stability codes A.749(18) and

MSC.267(85).

Input parameters for: IMO roll-back angle calculation

GM calculators

These calculators produce a GM measurement and may be referenced by the following criteria: Criteria that currently support roll-back angle calculations

GZ curve criteria Value of GMt at (calc) CTStdValueOfGMAt

Minimum GM calculator – Grain

The required GM for vessels carrying grain, as defined in IMO Resolution MSC.23(59), is

calculated as follows:

SF

VBBVBLGM

dd

0875.0

645.025.0

Where (using consistent units):

L is the combined length of all full compartments

Appendix F

Page 230

B is the moulded breadth of the vessel

SF is the stowage factor

Vd is the calculated average void depth

Δ is the vessel displacement

Input parameters for: Grain heeling min. required GM

Minimum GM calculator – Wind pressure

The GM required to withstand wind pressure is calculated as follows:

)sin(

)(cos)(

0

0

2

1

0

nHhAk

Lk

GM


L is the waterline length of the vessel (if the criterion required LPP or LOA then enter the

value directly rather than having it calculated by Hydromax.


0 is a critical heel angle which may be a fixed angle or a fraction of the deck-edge or

marginline immersion angle

A is the windage area which may be specified as a total area or as an area additional to the

area of the hull above the waterline; h is height of the centroid of A above the zero point.

H is the height of the assumed centre of lateral resistance of the vessel.

k0 and k1 are constants, for example:

For CFR 46, 170.170: ocean service:

k0 = 0.005 Ton/ft2 and k1 = 14200 ft

4/Ton

k0 = 0.055 t/m2 and k1 = 1309 m

4/t

For CFR 46, 170.170: service on partially protected water:

k0 = 0.0033 Ton/ft2 and k1 = 14200 ft

4/Ton

k0 = 0.036 t/m2 and k1 = 1309 m

4/t

For CFR 46, 170.170: service on protected water:

k0 = 0.0025 Ton/ft2 and k1 = 14200 ft

4/Ton

k0 = 0.028 t/m2 and k1 = 1309 m

4/t

Appendix B

Page 231

Input parameters for: Wind pressure min. required GM

Minimum GM calculator – Constant

The required GM is calculated as follows:

)(sin

)(cos

0

0

m

naGM


a is a constant arm or moment (depending on whether the vessel displacement is used)



m, n are the exponents for sine and cosine.

An example of where this calculation should be used is in CFR 46, 171.050:

)tan( 0K

NbGM with

K

Nba and m, n = 1.0

Where N is the number of passengers; b is their average transverse location and K is the number

of passengers per unit mass.

Input parameters for: Constant min. required GM

Minimum GM calculator – Constant with freeboard


)(sin

)(cos

0

0

m

n

aff

BaGM


Appendix F

Page 232


B is the vessel beam

f is the minimum freeboard for the upright (zero heel) condition to the deck-edge or

marginline.

fa is the additional freeboard allowance calculated as follows (additionally the freeboard

allowance may be limited to a maximum specified value):

1

02b

B

bb

L

lhkf a




B is the same as that used in the expression for GM

k is a dimensionless constant

h is a height, typically the height of the watertight trunk

l is a length, typically the length of the watertight trunk

b is a breadth, typically the breadth of the watertight trunk

b0 is a constant with the same units as b

b1 is a dimensionless constant

If desired, a heel adjustment may be included:




Parent Heeling Arms

As with the criteria, there is a list of parent heeling arms, from which custom heeling arms may

be derived:

Available heeling arms and moments

To learn how to cross reference these heeling arms into criteria, please see Heeling arm criteria

(xRef) on page 260.

Heeling Arm Definition

This section describes how to define heeling arms and is valid for both the parent heeling arms

that can be cross referenced into the heeling arm criteria, and for the Old heeling arm criteria

where the heeling arm is specified for each criterion separately.

Appendix B

Page 233

There are several heeling arms that are used for the criteria. They are defined below.

General heeling arm

General heeling arm with gust

General cos+sin heeling arm

User Defined Heeling Arm

Passenger crowding heeling arm

Wind

Turning

Lifting heeling

Towing heeling

Forces heeling arm

Trawling heeling arm

Grain heeling arm

Areas and leavers

Important note: heeling arm criteria dependent on displacement

Note:

When you are working with the parent heeling arms, make sure you copy them into

a custom heeling arms folder before editing them. Same as for the Parent criteria,

the Parent heeling arms will be reset to their default values each time you start up

Hydromax.

General heeling arm

The general form of the heeling arm is given below:

)(cos)( nAH where:

is the heel angle,

A is the magnitude of the heeling arm, ncos describes the shape of the curve.

Typically n=1 is used for passenger crowding and vessel turning since the horizontal lever for

the passenger transverse location reduces with the cosine of the heel angle. For wind n=2 is

often used for heeling because both the projected area as well as the lever decrease with the

cosine of the heel angle. However, some criteria, such as IMO Severe wind and rolling (weather

criterion) have a heeling arm of constant magnitude, in this case n=0 should be used.

Make sure you read Important note: heeling arm criteria dependent on displacement on page

240.

General heeling arm with gust

Some criteria require a Gust Ratio, this is the ratio of the magnitude of the wind heeling arm

during a gust to the magnitude of the wind heeling arm under steady wind.

steady

gust

H

HGustRatio

Both the steady and the gust heel arm have the same shape.

)(cos)( n

steady AH

)(cos)( n

gust GustRatioAH

Appendix F

Page 234

where:

is the heel angle,

A is the magnitude of the heeling arm, ncos describes the shape of the curve.

It should be noted, that in this case, the definition of gust ratio is the ratio of the heeling arms.

Some criteria specify the ratio of the wind speeds; if it is assumed that the wind pressure is

proportional to the square of the wind seed, the ratio of the heel arms will be the square of the

ratio of the wind speeds.

General cos+sin heeling arm

Some criteria, notably lifting of weights, require a heeling arm with both a sine and cosine

component:

)(sin)(cos)( mn BAkH

It should be noted that provided the indices are both unity, the same heeling arm form may be

used for computing towing heeling arms of the form:

)sin()cos()( BAkH

in this case a constant angle (in the case of towing, the angle of the tow above the horizontal) is

included.

It may be shown that this is equivalent to:

)sin()cos()( DCkH

where:

)(tan1 2

2RC

, )tan(CD , 222 BAR and A

Btan

Make sure you read Important note: heeling arm criteria dependent on displacement on page

240.

User Defined Heeling Arm

A user-defined heeling arm may be used in the criteria. With the heeling arm, the user can

specify the number of points and the shape of the heeling arm curve.

This heeling arm can then be cross-referenced into any of the heeling arm criteria. First, the

number of points is specified and then for each point the angle and magnitude of the curve can

be specified. These should be comma delimited for example <45 , 1.2> for a heeling arm

magnitude of 1.2 meters at 45 degrees angle of heel. (To aid input of the data, if only one value

is supplied it is taken as the heel angle – and the magnitude is left unchanged, and if a value

preceded by a comma is given, this is taken as the magnitude – and the heel angle is left

unchanged.) A single coefficient may be adjusted and this is used as a multiplication factor

(whist the shape of the curve remains unchanged).

Appendix B

Page 235

Passenger crowding heeling arm

The magnitude of the heel arm is given by:

)(cos)( npas

pc

MDnH

where:

pasn is the number of passengers

M is the average mass of a single passenger

D is the average distance of passengers from the vessel centreline

is the vessel mass (same units as M )

The heeling arm parameters are specified as follows:

Option Description Units

number of passengers:

nPass

Number of passengers none

passenger mass: M Average mass of one passenger mass

distance from

centreline: D

Average distance of the passengers from

the centreline length

cosine power: n Cosine power for curve - defines shape none

Wind heeling arm

In the case of the wind pressure based formulation, the wind heeling arm is given by:

)(cos)( n

wg

HhPAaH

where: a is a constant, theoretically unity

A is the windage area at height h

is the vessel mass

P is the wind pressure

H is the vertical centre of hydrodynamic resistance to the wind force

In the case of the wind velocity based formulation, the wind heeling arm is given by:

Appendix F

Page 236

)(cos)(2

n

wg

HhAvaH

where: a is now effectively an average drag coefficient for the windage area multiplied by the air

density and has units of density v is the wind speed.

And the other parameters are described as above.


constant: a Constant which may be used to modify

the magnitude of the heel arm, normally

unity for pressure based formulation or

0.5 ρair CD for the velocity formulation;

where ρair is the density of air and CD is

an average drag coefficient for the

windage area

none for

pressure

based

formulation;

mass/length3

for velocity

based

formulation

wind model Pressure or Velocity (type “P” or “V”)

wind pressure or

velocity

Actual velocity of pressure - depends on

wind model

mass/(time2

length) or

length/

time

area centroid height: h Height of user defined total or additional

windage area

length

total area: A User may specify either a total windage

area length

2

additional area: A Or, an area to be added to the windage

area computed by Hydromax based on

the hull sections

length2

height of lateral

resistance: H

There are four options for specifying H

(all options are calculated with the vessel

upright at the loadcase displacement and

LCG):

User specified

length

H = mean draft / 2 H is taken as half the mean draft. length

H = vert. centre of

projected lat. u'water

area

H is taken as the vertical centre of

underwater lateral projected area. length

H = waterline H is taken as the waterline length


Turning heeling arm

The magnitude of the heel arm is derived from the moment created by the centripetal force

acting on the vessel during a high-speed turn and the vertical separation of the centres of gravity

and hydrodynamic lateral resistance to the turn. The heeling arm is obtained by dividing the

heeling moment by the vessel weight. The heeling arm is thus given by:

)(cos)(2

n

t hRg

vaH

where (in consistent units): a is a constant, theoretically unity v is the vessel velocity

Appendix B

Page 237

R is the radius of the turn

h is the vertical separation of the centres of gravity and lateral resistance



constant: a Constant which may be used to modify the

magnitude of the heel arm, normally unity

none

vessel speed: v Vessel speed in turn length/time

turn radius: R Turn radius may be specified directly length

turn radius, R, as

percentage of LWL

Or, as some criteria require, as percentage

of LWL %

Vertical lever: h There are four options for specifying h (all

options are calculated with the vessel

upright at the loadcase displacement and

LCG):

User specified

length

h = KG h is taken as KG - position of G above

baseline in upright condition

length

h = KG - mean draft / 2 h is taken as KG less half the mean draft. length

h = KG - vert. centre of

projected lat. u'water

area

h is taken as the vertical separation of the

centres of gravity and underwater lateral

projected area.

length


Lifting heeling arm

This is used to simulate the effect of lifting a weight from its stowage position. (The weight is

lifted from a stowage position onboard the vessel by a crane on the vessel; i.e. the vessel

displacement remains constant, but there is an effective change of its centre of gravity.) The

magnitude of the heel arm is given by:

)sin()cos( )( vhM

H lw

where:

M is the mass of the weight being lifted

h is horizontal separation of the centre of gravity of the weight in its stowage position and the

suspension position (upper tip of lifting boom)

v is vertical separation of the centre of gravity of the weight in its stowage position and the

suspension position (upper tip of lifting boom)

is the vessel mass (same units as M )

Appendix F

Page 238

Just before lifting the weight off the vessel’s deck



Mass being lifted: M Mass of weight being lifted mass

vertical separation of

suspension from

stowage position: v

Vertical separation of suspension point

from weight‟s original stowage position on

the vessel. This value is positive if the

suspension position (upper tip of lifting

boom) is above the original stowage

position.

length

horizontal separation of

suspension from

stowage position: h

Horizontal separation of suspension point

(upper tip of lifting boom) from weight‟s

original stowage position on the vessel

This value is positive if the horizontal shift

of the weight should produce a positive

heeling moment.

length

Towing heeling arm

The magnitude of the heel arm is given by:

)sin()(cos )( hvg

TH n

tow

where:

T is the tension in the towline or vessel thrust, expressed as a force.

h is horizontal offset of the tow attachment position from the vessel centreline

v is vertical separation tow attachment position from the vessel‟s vertical centre of thrust

is the vessel mass

n is the power index for the cosine term which may be used to change the shape of the heeling

arm curve

is the (constant) angle of the towline above the horizontal. It is assumed that the towline is

sufficiently long that this angle remains constant and does not vary as the vessel is heeled.



tension or thrust: T Tension in towline or vessel thrust force

vertical separation of

propeller centre and tow

attachment: v

Vertical separation tow attachment

position from the vessel‟s vertical centre

of thrust. This value is positive if the

towline is above the thrust centre.

length

horizontal offset of tow

attachment: h

Horizontal offset of the tow attachment

position from the vessel centreline. This

value is positive if the offset is in the

direction of the tow.

length

angle of tow above

horizontal: tau

Angle of tow above the horizontal angle


Forces heeling arm

This heeling arm can be used to model up to two forces acting on the vessel forces, such as

those applied due fire-fighting or manoeuvring using thrusters. The magnitude of the heel arm is

given by:

Appendix B

Page 239

)(cosh )(cosh 1

)( 21

2211

nn

forces HAHAg

H

where:

1A and 2A are two forces acting on the vessel, expressed as a force, not a mass.

1h and 2h are the vertical heights (from the zero point) at which these forces act.

1n and 2n define the shapes of the heeling arms created by the two forces.

H is the assumed vertical position of the vessel‟s centre of lateral resistance (or the centre of

rotation from which the forces are applied)

is the vessel mass

g is acceleration due to gravity

Trawling heeling arm

This heeling arm can be used model the effects of trawl net snagging as defined in Annex G of

the Australian NSCV requirements:

)(cos)(trawling

n

m

ymH

where:

m is a mass parameter determined from the breaking load of the trawl gear and the downwards

angle of the trawl net.

y is the transverse distance of the line of action of the trawl wire from the vessel centreline

n defines the shape of the heeling arm.

is the vessel mass

Grain heeling arm

This heeling arm can be used model the effects of bulk grain shift as defined in IMO Resolution

MSC.23(59):

The heeling arm is defined by a straight line through two points A, B. It is mirrored about the

heel=0 axis and is not allowed to go below zero.

