Introduction

Department of Ship Technology, CUSAT, B.Tech (NA$SB), Batch – XXIX

1

CHAPTER 1

INTRODUCTION


2

1.1 Introduction

The idea of running an icebreaking vessel with the stern end with propellers first is over 100 years old. Since 1995 the operability of Azipod propulsion in severe ice conditions has been overwhelming. The tankers Uikku and Lunni (Ice class Tankers) have made several voyages in the Northern Sea Route. Sometimes the operation has required them to turn the ship around and break ice running astern. The experience during the second half of the last decade, both full-scale experience and further development of the concept utilizing model test, has made it more and more obvious that the Double Acting Ship concept has several advantages.

Before any big tankers could be designed and built, a lot of development work had to be done. Questions like stern shape, ice loads on propulsion unit and hull, behaviour in ballast condition and number of propellers had to be dealt with. The first Double Acting Tanker was built at the Sumitomo Heavy Industries yard, Japan and developed by Kvaerner Masa-Yards, Finland. It was delivered in the year 2002 and subsequently its sister ship Mastera delivered in the year 2003.

The Development of DAT:

Traditionally ice breaking ships have been quite poor in open water. The total efficiency has been 20-40 % less than a good open water vessel. This has been mainly due to the bow forms, which have been developed to break thicker and thicker ice. Open water characteristics have suffered. Several icebreakers have had propellers fitted to the bow. These propellers create a strong water stream, reducing friction and generating a pressure drop under the ice, helping the breaking process. This process is also present when going astern in ice and therefore, rather than fitting a bow propeller, the vessel goes astern to create the same phenomena. The use of Azipod has enabled this design to be much improved and fairing of the hull lines aft to provide icebreaking capability.

Traditional propulsion did not allow much further development in icebreaking when running astern. The development in the 90’s with electric podded propulsion devices, the model and full-scale testing and building of ships with podded drives, has lead to new ship concepts. In open water the vessel runs ahead and in severe ice conditions the vessel runs astern. The bow form is optimized like a conventional tanker and the stern is shaped like an icebreaker’s bow.

This gives following advantages: • Hull form can be optimized for all conditions. • Total economy has improved. • Improved Manoeuvrability. • More freedom of design. • Low Ice resistance (up to 50% in certain ice conditions) as well as low

power requirements (up to 40% less than conventional ice breaking tankers) • No need to stop propeller for reversing • No ramming in Double Acting operation.


3

Fig 1.1 Ice breaking capability of DAT

In the studies made so far and experience gained, it can be noted that some kind of revolution has taken place in ice navigation. Apart from Icebreaking tankers and icebreakers the concept has a huge potential when new ships are designed for operations in restricted waters (including canals), where traditional configurations have found it difficult to cope with the ice. The possibility to direct the propeller water flow to “eat” ice and push it away, opens new avenues. This way ships that were not able to move in midwinter conditions in inland canals were able to proceed through the most severe conditions.

The vessel is designed to follow the Double Acting principle and the hull form is designed accordingly. The vessel will be fitted with a bulbous bow. The bow shape is designed to be capable of operating in light ice conditions related to the Baltic Sea. The stern shape is of ice breaking type, planned to operate independently in the most severe ice conditions of the Baltic Sea. 1.2 Field search: • Ice conditions • Ice properties • Route selection • Design basis development The Baltic Sea:

The Baltic is a young sea, one of the youngest on the Earth. Over the last million years of our planet’s history, areas of northern Europe, including the present-day Baltic basin and the territory of Poland, were repeatedly covered by ice sheets. During each ice-sheet advance, the Baltic area was strongly eroded. It resulted in the formation of a vast depression, occupied today by the Baltic Sea. The Baltic Sea is a brackish inland


4

sea, the largest body of brackish water in the world. It is about 1610 km (870 nautical miles) long, an average of 193 km (104 KN) wide, and an average of 55 m (180 ft, 30 fathoms) deep. The maximum depth is 459 m (1506 ft, 251 fathoms), on the Swedish side of the center. The surface area is about 377,000 km² (145,522 sq m) and the volume is about 21,000 cubic km (3129 cubic miles). The periphery amounts to about 8000 km (4968 miles) of coastline. Ice conditions in Baltic Sea:

As a long-term average the Baltic Sea is ice covered for about 45% of its surface

area at maximum annually. The ice-covered area during such a normal winter includes the Gulf of Bothnia, the Gulf of Finland, Gulf of Riga and Vainameri in the Estonian archipelago. The Baltic Proper does not freeze during a normal winter, with the exception of sheltered bays and shallow lagoons such as the Courland Lagoon. The ice reaches its maximum extent in February or March; typical ice thickness in the northernmost areas in the Bothnian Bay is about 70 cm for landfast sea ice. The thickness decreases when moving south. Freezing begins in the northern coast of Gulf of Bothnia typically in early November, reaching the open waters of Bay of Bothnia, the northern basin of the Gulf of Bothnia, in early January. The Bothnian Sea, the basin south of it, freezes on average in late February. The Gulf of Finland and the Gulf of Riga freeze typically in late January.

Severe (337,000 km2) Mild (122,000 km2) Average (206,000 km2)

The ice extent depends on whether the winter is mild, moderate or severe. Severe winters can ice the regions around Denmark and southern Sweden, and on rare cases the whole sea is frozen, such as in 1942. In 1987 some 96% of the Baltic Sea was iced, leaving only a small patch of open water to the west of Bornholm in the Baltic proper. Contrary to this, in milder winters the Bay of Bothnia and Gulf of Finland are the only larger area that is ice covered, in addition to coastal fringes in more southerly locations such as the Gulf of Riga. In spring, the Gulf of Finland and the Bothnian Sea normally thaw during late April, with some ice ridges persisting until May in the eastern Gulf of Finland. In the Bay of Bothnia ice usually stays until late May; by early June it is practically always gone. During winter, fast ice which is attached to the shoreline develops first, rendering the ports unusable without the services of icebreakers. Level ice, ice sludge, pancake ice or rafter ice form in the more open regions. Offshore of the landfast ice the ice remains very dynamic all year, because of its thickness it is relatively easily moved around by winds and therefore makes up large ridges and pile up against the landfast ice and shores.


5

Temperature Range:

In general ice forms in marine waters when temperatures are below zero on the Celsius grade, exact freezing temperature depending on the salinity of the water; more saline water freezes at lower temperatures. Because of this seawater freezes at.-0.20o C in the Bothnian Bay but at -0.45o C in the more salt Baltic Proper.

During the spring the sun starts to warm the sea surface and first the warming water turns denser and sinks deeper. This is because the density maximum of freshwater is at 4oC and for the brackish Baltic seawater at 2.3-3.5oC. From this point on warming decreases the density and the thus heat is transported to the deeper layers by the forces of wind and waves. This is the way the summer thermo cline forms dividing the upper water layer in two. Temperatures may drop 10oC within a few meters in thermo cline depths, shallower in the spring but at around 15-20m during the end of August.

During summer the water below the thermo cline usually remains as cold as during the melting period in early spring or 2-4oC. Below the halocline salinity is the dominant factor in determining density; temperature is fluctuating less and stays at ca.4-6oC.

As the atmospheric temperatures above the surface start cooling during the fall the sea starts to transfer heat energy to the colder air. Water cools as a result and sinks until it meets water having temperatures within the density maximum. Thermo cline and thus the density differences in the upper layer disappear and wave and wind action mixes finally the whole layer above the halocline. As Baltic seawater reaches its freezing point 1 oC to 0.1oC it turns into ice.

Ice properties in Baltic Sea: The Baltic Sea is a brackish inland sea, the largest body of brackish water in the

world. Brackish water is water that is saltier than fresh water, but not as salty as sea water. It may result from mixing of seawater with fresh water, as in estuaries, or it may occur as in brackish fossil aquifers. Technically, brackish water contains between 0.5 and 30 grams of salt per liter. There are various types of ice defined by WMO (World Metrological Organization) in Baltic Sea as follows:

New ice: A general term for recently formed ice which includes frazil ice, grease ice, slush and shuga. These types of ice are composed of ice crystals which are only weakly frozen together (if at all) and have a definite form only while they are afloat. • Frazil ice: Fine spicules or plates of ice, suspended in water. • Grease ice: A later stage of freezing than frazil ice when the crystals have coagulated to form a soupy layer on the surface. Grease ice reflects little light, giving the sea a matt appearance. • Slush: Snow which is saturated and mixed with water on land or ice surfaces, or as a viscous floating mass in water after a heavy snowfall. • Shuga: An accumulation of spongy white ice lumps, a few centimetres across; they are formed from grease ice or slush and sometimes from anchor ice rising to the surface.


