Myanmar Maritime University

Department of Naval Architecture and Ocean Engineering

Design of a Pleasure Craft with Catamaran Hull

Htike Aung Kyaw

NA 18

Kaung Zaw Htet

NA 32

Paing Hein Htet Tin

NA 38

Htaik Thu Aung

NA 42

Final Year Project

November 2012

Thanlyin

Myanmar Maritime University

Department of Naval Architecture and Ocean Engineering

Design of a Pleasure Craft with Catamaran Hull

Htike Aung Kyaw

NA 18

Kaung Zaw Htet

NA 32

Paing Hein Htet Tin

NA 38

Htaik Thu Aung

NA 42

Final Year Project

November 2012

Thanlyin

Myanmar Maritime University

Department of Naval Architecture and Ocean Engineering

Design of a Pleasure Craft with Catamaran Hull

Htike Aung Kyaw

NA 18

Kaung Zaw Htet

NA 32

Paing Hein Htet Tin

NA 38

Htaik Thu Aung

NA 42

Final Year Project

November 2012

Thanlyin

Myanmar Maritime University

Department of Naval Architecture and Ocean Engineering

Design of a Pleasure Craft with Catamaran Hull

Htike Aung Kyaw

NA 18

Kaung Zaw Htet

NA 32

Paing Hein Htet Tin

NA 38

Htaik Thu Aung

NA 42

A Paper Submitted to the Department of Naval Architecture and Ocean

Engineering in Partial Fulfillment of the Requirements for the Award of

the Degree of Bachelor of Engineering (Naval Architecture)

November 2012

Thanlyin

Myanmar Maritime University

Department of Naval Architecture and Ocean Engineering

We certify that we have examined, and recommended to the

Department of Naval Architecture and Ocean Engineering for an acceptance

of the paper entitled “Design of a Pleasure Craft with Catamaran Hull”

submitted by Htike Aung Kyaw NA 18, Kaung Zaw Htet NA 32,

Paing Hein Htet Tin NA 38 and Htaik Thu Aung NA 42 in partial fulfillment

of the requirements for the award of the degree of Bachelor of Engineering

(Naval Architecture).

Board of Examiners:

1. Daw Myint Myint Khine

Associate Professor and Head of Department --------------------

Department of Naval Architecture & (Chairman)

Ocean Engineering

2. Daw Khin Khin Moe

Lecturer --------------------

Department of Naval Architecture & (Supervisor)

Ocean Engineering

3. U Tin Tun

Part-time Lecturer --------------------

(Member)

4. U Myint Khin

Chief Engineer --------------------

Myanmar Shipyard (Sinmalike) (External Examiner)

Yangon

5. Lt. Cdr. Tin Tun Aung

Design and Planing Department --------------------

Naval Dockyard Headquarters (External Examiner)

i

Acknowledgements

It took a team of four people and a lot of hard work to create a

complete design of a powered catamaran. We really don’t know how to

express our gratitude to all those who provide assistance, encouragement and

constructive criticism. We totally are indebted to our teachers, professors and

rector of Myanmar Maritime University, friends and family.

We are much obliged to Professor Charlie Than, Rector of

Myanmar Maritime University for all the guidance and references he has

given us. We also want to thank Teacher Daw Myint Myint Khine, Head of

Department of Naval Architecture and Ocean Engineering for her

instructions and suggestions.

We are also very grateful to Teacher Daw Khin Khin Moe, Lecturer of

Naval Architecture and Ocean Engineering Department, Myanmar Maritime

University for giving us guidelines, advices and close supervision.

We are much indebted to Sayar U Tin Tun for his suggestions,

advices, helps and for the time he has given us for this project.

We also thank U Htay Aung and U Sein Win from Dala Dockyard.

We would like to thank Maj. Aung Myo Khant, Sayar U Win Htun,

U Tin Aung Win and all those who have helped us in every ways.

ii

Abstract

This project will include the design of a motor catamaran. This

project approaches the basic design concepts. Using the ideas of new

inventions and technologies and applying them to reality, we may have more

decent designs. For some reasons, those designs may not always be

successful on the market or are not yet in common use. One of those designs

is possibly the catamaran design.

Catamaran is a type of boat, which would be in many ways superior to

old traditional boats. They are still scarcely produced, but the production is

booming in recent years. Although there is an increase in demand, the

technology of making catamaran is still old with slow improvements. Thus it

is still not a tradition of building catamarans.

This design study is about developing a powered catamaran design

and bringing it with new technologies available, more environmental

friendly and increasing the safety of the passengers. It will also bring the

market of catamaran building in Myanmar to a certain level. Design is made

with the most user-friendly, automatic and maintenance-free whilst keeping

the new technical possibilities.