Point A = (0 deg heel, λ0)

Point B = ( 1 deg heel, α λ0)

i.e the heeling arm magnitude is reduced by a factor α at a heel angle of 1 . The equation of the

line is given below:

1

0grain

)1(abs1)(H

Appendix F

Page 240

The heeling arm magnitude at zero heel, λ0, is given by:

StowFact

volHM0

Where:

volHM is the assumed volumetric heeling moment due to transverse grain shift in units of

Length3.Length;

StowFact is the stowage factor in units of Length3/Mass; and

is the vessel mass

Areas and levers

Some criteria require the evaluation of above and below water lateral projected areas and their

vertical centroids. The user may also specify additional areas and vertical centroids or the total

areas and vertical centroids. In all cases the vertical centroids are given in the

Maxsurf/Hydromax co-ordinate system; i.e.: from the model‟s vertical datum, positive upwards.

The lateral projected area and its centroid of area are calculated for the upright vessel (zero heel)

at the draft and trim defined in the loadcase or trim dialog. The area is calculated from the

hydrostatic sections used by Hydromax; thus, increasing the number of sections will increase

the accuracy of the area calculation; further, only “Hull” surfaces are included in the calculation

- “Structure” surfaces are ignored.

The vertical position of the keel, K, is assumed to be at the baseline (as set up in the Frame of

Reference dialog), even if the baseline does not correspond to the physical bottom of the vessel.

Important note: heeling arm criteria dependent on displacement

Some heeling arm criteria are dependent on the displacement of the vessel for the calculation of

the Heeling Arm. For example, the value “A” in:

)(cos)( nAH

,is manually calculated from:

MA , where

M = heeling moment

Δ = displacement.

For these types of heeling arms you should use the various heeling moment curves that are

available – see below:

Heeling moment curves

Parent Heeling Moments

Heeling moments work the same way as the Minimum GM Calculations in that they can be

cross referenced into criteria. The advantage of using heeling moments is that they provide a

constant heeling moment (varying heeling arm) as the vessel displacement changes (due to

different loadcases or during a limiting KG analysis).

These are in addition to the existing specific heeling arm curves for passenger crowding, wind

heeling etc., which take account of the vessel displacement as required.

Appendix B

Page 241

The following heeling moments are available in the Hydromax criteria dialog:

General heeling moment

General cos+sin heeling moment

General heeling moment with gust

User Defined Heeling Moment

General heeling moment

The general form of the heeling moment is given below. It allows you to specify a constant

heeling moment as opposed to a constant heeling arm:

)(cos)( nAH

where:

is the heel angle,

A is the magnitude of the heeling moment (mass.length) and the vessel displacement

(mass); thus A

is the magnitude of the heeling arm (length).

ncos describes the shape of the curve.

Typically n=1 is used for passenger crowding and vessel turning since the horizontal lever for

the passenger transverse location reduces with the cosine of the heel angle. For wind n=2 is

often used for heeling because both the projected area as well as the lever decrease with the

cosine of the heel angle. However, some criteria, such as IMO Severe wind and rolling (weather

criterion) have a heeling arm of constant magnitude, in this case n=0 should be used.

General cos+sin heeling moment

Some criteria, notably lifting of weights, require a heeling moment with both a sine and cosine

component:

)(sin)(cos)( mn BAk

H

where:

is the heel angle,

A and B the magnitudes of the cosine and sine components of the heeling moment

(mass.length) and the vessel displacement (mass); thus A

and B

are the magnitude of the

heeling arm (length).

It should be noted that provided the n and m indices are both unity, the same heeling moment

form may be used for computing towing heeling moments of the form:

)sin()cos()( BAk

H

in this case a constant angle (in the case of towing, the angle of the tow above the horizontal) is

included.

It may be shown that this is equivalent to:

)sin()cos()( DCk

H

where:

)(tan1 2

2RC

, )tan(CD , 222 BAR and A

Btan

Appendix F

Page 242

General heeling moment with gust

Some criteria require a Gust Ratio, this is the ratio of the magnitude of the wind heeling arm

during a gust to the magnitude of the wind heeling arm under steady wind.

steady

gust

H

HGustRatio

The general form of the heeling moment is given below. It allows you to specify a constant

heeling moment as opposed to a constant heeling arm. Both the steady and the gust heel moment

have the same shape.

)(cos)( n

steady

AH

)(cosGustRatio)( n

gust

AH

where:

is the heel angle,

A is the magnitude of the heeling moment (mass.length) and the vessel displacement

(mass); thus A

is the magnitude of the heeling arm (length).

ncos describes the shape of the curve.

It should be noted, that in this case, the definition of gust ratio is the ratio of the heeling arms.

Some criteria specify the ratio of the wind speeds; if it is assumed that the wind pressure is

proportional to the square of the wind seed, the ratio of the heel arms will be the square of the

ratio of the wind speeds.

User Defined Heeling Moment

With the User Defined Heeling Moment, the user can specify the number of points and the

shape of the heeling moment curve. Defining User Defined Heeling Moments works in much

the same as for User Defined Heeling Arm. This heeling moment can then be linked into a

Heeling arm criteria (xRef) for evaluation.

Parent Stability Criteria

The parent criteria are divided up into different categories depending on their basic types.

Criteria at Equilibrium

These criteria are calculated after an equilibrium analysis and relate to the equilibrium position

of the vessel after the analysis. The equilibrium criteria are only displayed in the report if you

run an equilibrium analysis.

Maximum value of Heel, Trim or Slope at Equilibrium

This criterion may be used to check the value of maximum Heel, Pitch or Maximum Slope

(compared with an originally horizontal and flat deck).


The angle of Choose from the following (case

insensitive auto-completion is used):

Heel

Pitch

MaxSlope

deg

Appendix B

Page 243

Shall be less than /

Shall not be greater than

Permissible value deg

Minimum Freeboard at Equilibrium

Checks whether the minimum freeboard is greater than a minimum required value. This could

be used to check margin line or downflooding point immersion.


The value of Choose from the following (case


Marginline

DeckEdge

DownfloodingPoints

PotentialDfloodingPoints

EmbarkationPoints

ImmersionPoints

length

Shall be greater than /

Shall not be less than

Permissible value length

Maximum Freeboard at Equilibrium

Check that the maximum freeboard is less than a maximum required value. This could be used

to check that an embarkation point is sufficiently close to the waterline.




Marginline

DeckEdge

DownfloodingPoints

PotentialDfloodingPoints

EmbarkationPoints

ImmersionPoints

length




To check that the freeboard lies within a specified range, use a combination of both forms of the

minimum/maximum freeboard criteria.

Value of GMT or GML at Equilibrium

This criterion is used to check that the GM (transverse or longitudinal) exceeds a specified

minimum value.




GMtransverse

GMlongitudinal)

length




GZ Curve Criteria (non-heeling arm)

These criteria, calculated from the GZ curve, are calculated from the Large Angle Stability

analysis in Hydromax.

Appendix F

Page 244

Value of GMt at

Finds the value of GMt at either a specified heel angle or the equilibrium angle. The criterion is

passed if the value of GMt is greater then the required value. GMt is computed from water-

plane inertia and immersed volume (not the slope of the GZ curve as this is inaccurate if the

heel angle resolution is insufficient).

In addition to a fixed required value, you may also select a calculation to provide the required

minimum GM.


Value of GMt at either

specified heel angle User specified heel angle deg

angle of equilibrium See Nomenclature deg

Select calculation from

list

Chose a calculation for the minimum

required GM from a copy of one of the

Parent calculations

length




Value of GZ at

Finds the value of GZ at either a specified heel angle, first peak in GZ curve, angle of maximum

GZ or the downflooding angle. The criterion is passed if the value of GZ is greater then the

required value.


Value of GZ at either


angle of first GZ peak See Nomenclature deg

angle of maximum GZ See Nomenclature deg

first downflooding

angle

See Nomenclature deg




Value of Maximum GZ

Finds the maximum value of GZ within a specified heel angle range. The criterion is passed if

the value of GZ is greater than the required value. If you want to check the value of GZ at a

certain angle you can set both specified angles as the required angle. If any of the calculated

angles for the upper limit are less than the lower limit, they will be ignored when selecting the

lowest. If all the upper limit values are less than the lower limit, then the criterion will fail. This

functionality is to allow criteria such as “The maximum GZ at 30deg or greater”.

Note: Upper limit and analysis heel angle range

It is required that the range of heel angles specified for the Large Angle Stability

analysis is equal, or exceeds, the upper range heel angle specified in the criterion.


Value of maximum GZ

in the range from the

greater of

Lower limit for heel angle range, the

greater of the following:


angle of equilibrium See Nomenclature

Appendix B

Page 245

to the lesser of Upper limit for heel angle range, the lesser

of the following:

specified heel angle User specified heel angle; this should

normally be specified and be less than or

equal to the upper limit of the range of

heel angles used for the Large Angle

Stability analysis.

deg



first downflooding

angle See Nomenclature deg




Value of Maximum GZ

Value of GZ at Specified Angle or Maximum GZ below Specified Angle

If the angle at which maximum GZ occurs is greater than a specified value, the value of GZ at

the specified angle is calculated. Otherwise the value of maximum GZ is calculated. The

required GZ value depends on the angle at which the maximum occurs, see graph below.


heel angle at which

required GZ is constant

If the angle of maximum GZ is greater

than or equal to this value, the required

value of GZ is constant and is taken at this

specified angle. Otherwise the required

value of maximum GZ varies as a

hyperbolic function with the angle of

maximum GZ. This is 0.

deg

Appendix F

Page 246


required value of GZ at

this angle is

Required value of GZ at the heel angle

specified above. This is 0GZ .

length

limited by first GZ peak

angle

Angle at which GZ is measured may be

limited to the location of the first peak in

the GZ curve.

deg

limited by first

downflooding angle

Angle at which GZ is measured may be

limited to first downflooding angle.

deg



Permissible value. length

If 0maxGZ

then 0GZ must be greater than the specified, constant value.

If 0maxGZ

then maxGZ must be greater than

0

0

max

GZGZ

where:

0 is the specified angle at which the required GZ value becomes a constant

maxGZ is the heel angle at which the maximum GZ of value occurs

0GZ is the GZ value at 0 and

maxGZ is the maximum value of GZ.

Variation of required GZ with angle of maximum GZ

The angle at which the GZ was measured is listed in the results.

Value of RM at Specified Angle or Maximum RM Below Specified Angle

As above (Value of GZ at specified angle or maximum GZ below specified angle) except the

righting moment rather than the righting lever is specified, measured and compared.

The righting moment RM is given by:

gGZRM

where:

is the vessel volume of displacement

is the density of the liquid the vessel is floating in

g is acceleration due to gravity = 9.80665m/s2

GZ is the righting lever.

Appendix B

Page 247

Ratio of GZ Values at Phi1 and Phi2

Calculates the ratio of the GZ values at two specified heel angles. The criterion is passed if the

ratio is less then the required value.

2

1RatioGZ

GZ


Ratio of GZ values at phi1 and phi2

Phi1, first heel angle,

the lesser of

First heel angle, the lesser of the

following:




first downflooding

angle


Phi2, second heel angle,

the lesser of

Second heel angle, the lesser of the

following:




first downflooding

angle




Permissible value %

Ratio of GZ values at phi1 and phi2

Appendix F

Page 248

Angle of Maximum GZ

Finds the angle at which the value of GZ is a maximum positive value, heel angle can be limited

by first peak in GZ curve and/or first downflooding angle. The criterion is passed if the angle is

greater then the required value.


Angle of maximum GZ

limited by first GZ

peak angle

The angle of maximum GZ shall not be

greater than the angle at which the first GZ

peak occurs

deg

limited by first

downflooding angle

The angle of maximum GZ shall not be

greater than the angle at which the first

downflooding occurs

deg




Angle of Equilibrium

Finds the angle of equilibrium from the intersection of the GZ curve with the GZ=0 axis. The

criterion is passed if the equilibrium angle is less then the required value.


Angle of equilibrium




Ratio of equilibrium heel angle to the lesser of

The equilibrium angle and the lesser of the selected angles are compared. If the ratio is less than

the required value, then the criterion is passed. Using a ratio gives more flexibility, e.g.: it is

possible to check that the equilibrium angle does not exceed half (or any other fraction) the

downflooding angle.

The user may choose the type of Key point to define the downflooding angle (downflooding

point, potential downflooding point, embarkation point, immersion point).

If the equilibrium angle is negative, the user is advised that the vessel should be heeled in the

opposite direction and the criterion is failed.


Ratio of equilibrium angle to the lesser of:

spec. heel angle Specified heel angle deg

angle of margin line

immersion

Angle of first immersion of the margin line deg

angle of deck edge

immersion Angle of first immersion of the deck edge deg

first flooding angle of

the

Smallest immersion angle of the specified

type of Key Point

deg

angle of first GZ peak Angle of first local peak in GZ curve deg

angle of max. GZ Angle at which maximum GZ occurs deg

angle of vanishing

stability Angle of vanishing stability deg



Permissible value %

Appendix B

Page 249

Equilibrium heel angle satisfies either

This criterion is nothing more than two “Ratio of equilibrium heel angle to the lesser of”

criteria. The actual criterion is passed if either of the individual criteria is passed. This type of

criterion is used to formulate criteria such as:

The maximum allowable angle of equilibrium is 15 degrees in the damage condition, but

this can be allowed to increase to 17 degrees if the deck edge is not immersed.

Angle of Downflooding

Finds the angle of first downflooding. The criterion is passed if the downflooding angle is

greater then the required value.


Angle of downflooding




Angle of Margin Line Immersion

Finds the first/minimum angle at which the margin line immerses. The criterion is passed if the

smallest angle at which the margin line immerses is greater then the required value.


Angle of margin line immersion




Angle of Deck Edge Immersion

Finds the first/minimum angle at which the deck edge immerses. The criterion is passed if the

smallest angle at which the deck edge immerses is greater then the required value.


Angle of deck edge immersion




Angle of Vanishing Stability

Finds the angle of vanishing stability from the intersection of the GZ curve with the GZ=0 axis.

The criterion is passed if the angle of vanishing stability is greater then the required value.


Angle of vanishing stability




Range of Positive Stability

The angular range for which the GZ curve is positive is computed. The criterion is passed if the

computed range is greater then the required value.