6

Nilas: A thin elastic crust of ice, easily bending on waves and swell and under pressure, thrusting in a pattern of interlocking 'fingers' (finger rafting). Has a matt surface and is up to 10 cm in thickness. Maybe subdivided into dark nilas and light nilas. • Dark nilas: Nilas which is under 5 cm in thickness and is very dark in colour. • Light Nilas: Nilas which is more than 5 cm in thickness and rather lighter in colour than dark nilas. • Ice rind: A brittle shiny crust of ice formed on a quiet surface by direct freezing or from grease ice, usually in water of low salinity. Thickness to about 5 cm. Easily broken by wind or swell, commonly breaking in rectangular pieces. Young ice: Ice in the transition stage between nilas and first-year ice, 10-30 cm in thickness. Maybe subdivided into grey ice and grey-white ice. • Grey ice: Young ice 10-15 cm thick. Less elastic than nilas and breaks on swell. Usually rafts under pressure. • Grey-white ice: Young ice 15-30 cm thick. Under pressure more likely to ridge than to raft. First-year ice: Sea ice of not more than one winter's growth, developing from young ice; thickness 30 cm - 2 m. May be subdivided into thin first-year ice/white ice, medium first-year ice and thick first-year ice. Thin first-year ice/white ice: First-year ice 30-70 cm thick. Thin first-year ice/white ice first stage: 30-50 cm thick. Thin first-year ice/white ice second stage: 50-70cm thick

The basic requirements set for the project are:

ICE CLASS: Finnish-Swedish 1A super

SIZE: ~ 150000 t dwt,

ICEBREAKING CAPABILITY: Baltic conditions There exist a number of interactions between the vessel and the ice. The

following is a list of some: 1. Proceeding in level ice 2. Going astern in level ice 3. Ramming ridges 4. Impact forward and quarters hips during a turn 5. Wedging between two ice pieces (or in a narrow lead) 6. Impact with a multi-year floe 7. Impact with an underwater projection of an iceberg 8. Impact with ice pieces in the track of an icebreaker 9. Ice pushed against by an icebreaker (similar to jamming ice between ship and quay when berthing) 10. Ice pieces impact bottom and bilge in shallow water 11. Ship beset in ice

1.3 Type of Propulsion System:


7

Pod propulsion system without any rudder and shafting and can generate thrust to arbitrary directions of 360 degrees. Utilizing this characteristic, double acting tanker (DAT) was built at Sumitomo Heavy Industries, Ltd. DAT is a double-bows tanker, which one bow is a bulbous bow and another is an ice breaking bow, in order to enable co-existence of icebreaking ability to navigate on ice sea area (strike through: “under water oil field”) with 0.8 meter thick ice and usual navigation ability on normal sea without loosing propulsive efficiency.

Bulbous bow can reduce resistance of the ship by about 15% from ordinary ice breaking ship with ice breaking bow (fuel economy 20%), and in addition during navigation on ice sea area, broken pieces of ice can be separated from hull by propeller flow and thus high ice breaking efficiency is expected. Main Advantages of the Azipod Propulsion

• Excellent dynamic performance and maneuvering characteristics, ideal even in harsh arctic and offshore environments.

• Eliminates the need for long shaft lines, rudders, transverse stern thrusters, CP-propellers and reduction gears.

• Combined with the power plant principle, it offers not only new dimensions to the design of machinery and cargo spaces, but also reduced levels of noise and vibration, less downtime, as well as increase safety and redundancy.

• Operational flexibility leads to lower fuel consumption, reduced maintenance costs, less exhaust emissions and increased redundancy with less installed power.

• The Azipod unit itself has a flexible design. It can be built for pushing or pulling, open water or ice conditions. The Azipod can be equipped with skewed propellers, with or without a nozzle.

• Excellent wake field due to improved hydrodynamics.

1.4 Hull Strengthening:

Hull strengthening due to Ice Load is dependent on:

• Ice conditions. • Type of operation.

Hull Strengthening can be based on

• Ice classification Rules. • Direct Calculations. • Combined.(Ice class rules as reference)

1.5 Trade Route:

The trade route is decided to carry crude oil from Belokamenka (Murmansk Russia) to Rotterdam (Netherlands) via Baltic Sea to the oil refineries. The ship will perform pendulum service between the two ports.


8

1.6 Classification:

The selection of classification depends on specific oceans and sea areas in the context of current and earlier commercial shipping developments for ice operation and applicable ice classes. For Baltic Sea region FSICR (Finnish - Swedish Ice Class Rules) 1A/1C, November ‘2004 (after amendments to the old rules) is used. The above selection of classification is done on the basis of:

• Requirements of Administrations • Area of operation (Ice level, Air/water temperature) • Chartered requirements, and • Future flexibility


9

CHAPTER 2

FIXING OF MAIN DIMENSIONS


10

2.1 Preliminary Investigation:

Russia ended 2006 with its seventh straight year of growth, averaging 6.4% annually since the financial crisis of 1998. High oil prices and a relatively cheap ruble are important drivers of this economic rebound. The Baltic is as a export outlet for Russian crude/products and increasing its importance in Europe’s energy needs. The Republic of Russia, has become second largest oil producer after Saudi Arabia in world, plans major energy infrastructure investments to keep up with increasing demand in European countries. The oil statistics of Russia:

Oil - production: 10.5 million bbl/day (2006 est.)

Oil - consumption: 2.9 million bbl/day (2006 est.)

Oil - exports: 7.6 million bbl/day (2006 est.)

Oil imports from Russia have increased in Europe. Various European countries shares the Russian oil Export; like Netherlands 9.1%, Germany 8%, Ukraine 6.4%, Italy 6.2%, China 6%, US 5% etc. Shipments in North Baltic:

• Export set to double in next 5 years. • Need of Ice Class Tankers up to Aframax/Suezmax size. • 100-150 million tons per year of oil transport is estimated for the future in the

arctic and far eastern areas of Russia.

The North Baltic, with a particular focus on the Port of Murmansk, is set to double output over the next five years. Presently 20% of all Russian oil export is finding its way to world market through the port of Murmansk. .The Russian Arctic region has oil reserves of about 100 Billion tons for the future which is 75% of total Russian oil reserves. Low temperatures and ice infestation of the waters in the north Baltic are a fact of life during the winter, typically November/December to March. The optimum size appears to be Aframax size around 110,000 dwt & Suezmax ships .


11

2.1.1 Mission Analysis: Type : Double skin segregated ballast crude oil

double acting Ice Class Tanker Type of cargo : Crude oil Trade Route : Belokamenka (Murmansk Russia) to Rotterdam (Netherlands) Feature of trade : Pendulum Service Relevant Rules and Regulations : IMO, ILLC, SOLAS, MARPOL etc Dead weight : 150,000 t Service speed : 15 Kn (open water) and 5 Kn (1.0 m thick Ice) Classification : FSICR, LRS Radius of Action : 3800 Nautical Miles Shape of Hull : Design from first principle Shape of Stern : Form like the Bow of a normal Ice Breaker Shape of Stem : Bulbous bow is provided as per normal

Tankers Before starting on the design, the design problem is defined analyzing the different frontiers that will influence the entire design. System operational requirements include cargo and ballast pumping capabilities, speed, crude oil washing (COW) system, inert gas system (IGS), emissions, and possibly ballast water exchange in the future. All of these systems must work together in a safe, timely manner, while accommodating the schedule constraints of a round trip. Constraints include:

• Propulsion power • Machinery box volume • Deckhouse volume • Cargo block volume • Deadweight tonnage • Stores capacity

2.1.1.1 Hold Capacity

Hold capacity depends on stowage factor for crude oil, 1.13 to 1.24 m3/t

2.1.1.2 Engine Plant

Space necessary for the engine plant and the mass of engine plant and the fitting of the podded thrusters are the deciding factors. Engine plant should be capable of providing power for propulsion as well as lighting, navigation, heating coils, heaters, steering gear etc. Engine room is located in the aft region.


12

2.1.1.3 Super structure & deck house

Superstructures are usually arranged towards the ends. The forecastle is helpful in preventing the shipping of green water. Normal sheer is not given to the ship, for ease of construction. Camber is given so that water can drain freely from main deck. Camber also increases local strength of the deck.

2.1.1.4 Shape of the hull, stern, stem The parameters describe the actual hull form with standard ship design coefficients: Beam to Draft Ratio, Length to Beam Ratio, Block Coefficient, and Depth to Draft ratio. These allow the optimizer to choose a variety of ship shapes and size. The following are the some of the important points in relation with shaping the hull;

• Minimization of Resistance , • Interaction between hull and propeller, • Favourable hull in connection with behaviour in both Ice and Open water. • Favourable hull in connection with production • Favourable hull related to stability.

Stern: As the stern part is to be capable of breaking the ice, it should be shaped like bow of an icebreaker with necessary arrangements to fit the Azipod. A bulbous bow is provided at aft in the vicinity of propeller.

Stem: The stem is as per the normal conventional tankers provided with a bulbous bow. Stem must be able to accommodate two bow thrusters.

2.1.1.5 Rules & Regulations Governing Double Hull Tanker Construction

The different rules and regulations governing double hull tanker construction are,

1. Classification Society Rules 2. IMO Regulations

1. International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978 relating thereto (MARPOL 73/78) - Annex I: Prevention of pollution by oil. (MARPOL).

The important parts of this convention are, • Annex I: Prevention of pollution by oil • Annex II: Control of pollution by noxious liquid substances • Annex III: Prevention of pollution by harmful substances in packaged form • Annex IV: Prevention of pollution by sewage from ships • Annex VI: Prevention of Air Pollution from Ships


13

There are lot of amendments and the 1992 amendments to Annex I of the convention which deals with pollution by oil brought in the "double hull" requirements for tankers, applicable to new ships (tankers ordered after 6 July 1993, whose keels were laid on or after 6 January 1994 or which are delivered on or after 6 July 1996) as well as existing ships built before that date, with a phase-in period. New-build tankers are covered by Regulation 13F, while regulation 13G applies to existing crude oil tankers of 20,000 dwt and product carriers of 30,000 dwt and above. Regulation 13G came into effect on 6 July 1995. Regulation 13F requires all new tankers of 5,000 tonne dwt and above to have to have their entire cargo length to be protected by ballast tanks or spaces other than cargo and fuel oil tanks as follows: (i) Wing tanks or spaces of width

w = 0.5 + dwt/20000 m or 2 m whichever is lesser. The min value of w = 1 m

(ii) Double Bottom tanks or spaces of height

At any cross section the depth of each double bottom tank space shall be such that the distance “h” between the bottom of cargo tanks and the moulded line of the bottom shell plating measured at right angles to the bottom shell plating is given by,

h = B/15 or 2 m, whichever is lesser The min value is of “h” 1m.

(iii) The aggregate capacity of ballast tanks.

On crude oil tankers of 20,000t deadweight and above, the aggregate capacity of wing tanks, double bottom tanks, fore peak tanks and aft peak tanks shall not be less than the capacity of segregated ballast tanks required to meet the requirements of regulation 13F.

(iv) Ballast and cargo piping

Ballast piping and other piping such as sounding and vent piping shall not pass through cargo tanks.

