Maxsurf Webinar 2 – Modelling Techniques

Philip Christensen

FormSys

Planning Surface Layout

• Think about surface topology

• Identify discontinuities

– Corners, knuckles, chines

• Identify constraints

– Straight lines, arcs, key curves (STL,

BTL)

• Choose surface corner locations

• Choose what edge types to use

– Trimming versus Bonding

– Prefer bonding over trimming where there

is smooth continuity

– Prefer trimming when intersections occur

• Plan surface stiffnesses especially adjacent

to bonded edges (5L x 4T is a good default)

Planning Surface Layout

Bonding Surface Edges

• Join 2 surfaces together along a common

edge so the 2 surfaces behave as 1 larger

surface

• Use for areas where you require a different

stiffness in the direction perpendicular to

the edge

– For example transitions to bowcones, knuckles in

hull, chine bilge radius, Curved transoms

• Optional tangential continuity across

bonded edge

Fairing in Maxsurf

• Fair net = Fair surface

• Fair Parametrics = Fair Surface

• Tools to create an accurate design

– Align control points to vector or plane

– Straighten control points to vector or

plane

– Smooth control points

– Tangent bonding of surface edges

• Tools to check fairness

– Compress view

– Curvature Porcupines

– Rendered image

– Curvature renderings

Surface Discontinuities

• Linear Stiffness

– Use for chines, tanks, transoms

• Compacting control points

– Modelling discontinuities in part of a

surface

– Fairing out Chines and knuckles

– Surface stiffness vs number of control

points

• Need to compact 1 less control point

than the surface stiffness

• Don’t use more than this

– Don’t compact points on edges when

trimming allows a fairer surface

Surface Trimming

• Dynamic surface trimming

• Maintains surface fairness

• Use for edge cuts & openings

– for example; transoms, steeped sheer lines,

appendages & bow thrusters

• Display surface to surface intersections

• Rules of trimming

– Intersection lines should form closed regions

– Sufficient overlap (>10mm)

– Shallow intersections are not desirable

– No surfaces lying exactly on top of each other

– Check that intersections happen at all surface

precisions before you start trimming

• Use trimming curves where possible

Working With Rhino

• Round trip data exchange with Rhino

– Surface information is exact

– Trimming information is exact from Maxsurf

(dynamic) to Rhino (static)

– Retrim may sometimes be required going from

Rhino to Maxsurf

• Start in Maxsurf for all major hull modelling

– High quality faired surfaces

– Maxsurf fairness evaluation tools

– Encourages good quality surfaces

• Use Rhino for additional modelling which is

more geometric in nature

• Maxsurf Rhino plugin can help manage

surfaces

Working With Rhino

Preparing Model for Analysis

• Set zero point, frame of reference and vessel

type

• Set surface usage for tanks and internals

• Check trimming

• Turn bonded edges on and off

• Check outside arrows in body plan

• Check hull sections in body plan

• Check surface thickness in Surfaces table

• Use Medium precision (High on occasion and

Highest almost never)

• Save design with precision and trimming

settings desired for analysis

Modelling Irregular Tanks

• Often easy to start with curves, then create

tank surfaces using extrusion

• Break up curves so that individual surfaces

are available for each tank side

• Make sure curves/surfaces are completely

closed transversely

Thank You

• Next Webinar Tuesday February 15th 2011

• Topic: “Intact Stability in Hydromax”

– How to use Hydromax to carry out intact

stability, check compliance with criteria

and generate stability book output”

• Have a suggestion for a future webinar topic?

– Email me: philc@formsys.com

• See you next time…