Range of positive stability

from the greater of Lower limit

Appendix F

Page 250




to the lesser of Upper limit of the range

first downflooding


angle of vanishing

stability





GZ Area between Limits type 1 - standard

The area below the GZ curve and above the GZ=0 axis is integrated between the selected limits

and compared with a minimum required value. The criterion is passed if the area under the

graph is greater than the required value.


GZ area between limits type 1 - standard

from the greater of Lower limit for integration, from greatest

angle of



to the lesser of Upper limit of integration, from lesser

angle of


spec. angle above

equilibrium

User specified heel angle above the

equilibrium heel angle deg



first downflooding


immersion angle of

Marginline or

DeckEdge


angle of vanishing

stability




Permissible value length.angle

Appendix B

Page 251

GZ area between limits type 1 - standard

GZ area between limits type 2- HSC monohull type

The area under the GZ curve is integrated between the specified limits. However the required

minimum area depends on the upper integration limit. The required area is defined below and is

based on the area required for IMO MSC.36(63) §2.3.3.2 and IMO A.749(18) §4.5.6.2.1. The

criterion is passed if the computed area under the graph is greater then the required value.

The required area is defined as follows:

If 2max : required area = 2A ;

If 1max : required area = 1A ;

If 2max1 : required area = max2

12

212

AAA

;

Where:

max is the upper integration limit;

1A is the area under the GZ curve required at the specified lower heel angle 1 ; and 2A is the

area under the GZ curve required at the specified higher heel angle 2 .

For example, if the lower angle was 15 and the required area at this angle was 0.07m.rad and

the upper angle was 30 and the required area at this angle was 0.055m.rad, then the required

area would be given by:

max301530

055.007.055.0A

or simplifying:

max30 001.055.0A

Appendix F

Page 252

Variation of required area with upper integration limit


GZ area between limits type 2- HSC

monohull type


angle of



to the lesser of Upper limit of integration, from smallest

angle of


spec. angle above

equilibrium


equilibrium heel angle

deg



first downflooding

angle


angle of vanishing

stability


lower heel angle Minimum angle that requires a GZ area

greater than... Until this angle the required

GZ area is constant

deg

required GZ area at

lower heel angle

Value of GZ area that is required until the

lower heel angle length.angle

higher heel angle Angle from which the required GZ area

remains constant onwards

deg

required GZ area at

higher heel angle

Value of GZ area that is required from the

higher heel angle onwards

length.angle


Shall not be less than Permissible value length.angle

Appendix B

Page 253

GZ area between limits type 2 - HSC monohull type

GZ area between limits type 3 - HSC multihull type

The area under the GZ curve is integrated between the specified limits. However the required

minimum area depends on the upper integration limit ( max11 /A ). The required area is defined below

and is based on the area required for IMO MSC.36 (63) Annex 7 §1.1. The criterion is passed if

the computed area under the graph is greater than the required value.

required area = max11 /A ;

Where:

max is the upper integration limit;

1A is the area under the GZ curve required at the specified heel angle 1 .

For example, if the specified angle ( 1 ) was 30 and the required area at this angle ( 1A ) was

0.055m.rad, then the required area would be given by:

max/30055.0A

Appendix F

Page 254

Variation of required area with upper integration limit


GZ area between limits type 3 - HSC

multihull type


angle of



to the lesser of Upper limit of integration, from lesser

angle of


spec. angle above

equilibrium


equilibrium heel angle deg



first downflooding


angle of vanishing

stability


higher heel angle Heel angle at which required GZ area is

specified

deg

required GZ area at

higher heel angle

Value of GZ area that is required until the

higher heel angle length.angle



Permissible value length.angle

Appendix B

Page 255

GZ area between limits type 3 - HSC multihull type

Ratio of GZ area between limits

This criterion calculates the ratio of the two areas between the GZ curve and the GZ=0 axis.

Ratio = 2 Areaabs

1 Area =

dGZ

dGZ

4

3

2

1

abs

, where “abs” means the absolute value of.


Ratio of GZ area between limits

Area 1 from the greater of Area 1 lower integration limit, 1



Area 1 to the lesser of Area 1 upper integration limit, 2 deg




first downflooding angle See Nomenclature deg

angle of vanishing stability See Nomenclature deg

Area 2 from the lesser of Area 2 lower integration limit, 3






Appendix F

Page 256


Area 2 to Area 1 upper integration limit, 4




Permissible value %

This criterion is designed to be calculated on the positive side of the GZ curve only; GZ areas

below the GZ=0 axis on the negative heel angle side of the GZ curve are not considered

positive. Typically, Area 1 would be from equilibrium to vanishing stability and Area 2 would

be from vanishing stability to 180 deg, see graph below.

In the example below, the lower and upper integration limits for Area 1 are equilibrium and

vanishing stability, respectively and the limits for Area 2 are vanishing stability and 180 deg.

Ratio of GZ area between limits – Example 1

In the following example the upper limit for Area 1 has been set to the downflooding angle. The

limits for Area 2 remain unchanged.

Appendix B

Page 257


In the final example, the lower integration range for Area 2 has been reduced to the

downflooding angle. Note that Area 2 is now A1 – A2.


Ratio of positive to negative GZ area between limits

This criterion calculates the ratio of GZ area above the GZ=0 axis to that below the axis in the

given heel angle range.


Appendix F

Page 258


Ratio of positive to negative GZ area

between limits

in the heel angle range from User specified lower limit heel angle deg

to User specified upper limit heel angle deg



Permissible value %

Ratio = 2 Areaabs

1 Area,

where “abs” means the absolute value of. And the areas are defined as follows:

If both heel angle limits are ≥ zero: Area 1 is the total area between the GZ curve and GZ=0

axis, where the value of GZ > 0; Area 2 is the total area between the GZ curve and GZ=0 axis,

where the value of GZ < 0. Area 1 is positive, Area 2 is negative.

Ratio of positive to negative GZ area between limits. Positive heel: lower limit = 0deg, upper limit = 180deg.

If both heel angle limits are < zero: Area 1 is the total area between the GZ curve and GZ=0

axis, where the value of GZ < 0; Area 2 is the total area between the GZ curve and GZ=0 axis,

where the value of GZ > 0. Area 1 is positive, Area 2 is negative.

Appendix B

Page 259

Ratio of positive to negative GZ area between limits. Negative heel: lower limit = -180deg, upper limit = 0deg.

If the lower heel angle limit < zero, and the upper heel angle limit > zero (the upper limit is

assumed to be greater than the lower limit): Area 1 is the total area between the GZ curve and

GZ=0 axis, where the value of GZ > 0 for heel angles ≥ 0 plus the area between the GZ curve

and GZ=0 axis, where the value of GZ < 0 for heel angles < 0; Area 2 is the total area between

the GZ curve and GZ=0 axis, where the value of GZ < 0 for heel angles ≥ 0 plus the area

between the GZ curve and GZ=0 axis, where the value of GZ > 0 for heel angles < 0. Area 1 is

positive, Area 2 is negative.

Ratio of positive to negative GZ area between limits. Positive and negative heel: lower limit = -180deg, upper limit = 180deg.

Appendix F

Page 260

Subdivision Index s-factor - MSC 19(58)

Probabilistic damage s-factor according to MSC 19(58)


Lower angle of range : the

greater of

The greater of the selected angles is be

to specify the lower limit of the range

of positive stability and the range in

which the maximum value of GZ

should be found.



Upper angle of range: lesser

of

The lowest of the selected angles is be

to specify the upper limit of the range

of positive stability and the range in

which the maximum value of GZ

should be found.

specified heel angle See Nomenclature deg

spec. angle above

equilibrium





immersion angle of

Marginline or DeckEdge See Nomenclature deg


Max. GZ limit Upper limit of allowable maximum

GZ value when computing s

length

Range limit Upper limit of allowable range of

positive stability when computing s

deg

S = C sqrt( 0.5 GZmax . range)

Both the values of maximum GZ and range of positive stability can be clipped.

Heeling arm criteria (xRef)

The cross-reference heeling arm criteria are set up to allow you to define heeling arms or

heeling moments in a central location and then cross-reference or link them into the criteria. The

criteria themselves work much the same as the Heeling arm criteria (page 264), except for the

fact that you don‟t have to specify the heeling arm for each criterion separately, but can simply

select which heeling arm you wish to apply.

After you have defined your heeling arms, these can be cross-referenced into new heeling arm

criteria:

Appendix B

Page 261

The heeling arms are cross-referenced simply by selecting the desired heeling arm from the

pull-down list:

For information on defining heeling arms or moments, see Minimum GM calculator – Grain

The required GM for vessels carrying grain, as defined in IMO Resolution MSC.23(59), is

calculated as follows:

SF

VBBVBLGM

dd

0875.0

645.025.0


L is the combined length of all full compartments

B is the moulded breadth of the vessel

SF is the stowage factor

Vd is the calculated average void depth


Input parameters for: Grain heeling min. required GM

Appendix F

Page 262

Minimum GM calculator – Wind pressure

The GM required to withstand wind pressure is calculated as follows:

)sin(

)(cos)(

0

0

2

1

0

nHhAk

Lk

GM







A is the windage area which may be specified as a total area or as an area additional to the

area of the hull above the waterline; h is height of the centroid of A above the zero point.

H is the height of the assumed centre of lateral resistance of the vessel.

k0 and k1 are constants, for example:

For CFR 46, 170.170: ocean service:

k0 = 0.005 Ton/ft2 and k1 = 14200 ft4/Ton

k0 = 0.055 t/m2 and k1 = 1309 m4/t

For CFR 46, 170.170: service on partially protected water:


k0 = 0.036 t/m2 and k1 = 1309 m4/t

For CFR 46, 170.170: service on protected water:


k0 = 0.028 t/m2 and k1 = 1309 m4/t

Input parameters for: Wind pressure min. required GM

Minimum GM calculator – Constant


)(sin

)(cos

0

0

m

naGM





Appendix B

Page 263


An example of where this calculation should be used is in CFR 46, 171.050:

)tan( 0K

NbGM with

K

Nba and m, n = 1.0

Where N is the number of passengers; b is their average transverse location and K is the number

of passengers per unit mass.

Input parameters for: Constant min. required GM

Minimum GM calculator – Constant with freeboard


)(sin

)(cos

0

0

m

n

aff

BaGM



B is the vessel beam

f is the minimum freeboard for the upright (zero heel) condition to the deck-edge or

marginline.

fa is the additional freeboard allowance calculated as follows (additionally the freeboard

allowance may be limited to a maximum specified value):

1

02b

B

bb

L

lhkf a




B is the same as that used in the expression for GM

k is a dimensionless constant

h is a height, typically the height of the watertight trunk

l is a length, typically the length of the watertight trunk

b is a breadth, typically the breadth of the watertight trunk

b0 is a constant with the same units as b

b1 is a dimensionless constant

If desired, a heel adjustment may be included:




Parent Heeling Arms on page 229.

Appendix F

Page 264

Heeling arm criteria

The preferred method is to use the xRef heeling arm criteria rather than the stand alone heeling

arm criteria. This is because a wider range of heeling arm formulations is available and for some

criteria, they only exist in xRef form.

The heeling arm criteria available in the Hydromax Criteria dialog are listed below. Also

available are:

Multiple heeling arm criteria; these are where the same criterion is applied to up to three

heeling arms and/or combinations of these heeling arms

Heeling Arm, combined criteria; these are where several criteria are applied to the same

heeling arm

Value of GMT at equilibrium - general heeling arm

Calculates the transverse metacentric height (GMT) at the intersection of the GZ and heel arm

curves. The criterion is passed if the GMT value is greater then the required value. GMT is

computed from the waterplane inertia and the displaced volume at the equilibrium heel angle.

Ratio of GMT and heeling arm

Calculates the following ratio and the criterion is passed if the ratio exceeds the specified value.

)()sin( HAGM

Where the heel angle, , is the lesser of: a user-specified heel angle; angle of margin line

immersion; angle of deck edge immersion; or first flooding angle of the specified key point

type. In addition, this angle may also be multiplied by a user-specified factor. The specified

cross-referenced heel arm is then evaluated at this heel angle to give: )(HA . Finally, The

transverse GM is taken at a user-specified heel angle or angle of equilibrium (without heel arm).

Ratio of GMt and heel arm criterion

Value of GZ at equilibrium - general heeling arm

Calculates the value of the GZ curve at the equilibrium intersection of the GZ and heel arm

curves. The criterion is passed if the GZ value is greater then the required value.

Appendix B

Page 265

Value of GZ at equilibrium - general heeling arm

Value of maximum GZ above heeling arm

Finds the maximum value of (GZ - heel arm) at or above a specified heel angle. The first

downflooding angle may be selected as an upper limit. The criterion is passed if the value of

(GZ - heel arm) is greater then the required value.

Appendix F

Page 266

Value of maximum GZ above heeling arm

The upper limit may be specified as a certain percentage of the selected limits. This is applied to

all selected upper angle limits, including “specified heel angle”. However this option would

normally be used to specify an upper limiting angle of “half the angle of margin line

immersion”.

Maximum ratio of GZ to heeling arm

This criterion calculates the maximum ratio of GZ : Heeling arm (for the same heel angle)

within the range of heel angles specified. The value of GZ at this heel angle must be greater

than zero. If the heeling arm is zero or negative in the range, then the point with maximum

positive GZ (where the heeling arm 0.0) will be selected.




immersion”.

Examples:

Upper limit is 50% of angle of margin line immersion (43 / 2 = 21.5 ). In the range 0 to 21.5 , the maximum ratio of

GZ:heel arm occurs at 21.5 . At this heel angle the value of GZ is 0.553m and the heel arm 0.930m giving a ratio of 59%.

Appendix B

Page 267

In this case a constant heeling arm is used, thus the maximum ratio occurs at the angle of maximum GZ (62.4 ). At this heel angle the value of GZ is 1.122m and the heel arm 0.5m giving a ratio of 224%.

Finally, the downflooding angle is 94.3 , at this heel angle the heel arm is zero (thus the ratio infinite). Hence the criterion is passed. The angle and value of GZ is given for the location where it is a maximum (in the region where the heel arm is zero; the exact value will depend slightly on the heel angles tested in the Large Angle Stability analysis.)