The amendments also considerably reduced the amount of oil which can be discharged into the sea from ships (for example, following the cleaning of cargo tanks or from engine room bilges). Originally oil tankers were permitted to discharge oil or oily mixtures at the rate of 60 litres per nautical mile. The amendments reduced this to 30 litres. For non tankers of 400 grt and above the permitted oil content of the effluent which may be discharged into the sea is cut from 100 parts per million to 15 parts per million.

Regulation 24(4), which deals with the limitation of size and arrangement of cargo tanks, was also modified. Regulation 13G applies to existing crude oil tankers of 20,000 dwt and product carriers of 30,000 dwt and above. Tankers that are 25 years old and which were not constructed according to the requirements of the 1978 Protocol to MARPOL 73/78 have to be fitted with double sides and double bottoms. The Protocol applies to tankers ordered after 1 June 1979, which were begun after 1 January 1980 or completed after 1 June 1982. Tankers built according to the standards of the Protocol


14

are exempt until they reach the age of 30. Existing tankers are subject to an enhanced programme of inspections during their periodical, intermediate and annual surveys. Tankers that are five years old or more must carry on board a completed file of survey reports together with a conditional evaluation report endorsed by the flag Administration. Tankers built in the 1970s which are at or past their 25th must comply with Regulation 13F. If not, their owners must decide whether to convert them to the standards set out in regulation 13F, or to scrap them. Another set of tankers built according to the standards of the 1978 protocol will soon be approaching their 30th birthday - and the same decisions must be taken.

2. The delivery of which are on or after 6th July 1996 have to have their International Convention for the Safety of Life at Sea (SOLAS), 1974

The important parts of this convention are, • Chapter II-1 - Construction - Subdivision and stability, machinery and

electrical installations. • Chapter II-2 - Fire protection, fire detection and fire extinction • Chapter III - Life-saving appliances and arrangements • Chapter IV - Radio communications • Chapter V - Safety of navigation • Chapter VI - Carriage of Cargoes (except liquids and gases in bulk) • Chapter VIII - Nuclear ships • Chapter IX - Management for the Safe Operation of Ships • Chapter X - Safety measures for high-speed craft • Chapter XI-1 - Special measures to enhance maritime safety • Chapter XI-2 - Special measures to enhance maritime security • Chapter XII - Additional safety measures for bulk carriers

The Protocol of 1978

The 1978 Protocol was adopted at the International Conference on Tanker Safety and Pollution Prevention, which was convened in response to a spate of tanker accidents in 1976-1977. The conference adopted measures affecting tanker design and operation, which were incorporated into both the SOLAS Protocol of 1978 as well as the Protocol of 1978 relating to the 1973 International Convention for the Prevention of Pollution from Ships (1978 MARPOL Protocol). The 1978 SOLAS Protocol made a number of important changes to Chapter I, including the introduction of unscheduled inspections and/or mandatory annual surveys and the strengthening of port State control requirements. Chapter II-1, Chapter II-2 and Chapter V were also improved.

The main amendments included the following: 1. New crude oil carriers and product carriers of 20,000 dwt and above are required

to be fitted with an inert gas system. 2. An inert gas system became mandatory for existing crude oil carriers of 70,000

dwt and above by 1 May 1983, and by 1 May 1985 for ships of 20,000-70,000 dwt.


15

3. In the case of crude oil carriers of 20-40,000 dwt there is provision for exemption by flag States where it is considered unreasonable or impracticable to fit an inert gas system and high-capacity fixed washing machines are not used. But an inert gas system is always required when crude oil washing is operated.

4. An inert gas system was required on existing product carriers from 1 May 1983 and by 1 May 1985 for ships of 40-70,000 dwt and down to 20,000 dwt which are fitted with high capacity washing machines.

5. In addition to requiring that all ships of 1,600 grt and above shall be fitted with radar, the Protocol requires that all ships of 10,000 grt and above have two radars, each capable of being operated independently

6. All tankers of 10,000 grt and above shall have two remote steering gear control systems, each operable separately from the navigating bridge.

7. The main steering gear of new tankers of 10,000 grt and above shall comprise two or more identical power units, and shall be capable of operating the rudder with one or more power units.

The May 1994 amendments (MSC) Adoption: 25 May 1994 Entry into force: 1 January 1996

Regulation 15.1 requires all tankers of 20,000 dwt and above built after 1 January 1996 to be fitted with an emergency towing arrangement to be fitted at both ends of the ship. Tankers built before that date had to be fitted with a similar arrangement not later than 1 January 1999. The December 1996 amendments Adoption: 6 December 1996 Entry into force: 1 July 1998

Chapter II-2 was considerably modified, with changes to the general introduction, Part B (fire safety measures for passenger ships), Part C (fire safety measures for cargo ships) and Part D (fire safety measures for tankers). The changes made mandatory a new International Code for Application of Fire Test Procedures intended to be used by Administrations when approving products for installation in ships flying their flag.

Regulation 12-2

Access to spaces in the cargo area of oil tankers 1. This regulation applies to oil tankers constructed on or after 1 October 1994 2. Access to cofferdams, ballast tanks, cargo tanks and other spaces in the cargo areas

shell be direct from the open deck and such as to ensure their complete inspection. Access to double bottom spaces may be through a cargo pump room, pump room, deep cofferdam, pipe tunnel or similar compartments subject to considerations of ventilation aspects.

3. For the access through horizontal openings, hatches or manholes, the dimension shall be sufficient to allow a person wearing a self contained air breathing apparatus and protective equipment to ascend or descend and ladder without


16

obstruction and also to provide a clear opening to facilitate the hoisting of an injured person from the bottom of the space. The minimum clear opening should not be less than 600mmx600mm.

4. For access through vertical openings or manholes providing passage through the length and breadth of the space, the minimum clear opening should be not less than 600mmx800mm at a height of not more than 600mm from the bottom shell plating unless or other footholds are provided.

5. International Convention on Load Lines, 1966 The Convention includes Annex I, divided into four Chapters: • Chapter I - General • Chapter II - Conditions of assignment of freeboard • Chapter III - Freeboards • Chapter IV - Special requirements for ships assigned timber freeboards

Annex II covers Zones, areas and seasonal periods. Annex III contains certificates, including the International Load Line Certificate.

2.1.1.6 Vessel Belokamenka (Murmansk, Russia)

IMO NO : 7708314

Latitude: 69° 07'N, Longitude: 033° 16'E Flag Russian federation DNV ID : 11713 GT : 188728 NT : 125883 Capacity : 350000 Dwt

Draft : 23 meters

2.1.1.7 Port of Rotterdam (Netherlands)

Code: NL0051, UNTAD Code: NLRTM

Latitude: 51° 54.100'N, Longitude: 004° 26.100'E

There are no restrictions regarding length and beam of the ship. Maximum draft allowed is 22.55 m.


17

The size of the port’s industrial area and its position at the gateway of the European inland waterway network makes the port of Rotterdam ideally located for the transshipment of cargo. The port of Rotterdam is well equipped for handling bulk and general cargoes, coal and ores, crude oil, agricultural products, chemicals, containers, cars, fruit, and refrigerated cargoes.

2.1.2 Evaluation of DAT and conventional tanker

In order to evaluate the new concept DAT in a more realistic way, the tanker and a route was considered based on following assumptions:

(1) Size of vessel :Suezmax (2) Route : Baltic Sea (3) Main engine output : Based on charts or model tests (4) Ice conditions around the route : statistical data between 1990-2003

In the calculation, the principal dimensions of DAT are almost the same as a conventional tanker because of its geometrical similarity with the conventional Tankers. Table 2.1 Principal dimensions as estimated by ARCOP

Double acting ships (Ice Class): (main characteristics)

DWT (t) 63,000 90,000 120,000 LOA (m) 219.5 252.0 289.0 LBP (m) 202.0 228.0 268.0 B (m) 34.0 40.0 46.0 T (m) 13.0 14.0 15.0 D (m) 17.0 19.0 22.0 Power 14.5 18.0 22.0

2.1.2.1 Principal particulars of the Tempera/Mastera: Ship type: Crude oil and oil product carrier LOA: Approx. 252.00m LBP: 230.00 m Bm: 44.00 m Dm: 22.50 m TDesigned: 14.50 m TScantling: 15.30 m Speed: 13.5 knots in open water and 3 knots in 1 m thick Ice condition (Ice class 1AS) Propulsive power: 21MW Power: nominal output is 16 MW


18

Size of the DAT influences by

• Limitations for the Draught

• Icebreaking assistance: the Beam of the ship Table 2.2 Some Ice class ships: S. No. Imo No Dwt(t) T(m) VS(Kn) LBP(m) B(m) D(m)

1 114639 14.80 15.10 240.90 44.00 21.00 2 9305568 117153 15.40 14.00 240.79 44.00 22.00 3 9000584 154970 17.52 14.60 260.76 43.90 24.40 4 hull 5310 157300 17.00 16.00 261.00 48.00 23.70 5 9290385 159062 17.00 15.37 261.80 48.00 23.10 6 9311622 162362 16.50 15.00 263.50 50.00 23.00 7 9320726 166546 16.50 15.30 270.41 50.00 22.50

Above data shows:

• The Double Acting Tankers have more breadth than the conventional tankers of same deadweight.

• Beam of the DAT is more because of good Ice breaking capability; also the smaller length reduces the lightship weight by some amount and subsequent reduction in cost.

• For the same length of tankers, DAT is having more or less same deadweight as conventional tankers with more breadth for Suezmax size tankers because of the increased Engine plant mass and space for HFO and Stores and long operation time.


19

Sketches

Typical general arrangement of the vessel is given below. The sketches are not to the scale.

BODY PLAN

Department of

Fig 2

f Ship Technol

20

2.1 Typical

logy, CUSAT, B

GA

B.Tech (NA$SBB), Batch – XX

XIX


21

2.2 First estimates of displacement/volume

Preliminary calculation of displacement is based on the displacement coefficient CD

CD = Deadweight/Displacement

For DAT, the value of CD is taken as 0.823 (Parent ship data).