Appendix F

Page 268

The same is true if an unusual user-defined heeling arm is used. In this case the heeling arm is zero between 50 and

70 . Hence the maximum ratio reported is infinity and occurs at the angle where GZ is maximum in this heel angle range.

Minimum ratio of GZ to heeling arm

This criterion calculates the minimum ratio of GZ : Heeling arm (for the same heel angle)

within the range of heel angles specified. And checks that this ratio is greater than a specified

value. This criterion can be used to check that the GZ is at least as great as the heeling arm over

the specified range. If a heeling arm with zero amplitude is used, the same criterion may be used

to check that the GZ is positive over the specified range.




immersion”.

Ratio of GZ values at phi1 and phi2 - general heeling arm

Used to check the ratio of GZ values at two points on the GZ curve. The heel arm is used to

define the equilibrium angle and the heel angle where (GZ - heel arm) is maximum. The

criterion is passed if the ratio is less than the required value.

Ratio = 2

1

GZ

GZ

Angle of maximum GZ above heeling arm

Calculates the heel angle at which the difference between the GZ curve and the heeling arm is

greatest (GZ - Heel Arm is maximum, positive). The criterion is passed if the angle is greater

then the required value.

Appendix B

Page 269

Angle of maximum GZ above heeling arm - general heeling arm

Angle of equilibrium - general heeling arm

Calculates the angle of equilibrium with the specified heeling arm. The equilibrium angle is the

smallest positive angle where the GZ and heeling arm curves intersect and the GZ curve has

positive slope. The criterion is passed if the equilibrium angle is less then the required value.

Angle of equilibrium - general heeling arm

Appendix F

Page 270

Angle of equilibrium ratio - general heeling arm

Calculates the ratio of the angle of equilibrium (with the specified heeling arm) to another,

selectable angle. The angle of equilibrium is computed as described in §Angle of equilibrium -

general heeling arm.

Ratio =

specified

mequilibriu

The other angle used to compute the ratio may be one of the following:

Required angle for ratio calculation Auto complete text

Marginline immersion angle MarginlineImmersionAngle

Deck edge immersion angle DeckEdgeImmersionAngle

Angle of first GZ peak DownfloodingAngle

Angle of maximum GZ MaximumGZAngle

First downflooding angle FirstGZPeakAngle

Angle of vanishing stability with heel arm VanishingStabilityWithHeelArmAngle

Angle of vanishing stability - general heeling arm

Calculates the location of the first intersection of the GZ curve and heel arm curve where the

slope of the GZ curve is negative. The criterion is passed if the angle is greater then the required

value. This criterion should not be confused with the range of positive stability.

Angle of vanishing stability - general heeling arm

Range of positive stability - general heeling arm

Computes the range of positive stability with the heeling arm.

[Range of stability] = [Angle of vanishing stability] – [Angle of equilibrium]

The criterion is passed if the value of range of stability is greater then the required value.

Appendix B

Page 271

Range of positive stability - general heeling arm

GZ area between limits type 1 - general heeling arm

Computes the area below the GZ curve and above the heel arm curve between the specified heel

angles. The criterion is passed if the area is greater than the required value.

Area =

2

1

)(arm heel)( dGZ


Appendix F

Page 272


The area between the GZ curve and heel arm and the area under the GZ curve is computed

(Area 1). The required value is based on a constant plus a proportion of the area under the GZ

curve (Area 2). The criterion is passed if the ratio is greater than the required value.

Area 1 =

2

1

)(arm heel)( dGZ;

Area 2 =

4

3

)( dGZ;

2 Areaconstant1 Area k


Ratio of areas type 1 - general heeling arm

The ratio of the area between the GZ curve and heel arm and the area under the GZ curve is

computed. This criterion is based on the area ratio required by various Navies‟ turning and

passenger crowding criteria. Type 1 stands for which areas are being integrated to calculate the

ratio (see graph). The criterion is passed if the ratio is greater than the required value.

Area 1 =

2

1

)(arm heel)( dGZ;

Area 2 =

4

3

)( dGZ;

Appendix B

Page 273

Ratio = 2 Area

1 Area



This criterion is used to simulate the effects of wind heeling whilst the vessel is rolling in

waves. Because of the many different ways in which this criterion is used it has several options

for defining the way in which the areas are calculated.

If a gust ratio of greater than 1.0 is used, the vessel is assumed to roll to windward (under the

action of waves with the steady wind pressure acting on it, then roll to leeward under a gust.

Hence the rollback angle is taken from the equilibrium angle with the steady wind heeling arm,

but the integration for Area 1 is taken from the equilibrium with the gust wind heeling arm.

The roll back may be specified as either a fixed angular roll back from the angle of equilibrium

with the steady wind heel arm or can be rolled back to the vessel equilibrium angle ignoring the

wind heeling arms (i.e.: where the GZ curve crosses the GZ=0 axis with positive slope).

Note

The Large Angle Stability analysis heel angle range should include a sufficient

negative range to allow for the rollback angle. For more information see: §Heel.

Area 1 =

2

1

)(arm heelgust )( dGZ

Area 2 = 2

1

)()(arm heelgust dGZ

Appendix F

Page 274

Ratio = 2 Area

1 Area



The ratio of the area under the GZ curve to the area under the heel arm curve is computed. This

criterion is based on the area ratio required by BS6349-6:1989. The criterion is passed if the

ratio is greater than the required value. Areas under the GZ=0 axis are counted as negative.

Area GZ = 2

1

)( dGZ ;

Area HA = 2

1

)(arm heel d ;

Ratio = HA Area

GZ Area

Appendix B

Page 275


Multiple heeling arm criteria

These criteria are used to check the effects of combinations of up to three heeling arms and their

combinations, for example passenger crowding, turning, wind.

The combined heeling arms are computed by adding the values of the individual heeling arms at

each heel angle.

Ratio of GZ values at phi1 and phi2 - multiple heeling arms

Checks the ratio of GZ values as per §Ratio of GZ values at phi1 and phi2 - general heeling arm

with the specified heeling arms.

Appendix F

Page 276

Ratio of GZ values at phi1 and phi2 - multiple heeling arms

Angle of equilibrium - multiple heeling arms

Checks the equilibrium heel angle as per §Angle of equilibrium - general heeling arm with the

specified heeling arms.

Angle of equilibrium - multiple heeling arms

GZ area between limits type 1 - multiple heeling arms

Checks the area under the heel angle as per §GZ area between limits type 1 - general heeling

arm with the specified heeling arms.

Appendix B

Page 277



Checks the area under the heel angle as per §GZ area between limits type 2 - general heeling

arm with the specified heeling arms.

Area 1 =

2

1

)(arm heel)( dGZ;

Area 2 =

4

3

)( dGZ;

2 Areaconstant1 Area k

Appendix F

Page 278


Ratio of areas type 1 - multiple heeling arms

Checks the area under the heel angle as per §Ratio of areas type 1 - general heeling arm with the

specified heeling arms.

Appendix B

Page 279

Ratio of areas type 1 - multiple heeling arms

Subdivision Index s-factor - MSC_216(82)

The Subdivision Index s-factor as described in IMO MSC.216(82) is computed. Several extra

options are presented to the user.

Appendix F

Page 280


Subdivision Index s-factor –

MSC.216(82)

Vessel type :

Passenger, Cargo,

User

The type of vessel being analysed. This

is used to determine default parameters

and which s-factors should be

computed.

Upper angle of range:

lesser of

The lowest of the selected angles can

be used to specify the upper limit of the

range of positive stability. The

beginning of the range of positive

stability is taken as the first positive

equilibrium angles

first downflooding

angle


angle of vanishing

stability


Immersion angle of

Marginline or

DeckEdge


s-Final Parameters for computing the s-Final

factor

Max. GZ limit Upper limit of allowable maximum GZ

value when computing s-Final

length


positive stability when computing s-

Final

deg

K-factor min. heel Theta_min used to determine K deg

K-factor max. heel Theta_max used to determine K deg

s-Intermediate Parameters for computing the s-

Intermediate factor

Max. GZ limit Upper limit of allowable maximum GZ

value when computing s-Intermediate

length


positive stability when computing s-

Intermediate

deg

Max. allowable

equilibrium heel angle

Maximum allowable equilibrium heel

angle after damage. If the equilibrium

heel angle exceeds this value then s-

Intermediate is zero.

deg

s-Moment Parameters for computing the s-

Moment factor

intact displacement at

subdivision draft

Displacement of the intact vessel at the

subdivision draft

mass

GZ reduction Reduction to be applied to maximum

GZ

length

Passenger heel Link to passenger heeling moment mass.length

Appendix B

Page 281

moment

Wind heel moment Link to wind heeling moment mass.length

Select survival craft

heel moment

Link to heeling moment that defines

the effect of launching survival craft

mass.length



Permissible minimum value for s-

factor

Vessel type:

If Passenger is selected, then s-Intermediate and s-Moment factors are computed. For the s-Final

factor, the minimum and maximum heel angles are set to 7 and 15 deg. respectively. The

criterion result is then the minimum value of s-Intermediate and (s-Final * s-Moment).

If Cargo is selected, then only the s-Final factor is computed and in this case, the minimum and

maximum heel angles are set to 25 and 30 deg. respectively.

If User is selected, then all three s-factors are computed as for the Passenger ship, and any

values for the s-Final factor minimum and maximum heel angles may be specified.

s-Final = K. {GZmax / limitGZmax . Range / limitRange}1/4

where:

K = 1 if equilibrium heel <= Theta_min

K = 0 if equilibrium heel >= Theta_max

K = {(Theta_max – equilibrium heel) / (Theta_max – Theta_min)}1/2

s-Intermediate = {GZmax / limitGZmax . Range / limitRange}1/4

if equilibrium heel > Max. allowable equilibrium heel angle then s-Intermediate = 0

s-Moment = (GZmax – GZ reduction) . Displacement / Mheel

where: Mheel is the maximum of the three selected heeling moments.

The result is the minimum of s-Intermediate and (s-Final * s-Moment).

All s-factors are in the range 0 <= s <= 1

Heeling arm, combined criteria

Several criteria require the evaluation of several individual criteria components. Although it is

possible to evaluate these criteria by evaluation of their individual components, for simplicity

the common combinations have been combined into single criteria.

Note:

At least one of the individual criteria has to be selected.

Combined criteria (ratio of areas type 1) - general heeling arm

This is a combined criterion where three individual criteria must be met. These are:

1. Angle of steady heel must be less than a specified value. The Angle of steady heel is

obtained as per §Angle of equilibrium - general heeling arm.

2. The area ratio must be greater than a specified value. The area ratio is evaluated as per §


3. The ratio of the value of GZ at equilibrium to the value of maximum GZ must be less than a

specified value.

Appendix F

Page 282

Combined criteria (ratio of areas type 1) - general heeling arm

Combined criteria (ratio of areas type 2) - general wind heeling arm

This is a widely applicable wind heeling criterion in its most generic format. The heeling arm is

specified simply by a magnitude and cosine power. Optionally, a gust wind can be applied.

1. Angle of steady heel must be less than a specified value. The angle of steady heel is obtained

as per Angle of equilibrium - general heeling arm.

2. The area ratio must be greater than a specified value. The area ratio is evaluated as per Ratio

of areas type 2 - general heeling arm.

3. The ratio of the value of GZ at equilibrium to the value of maximum GZ must be less than a

specified value.

Note



Appendix B

Page 283

Area definition

If required, a reduction of the GZ curve may be applied. If this is done, all calculations are done

using a reduced GZ‟ curve which is computed at each heel angle as follows:

)(cos)()(' mBGZGZ

This criterion may be used to evaluate the following specific criteria (as well as many others of

similar format):

Appendix F

Page 284

US Navy DDS079-1: §079-1-c(9) 1, §079-1-c(9) 4,

Royal Navy NES 109: §1.2.2, §1.3.5, §1.4.2 Initial impulse and Wind heeling criteria

RAN A015866: §4.4.4.2, §4.8, §4.9.5

IMO A.749(18) Code on intact stability: §3.2

IMO MSC.36(63) High-speed craft code §2.3.3.1

ISO/FDIS 12217-1:2002(E) Small Non-Sailing Boats §6.3.2

Combined criteria (ratio of areas type 2a) - general heeling arm

This criterion is based on the calculations required for the Bureau Veritas criterion that ensures

safety when cargo is accidentally lost while lifting. The criterion evaluates two checks: ratio of

Area2 / Area1 and the remaining range of stability (phi3 – phi2).

PhiC is fixed at the angle of equilibrium with the heeling arm (first up-crossing intersection of

GZ curve with heeling arm).

Area2 / Area1 must be greater than the required value

phi2 - phi3 must be greater than the required value

Appendix B

Page 285


Combined criteria (ratio of areas type

2a)

Area1 integrated from

the greater of (phi1)

Angle that defines the lower heel angle

for the integration range of Area1. The

lesser of the following three options

spec. heel angle

(equilibrium angle

during lifting)

A specified, fixed heel angle deg

roll back from angle

of equilibrium with

heeling arm

A roll-back angle (positive) from the

angle of equilibrium with the heeling

arm (first up-crossing intersection of

the GZ and heeling arm curves)

deg

angle of equilibrium

(without heel arm)

Roll back to the angle of equilibrium of

the vessel (ignoring the heeling arm)

deg

Area2 integrated to

the lesser of (phi2)

Upper integration limit of Area2

chosen from the lesser of the seven

options.

deg

Max. heeling angle

due to roll taken as the

lesser of (phi3)

This angle is used to evaluate the

second part of the criterion: the

difference phi2-phi3 must be greater

than the required value.

phi3 may be determined from a number

of features of the GZ curve including

being chosen such that Area3/Area1 is

some specified value.

deg

angle at which Area3 /

Area1 is

The required ratio of Area3/Area2 used

to determine the angle phi3

deg

Note



Derived heeling arm criteria

For these criteria, the magnitude of the heeling arm is derived (rather than specified directly)

from a required relationship between the GZ curve and the heeling arm curve. The shape of the

heeling arm (e.g. cos1.3

) must be specified. The heeling arm is normally derived from a GZ

value, GZ area or angle of equilibrium requirement.

The criterion is then evaluated by comparing some requirement of the derived heeling arm with

a specified value.

GZ derived heeling arm

This criterion is used to calculate the amplitude of a heeling arm derived from the value of GZ

at a certain heel angle. The GZ value used to define the heeling arm is the GZ at one of the

following heel angles:

Appendix F

Page 286

specified angle of heel

angle of first peak in GZ curve

angle at which maximum GZ occurs

angle of first downflooding

immersion angle of margin line or deck edge

The heeling arm is then calculated as described by the equation below, and is then compared

with a minimum required value.

n

GZA

cos

where:

A Amplitude of heeling arm

n Shape of heeling arm (n = 0 for constant heeling arm)

Specified heel angle

GZ Value of GZ at specified heel angle

Required ratio = HAGZ /

GZ area derived heeling arm type 1

This criterion is used to calculate the amplitude of a heeling arm derived from the area under the

GZ curve between specified limits. The area under both the GZ and heeling arm curves is

integrated between the same specified limits, see below.

Lower integration limit, 1 :

specified angle of heel

angle of equilibrium

Upper integration limit, 2 :

spec. heel angle

spec. angle above equilibrium

angle of first GZ peak

angle of max. GZ

first downflooding angle

angle of vanishing stability

It is also possible to specify a minimum heel angle for the upper integration limit. Any negative

areas (due to negative GZ) up to this minimum upper integration heel angle will be deducted

from the total area under the GZ curve.

The amplitude of the heeling, which satisfies the equation below arm is then found and

compared with a minimum required value. 2

12

1

d d cos

GZA n

A Amplitude of heeling arm

n Shape of heeling arm (n = 0 for constant heeling arm)

heel angle

GZ GZ curve

Required ratio

Appendix B

Page 287

GZ area derived heeling arm type 2

This criterion is used to simulate the effects of wind heeling whilst the vessel is rolling in

waves. Because of the many different ways in which this criterion is used it has several options

for defining the way in which the areas are calculated. With the wind pressure acting on it, the

vessel is assumed to roll to windward under the action of waves and then roll to leeward. The

rollback angle is taken from the equilibrium angle with the wind heeling arm.

A heeling arm of prescribed shape is found such that the specified area ratio is met. The

amplitude of the heeling arm is then compared with a required minimum value.

The roll back may be specified as either:

a fixed angular roll back from the angle of equilibrium with the wind heel arm;

roll back to the vessel equilibrium angle ignoring the wind heeling arms (i.e.: where the GZ

curve crosses the GZ=0 axis with positive slope); or

roll back to a specified heel angle.

Note



Area 1 = 2

1

)(arm heel)( dGZ

Area 2 = 2

1

)()(arm heel dGZ

Ratio = 2 Area

1 Area

GZ area derived heeling arm (type 2) - general heeling arm

Angle of equilibrium - GZ derived wind heeling arm

The derived wind heeling criterion is used to check that the steady heel angle due to wind

pressure exceeds a certain value. The steady heel arm is derived from a gust of specified ratio.

The wind gust will cause the vessel to heel over to the lesser of a specified heel angle, angle of

the first GZ peak, angle of maximum GZ or the first downflooding angle.

Appendix F

Page 288

The vessel is assumed to be safe from gusts up to the specified ratio, if the angle of steady heel

is greater than the angle. This means that the lesser of: a specified heel angle, first peak in GZ

curve, angle of maximum GZ or the first downflooding angle, should be large enough to

withstand a gust from a steady wind heeling angle larger than ….

Angle of equilibrium - derived wind heeling arm

Ratio of equilibrium angles - GZ area derived heeling arm

This criterion is used to compare the equilibrium angles with two different heeling arms. The

first equilibrium angle, φ1, is the angle of equilibrium with a derived heeling arm. The second

equilibrium angle, φ2, is the angle of equilibrium with a specified heeling arm.

The derived heeling arm is chosen such that the areas, A1 and A2, are in the specified ratio.

There are several options which can be used to define the upper and lower ranges for the area

integrations. The specified heeling arm is specified by an amplitude and cosine power; the same

cosine power is used for both the specified and the derived heeling arms.

Appendix B

Page 289

Ratio of equilibrium angles - derived heeling arm

Area 1 = 2

1

)(arm heel)( dGZ

Area 2 = 2

1

)()(arm heel dGZ

Ratio of areas = 2 Area

1 Area

φ1 = Angle of equilibrium with heeling arm derived from required area ratio (purple heeling

arm)

φ2 = Angle of equilibrium with specified heeling arm (orange heeling arm)

The criterion is passed if the ratio φ2 : φ1 is less than the required value. Thus if it is required

that φ2 be less than φ1, then the ratio φ2 : φ1 must be less than unity.


A Magnitude of specified heeling arm length

n Cosine power to describe shape of both

specified and derived heelning arms

required area ratio

Area1 / Area2

The required area ratio used to find the

derived heeling arm magnitude

options Specify lower integration limit for Area1 deg

options Specify upper integration limit for Area1 deg

options Specify lower integration limit for Area2; the

upper integration limit is always the angle of deg

Appendix F

Page 290

equilibrium with derived heel arm

required value Specifies the maximum allowable ratio of

equilibrium heel angle with the specified heel

arm to the equilibrium heel angle with the

derived heel arm (phi2 / phi1). This value is

normally less than or equal to 100%,

indicating that the equilibrium heel angle with

the specified heel arm must be less than the

equilibrium heel angle with the derived heel

arm

Note



Other combined criteria

Other criteria, which do not easily fall into the categories above, are found here.

Other criteria - STIX

The stability index criterion or STIX criterion as described in ISO/FDIS 12217-2:2002(E) is

used to assess the stability of sailing craft. The required input parameters are described below.

Please refer to ISO/FDIS 12217-2:2002(E) for exact definitions of parameters and how they

should be calculated.


delta Adjustment to STIX rating, either 0 or 5.

5 if the vessel, when fully flooded

with water, has reserve buoyancy and

positive righting lever at a heel angle of 90º

. 0 in all other cases.

AS, sail area ISO 8666 Sail area as defined in ISO 8666. Note that

no additional windage areas are calculated

by Hydromax for this criterion.

length2

height of centroid of

AS

Height of sail area centre of effort from

model‟s vertical datum (not necessarily the

waterline, this is not the same as the STIX

variable CEh which is measured from the

waterline, positive up).

length

LH, length Hull length as defined by ISO 8666. This

may be either specified or calculated by

Hydromax. Hydromax calculates this

parameter as the overall length of the

vessel (all hull surfaces) in the upright,

zero trim condition.

length

BH, beam of hull Hull beam as defined by ISO 8666. This



parameter as the overall beam of the vessel

(all hull surfaces) in the upright, zero trim

condition.

length

Appendix B

Page 291


LWL, length waterline Hull waterline length in the current load

condition as defined by ISO 8666. This



parameter as the waterline length of the

vessel (all hull surfaces) at zero heel and at

the loadcase displacement and centre of

gravity; if the analysis is carried out free-

to-trim, the waterline of the trimmed vessel

is used.

length

BWL, beam waterline Hull waterline beam in the current load

condition as defined by ISO 8666. This



parameter as the waterline beam of the

vessel (all hull surfaces) at zero heel and at




is used.

length

height of immersed

profile area centroid Height of centre of the lateral projected

immersed area of the hull from model‟s

vertical datum (not necessarily the

waterline, this is not the same as the STIX

variable LPh ); may be specified or

calculated by Hydromax. Hydromax

calculates this parameter at zero heel and at




is used.

length



Hydromax uses the numerical STIX rating

value rather than the STIX design category.

Hydromax calculates the various factors and STIX rating according to ISO/FDIS 12217-

2:2002(E). Note that a downflooding angle is required to calculate the STIX index. Hence, if no

downflooding points are defined, or defined downflooding points do not immerse within the

selected heel angle range, the angle of downflooding is taken to be the largest heel angle tested.

This affects the calculation of the Wind Moment and Downflooding factors.

Specific stand alone heeling arm criteria

These criteria provide some specific stand alone heeling arm criteria. They are included for

compatibility with criteria sets defined in earlier versions of Hydromax, but it is highly

recommended to use the equivalent xRef criteria with the desired heeling arms.

Stand alone heeling arm criteria

Angle of equilibrium - passenger crowding heeling arm

Calculates the angle of equilibrium with the heeling arm due to passenger crowding applied.

The heeling arm is calculated from the number, weight and location of the passengers, see

§Passenger crowding.

Appendix F

Page 292

Angle of equilibrium - high-speed turn heeling arm

Calculates the angle of equilibrium with the heeling arm due to high speed turning applied. The

heeling arm is calculated from the turn radius, vessel speed and height of the vessel‟s centre of

gravity, see §Turning.

Ratio of areas type 1 - general cos+sin heeling arm

This is a very similar criterion to § Ratio of areas type 1 - general heeling arm; the only

difference being the shape of the heel arm. In this criterion the heel arm has both a sine and a

cosine component. This is used to simulate the effects of lifting weights and is used by several

Navies.

The modified form of the heeling arm is given below, for further information also see §General

cos+sin heeling arm

)(sin)(cos)( mn BAkH

Area 1 =

2

1

)(arm heel)( dGZ ;

Area 2 =

4

3

)( dGZ ;

Ratio = 2 Area

1 Area

Stand alone heeling arm combined criteria

Combined criteria (ratio of areas type 1) - passenger crowding

This criterion is essentially the same as its generic form: Combined criteria (ratio of areas type

1) - general heeling arm, however the heel arm is the specific passenger crowding form.

Combined criteria (ratio of areas type 1) - high-speed turn


1) - general heeling arm, however the heel arm is the specific high-speed turning form.

Combined criteria (ratio of areas type 1) - general cos+sin heeling arm

The lifting criterion is the same as the Combined criteria (ratio of areas type 1) - general heeling

arm except that the heel arm has both a cos and sin component.

Appendix B

Page 293

Combined criteria (ratio of areas type 1) – cos+sin heeling arm

Combined criteria (ratio of areas type 1) - lifting weight


1) - general cos+sin heeling arm, however the heel arm is the specific lifting of a heavy weight

form.

Combined criteria (ratio of areas type 1) - towing


1) - general cos+sin heeling arm, however the heel arm is the specific towing form.

Combined criteria (ratio of areas type 2) - wind heeling arm

This criterion is exactly the same as §Combined criteria (ratio of areas type 2) - general wind

heeling arm except that the magnitude of the heeling arm is automatically calculated from the

wind pressure (or velocity), projected area and area lever information.

Area definition

Appendix F

Page 294

Note



Appendix B

Page 295

Appendix D: Specific Criteria

In Hydromax, we have tried to distil the essence of the various stability criteria and present

them in their simplest form whilst preserving the physical significance of the stability

characteristic under assessment. In some cases, what is essentially the same criterion, is

presented in quite different ways by different regulatory bodies. In Hydromax we have always

sought to keep the physical significance transparent in the formulation – for this reason,

constants such as acceleration due to gravity are explicitly shown in the formulations and

consistent units are used – thus removing the need for obscure constants with strange units.

In this section we look at some common criteria and demonstrate how they may be evaluated in

Hydromax.

Dynamic stability criteria

In some cases the criteria are expressed in terms of the so-called dynamic stability curve. This is

the integral of the GZ curve where the ordinate is the area under the GZ curve integrated from

zero to the heel angle in question. Remembering this relationship and that the slope of the

dynamic stability curve is the value of GZ it is often possible to reformulate the same criterion

in terms of one based on the GZ curve.

Capsizing moment

Often a capsizing moment is determined from the dynamic stability curve by drawing a line

through the origin which is tangent to the GZ area curve. This is the dynamic heeling arm curve

(blue) and is the integral of a constant value heeling arm. The capsizing moment is taken as the

magnitude of GZ at this tangent heel angle 2 . The problem is to reformulate this so that this

capsizing moment can be found from the GZ curve:

Dynamic stability curve and Dynamic heeling arm.

From the figure above we can see that the slopes of both curves are the same at 1 and 2 ;

from this we can deduce that the value of GZ and Heeling arm are the same at these angles.

Furthermore, at 2 , the values are the same indicating that the areas under each curve from 0 to

2 are the same. Finally since the dynamic heeling arm is a straight line with constant slope we

know that the corresponding heeling arm is a constant value. From these facts we can derive the

following GZ and heeling arm curves:

Appendix F

Page 296

Stability curve, Area 1 corresponds to the area under the heeling arm curve up to the second intercept

Stability curve, Area 2 corresponds to the area under the GZ curve up to the second intercept

Knowing that Area1 = Area2 we can deduce that Area 3 = Area 4 in the figure below:

Appendix B

Page 297

The magnitude of the heeling arm must be chosen so that Area 3 = Area 4

So the capsizing moment can also be determined by finding the heeling moment that gives

Area3 = Area4. This can easily be done in Hydromax using the GZ area derived heeling arm

type 2 criterion.

Heeling arms for specific criteria - Note on unit conversion

There are quite a few different ways in which different authorities define their heeling arms. The

approach that has been taken in Hydromax is to reflect the physics of what is generating the

heeling moment.

Be careful as some criteria specify heeling arms and some specify heeling moments or

“moments” in mass.length. All Hydromax criteria use a heeling arm since this is what is

ultimately plotted on the GZ curve. To obtain the heeling arm from the heeling moment, it is

necessary to divide by vessel weight ( g ); and in the case of “moments” in mass.length, it is

necessary to divide by vessel mass.

Hydromax uses an internal conversion of knots to m/s based on the International Nautical mile

which is defined as exactly 1852m (International Hydrographic Conference, Monaco, 1929).

Thus 1 knot = 1852/3600 = 0.5144444... m/s.

(Note that the UK nautical mile is 6080ft = 1853.184m; giving a conversion multiplier for knots

to m/s of 0.51477333...)

In the following section, the conversions for some common criteria have been explained.