Displacement = 150000/0.823 = 182260.02 t

2.3 Preliminary selection of main & auxiliary machinery

From empirical relation for calculating power delivered for conventional tanker. Power delivered, PD = (Δ0.567 × VT

3.6)/1000 (Volker’s Formula) Where VT = Trial speed PD = 16471.78 KW PB = 1.12* PD = 18448.39 KW

Minimum required propulsion SMCR power demand (CP-propeller) for average-size tankers with Finnish-Swedish ice class notation (for FP-propeller add +11%) [Ref. 1] Fig 2.2


22

SMCR of engine considering FP Propeller =32000kw [Ref. 1] Selected Engine

Type: 9TM620 Number:3 Manufacture: STORK WARTSILA DIESEL CO. Holland [Ref. 7] Rated output: 12,750KW Rated speed: 428rpm Consumption of heavy fuel oil: 174G/KWH +5% Consumption of lube oil: 1.3+0.3G/KWH Greatest weight/piece: 270T Highest exhaust temperature ahead of the turbine:550 C degrees Highest exhaust temperature of single cylinder: 425 C degrees Ambient temperature: 38Centigrade (ISO)

Auxiliary Machinery As an approximation the power of auxiliary engines is taken as 15 % of the main engine power.

15 % of main engine power = 0.15*12.75x3 = 5737 KW.

2.4 First estimate of main dimensions and coefficients

The main dimensions have a decisive effect on many of the ship characteristics. It affects

Stability Hold capacity Hydro dynamic qualities such as resistance, manoeuvring, sea keeping Economic efficiency Initial cost

Determining the main dimensions, proportions and form coefficients is one of the most important phases of overall design.

Crude oil tankers are essentially slow speed ships carrying imperishable cargo. The shipment of crude oil over the last two decades has increased tremendously. Hence the need for economic optimality in design, capacity etc is necessitated.

The double skin tankers have a slightly reduced L/D ratio as compared to single skin tankers. But both have similar B/T and L/B ratios.

2.4.1 Symbols list and their units Dwt - Dead weight (t) Δ - Displacement (t) LBP - Length between perpendiculars (m) V - Velocity (kn)


23

g - Acceleration due to gravity (m/s2) B - Moulded breadth of the ship (m) D - Moulded depth of the ship (m) T - Draft of the ship (m) CB - Block coefficient of the ship Fn - Froude number PD - Power delivered (KW) ΔEP - Engine plant mass (t) ΔSE - Steel mass (t) Δou - Out fit mass (t) E - Lloyd’s equipment number

2.4.2 The stepwise procedure to find the length of a 150,000 ton DAT can be summarized as below:

• Find Range of length by Danckwardt formula for a conventional tanker of 150,000 ton.

• Estimate the Block coefficient. • Determination of B, T and D from the ratios (L/B, B/T and L/D) obtained from

the registered ice class ships ranging form 115,000 to 160,000 ton deadweight. The ratios must be chosen to provide more breadth than conventional tankers or L/B and L/D ratios should be comparable to Tempera/Mastera.

• Select the ratios. • Iterate the length found to satisfy the required deadweight.

Danckwardt formula:

LBP = (5.2 ±0.2-0.15×Δ×10-5)×Δ1/3

LBP = 267.98 m to 290.66 m [Ref. 2]

Range of length selected:

From the lengths obtained by the above formulae a range of length is selected. The range is from 260 m to 290 m

2.4.2.1. Estimation of Block Coefficient (CB) CB = 0.975-(0.9×Fn) +- 0.02 Danckwardt Formula [Ref. 2] Fn = V/√ (gL) [Ref. 2]

CB corresponding to the length found above is thus calculated. Range of CB is from 0.817 to 0.857 Selected CB = 0.837


24

2.4.2.2. Determination of B, T, D

B, T and D are calculated from the ratios (L/B, B/T, L/D) obtained from parent ships.

Table 2.2 Ratios of Main Dimensions Ratio Range Taken L/B 5.27-5.94 5.40 B/D 1.799 -2.222 2.05 T/D 0.700 - 0.736 0.71

B/T 2.506 – 3.03 2.86

L/T 14.884 – 16.38 15.70

Fn 0.148 – 0.163 0.16

First Iteration Selected length is L = 260 m

Breadth We have the value of L/B = 5.40 B = 48.15 m

Draught We have the value of L/T = 15.70 T = 16.56 m

Depth We have the value of B/D = 2.05 D = 23.49 m

Displacement Δ = L.B.T.CB × 1.008 × 1.006

= 175958.6 t (1.006 is for skin correction) Equipment Number (E) E = L (B + T) + 0.85L (D-T) + 250 = 18605

Steel mass [Ref . 2] ΔSE = Δ7

SE [1+0.5× (CB8 – 0.7)] + 900 t (addition for Ice Class 1A)

Δ7SE = K.E1.36

(K= 0.029 to 0.035 for tankers with 1500 < E <40,000)

E = 1500 – 40000 for tankers Take K = 0.035


25

Δ7SE = 22426.6

CB

8 = Block Coefficient at 0.8D = CB + (1- CB) (0.8D – T) /3T = 0.843

ΔSE = 24933.5 t

Out fit mass

ΔOU = MOU× L × B + 100 t (approx additional weight for Helipad and helicopter) MOU = 0.24 [Ref. 2]

ΔOU = 3104.44t Delivered Power SMCR = 32000 KW [Ref. 36] Engine Plant mass

ΔEP = 0.72X(SMCR) 0.78 = 2351.52, Light ship weight, ΔLS

= (ΔSE + ΔOU + ΔEP) X1.02, = 30997.331 t

Dwt = Δ - ΔLS = 144961.31t

Table 2.3 Results of First Iteration

LBP 260.0m

B 48.15 m

T 16.56m

D 23.49m

CB 0.837

Δ 17598.6 t

ΔSE 24933.6 t

ΔOU 3104.4 t

ΔEP 2351.5 t

ΔLS 30997.3 t

DWT 144961.3 t


26

Similar iterations were done using the same procedure. Results are given in the table below

Table 2.4 Results of Iterations

DWT V/S Length, a graph is plotted got from several iterations. The graph is given below. In X-axis length is plotted, Dwt in Y- axis

LENGHT(m) 263

150000

Dwt (t)

Fig 2.3 Graph for DWT V/S Length

LBP (m)

B (m) D (m) T (m) CB Δsteel(t) ΔOU (t) ΔEP(t) ΔLS (t) Dwt(t)

253.00 46.85 22.85 16.11 0.836 23227 2945 2352 29094 132838255.00 47.22 23.04 16.24 0.836 23703 2990 2352 29626 136177257.00 47.59 23.22 16.37 0.836 24186 3036 2352 30165 139570260.00 48.15 23.49 16.56 0.837 24934 3104 2352 30997 144961261.00 48.33 23.58 16.62 0.837 25182 3128 2352 31275 146722262.00 48.52 23.67 16.69 0.838 25444 3151 2352 31565 148700263.00 48.70 23.76 16.75 0.838 25696 3174 2352 31846 150491264.00 48.89 23.85 16.82 0.838 25950 3198 2352 32129 152296265.00 49.07 23.94 16.88 0.839 26217 3221 2352 32425 154326


27

Table 2.5 Results of Final Iteration

LBP 263.0 m

B 48.7 m

D 23.76 m

T 16.75 m

CB 0.838

Δse 25696 t

ΔOU 3174 t

ΔEP 2352 t

ΔLS 31846 t

DWT 150491t

The Dwt obtained satisfies the requirements with an extra safety of margin

2.4.3 Water Plane Area Coefficient

CW = 0.76CB + 0.273 [Ref. 3]

= 0.76*0.838 + 0.273 = 0.91

2.4.4 Midship Section Coefficient:

CM = 0.9 + 0.1* CB [Ref. 4]

= 0.984

2.4.5 Prismatic Coefficient:

CP = CB / CM = 0.852 [Ref. 8]

2.5 Development of preliminary lines

Having fixed the main dimension and coefficients the next step is to develop the lines plan of ship. Hull form of the ship has a decisive effect on almost all the aspects of ship performance like: a) Trim & stability b) Resistance c) Controllability d) Sea keeping


28

It also has to satisfy the requirements regarding displacement, volume and freeboard. A design from first principles is generally the rule.

Within the selected values of L, B, T, D, CB etc there are infinite number of shapes and forms, which will satisfy the displacement equation.

Development of lines by first principles involves a lot of trial and error and quality of lines depends largely on experience. Computer software AutoCAD can be used to develop lines. Bulbous bow is designed according to a paper by Alfred M. Eracht “Design of Bulbous bow” SNAME transaction vol. 89 (1979)

2.5.1 Stem Design:

Stem is designed as per the conventional tankers with a bulbous bow.

2.5.2 Stern Design

Cruiser stern designed because while running aft, the vessel may encounter severe ice loads. To distribute the ice loads, cruiser stern is more suitable. Because of its smooth curvature it is more suitable for running aft.

2.6 Preliminary General Arrangement

The allocation and dimensions of main spaces like length of cargo tanks, width of double skin and height of double bottom etc of double hull tankers are determined by the regulation 13 F MARPOL 73/78 [ref6] for the construction of new tankers. All new tankers of dead weight above 5000 t are to have either a double hull or mid deck or an alternative arrangement for the prevention of oil out flow in case of damage to the hull due to collision or grounding.

The Mid Deck arrangement makes use of a horizontal subdivision (mid deck) of the cargo spaces so that the oil pressure is reduced to a level less than the hydrostatic pressure. As a result of this even if the hull is damaged the oil out flow will be considerably reduced.

Double hull construction makes use of wing tanks and double bottom spaces throughout the cargo region, so that even if the outer hull is damaged, oil out flow will not occur. Double hull construction is the modern trend.

2.6.1 Ballast Tanks or Spaces

According to regulations 13F and 13G of MARPOL 73/78, the entire cargo length should be protected by ballast tanks or spaces other than cargo and fuel oil tanks.

a) Wing Tanks or Spaces

Wing tanks or spaces should extend for the full length of ships side, from the top of the double bottom to the upper most deck, disregarding a rounded gunwale where fitted. They should be arranged such that the cargo tanks are located in board of the moulded line of side shell plating nowhere less than the distance W at any cross section is measured at right angles to the side shell, as specified below.


29

w = 0.5 + Δ / 20000 m = 9.61 m or, w = 2 m, which ever is the lesser.

The minimum value of w is 1m. w is taken as 3.0 m to satisfy the ballast requirements.

b) Double Bottom Tanks or Spaces

At any cross section the depth of each double bottom tank or space is such that the distance h between the bottom of the cargo tanks and the moulded line of the bottom shell plating measured at right angles to the bottom shell plating is not less than specified below.

h = B /15 = 3.25 m OR h = 2 m, whichever is lesser

The minimum value of h is 1.0m Therefore h = 3.0 m to satisfy the ballast requirements.

2.7 Initial estimates of consumables, stores and cargo Range = 3773 nm Speed = 15.0 Knot (open water) = 5.0 Knot (Most severe Ice conditions)

∴Max Hours of travel, H = 754.6 Hrs Hours in port = 48 Hrs No of officers = 21 No of crew = 23

2.7.1 Volume of heavy fuel oil (VHFO) Specific fuel consumption, SFC = 185 g / KWh. (Assumed for a slow speed large bore diesel engine) Brake power, PB = 32000 KW Mass of heavy fuel oil, MHFO = SFC × PB × H / 1000000 +20% (Allowance) = 5360 t Volume of HFO, VHFO = MHFO /0.95 = 5643 m3

2.7.2 Volume of diesel oil (VDO) SFC = 220 g /KWh Power of auxiliary machinery, PAUX

= (1554 + 38.4 X1 – 0.269 X2 + 0.046X12 +16.21 X2

2

- 2.31X1.X2) 0.76 (H. SCHREIBER, HANSA 114 (1977) NO 23 P 2117)

Where X1 = 0.001 × Dwt = 150.5


30

X2 = 0.001 PB’ ≈ 18.45

∴ PAUX = 10522 KW Mass of diesel oil, MDO = SFC × PAUX × H/1000000

= 1858 t Volume of diesel oil, VDO = MDO/0.85

= 2186 m3

2.7.3 Volume of lubricating oil (VLO) Mass of lube oil, MLO = 0.03 (MHFO + MDO)

= 216.6 t Volume of lube oil = 59/0.9 = 240.6 m3

2.7.4 Volume of fresh water, (VFW) Consumption of fresh water = 20 litres / person / day Mass of fresh water, M FW = 27.6 t Volume of fresh water, VFW = 27.6 m3

2.7.5 Volume of washing water (VWW)

Consumption 120 liters /person/ day for officers 60 liters /person/ day for crew Mass of washing water, MWW = 130.4 t Volume of washing water, VWW = 130.4 m3

2.7.6 Mass of crew and effects Assume 150 kg per officers and 120 kg per crew Mcrew = 150*21 + 23*120 = 5.91 t

2.7.7 Mass of Provision

Assume 8 kg/officer/day and 6 kg/crew/day

Mass of provision = 9.6 t Mass of stores & crew = MHFO + MDO + MLO + MFW + MWW + MCRW +MPRO = 7609 t

2.7.8 Mass of Cargo

Mass of cargo, MCR = Dwt - Total mass of stores & crew

= 150491 – 7609

= 142882 t

2.8 Checks on hold and tank capacity


31

The total capacity of the ship is the volume required for cargo plus the minimum volume required for ballast.

2.8.1 Volume of hold VHD = (VDD + VSH + VCA + VHT + VHS)-(VFP + VAP + VER + VDB

+ VTA + VSS + VCOF) Where: VHD = volume of hold VDD = volume up to upper deck VSH = volume of sheer VCA = volume of camber. VHT = volume of hatchway trunks VHS = volume of holds in superstructure VFP = volume of forepeak tank VAP = volume of aft peak tank VER = volume of engine VDB = volume of double bottom VTA = volume of tank in the hold VSS = volume of side tanks

(1) VSH = VHT = VHS = VTA = 0 (2) VDD = LBT CB (D/T)C

B/C

W ; CW = 0.76×CB+0.273= 0.92 [Ref. 3] (3) CB = 0.838

VDD = 247196 m3

(4) VAP = KAP (LAP/LBP)2 L.B.D.CBD [Ref. 3] Where KAP = 2.16 (2-K)

K = 3.33 AB/L –0.667 = 1.0745 AB = 0.523 L when CB > 0.72 BSRA REPORT NO 333 KAP = 1.998 LAP = 0.05 LBP = 13.15 m

CBD = block coefficient at uppermost deck. [Ref. 3] = CB + 0.25/T (D-T)*(1-CB) = 0.855 ∴ VAP = 1299 m3

(5) VFP = KFP (LFP/LBP) 2 .L.B.D.CBD [Ref. 3]

Where KFP = 1.7 K.b b = 1.4 (with bulbous bow) KFP = 2.5573


32

LFP = 0.07 L = 18.41 m ∴ VFP = 3260 m3

(6) VER = B.(D-DDB).LER K ((KERA+KERF)/2) [Ref. 3] Where LER = 0.12 L = 31.56 m.

KERA = 5.4 XERA /L +0.11 XERA = 0.05*L = 13.15 m KERA = 0.38 KERF = 5.4 XERF /L +0.11 = 1.028 XERF = 0.17*L = 39.066

∴VER = 24717 m3

(6) VCA = (2/3) × (L-LAP- LER - LFP – LCOF) × B/50 × B × C3

Where C3 = 0.76CB + 0.273 = 0.909 ∴VCA = 5659 m3

(7) VCOF = LCOF ×B×D = 3471m3 (Length of Cofferdam taken as 3 m)

In segregated ballast tankers the ballast water is carried in the wing tanks and the double bottom tanks. Therefore the volume required for ballast water must be subtracted from the volume of hold, to get the actual volume available for the carriage of cargo.

2.9.2 Volume of Required Minimum Segregated Ballast Water

The minimum volume of ballast water that the vessel should carry is given by the MARPOL 73/78, Regulation 13.

Draft at aft, Ta = 0.7T (for full propeller immersion) = 11.725 m. Minimum draft, Tm = 2+0.02L = 7.26 m. Maximum trim by stern, tm = 0.015L

= 3.945 m. Draft at fore, T f = Ta–tm = 7.78 m.

Tmean = (Ta + Tf)/2 = 9.75 m. Mean draft, Tmean > Tm Ballast displacement, ΔB = (Tmin /T) (CW

/CB

)* Δ ∴ΔB = 73548 t Mass of ballast water = ΔB-ΔLS

= 41702 t Minimum volume of ballast water = 41702 /1.008 = 41371 m3


33

Available volume of ballast water

Total length of double bottom = LBP- LAP - LFP - LER - LCOF ≈ 196.88 m

Depth of double bottom = 3.0 m

Width of side skin = 3.0 m

Volume of double bottom = LDB*BDB*DDB*0.7

= 196.88*48.7*3*0.7

= 20135 m3 Total length of side skin = LBP- LAP - LFP - LER - LCOF ≈ 196.88m Width of side skin = 6 m Depth of side skin = 23.76 – 3 = 20.76 m Volume of side skin = 196.88*6*20.76*0.95 = 23297 m3 Total ballast volume available = Volume of double bottom + Volume of side skin + Volume of Aft peak tank = 20135 + 23297 + 1299 = 44731 m3 Available volume of ballast water is greater than the minimum required.

2.9.3 Volume of Cargo Required

Volume of Cargo required = (Mass of cargo, MCR)/0.85

= 142882/0.85 =168096 m3

2.9.4 Volume of Cargo Available

Volume of Cargo available = (VHOLD - VBALLAST)*0.98

The cargo hold is filled up to 98% of the capacity in order to account for the expansion of the oil (Ref: Principles of Naval Architecture)

VHD = (247196 + 5659) – (3260 + 24717/(D - DDB) + 3471 + 1299)

= 254394 m3

Volume of ballast water in cargo space = Volume of ballast water in double bottom and double skin = 33259 m3

Volume of cargo available = (254394 – 4473 )*0.98


34

= 205469 m3

Available volume is greater than required volume.

Stowage factor = Available volume/Mass of cargo

= 205469/142882 ≈ 1.4 m3 / t

2.10 Preliminary resistance calculation and propeller performance

The preliminary powering estimation is done by the method presented by Guldhammer and Harvald

2.10.1 Residual Resistance Coefficient LBP = 263 m LWL = 103 % LBP = 1.03*229.8 = 270.89 m CBL = (LBP / LWL) * CB = 0.838/ 1.03 = 0.813 ∇ = 263*48.7*16.75*0.838*1.006 = 182337 m3

LWL/∇1/3 = 236.694/182337 1/3 = 4.79 From graph LWL/∇1/3 = 5 103 CR = 1.58 LWL/∇1/3 = 4.5 103 CR = 1.95 LWL/∇1/3 = 4.79 103 CR ≈ 1.77 CML = 0.9 + 0.1* CBL = 0.9813 CP = CBL / CML = 0.828

Various corrections applied are 1) B/T correction 103CR corrected = 103 CR +0.16(B/T-2.5) = 1.36 + 0.16(48.7/16.75-2.5) = 1.835

2) LCB correction Assuming LCB aft of midship .hence no correction is required.