IMO Code on Intact Stability A.749(18) amended to MSC.75(69)

3.1.2.6 - Heeling due to turning

Heeling moment defined by:

22.0

2

0 dKG

L

VM tonneR

[kNm]

Where:

RM = heeling moment in kNm

0V = service speed in m/s

L = length of ship at waterline in m

tonne = displacement in tonne

Appendix F

Page 298

d = mean draft m

KG = height of centre of gravity above keel in m

Hence the heeling arm, gMH RR /1000 [m], is given by:

22.0

1000

210002.0

2

0

2

0 dKG

Lg

V

g

dKG

L

VH R

[m]

Where:

g = standard acceleration due to gravity = 9.80665 m/s2

= displacement in kg

The heeling arm in Hydromax is defined as:

hRg

VaH R

2

[m],

Where:

V = vessel speed in m/s

R = radius of turn in m

h = height of centre of gravity above centre of lateral resistance in m

a = non-dimensional constant (theoretically unity)

Thus equating the required IMO heeling arm to the Hydromax heeling arm, we obtain:

22.0

2

0

2d

KGLg

Vh

Rg

Va

Equating similar terms:

2

dKGh

0VV and assuming that the ratio of the turn radius to the vessel length is 5.1:1, we obtain:

%510

L

R

and

02.1%5102.0a

Note that it suffices that 02.1R

La and any ratio of turn radius to vessel length and constant

a that satisfies this relationship may be chosen, the choice of a ratio of 5.1:1 merely gives a

constant approaching the theoretically correct value of unity.

3.2 - Severe wind and rolling criterion (weather criterion)

Heeling arm defined by:

tonne

wg

PAZl

81.9

11000 [m]

Where:

1wl = heeling arm in m

P = wind pressure in Pa

Appendix B

Page 299

A = projected lateral windage in m2

Z = vertical separation of centroids of A and underwater lateral area in m


81.9g = IMO assumed value of gravitational acceleration - 9.81m/s2


g

HhPAaHw

)(

[m]

Where:



h = height of centroid of A in m

H = height of centroid of underwater lateral area in m



tonneg

PAZ

g

HhPAa

81.91000

)(


ZHh

and

99966.081.9

80665.9

81.9g

ga

IMO HSC Code MSC.36(63)

Annex 6 1.1.4 - Heeling moment due to wind pressure

Heeling moment defined by:

PAZM v 001.0 [kNm]

Where:

vM = heeling moment in kNm



Z = vertical separation of centroids of A and underwater lateral area in m

Hence the heeling arm, gMH vv /1000 [m], is given by:

g

PAZ

gPAZHR

1000001.0

[m]

Where:




Appendix F

Page 300

g

HhPAaHw

)(

[m]

Where:







g

PAZ

g

HhPAa

)(


ZHh and

0.1a

Annex 7 1.3 - Heeling due to wind

Heeling arm defined by:

tonne

PAZHL

98001

[m]

Where:

1HL = heeling arm in m



Z = vertical separation of centroid of A and half the lightest service draft in

m



g

HhPAaHw

)(

[m]

Where:




H = height of half the lightest service draft in m




ZHh

Appendix B

Page 301

and

00068.18.9

80665.9

9800 tonne

ga

Where the effect of wind plus gust is required, the factor a should be multiplied by the gust

factor – typically 1.5. Hence, in the case of wind plus gust, a becomes 1.50102

USL code (Australia)

USL C.1.1.3 - Wind heeling moment

USL wind heeling “moment” is specified as:

)(000102.0 HhPAM [tonne.m]

Where:





Thus the heeling arm is given by:

1000)(000102.0 HhPAH

[m]


g

HhPAaH

)(

[m]

Where:




Thus equating:

1000)(000102.0

)(HhPA

g

HhPAaH

simplifying and rearranging:

0002783.180665.9102.00.1000000102.0 ga

USL C.1.1.4 - Heeling moment due to turning

USL wind heeling “moment” is specified as:

L

hvM tonneskts

2

0053.0 [tonne.m]

Where:

ktsv = vessel speed in knots


Appendix F

Page 302


L = waterline length of vessel in m

Thus the heeling arm is given by:

0.10001

0053.02

L

hvH tonneskts

[m]

Where:



hRg

VaH

2

[m],

Where:

V = vessel speed in m/s

R = radius of turn in m



Thus equating the required USL heeling arm to the Hydromax heeling arm, we obtain:

0.10001

0053.022

L

hvh

Rg

Va tonneskts

simplifying and rearranging:

0.1000

1

5144.0

13.53.5

22

2

L

Rg

V

v

L

Rga tonneskts

finally, with g = 9.80665 [ms-2

]:

L

Ra 196424.0

Assuming that the ratio of the turn radius to the vessel length,%509

L

R

gives a value for a:

999798.0%509196424.0a

Note that it suffices that 196424.0

L

Ra

, and any ratio of turn radius to vessel length and

constant a that satisfies this relationship may be chosen, the choice of a ratio of 509% merely

gives a constant approaching the theoretically correct value of unity.

ISO 12217-1:2002(E)

This section explains how the ISO 12217-1 code calculates the heeling arm and how you can

replicate this calculation with a Hydromax criterion.

“6.3.2 Rolling in beam waves and wind

The curve of righting moments of the boat shall be established up to the downflooding angle or

the angle of vanishing stability or 50°, whichever is the least, using annex D. The heeling

moment due to wind, MW, expressed in newton metres, is assumed to be constant at all angles

of heel and shall be calculated as follows:

Appendix B

Page 303

MW = 0.3 ALV * (ALV / LWL + TM)* vW2

Where

LWL is the waterline length;

TM is the draft at the mid-point of the waterline length, expressed in metres;

vW = 28 m/s for design category A, and 21 m/s for design category B;

ALV is the windage area as defined in 3.3.7, but shall not be taken as less than 0.55*LH *

BH.”

Basically they are using moment = force * lever, where

the force is calculated as 0.3 * ALV * vW2, and

the lever is (ALV / LWL + TM)

This lever is a bit confusing so let‟s concentrate on that.

Hydromax‟ wind heeling arm calculation uses H for the vertical height of the hydrodynamic

centre (underwater area) and h as the vertical height of the aerodynamic centre (windage area) –

all measured consistently from the zero point, positive up.

Thus the lever is (h-H) in Hydromax should be the same as the (ALV / LWL + TM) lever from ISO.

You can calculate (ALV / LWL + TM) manually and then make sure the (h-H) value in Hydromax is

the same by specifying:

Velocity based heeling arm;

H = 0.0;

h = (ALV / LWL + TM);

a = 0.3 kg/m3

Note: the centre of the windage area -h- applies to the additional windage area or the total

windage area depending on which option you have selected. Make sure you check your total

windage lever in the intermediate results in the criteria results tab of the Results window.

For example, supposing we have a vessel with the following characteristics:

Displacement 105.7 tonne = 1037 kN

LH 24 m

BH 5 m

LWL 21.1 m

TM 1.9 m

vW 28 m/s for design category A

ALV 72 m2 ( this is greater than 0.55 LH BH = 66 m

2)

Thus according to the ISO 12217 formula, the heeling moment is given as:

MW = 0.3 * 72 * (72 / 21.1 + 1.9) * 282 = 89961 Nm

Thus the heeling arm = MW / Displacement = 89961 / 1037000 = 0.0868 m

The input for Hydromax requires:

Total area A = 72 m2;

area centroid height: h = ALV / LWL + TM = 72 / 21.1 + 1.9 = 5.312 m;

a = 0.3 kg/m3

giving the expected result for heeling arm amplitude:

Appendix F

Page 304

Intermediate results for the wind heeling arm.

ISO 12217: Small craft – stability and buoyancy assessment and categorisation.

This section gives some details on implementing the ISO 12217 stability criteria in Hydromax.

See also the note on converting units for the definition of the heeling arms in ISO 12217-

1:2002(E).

Part 1: Non-sailing boats of hull length greater than or equal to 6m

In many cases the user must determine the required pass value for the criteria, which depends on

the category and length of vessel being tested. In most cases the default required value would

exceed the worst case.

6.1.2: Downflooding height

Minimum freeboard to downflooding points must be determined from Figures 2 and 3 (Section

6.1.2) and entered into the required value field; the default value is set at 1.42m which is slightly

greater than the height required for a category A vessel of 24m in length.

6.1.3: Downflooding angle

Must be greater than a certain value as determined according to the design category; see Tables

3 and 4 (Sections 6.1.3, 6.2). The default value is set to 49.7

6.2: Offset-load test

There are several ways of evaluating this criterion:

1. Define a heeling arm and calculate the intersection of the heeling arm with the GZ

curve to determine the angle of equilibrium.

2. Specify a loadcase with the offset load specified and carry out an equilibrium analysis.

Verify that the angle of equilibrium does not exceed the maximum permissible value.

An additional requirement in this section is that a specified freeboard must be exceeded.

6.3: Resistance to wind and waves

Determine the windage area and lever and enter them in the appropriate fields in the criterion.

Also determine the required wind speed and roll-back angle (depending on the design category)

and enter these values.

In Hydromax, there is no option for placing the height, H, of the centre of lateral resistance at

the bottom of the vessel, so this must be specified manually (it is measured from the model zero

point, positive upwards).

6.3.3: Resistance to waves

This criterion comprises two parts, one to check that the righting moment is sufficient and a

second to determine whether the righting lever is sufficient.

6.4: Heel due to wind action

Appendix B

Page 305

Determine the parameters required for calculation of the wind heeling moment as per 6.3, but

note the different wind speeds to be used. Determine the limiting heel angle from Table 4

(Sections 6.2)

Part 2: Sailing boats of hull length greater than or equal to 6m

6.2.2: Downflooding height

Minimum freeboard to downflooding points must be determined from Figure 2 (Section 6.2.2)

and entered into the required value field, the default value is set at 1.42m which is slightly


6.2.3: Downflooding angle

Must be greater than a certain value as determined according to the design category, see Tables

3 (Sections 6.2.3). The default value is set to 40

6.3: Angle of vanishing stability

Determine the required angle of vanishing stability which depends on design category and

vessel displacement. The default value is 130.

6.4: Stability index (STIX)

Determine the required STIX value depending on the design category, see Table 5 (Section

6.4.9). Also specify the sail area and vertical position of the sail area centroid and enter these

values in the appropriate fields in the criterion. If desired you can specify the other values or let

Hydromax calculate them for you.

6.5: Knockdown-recovery test

The test can be approximated by examining the angle of vanishing stability in the flooded

condition. If the flooded vessel has positive GZ at the knockdown angle, it should self right.

6.6.6: Wind stiffness test

Determine the wind heeling moment as defined in 6.6.6 for the wind speed of interest (Table 6,

Section 6.6.7). Convert this to a heeling lever. Calculate the GZ curve with the crew seated to

windward, this criterion will then look at the angle of equilibrium of the vessel under the

applied wind heeling arm.

Part 3: Boats of hull length less than 6m

These criteria are evaluated after an equilibrium analysis under the specified loading condition.

Non-Sailing Boats:

6.2.2: Downflooding-height tests

Determine the required downflooding height and specify the appropriate loading condition. The

criterion is evaluated after an equilibrium analysis.

6.3: Offset-load test

This criterion is most effectively evaluated by performing an equilibrium analysis with the

required offset loading condition

Sailing Boats:

7.2: Downflooding height

Minimum freeboard to downflooding points must be determined from Figure 2 (Section 6.2.2)

and entered into the required value field, the default value is set at 1.42m which is slightly


7.5: Knockdown-recovery test

The test can be approximated by examining the angle of vanishing stability in the flooded

condition. If the flooded vessel has positive GZ at the knockdown angle, it should self right.

7.6.6: Wind stiffness test

Appendix F

Page 306

Determine the wind heeling moment as defined in 6.6.6 for the wind speed of interest (Table 6,

Section 6.6.7). Convert this to a heeling lever. Calculate the GZ curve with the crew seated to

windward, this criterion will then look at the angle of equilibrium of the vessel under the

applied wind heeling arm.

Appendix B

Page 307

Appendix E: Reference Tables

This appendix contains the following reference tables:

File Extension Reference Table

Analysis settings reference table

File Extension Reference Table

The following table lists files that are used in Hydromax. The .hmd file contains all the

additional information that defines the Hydromax model and you need only save this file when

working in Hydromax. However, if you wish to transfer loadcases or compartment definitions

from one model to another, this can be done by going to the appropriate window and saving it to

a separate file.

File Extension Description

Maxsurf Design .msd Contains control point and surface information. E.g.

precision, flexibility, thickness, outside arrows,

trimming, colour

When opening a .msd file Hydromax looks for a .hmd

file with the same name.

Hydromax Design .hmd Contains hydrostatic sections information and all Input

information that may also be stored separately in the

files below

The .hmd file does not contain:

- Maxsurf surface information

- Links to or information on the Stability Criteria

Library

- Links to or information on the Results tables

- Links to or information on the Report

Separate Input files Extension Description

Loadcase .hml Each loadcase can be saved separately

Compartments .htk The compartment definition can be saved separately

Damage cases .dcs The damage case definition can be saved separately

All Input window tables .txt All tables in the input window can be saved as text

files. Downflooding/embarkation points, margin lines,

sounding pipes and modulus

Output files Extension Description

All Result Window tables .txt Result tables can be saved separately

Results tables can not be opened in Hydromax

Report .rtf The report can be saved separately

Library Extension Description

Hydromax Criteria Library .hcr The library is not related to the Hydromax Design File,

i.e. is not model related. The library is loaded when the

program starts, not when the model is opened. For

more information see the section on criteria.

Appendix F

Page 308

Analysis settings reference table

The following table can be used as a reference to the various analysis settings for each analyses

type.

Analysis Settings

Analyses type Trim Heel Draft Displace-

ment

LCG TCG VCG

Upright stability S Upright R result n/a n/a For GM

etc.

Large Angle

Stability

S /

FTTLC R result LC LC LC LC

Equilibrium result result result LC LC LC LC

Specified Condition S S S S / LC S / LC S / LC S / LC

KN values S / FTT R result R S /

FTT

S /

LC4 S1

Limiting KG S / FTT R result R S /

FTT

S /

LC4 result2

Floodable Length FTT Upright result R FTT n/a S3

Tank Calibration S Upright n/a n/a n/a n/a n/a

Where,

result Cannot be specified – they are a calculated resul

S Specific (fixed, single) value to be set by user

R Varied within Range specified by user

LC Calculates values from loadcase – specifies displacement and COG only

FTTLC Free-to-trim to loadcase CG

FTT Free-to-trim to LCG calculated from a specific initial trim angle or

specified LCG (and VCG) 1 The VCG is used in two ways in the KN analysis.

a) The VCG only has an effect on the results if the analysis is free-to-trim.

b) The GZ curve is calculated for the specified VCG and then the normalised KN curve is

calculated as KN = GZ + VCG*SIN(heel).

2 The VCG is not required for the Limiting KG analysis. When calculating the LCG from a

specified trim and displacement, the current VCG is used.

3 The VCG is required for the floodable length analysis because of its effect on trim. During the

floodable length analysis, the trim can be substantial and the vertical separation of CG and CB

needs to be taken into account.

4 The TCG may be specified directly of derived from the lost cargo / ballast water in damaged

tanks from the current loadcase.

Appendix B

Page 309

Appendix F: Quality Assurance

This appendix describes the quality assurance processes used to ensure Hydromax gives reliable

and accurate results.

Quality Assurance

Many Hydromax users ask us how we know that Hydromax produces the correct results. This

following explains how Formation Design Systems has verified that Hydromax gives accurate

results and what steps we take to make sure that each version of the software we ship is as

reliable as possible.

Quality Principles

While it is impossible to ensure that any software product is completely free of bugs, we follow

a series of engineering and testing principles and procedures to ensure that Hydromax will

produce results which are consistent with the level of accuracy and thoroughness a professional

engineer applies to design work. To this end we follow a development and testing path which

includes use of structured programming techniques, verification of the underlying algorithms,

testing of the computer implementation of those algorithms, testing of real world problems in-

house and beta testing in the field at Hydromax user sites.

Structured Programming

The best defence against bugs in software is to use structured programming techniques that have

been proven to improve software reliability. Without going into the technical details of our

software development methodology, we summarize by saying that we utilize structured code,

object oriented design, data hiding and encapsulation and fault tolerant programming practices

to enhance our software's reliability. Hydromax is a complex software system of over 400,000

lines of code and we believe our history of reliability reflects the effort we have put into using

reliable coding practices.

Verification of Algorithms

When new design or analysis algorithms are introduced into Hydromax, we first carry out

testing on the algorithms on Reference Designs – these are proven test cases with known

analytical solutions, see Reference Calculations.

Reference Designs

A folder of reference hull shapes is included with Maxsurf and Hydromax. These designs are of

simple geometric shapes and can be used to validate calculations performed by Hydromax.

Below is a table of results derived analytically from these shapes compared with results

obtained from Maxsurf and Hydromax at different precisions.

Appendix F

Page 310

Reference Calculations

Hydrostatics calculations for various reference designs, comparison of Maxsurf and Hydromax with analytical values

sphere 10m diam at 5m

draft

Volume

m^3

WP Area

m^2

VCB

m

LCB

m Trans. I m^4 Long. I m^4 Volume WP Area Trans. I Long. I

Analytically derived 261.79939 78.53982 -1.875 0 490.873852 490.87385 % error % error % error % error

Hydromax High Precision 261.764 78.534 -1.875 0 488.6807269 489.14247 -0.01% -0.01% -0.01% -0.02%

Hydromax Low Precision 260.34279 78.357 -1.874 0 488.564741 488.93873 -0.56% -0.23% -0.47% -0.39%

Maxsurf Hi Precision 261.532 78.341 -1.875 0 490.57 485.761 -0.10% -0.25% -0.06% -1.04%

Maxsurf Low Precision 257.105 77.849 -1.871 0 483.191 480.89 -1.79% -0.88% -1.57% -2.03%

10m Cylinder 10m diam. at 5m draft

Volume

m^3

WP Area

m^2

VCB

m

LCB


Analytically derived 392.699 100 -2.122 0 833.333333 833.33333 % error % error % error % error

Hydromax High Precision 392.673 100 -2.121 0 833.257 833.308 -0.01% 0.00% 0.01% 0.00%

Hydromax Low Precision 391.991 100 -2.121 0 833.333333 833.33333 -0.18% 0.00% 0.00% 0.00%

Maxsurf Hi Precision 392.522 100 -2.122 0 833.333 833.333 -0.05% 0.00% 0.00% 0.00%

Maxsurf Low Precision 389.874 100 -2.118 0 833.333 833.333 -0.72% 0.00% 0.00% 0.00%

Box 20m long 10m beam at 5m draft

Volume

m^3

WP Area

m^2

VCB

m

LCB


Analytically derived 1000 200 -2.5 0 1666.666666 6666.6667 % error % error % error % error

Hydromax High Precision 1000 200 -2.5 0 1666.666666 6666.6667 0.00% 0.00% 0.00% 0.00%

Hydromax Low Precision 1000 200 -2.5 0 1666.666666 6666.6667 0.00% 0.00% 0.00% 0.00%

Maxsurf Hi Precision 1000 200 -2.5 0 1666.667 6666.667 0.00% 0.00% 0.00% 0.00%

Maxsurf Low Precision 1000 200 -2.5 0 1666.667 6666.667 0.00% 0.00% 0.00% 0.00%

Parabolic Wigley type Hull, LWL=15m,B=1.5m,D=0.9375

Volume

m^3

WP Area

m^2

VCB

m

LCB


Analytically derived 9.375 15 -0.352 0 1.92875 168.75 % error % error % error % error

Hydromax High Precision 9.368 14.998 -0.352 0 1.92527 168.4685 -0.07% -0.01% -0.04% -0.01%

Hydromax Low Precision 9.351 14.98 -0.352 0 1.92418 168.3773 -0.26% -0.13% -0.24% -0.22%

Maxsurf Hi Precision 9.372 14.999 -0.351 0 1.927 168.63 -0.03% -0.01% -0.09% -0.07%

Maxsurf Low Precision 9.302 14.942 -0.351 0 1.91 167.621 -0.78% -0.39% -0.97% -0.67%

Appendix C

Page 312

Testing of Implementation

Once the basic algorithms have been proven correct, testing is then carried out on more complex

sample problems to which a solution has already been established using a proven analysis

program. These results may either come from Naval Architecture and Marine Engineering texts

such as well as from other results carried out by Formation Design Systems or other engineers

using other software products such as NAPA, AutoShip etc.

Testing of Upgrades

As each new version of Hydromax is released we perform a series of tests to ensure it functions

correctly. At each release the results from these tests are compared with the results from the

previous release to ensure conformance with answers which have been established as being

correct.

Beta Testing

Immediately prior to the release of each new version of Hydromax, we conduct a beta test of the

software. This involves sending the software to practicing engineers and having them use it on

design work in progress to determine its reliability for actual design use. These beta testers

provide us with feedback on the reliability and accuracy of the program as well as its useability

and suitability for everyday work. Once the beta test program is completed and all testers are

happy with the program, we begin shipping the commercial version.

Version Control

Each new version of Hydromax displays a version number indicating the version and the date

the software was first shipped. If the version is a development, alpha test or beta test release,

the version number may also include a letter and number suffix indicating the type and number

of the release. A development version is usually only for internal use and is a very early

demonstration of a possible new product or feature. It is highly experimental and not reliable.

An alpha release is a first public release of a program for initial testing and comment, it is not

reliable. A beta release is a final test version of the program released for field testing prior to

commercial release. It is mostly reliable but may contain some bugs. A commercial release is a

completed, debugged program reliable and ready for professional use.

For example

1.0d1 The first development release of version 1.0

1.5a2 The second alpha test release of version 1.5

1.6b2 The second beta test release of version 1.6

1.64 A commercial release of version 1.64

But we're not Perfect

We make every effort to ensure that our software will meet our users' needs and perform

accurately. However, as with all complex software systems, it is possible for errors to occur. If

you suspect a problem with Hydromax, please contact our technical support staff by email at

[email protected] and explain what you believe the problem to be. In the unlikely event of

a problem being found, we will correct it as soon as practicable, and send you a new corrected

version of the program.

To get accurate results from Hydromax, it is necessary for you to model the problem correctly

and to correctly interpret the results produced. It is the users' responsibility to correctly model

the structure and assume responsibility for the results.