3) Shape correction Assuming section not extremely U no correction is applied

4) Bulbous bow correction Assuming ABT/AX = 1.0 no corrections are made. Where ABT is the area of the

bulbous bow at the fore perpendicular and AX is the area of midship section. 5) Appendages

No rudder and bilge keel corrections are made 6) Incremental Resistance

For L = 200, 103 CA = 0 L = 250, 103 CA = -0.2 For L = 263, 103 CA = -0.2 Therefore 103 CR = 1.835 – 0.2 = 1.635

7) Air Resistance 103 CAA = 0.07


35

103 CR = 1.635+ 0.07= 1.705 8) Steering Resistance

103 CAS = 0.04 103 CR = 1.705 + 0.04 = 1.745 CR = 0.001745

2.10.2 Frictional Resistance Coefficient CF

Frictional resistance coefficient is calculated using the ITTC 1957 formula, CF =0.075/ (log10 Rn -2)2

Rn , Reynolds number = VLWL/ν V = 15.0 Knot = 7.716 m/s LWL = 270.8 m ν = 1.16*10-6 m2s-1 at T = 0 0C Rn = 18.01 * 108 CF, Frictional resistance = 0.00142 CT, Total resistance ≈ 0.00142 +0.001745 = 3.165 x 10-3

2.10.3 Total resistance

RT = CT*1/2ρSV2 where S is wetted surface area and it is calculated by using the following formula

S = 1.7LWL T + ∇/T (Mumford’s Formula)

= 18513 m2

There fore total resistance

RT = 3.165 x 10-3*0.5*1.008*18513*(7.716)2

= 1758 KN

RT (with allowance of 20 %) = 2109

PE = RT V = 2109*7.716KW

= 16279 KW PB = PE /( ηm x ηt x ηg x ηH ) η H = Hull efficiency (Twin screw ships)

= 0.9 ηm = Efficiency of motor

= 0.96 η t = Efficiency of transformer (ABB Finland)

= 0.97

η g = Efficiency of generator


36

= 0.96

PB = 20233 KW 2.11 Initial stability and Freeboard calculations

2.11.1 Freeboard Check (Practical Ship Design by DGM Watson)

Minimum freeboard is a statutory requirement for all vessels under the Merchant Shipping Act of 1968. The freeboard assigned should be in accordance with the 1966 IMO Load line Convention Rules. The conventional tankers fall into IMO’s type A ship with regard to freeboard. It is observed that double hull tankers have excess freeboard. This is due to segregated ballast tank volume, which remains empty in the loaded condition. Thus higher freeboard is inevitable

Tabular freeboard (for type A ship) for L = 263 m is 3089 mm

(After interpolation from table given in Ship Design and Construction by Taggard)

This is the basic freeboard to which various corrections wherever applicable is applied

a) Correction for CB

When CB is greater than 0.68, the basic freeboard is multiplied by = (CBD +0.68)/1.36 = 1.116 Corrected freeboard = 3089*1.116 = 3447.32 mm

b) Correction for Depth

Freeboard is increased by (D – L/15) R, where R is 250 for ships with L > 120m.

R = 250, since L>120m

Correction to be added

= (D-L/15)×R, since D>L/15

= (23.76-263/15)×250

= 1556.66 mm

Corrected freeboard

= 3447.32 + 1556.66

= 5003.98 mm


37

c) Correction for Superstructure

For lengths 125m and above, the standard height of superstructure is 2.3 m. the effective length of a superstructure of standard height can be taken as its length itself. Assuming standard height of superstructure for the ship, the length of superstructure is taken from a similar ship as 0.15 LBP and the length of forecastle is assumed to be 0.07 LBP Length of superstructure = 0.15 L Length of forecastle = 0.07L Effective length of superstructure = 0.15L + 0.07L = 0.22 L

When the effective length of superstructure and trunks of a ship is 1.0 L the basic freeboard shall be reduced by an amount 1070 mm (from table).

When the effective length of superstructure and trunks is less than 1.0 L the basic freeboard shall be reduced by an amount x % of 1070 mm Therefore Correction x =15.7% Therefore Correction factor to be added = 0.157*1070 = 167.99mm Corrected freeboard = 5003.98 – 167.99 = 4835.99 mm

d) Correction for Sheer

No sheer is given. So there is sheer deficiency and penalty for no sheer is to be applied.

Sheer Deficiency = (SAft+SFor’d)/16 SAft = 22.23L + 667 = 6513.5 mm SFor’d = 44.47×L+1334 = 13029.6 mm Sheer Deficiency (SD) = (SAft+SFor’d)/8×1/2 = (6513.5 +13029.6)/16 = 1221.4 mm Correction = SD {0.75- E/2L}; Where E is the effective length Of super structure = + 781.6 mm Correction for Ice thickness of 1000 mm = 8/9*(1.0) = 888.8 mm Corrected freeboard = 4835.99 + 781.6 + 888.8 = 6506.4 mm Available freeboard = 7010 mm

Hence the vessel has sufficient free board as per load line regulations 1966


38

d) Minimum Bow Height

Minimum bow height = 56*L (1-L/500)*(1.36/ (CB+0.68)) mm

(LRS PART 3, CHAPTER 3, SECTION 6)

= 6254 mm

A forecastle deck is 2.3 m high above main deck.

Available freeboard = 7010 mm

Total bow height = Available freeboard + 2300

= 9320 mm

Hence minimum bow height required is satisfied.

2.11.2 Preliminary Stability Check

Preliminary Stability check is done by Prohaska’s first approximate method (Transactions of the Institution of Naval Architects, 1947)

h* A non dimensional parameter referred to as residuary stability coefficient.

GZ = h*BM+GMSinθ

GM = KB+ BM- KG [Ref. 3]

1). KB = T* (0.9-0.3*CM – 0.1*CB) [Ref. 4] CM = 0.9+0.1* CB = 0.983 KB = 8.73 m 2). BM = IT/Volume displacement [Ref. 4] = (f (CW)*B2)/ (12*T* CB ) f (CW) = 0.096+0.89*CW

2 (Normand’s Formula) CW = 0.95* CP + 0.17*(1-CP)1/3 [Ref. 4] = 0.899 f (CW) = 0.815 BM = 11.47 m 3). KG = 0.58 D [Ref. 3] = 13.78 m GM = 8.73 + 11.47 – 13.783 = 6.42 m GM/B = 6.42/48.7 = 0.131 [Ref. 3] Required range of GM/B is 0.08 to 0.25, the calculated value is under the acceptable range, hence the stability is satisfactory.


39

For the given values of T/B and D/B h* is read for the six angles of heel Viz.15º, 30º, 45º, 60º, 75º, 90º.

Table 2.6 GZ at different angles of heel Angle of Heel

(θ) h* GMSinθ BM x h* GZ (m)

0 0 0 0 0

15 0.009 1.66 0.103 1.763

30 0.09 3.21 1.03 4.24

45 -0.185 4.53 -2.12 2.41

60 -0.325 5.55 -3.72 1.83

75 -0.475 6.20 -5.44 0.76

90 -0.62 6.42 -7.11 -0.69

The curve of intact stability is plotted and checked according to the guidelines set by IMO A. 167

Fig 2.4 Preliminary GZ curve

30

0.8

7.2

6.4

5.6

4.8

4.0

3.2

2.4

1.6

ANGLE OF HEEL(deg)

RIG

HTI

NG

LEV

ER G

Z (m

)

807060402015105

8.0

50


40

Table 2.7 IMO Requirements

Description Requirement Available

Area under GZ curve upto 30° Should not be less than 0.055 m rad 1.021 m-rad

Area under GZ curve upto 40° Should not be less than 0.09 m rad 1.69 m-rad

Area under GZ between 30° & 40° Should not be less than 0.03 m rad .66 m-rad

Maximum righting lever, GZmax

Should be at least 0.2 m at angle of heel greater than 30° 4.26 m

Angle of GZmax Should occur at an angle greater than

30° 31.5o

Initial GM Should not be less than 0.15 m 6.42 m

The IMO conditions are satisfied.

2.12 Flowchart of Design Process: The flowchart of design process given below is not standard flowchart of any

ship design process. The flowchart is prepared based on the direction given by the project coordinator and comply with the design guidelines given to us.


41

B

FLOW CHART OF DESIGN

READ DEADWEIGHT, SPEED AND RANGE

CALCULATE THE MAIN DIMENSIONS

ESTIMATE DISPLACEMENT FROM – L x B x T x CB x ρSW x k

ESTIMATE LIGHT SHIP WEIGHT

DWT = DISPLACEMENT – LIGHTWEIGHT

A INPUT, DIMENSIONAL RATIOS FROM


42

C

YES

FBD. ≥ REQUIRED FBD.

YES

DWT ≥ GIVEN DWT

A CHECK WITH IMO REQUIREMENTS

YES

A

A

B

NO

CALCULATE INITIAL STABILITY


43

D

C

A STOWAGE FACTOR

WITHIN THE REQUIRED RANGE

YES

NO

ESTIMATE CAPACITY

PRELIMINARY GENERAL ARRANGEMENT

RESISTANCE AND POWERING

SELECTION OF MAIN ENGINE, POD AND AUXILIARY MACHINERY

DETAILED GENERAL ARRANGEMENT


44

E

D

CHECK FOR VOLUME

REQUIREMENTS

A CHECK WITH IMO CRITERIA

D

NO YES NO YES

DETAILED CAPACITY CALCULATION

DETAIL CALCULATION OF STABILITY AND TRIM FOR MOST SEVERE CONDITION


45

E

CHECK WITH MIN CALCULATED

SECTION MODULUS

NO YES

MIDSHIP SECTION DESIGN

DESIGN SUMMARY AND CONCLUSION

STOP


46

2.13 Final Main dimensions:

After all the requirements, the final dimensions are fixed and are shown in following table given below.

Table 2.7 Final Dimensions LBP 263.0 m

B 48.7 m

D 23.76 m

T 16.75 m

CB 0.838

Δse 25696 t

ΔOU 3174 t

ΔEP 2352 t

ΔLS 31846 t

DWT 150491t

Hence the final dimensions of the ship are fixed. Now the next step is to generate the hull form that satisfies the above dimensions.


47

CHAPTER 3

HULL GEOMETRY


48

3. HULL GEOMETRY

3.1 Lines Design

Having fixed the main dimension and coefficients the next step is to develop the lines plan of ship. Hull form of the ship has a decisive effect on almost all the aspects of ship performance like:

e) Trim & stability f) Resistance g) Controllability h) Sea keeping

It also has to satisfy the requirements regarding displacement, volume and freeboard. A design from first principles is generally the rule. But such a hull form should be tank tested to determine its resistance and propulsion characteristics, which is beyond the scope of this project. Hence lines plan is designed using the standard data available.

Within the selected values of L, B, T, D, CB etc there are infinite number of

shapes and forms, which will satisfy the displacement equation. A standard hull form

has been selected from B.S.R.A (British Ship Research Association) report no. 333.

Other advantages in choosing a BSRA standard form are:

1) Development of lines by first principles involves a lot of trial and error and

quality of lines depends largely on experience. This can be avoided by selecting a

standard hull form.

2) Fairing of lines is minimized.

3) Standard lines are tank tested and found satisfactory in resistance & sea keeping

qualities.

Standard lines give offsets for bulbous bow. So separate design of bulbous

bow is avoided.


49

3.1.1 Design Procedure

B.S.R.A presents waterline offsets for normal forms and bulbous bow forms on a

base of block coefficient. The offsets are presented in terms of the ratio (waterline

ordinate/full half breadth) for each of the standard B.S.R.A water lines as shown in table 3.1.

Table 3.1 offsets of standard B. S. R. A. waterlines Stn/ WL A B C D E F G H J K % of T 7.69 15.38 23.08 38.46 53.85 69.23 84.62 100 115.4 130.77Real WL 1.29 2.58 3.87 6.44 9.02 11.6 14.17 16.75 19.33 21.9

0 0 0 0 0 0 0.57 5.92 6.37 10.47 11.73 0.5 0.57 0.57 0.8 1.03 1.82 5.23 9.68 12.41 14.22 15.71

1 1.71 2.51 3.3 4.43 6.26 9.68 13.08 15.48 16.16 18.67 1.5 3.72 5.18 6.2 5.97 9.36 13.3 16.12 18.04 19.73 20.97

2 6.14 7.85 9.33 11.84 14.11 16.5 18.78 20.26 21.62 22.53 3 10.6 13.87 15.57 18.16 19.84 21.31 22.11 22.9 23.45 24.13 4 16.9 18.95 20.21 22.13 23.16 23.62 23.96 24.19 24.19 24.35 5 20.49 22.19 23.22 24.13 24.35 24.35 24.35 24.35 24.35 24.35 6 22.65 23.56 24.13 24.35 24.35 24.35 24.35 24.35 24.35 24.357 23.79 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35 8 23.84 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35

9 -16 23.9 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.3517 21.75 22.87 23.44 23.67 23.67 23.79 24.01 24.24 24.35 24.35 18 17.19 18.78 19.92 20.82 20.82 20.82 21.29 22.19 23.33 24.13

18.5 13.65 15.36 16.28 17.07 17.3 17.3 17.76 19.12 20.72 22.53 19 9.56 11.27 12.41 13.31 13.2 12.97 13.65 15.14 16.85 19.01

19.5 4.43 6.37 7.51 8.31 7.97 7.17 7.4 8.31 9.68 11.61 20 1.71 3.08 3.86 4.09 2.57 1.14 0.23 0 0.57 1.71

.

b) Stern Design Stern is design with a O-type bulbous bow with assumed height of 4.5 m, the shape of bulb is given by iteration on AutoCAD after drawing the half breadth plan and cross checking of all three views until the design is not satisfactory. Also the Icebreaking stern is designed like a bow of an Icebreaker.


50

Table 3.1 Stem Stern offsets Stern offsets (m) with respect to AP

wl 0 0.5 1 1.5 2 3 4 5 6 7 8 9 10 11 MDK

offset 14 7.5 6 5.6 6.1 10.5 11 11 7.62 -4.2 -

7.84 12.29 -

17 -

18 -19.5

Stem offsets (m) with respect to FP

wl 0 0.5 1 2 3 4 5 6 7 8 9 10 11 MDK

offset -

0.6 1.9 2.9 4.3 4.54 3.8 2.6 1.59 0.76 0.41 0.41 1.56 3.06 4.7 .

c) Pod Dimensions

Assumed pod entrance diameter = 4.3 m (calculated from a scaled drawing with some geometrical assumptions, Actual diameter can only be decided after the final selection of the pod)

3.1.1 Final Lines

The offset values obtained are plotted and a body plan is drawn. The station curves are extended up to the main deck / forecastle deck. Offsets at regular intervals of waterline are measured. The fairness is to be checked by drawing the half-breadth plan and profile plan.

The offsets so obtained are presented in table 3.2

WL spacing = 2.0 m LWL is 16.75 m above the base line. MDK is 23.76 m above the base line. STN spacing = 13.15 m. and STN 9 to STN 16 is parallel middle body = 92.05 m.

Φ1 = 27o, Φ2 = 24o (buttock angles), α = 70o (all values are under allowable limits) Measured flare angle (ψ) = tan-1[tan(Φ2)/sin(α)] = 45


51

FAIRED OFFSETS Station Spacing=13.15m waterline Spacing=2m

stn/wl 0 0.5 1 1.5 2 3 4 5 6 7 8 lwl 9 10 11 MDK

‐1 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 8.91 10.09 10.86

‐0.5 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 7.8 9.84 11.45 12.7 13.47 14

0 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 11.65 13.39 13.7 14.21 14.94 15.51 16.01

0.5 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 13.44 14.44 14.7 15.12 15.69 16.26 16.74

1 ‐ 2.34 3.3 4.15 4.88 6.06 7.23 10.65 13.79 15.39 16.45 16.76 17.16 17.78 18.27 18.7

1.5 1.56 4.09 5.62 7.06 8.41 10.69 12.57 14.43 15.97 17.01 17.78 18.08 18.51 19.02 19.46 19.9

2 3.74 6.75 8.93 10.42 11.73 13.86 15.4 16.72 17.86 18.77 19.41 19.61 19.88 20.26 20.61 20.91

3 7.79 12.06 14.07 15.5 16.62 18.27 19.3 20.14 20.84 21.23 21.55 21.67 21.86 22.13 22.38 22.62

4 11.71 15.89 17.88 19.31 20.34 21.68 22.45 22.94 23.23 23.4 23.51 23.51 23.6 23.69 23.69 23.85

5 14.66 18.19 19.99 21.09 21.89 22.93 23.49 23.76 23.91 24.06 24.16 24.19 24.23 24.35 24.35 24.35

6 16.97 20.06 21.58 22.51 23.08 23.72 24.05 24.16 24.16 24.21 24.28 24.3 24.35 24.35 24.35 24.35

7 18.37 21.23 22.6 23.31 23.72 23.73 24.08 24.26 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35

8 to 16 19.02 22.27 23.3 23.84 24.15 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35 24.35

17 18.33 21.32 22.45 22.99 23.32 23.7 23.91 24.06 24.91 24.29 24.35 24.35 24.35 24.35 24.35 24.35

18 14.82 17.5 18.81 19.63 20.16 20.73 21.03 21.26 21.51 21.82 22.22 22.4 22.72 23.25 23.81 24.3

18.5 10.84 13.56 14.98 15.95 16.64 17.45 17.84 18.09 18.3 18.58 19.19 19.25 19.78 20.68 21.66 22.58

19 5.96 9.4 10.62 11.58 12.3 12.99 13.11 13.11 13.34 13.88 14.71 15.67 15.67 16.67 17.81 18.8

19.5 1.81 5.27 6.55 7.35 7.86 8.32 8.14 7.56 7.1 7.2 7.88 8.25 8.94 10.17 11.52 12.75

20 0 1.36 2.55 3.39 3.9 4.15 3.57 2.48 1.48 0.69 0.11 0 0.29 1.7 3.55 5.23

Half Breadth ordinates (m)

Table 3.2


52

3.2 BONJEANS AND HYDROSTATIC CURVES

3.2.1. Bonjean Calculations.

In the Bonjean calculation the sectional area and moment of each station up to each waterline is calculated. This enables the calculation of displacement, LCB and VCB for any waterline for even keel and also trimmed condition.

The uses of Bonjean are: 1) Hydrostatic calculations 2) For flooding calculations. 3) Launching calculations 4) Longitudinal strength calculations.