Index

Page 313

Index

A

About Hydromax ....................................... 213

Activate GHS Export ................................. 202

Add Damage case ...................................... 204

Add Load ..................................................... 42

Add Surface Areas ..................................... 202

Allowable shears and moments ................... 77

Analysis

Menu ...................................................... 204

Output .................................................... 156

Settings ................................................... 309

Toolbar ................................................... 195

Analysis in waves ........................................ 90

Analysis type

Equilibrium .............................................. 88

Floodable Length ................................... 103

KN Values Analysis ................................. 93

Large Angle Stability ............................... 82

Limiting KG ............................................. 96

Longitudinal Strength ............................ 106

Specified Conditions ................................ 91

Tank Calibrations ................................... 108

Upright Hydrostatics ................................ 79

Animate ...................................................... 211

Arrange Icons ............................................. 212

Assembly View .......................................... 181

Automation Reference ............................... 213

B

Background ................................................ 210

Batch Analysis ........................................... 139

Beam .......................................................... 218

Beta Testing ............................................... 313

Block Coefficient ....................................... 221

Boundary Box .............................................. 52

Bulkheads ............................................. 78, 185

C

Calibration Increment .................................. 71

Cascade ...................................................... 212

Case

Menu ...................................................... 204

Cell Border ................................................. 201

Cell Shading ............................................... 201

Centre of buoyancy .................................... 181

Centre of flotation ...................................... 181

Centre of gravity ........................................ 181

Check for Updates ...................................... 213

Closing a Loadcase ...................................... 42

Coefficient parameters ............................... 216

Coefficients,

calculation of .......................................... 211

Hydrostatic ............................................... 36

Colour ........................................................ 203

Compartment Definition .......................51, 184

New .......................................................... 52

Saving .................................................... 161

Compartment types ...................................... 69

Compartments .......................................... 70

Linked ...................................................... 70

Linked Tanks ........................................... 70

Non-Buoyant Volumes ............................ 70

Tanks ........................................................ 70

Compartments,

add, delete ................................................ 52

Forming .................................................... 62

Convergence Error ..................................... 147

Coordinate system ........................................ 34

Copy ....................................................158, 200

Copying Graphs ......................................... 191

Copying Tables .......................................... 159

Corrected VCG .......................................... 150

Create cases from Zone Damage ............... 204

Creating a Compartment definition file ....... 52

Creating a new Loadcase File ...................... 39

Criteria ....................................................... 205

Criteria File Format.................................... 174

Criteria Libraries ........................................ 172

Criteria, Main

Import..................................................... 199

Save As .................................................. 200

Criteria, Prob Damage

Import..................................................... 200

Reset to defaults ..................................... 200

Save As .................................................. 200

Curve of Areas ............................................. 84

Curves of Form ............................................ 84

Cut .............................................................. 200

D

Damage .................................................72, 155

Damage Case

Add........................................................... 72

Delete ....................................................... 72

Display ..................................................... 73

Extent of damage ..................................... 74

Rename .................................................... 72

saving ..................................................... 161

Select ........................................................ 73

Damage Window ....................................... 183

Data Format ........................................185, 207

Index

Page 314

Data layout ................................................. 186

Data Menu .................................................. 211

Deactivate GHS Export .............................. 202

Delete Cells ................................................ 201

Delete Damage case ................................... 204

Delete DXF background ............................ 210

Density ............................................... 151, 205

Design Grid ................................................ 211

Design Grid Toolbar .......................... 195, 196

Design Preparation ....................................... 18

Design,

coherence ................................................. 20

Saving .................................................... 160

Displacement...................................... 146, 205

Display

Background ............................................ 210

Display Menu ............................................. 207

Downflooding Angles .................................. 87

Downflooding points ........................... 75, 185

Linking to tanks or compartments ........... 76

Draft .............................. 80, 145, 205, 219, 220

Draft marks ............................................ 18, 35

DWL ............................................................ 80

DXF export ................................................ 162

DXF, Export ............................................... 198

Dynamic Stability ........................................ 83

E

Edge Visibility Toolbar .............................. 196

Edit Damage case ....................................... 204

Edit Loadcase ............................................. 204

Edit Menu .................................................. 200

Edit Toolbar ............................................... 194

Edit,

Add ......................................................... 201

Delete ..................................................... 201

Move Items Down .................................. 202

Move Items Up ...................................... 202

Sort Items ............................................... 201

Emergence Angles ....................................... 87

Equilibrium .............................................. 9, 88

Equilibrium Condition ................................... 9

Export ......................................................... 198

Export Bitmap ............................................ 199

Exporting ................................................... 161

Extent of Damage ...................................... 204

External Tanks ............................................. 56

Extra Buttons Toolbar ................................ 196

F

File Extension Table .................................. 308

File Menu ................................................... 197

File Toolbar ................................................ 194

File,

Close ...................................................... 197

Exit ......................................................... 200

Hydromax Version 8.0 ........................... 162

New ........................................................ 197

Open ..................................................21, 197

Save ........................................................ 197

Save As .................................................. 197

Fill Down ................................................... 201

Floodable Length ......................................... 12

Floodable Length Criteria dialog ............... 205

Flooding ....................................................... 73

Fluid analysis method ................................ 149

Fluid VCG .............................................51, 151

Fluids ......................................................... 205

Font ............................................................ 203

Form parameters ........................................ 214

Frame of Reference .........................18, 35, 211

Fredyn ........................................................ 199

Free Surface Moment ............................51, 150

Freeboard ..................................................... 89

Full Screen ................................................. 204

G

GHS, Export ............................................... 198

GHS, Import ............................................... 198

Graph ......................................................... 212

Curve of Areas ....................................... 189

Curves of Form ...................................... 189

Data interpolation................................... 189

double click ............................................ 190

get data ................................................... 190

Righting Lever (GZ) .............................. 189

Type ....................................................... 189

Graph colours ............................................. 190

Graph Formatting ....................................... 190

Graph Printing to Scale .............................. 159

Graph Window ........................................... 188

Graphs ........................................................ 189

Grid ............................................................ 210

Grounding ...........................................154, 206

GZ .................................................................. 8

H

Heel .....................................................142, 205

Heeling Moments ....................................... 240

Help Menu ................................................. 212

Hide DXF ................................................... 210

Home View .........................................181, 202

Horizontal lever ........................................... 43

Hull Sections

Recalculate ............................................. 206

Hydromax v8.0 file, Export ....................... 198

Index

Page 315

I

IGES, Export .............................................. 198

Immersed depth .................................... 35, 220

Immersion .................................................. 223

Immersion Angles ........................................ 87

Import ......................................................... 197

Import DXF Background ........................... 198

Import Image Background ......................... 198

Individual Loadcase ................................... 210

Initial Conditions ......................................... 34

Input ........................................................... 212

Input Tables, saving ................................... 161

Input Window ............................................ 184

Insert New Table ........................................ 201

Insert Row .................................................. 201

Installing Hydromax .................................... 16

ISO 12217-1 ............................................... 303

K

Key points ............................................ 75, 185

adding ....................................................... 75

Data .......................................................... 87

deleting ..................................................... 76

editing ...................................................... 76

Results .................................................... 186

KN Values .............................................. 10, 93

L

Large Angle Stability ......................... 8, 82, 84

lateral projected area .................................. 240

LCB, LCG .................................................. 222

Length ........................................................ 217

Libraries ..................................................... 172

Limiting KG ........................................... 11, 96

Linked negative compartments .................... 58

Loadcase .............................................. 38, 212

Adding and Deleting loads ....................... 42

Distributed loads ...................................... 45

Editing loads ............................................ 42

Free surface correction ............................. 51

maximum number .................................... 42

Renaming ................................................. 41

saving ..................................................... 161

Update ...................................................... 47

Loadcase Colour Formatting ........................ 44

Loadcase Formatting .................................... 43

Blank lines ............................................... 43

Grouping tanks ......................................... 44

Headings lines .......................................... 43

Totals ....................................................... 44

Loadcase Sorting .......................................... 43

Loadcase Template ...................................... 40

Loadcase Window ...................................... 183

Loadcase, cross referencing ......................... 47

Loadcase, density ......................................... 49

Loadcase, Distributed Loads ........................ 45

Loadcase, formatting, column selection ...... 44

Loadcase, max. number ............................. 204

Loadcase, Tank loads ................................... 46

Loadgroup ...............................................38, 47

Loadgroup, Workshop structure .................. 51

Loading a Saved Loadcase ........................... 41

Longitudinal Strength ...........................13, 106

M

Margin Line points ................................77, 185

Margin Line, Snap to hull .......................... 206

MARPOL ..................................................... 14

MARPOL oil outflow ................................ 113

Max. Area Section ..................................... 220

Maximum deck inclination ........................ 223

Maximum shears and moments ................... 77

Measurement reference frames .................. 214

Menus......................................................... 197

MEPC.117(52) Reg.23............................... 113

MEPC.141(54) Reg.12A ............................ 113

Merge Cells ................................................ 201

Midship Section ......................................... 220

Modulus points .......................................... 185

Modulus Window ........................................ 77

Moment to trim .......................................... 223

MSC.19(58) ............................................... 116

MSC.216(82) ............................................. 116

N

Non-Buoyant Volume Definition ................ 51

nuShallo, Import ........................................ 198

O

Online Support ........................................... 213

Outside arrows ............................................. 20

overlap ......................................................... 59

P

Page Setup .................................................. 200

Pan ......................................................181, 202

Paste ........................................................... 201

Permeability ............................ 13, 58, 146, 205

Perspective view ........................................ 182

Precision, surface ......................................... 22

Preferences ............................................16, 202

Print ............................................................ 200

Print Preview .............................................. 159

Printing ....................................................... 159

Printing to scale ......................................... 159

Prismatic Coefficient ................................. 221

Prob damage zones .................................... 209

Index

Page 316

Probabilistic Damage ........................... 15, 116

Probabilistic Damage – Analysis ............... 136

Probabilistic Damage – Inputs ................... 119

Probabilistic Damage – log file .................. 117

Probabilistic Damage – Principles ............. 116

Probabilistic Damage – Saving input

parameters .............................................. 119

Properties ................................................... 203

Property Sheet ............................................ 181

Q

Quality Assurance ...................................... 310

Quality Principles....................................... 310

R

Ratio of equilibrium angles – GZ area derived

heeling arm............................................. 289

Reference Calculations .............................. 311

Reference Designs ..................................... 310

Relative Density ................................... 60, 151

Render ........................................................ 211

Render Transparent .................................... 211

Report Toolbar ........................................... 196

Report Window .......................................... 191

Keystrokes.............................................. 193

Reporting ................................................... 156

Results ........................................................ 212

Results Window ......................................... 185

Results, saving ........................................... 161

Resume Analysis ................................ 138, 206

Righting Moment ....................................... 224

Rotate ......................................................... 202

Row Positioning ......................................... 201

S

Safe steady heeling angles ........................... 84

Save ............................................................ 161

Saving Densities......................................... 152

Section Area Coefficient ............................ 221

Section, show single ................................... 210

Sectional Area Curve ................................... 31

Sections, Forming ........................................ 27

Select All .................................................... 201

Select View from Data ....................... 160, 209

Set Analysis Type ...................................... 206

Set Home View .......................................... 202

Set Vessel to DWL ..................................... 209

Shift Key ...................................................... 16

Show DXF ................................................. 210

Show Grid .................................................. 201

Show single hull section .............................. 30

Shrink ................................................. 181, 202

Simulate fluid movement ........................... 151

Skin Thickness ............................................. 19

Sounding Pipes .....................................70, 184

Calibration Increment .............................. 71

Edit ........................................................... 70

Specific Gravity ....................................60, 151

Specified Condition ........................10, 91, 205

Specified Conditions, dialog ...................... 146

Split Cell .................................................... 201

Spool to Report .......................................... 207

Stability booklet ......................................... 150

Stability criteria ............................................ 78

Stability Criteria Results ............................ 187

Stability criteria, angle calculators ............. 228

Stability criteria, Angle of deck edge

immersion .............................................. 250

Stability criteria, Angle of downflooding .. 249

Stability criteria, Angle of equilibrium ...... 248

Stability criteria, Angle of equilibrium -

general heeling arm .........................269, 270

Stability criteria, Angle of equilibrium - GZ

derived wind heeling arm ....................... 288

Stability criteria, Angle of equilibrium - high-

speed turn heeling arm ........................... 293


multiple heeling arms ............................. 277


passenger crowding heeling arm ............ 292

Stability criteria, Angle of margin line

immersion .............................................. 249

Stability criteria, Angle of maximum GZ .. 248

Stability criteria, Angle of maximum GZ

above heeling arm .................................. 268

Stability criteria, Angle of vanishing stability

............................................................... 250

Stability criteria, Angle of vanishing stability -

general heeling arm ................................ 270

Stability criteria, Areas and levers ............. 240

Stability criteria, capsizing moment........... 296

Stability criteria, check boxes .................... 171

Stability criteria, Combined criteria (ratio of

areas type 1) - general cos+sin heeling arm

............................................................... 293


areas type 1) - general heeling arm ........ 282


areas type 1) - high-speed turn ............... 293


areas type 1) - lifting weight .................. 294


areas type 1) - passenger crowding ........ 293


areas type 1) - towing ............................. 294


areas type 2) - general wind heeling arm 283

Index

Page 317


areas type 2) - wind heeling arm ............ 294


areas type 2a) - general heeling arm ...... 285

Stability criteria, copying criteria............... 170

Stability criteria, criteria library file .......... 172

Stability criteria, damage and intact settings

............................................................... 172

Stability criteria, defining custom criteria .. 170

Stability criteria, equilibrium ..................... 242

Stability criteria, General cos+sin heeling arm

............................................................... 234

Stability criteria, General heeling arm ....... 233

Stability criteria, glossary .......................... 179

Stability criteria, GM calculators ............... 229

Stability criteria, Gust ratio ........................ 233

Stability criteria, GZ area between limits type

1 - general heeling arm .......................... 271


1 - multiple heeling arms ....................... 278


1 - standard ............................................. 250


2 - general heeling arm .......................... 272


2 - multiple heeling arms ....................... 278


2- HSC monohull type ........................... 251


3 - HSC multihull type ........................... 253

Stability criteria, GZ area derived heeling arm

type 1 ...................................................... 287

Stability criteria, GZ area derived heeling arm

type 2 ...................................................... 288

Stability criteria, GZ curve features ........... 176

Stability criteria, GZ definitions ................ 178

Stability criteria, GZ derived heeling arm . 286

Stability criteria, GZ, non-healing arm ...... 244

Stability criteria, heeling arm definition .... 232

Stability criteria, heeling arm dependency on

displacement .......................................... 240

Stability criteria, heeling arm units ............ 298

Stability criteria, Heeling due to arbitrary

forces ...................................................... 239

Stability criteria, Heeling due to bollard-pull

............................................................... 238

Stability criteria, Heeling due to grain shift 239

Stability criteria, Heeling due to lifting of

weights ................................................... 237

Stability criteria, Heeling due to passenger

crowding ................................................ 235

Stability criteria, Heeling due to towing .... 238

Stability criteria, Heeling due to trawling .. 239

Stability criteria, Heeling due to turning .... 236

Stability criteria, Heeling due to wind ....... 235

Stability criteria, IMO Code on Intact Stability

A.749(18) ............................................... 298

Stability criteria, IMO HSC Code MSC.36(63

............................................................... 300

Stability criteria, IMO roll back angle

calculator ................................................ 229

Stability criteria, importing .................172, 173

Stability criteria, ISO 12217 ...................... 305

Stability criteria, list ................................... 163

Stability criteria, Maximum Freeboard at

equilibrium ............................................. 243

Stability criteria, Maximum ratio of GZ to

heeling arm ............................................ 266

Stability criteria, Maximum value of heel,

pitch or slope at equilibrium .................. 242

Stability criteria, Minimum Freeboard at

equilibrium ............................................. 243

Stability criteria, minimum GM calculator –

Constant ..........................................231, 262


Constant with freeboard ..................231, 263


Grain ...............................................229, 261


Wind pressure .................................230, 262

Stability criteria, Minimum ratio of GZ to

heeling arm ............................................ 268

Stability criteria, moving criteria ............... 170

Stability criteria, Other criteria - STIX ...... 291

Stability criteria, parent criteria ..........165, 242

Stability criteria, pass/fail test .................... 172

Stability criteria, Range of positive stability

............................................................... 250

Stability criteria, Range of positive stability -


Stability criteria, Ratio of areas type 1 -

general cos+sin heeling arm ................... 293




multiple heeling arms ............................. 279





Stability criteria, Ratio of GMT and heeling

arm ......................................................... 264

Stability criteria, Ratio of GZ area between

limits ...................................................... 255

Stability criteria, Ratio of GZ values at phi1

and phi2 .................................................. 247

Index

Page 318


and phi2 - general heeling arm ............... 268


and phi2 - multiple heeling arms............ 276

Stability criteria, Ratio of positive to negative

GZ area between limits .......................... 257

Stability criteria, report and batch processing

............................................................... 176

Stability criteria, results ............................. 174

Stability criteria, saving ............................. 173

Stability criteria, selecting for analysis ...... 170

Stability criteria, Subdivision Index s-factor -

MSC 19(58 ............................................. 260

Stability criteria, Survivability Index -

MSC_216(82) ........................................ 280

Stability criteria, tree list ............................ 169

Stability criteria, User Defined Heeling Arm

............................................................... 234

Stability criteria, USL code ........................ 302

Stability criteria, Value of GMt at ............. 244

Stability criteria, Value of GMt at equilibrium

- general heeling arm ............................. 264

Stability criteria, Value of GMt or GMl at

equilibrium ............................................. 243

Stability criteria, Value of GZ at ................ 244

Stability criteria, Value of GZ at equilibrium -


Stability criteria, Value of GZ at specified

angle or maximum GZ below specified

angle ....................................................... 245

Stability criteria, Value of maximum GZ .. 244

Stability criteria, Value of maximum GZ

above heeling arm .................................. 265

Stability criteria, Value of RM at specified

angle or maximum RM below specified

angle ....................................................... 246

Start Analysis ..................................... 138, 206

Start Batch Analysis ................................... 207

Starting Hydromax ....................................... 16

Status Bar ................................................... 203

Stop Analysis ..................................... 138, 207

Streaming results to Word ......................... 156

Surface Use .................................................. 19

T

Table .......................................................... 201

Tank

adding, deleting ........................................ 52

Fluids ....................................................... 60

Ordering ................................................... 61

Permeability ....................................... 58, 60

Saving .................................................... 161

Surface Thickness .................................... 61

Visibility .................................................. 61

Tank Calibrations ..................................13, 108

Tank Type

external ..................................................... 56

linked ....................................................... 54

simple ....................................................... 52

tapered ...................................................... 53

tanks

overlap ..................................................... 59

Tanks

Recalculate ............................................. 206

Tanks within Compartments ........................ 58

Tanks,

boundary surfaces .................................... 54

complex .................................................... 54

Non-Buoyant Areas ................................. 56

Recalculate ............................................. 195

TCG, Limiting KG, KN ............................. 145

Tile Horizontal ........................................... 212

Tile Vertical ............................................... 212

Tolerances .................................................. 147

Toolbars ..............................................194, 203

Trapezoidal integration ................................ 27

Trim ....................................................143, 205

Fixed ...................................................... 144

Free-to-trim to a specified LCG value ... 145

Free-to-trim using a specified initial trim

value ................................................... 145

Trim angle .................................................. 223

Trimmed surfaces, checking ........................ 20

U

Undo........................................................... 200

Units ......................................................37, 211

Update Loadcase ........................................ 206

Upright Hydrostatics .................................7, 79

V

Validate Hydromax model ........................... 30

VCG for trim balance................................. 145

View (extended)Toolbar ............................ 196

View Direction ........................................... 212

View Menu ................................................ 202

View Toolbar ............................................. 194

View Window ............................................ 181

Visibility .................................................... 209

Visibility Toolbar ................................195, 196

W

Waterplane Area Coefficient ..................... 222

Wave definition .......................................... 153

Wave height ............................................... 154

Waveform .................................................. 205

sinusoidal ............................................... 153

trochoidal ............................................... 153

Index

Page 319

Wavelength ................................................ 154

Wetted surface area, integration of ............ 224

Window Menu ........................................... 212

Window Toolbar ........................................ 195

Windows Registry ........................................ 16

Word, report streaming to .......................... 156

Word, report templates ............................... 157

Z

Zero Point ........................................ 18, 35, 43

Zoom .................................................. 181, 202

HMManual

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Transcript of HMManual