The calculations are done by MS-excel 2007 with combining simpson’s and trapezoidal rules of integration. The results are given in the table 3.3 (area table) and table 3.4 (moment table)


53

Table 3.3 (Area values) Sectional Areas in m2

Table 3.3

BONJEAN AREAS Station Spacing=13.15m Waterline Spacing=2m wl/stn 0 0.5 1 1.5 2 3 4 5 6 7 8 lwl 9 10 11 MDK

‐1 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 0.00 11.88 49.88 86.75 ‐0.5 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 0.00 10.40 25.1 50.50 98.80 151.14 199.49 0 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 0.00 29.35 79.99 100.39 135.25 193.55 254.45 309.92 0.5 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 0.00 35.03 90.93 106.5 150.13 211.75 275.65 333.73 1 0 2.80 8.44 15.93 24.96 47.69 73.43 108.53 158.25 216.80 280.65 305.54 347.93 417.81 489.91 554.98 1.5 0 5.98 15.69 28.40 43.87 82.51 128.86 183.04 243.87 310.13 379.59 406.51 452.32 527.38 604.34 673.61 2 0 10.60 26.45 45.86 68.01 119.53 178.10 242.43 311.62 385.01 461.42 490.68 540.06 620.34 702.08 775.16 3 0 20.51 46.73 76.41 108.53 178.55 253.86 332.69 414.79 499.00 584.54 616.96 671.39 759.37 848.39 927.59 4 0 28.28 62.10 99.42 139.07 223.39 311.75 402.61 495.01 588.29 682.13 717.41 776.35 870.93 965.69 1049.36 5 0 33.29 71.61 112.79 155.77 245.59 338.57 433.13 528.49 624.41 720.90 757.15 817.65 914.81 1012.21 1097.92 6 0 37.48 79.19 123.40 168.99 262.79 358.34 454.90 551.47 648.25 745.18 781.63 842.49 939.89 1037.29 1123.00 7 0 39.98 83.93 129.94 176.97 271.53 367.26 463.94 561.22 658.62 756.02 792.54 853.42 950.82 1048.22 1133.93

8to16 0 41.94 87.60 134.82 182.81 279.94 377.34 474.74 572.14 669.54 766.94 803.46 864.34 961.74 1059.14 1144.85 17 0 40.14 84.04 129.55 175.86 268.03 365.23 459.23 558.65 656.55 753.87 790.4 851.27 948.67 1046.07 1131.79 18 0 32.71 69.09 107.62 147.41 229.34 312.89 397.49 483.00 569.65 657.68 691.14 747.54 839.48 933.60 1018.27 18.5 0 24.78 53.37 84.40 116.99 184.99 256.03 327.52 400.69 474.01 549.77 578.66 627.51 708.43 793.11 870.97 19 0 16.09 36.12 58.40 82.28 133.08 185.44 237.80 290.63 344.93 402.05 424.38 462.79 527.47 596.43 660.86 19.5 0 7.74 19.63 33.62 48.83 81.40 114.54 145.99 175.18 203.53 233.55 245.63 267.08 305.30 348.68 391.40 20 0 1.41 5.33 11.38 18.67 34.61 50.76 62.49 70.72 74.61 76.52 76.48 76.50 80.48 90.98 106.43

Area in m^2


54

Table 3.4 (Moment Values)

Moment about baseline in Table 3.3

BONJEAN MOMENTS Station Spacing=13.15m Waterline Spacing=2m stn/wl 0 0.5 1 1.5 2 3 4 5 6 7 8 lwl 9 10 11 MDK ‐1 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 0.00 237.60 1037.96 1882.78 ‐0.5 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 0.00 166.40 401.4 850.47 1770.67 2871.35 3978.35 0 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 0.00 393.45 1155.52 1492.7 2094.57 3203.73 4483.77 5753.82 0.5 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ 0.00 471.65 1311.57 1674 2317.63 3489.55 4832.59 6162.20 1 0 1.82 10.64 29.28 61.25 174.59 358.32 673.55 1224.08 1985.39 2944.77 3352.2 4088.24 5417.20 6932.28 8421.68 1.5 0 3.16 18.40 49.98 104.80 301.00 625.81 1115.24 1785.01 2647.24 3689.92 4142.9 4926.23 6353.39 7970.43 9556.09 2 0 5.31 29.91 78.27 156.45 415.60 826.80 1406.48 2168.56 3122.83 4269.89 4748.9 5606.64 7132.72 8849.96 10522.393 0 10.94 50.92 125.02 238.00 588.59 1117.15 1826.75 2730.59 3825.33 5108.93 5639.6 6585.20 8257.36 10127.28 11939.754 0 14.91 66.21 159.48 298.77 721.25 1340.48 2158.43 3175.09 4387.81 5795.52 6373.2 7397.20 9194.40 11184.36 13098.995 0 17.16 75.16 178.08 328.91 778.36 1429.97 2280.84 3330.29 4577.00 6024.75 6618.2 7669.29 9515.57 11560.97 13522.066 0 19.33 82.27 192.82 352.67 822.95 1491.33 2360.97 3422.96 4681.27 6135.17 6732 7789.48 9640.08 11685.48 13646.577 0 20.50 86.75 201.80 366.61 838.73 1509.33 2379.45 3449.65 4715.85 6176.85 6774.9 7832.65 9683.25 11728.65 13689.74

8to16 0 21.73 90.45 208.52 376.64 862.57 1544.37 2420.97 3492.37 4758.57 6219.57 6817.6 7875.37 9725.97 11771.37 13732.4617 0 20.65 86.79 200.58 362.83 810.23 1500.64 2340.79 3437.44 4709.24 6169.12 6767.2 7824.92 9675.52 11720.92 13682.0118 0 16.85 71.75 168.10 307.63 717.12 1302.83 2063.71 3005.17 4131.12 5452.59 6000.3 6979.81 8727.73 10705.37 12643.4618.5 0 12.84 56.13 133.67 248.08 583.07 1085.52 1725.04 2533.41 3484.27 4622.91 5095.7 5943.36 7482.64 9262.88 11045.8019 0 8.82 39.23 94.89 178.83 431.64 799.95 1269.72 1852.43 2557.37 3416.05 3781.3 4447.80 5678.72 7129.16 8604.93 19.5 0 4.64 22.79 57.79 111.28 272.45 506.27 787.12 1109.89 1476.72 1929.20 2126.6 2498.11 3226.75 4140.43 5119.66 20 0 0.89 7.03 22.18 47.95 119.80 239.63 338.39 433.65 479.05 511.20 509.6 508.28 586.72 810.92 1167.08

Moments in m^3


55

3.2.2 Hydrostatic Calculations

It is mandatory in the design of a ship to calculate and plot as curves a number of hydrostatic properties of the vessel’s form at a series of drafts. Through out its life a ship changes its weight, trim & freeboard. Its condition at any state of circumstances can be found from hydrostatic curves. Hydrostatic particulars corresponding to different waterlines are calculated. The calculations are done with MS-Excel software and the results are given in the table 3.4

List of formulae used. (Integration is performed using Simpson’s rule for port side and then doubled to get the total volume)

AWP = 2/3 h Σ f (A)

Mx = 2 h2/3 Σ f (M)

LCF, x =

IL = (2h3/3) Σ f (IL)

IF = IL – AWP x LCF2

IT = (2 h/9)Σ f (IT)

TPC =

∇ = (h/3) Σ f (∇)

Δ = ∇ x 1.008 x 1.006

MT = (h/3) Σ f (MT)

ML = (h2/3) Σ f (ML)

KB = MT/∇

BMT =

BML =

MCT1cm =

KM = BM +KB

TPC = AWP x ρ/100

h × Σ f (M)

Σ f (A)

AWP × 1.008100

IT

∇ IL

∇

ΔGML

100 LWL


56

LCB = ML/∇

CB =

CM =

CW =

CP =

∇

A ⊗BT

AWP

LB

CB

CM

LBPBT


57

Table 3.5

WL/PROP

V Δ LCBФ LCFФ TPC IL IT KB BML KMT MCT1cm CB CW CM CP

(m^3) (t) m (m) (t/cm) (m^4) (m^4) (m) (m) (m) (tm/cm)

0 13.49 75.17 27343723 770144 0.582

0.5 8,416 8,534 12.35 11.51 91.67 35917441 1268909 0.52 4124.76 152.99 1338.45 0.657 0.710 0.861 0.763

1 17,873 18,124 11.52 10.23 98.45 39922567 1504622 1.04 2176.51 85.23 1499.92 0.698 0.763 0.899 0.776

1.5 27,873 28,264 10.88 9.29 102.60 42638410 1652580 1.57 1498.26 60.86 1610.16 0.725 0.795 0.923 0.786

2 38,190 38,726 10.38 8.51 105.42 44609236 1753947 2.09 1148.26 48.02 1690.79 0.745 0.817 0.938 0.794

3 59,350 60,184 9.48 7.35 108.34 46884418 1858004 3.12 780.17 34.43 1785.33 0.772 0.839 0.958 0.806

4 81,195 82,335 8.58 5.72 110.26 48649183 1915912 4.17 594.76 27.76 1861.96 0.792 0.854 0.969 0.818

5 103,218 104,668 7.58 4.08 111.74 50079080 1961168 5.20 483.39 24.20 1923.78 0.806 0.865 0.975 0.827

6 125,759 127,525 6.67 2.56 113.66 52175224 2019406 6.23 414.29 22.29 2008.86 0.818 0.880 0.979 0.836

7 147,867 149,944 6.26 ‐0.75 116.51 56704169 2045824 7.27 383.44 21.11 2186.09 0.825 0.902 0.982 0.840

8 171,277 173,683 5.15 ‐1.72 118.16 59028911 2082660 8.33 344.44 20.49 2274.64 0.836 0.915 0.984 0.849

lwl 180,113 182,643 4.79 ‐2.01 118.81 59988798 2095122 8.73 332.80 20.36 2311.14 0.840 0.920 0.985 0.852

9 195,044 197,784 4.11 ‐2.53 119.88 61530147 2118420 9.38 315.08 20.24 2369.48 0.846 0.929 0.986 0.858

10 219,419 222,501 3.03 ‐4.46 122.90 66662641 2161410 10.45 302.71 20.30 2560.97 0.857 0.952 0.987 0.867

11 243,769 247,194 2.30 ‐4.24 124.23 68593246 2196343 11.50 280.48 20.51 2636.21 0.865 0.962 0.989 0.875

MDK 264,657 268,375 2.16 ‐3.13 124.66 68960547 2224990 12.41 260.11 20.81 2654.22 0.870 0.966 0.989 0.879

HYDROSTATIC PROPERTIES NOTE 1) + means Fwd of midship 2) ‐ ve means aft of midship


58

Hydrostatic parameters at designed load water line

∇ = 180,113m3

Δ = 182,643ton KB = 8.73m KMT = 20.36m KML = 341.5 m IL = 59988798m4 IT = 2095122 m4 TPC = 118.81ton MCT1cm = 2311.14ton-m LCF = -2.01m LCB = 4.79m CB = 0.840 CP = 0.852 CW = 0.920 CM = 0.985 The value of CB and Displacement are approximately same and hence the lines design is satisfactory.

Introduction

Documents

Transcript of Introduction