Our project will introduce an easy to construct fiber boat, used as a

pleasure craft, build with a catamaran hull form. The details of designing

concepts will be included in this project.

iii

Table of Contents

Page

Acknowledgements i

Abstract ii

Table of Contents iii

List of Figures vi

List of Tables x

Nomenclature xi

Chapter Title

1 Introduction 1

1.1 Developments 1

1.2 General Definitions 2

1.2.1 Multihulls 2

1.2.2 Pleasure Crafts/Luxury Crafts 2

1.3 Objectives and Scope of Project 3

1.3.1 Objectives 3

1.3.2 Scope of Project 3

2 Types of Pleasure Crafts, Yachts and Catamarans 5

2.1 Yachts 5

2.1.1 Definition 5

2.1.2 History 6

2.2 Motor Yachts Classification 7

2.3 Luxury Crafts or Pleasure Crafts 8

2.4 Types of Hull Forms 8

2.4.1 Displacement Hull 9

2.4.2 Semi-displacement or Semi-Planing Hull 10

2.4.3 Planing Hull 11

iv

2.4.4 Mono-hull and Multi-hulls 12

2.5 Catamarans 12

2.5.1 Definition, History, Advantages and Disadvantages 12

2.5.2 Types of Catamaran Hulls 14

3 Designing Concepts and Detail Design of Pleasure Craft with 27

Catamaran Hull

3. 1 Principal Particulars 27

3.2 Reference Ship Data and Contents 27

3.3 Step-by-Step Designing Procedures 30

3.4 Intended Voyage of the Designed Catamaran 33

3.5 Lines Plan and Bare-Hull Form Generation 34

3.6 General Arrangement Plan 35

3.7 Designed Ship’s 3D Image Renderings Including 38

Superstructure

3.8 Power Prediction by NavCad 42

3.9 Propulsion System with Volvo Penta IPS 600 44

(Inboard Performance System)

3.10 Sewage System 49

4 Rules and Regulations which this Pleasure Craft Complies 52

4.1 SOLAS 52

4.1.1 SOLAS Chapter IV, Part C (Ship’s Requirements) 52

4.1.2 SOLAS V for Pleasure Crafts 53

4.2 Rules and Regulations for the Classification of Yachts 54

and Small Craft, (Lloyd’s Register of Shipping)

4.2.1 Requirements from Part 2 55

4.2.2 Requirements from Part 3 57

v

5 Design Calculations for Pleasure Craft 61

5.1 Stability Calculation 61

5.1.1 Hydrostatic Curve Calculation 61

5.1.2 Cross Curve Calculation 63

5.1.3 Large Angle Stability (GZ Curve) 64

5.1.4 Equilibrium Condition (Still Water) 66

5.1.5 Equilibrium Condition (Sinusoidal Wave) 68

5.1.6 Limiting KG 70

5.1.7 Tank Calibration 71

5.2 Resistance and Powering Calculation 72

5.2.1 Viscous and Wave Interference Effects 72

5.2.2 Insel and Molland (1992) 73

5.2.3 Resistance Test Results of Ship Model, 74

Carried out in Towing Tank

5.2.4 Calculation from Towing Tank Results 75

5.3 Strength Calculation 81

5.3.1 Longitudinal Strength 81

5.3.2 Hull Construction by Glass Reinforced Plastics 83

(GRP/FRP), Requirements by Rules and Regulations

for the Classification of Yachts and Small Crafts,

Lloyd’s Register of Shipping

6 Model Making 89

7 Conclusion and Recommendations 99

7.1 Conclusion 99

7.2 Recommendations 100

References 102

Appendix 103

vi

List of Figures

Figure No Figure Name Page

Fig. 1.1 Typical sailing catamaran 2

Fig. 1.2 Typical racing trimaran 2

Fig. 1.3 Monohull pleasure craft 2

Fig. 2.1 Yacht 5

Fig. 2.2 General hull forms 8

Fig. 2.3 Hull forms 9

Fig. 2.4 General catamaran hull types 14

Fig. 2.5 Type-A catamaran hull 15

Fig. 2.6 Type-B catamaran hull 16

Fig. 2.7 Type-G catamaran hull 17

Fig. 2.8 Type-C catamaran hull 18

Fig. 2.9 Type-D catamaran hull 19

Fig. 2.10 Type-E catamaran hull 20

Fig. 2.11 Type-F catamaran hull 21

Fig. 2.12 Type-H catamaran hull 22

Fig. 2.13 HySuCat working principle 22

Fig. 2.14 Type-I catamaran hull (Bobkat) 24

Fig. 2.15 Type-J catamaran hull (Bobkat with HySuCat) 25

Fig. 3.1 Lines plan of Thidar catamaran 28

Fig. 3.2 Technical layout design of eCAT hybrid catamaran 28

Fig. 3.3 Body plan of designed hull 30

Fig. 3.4 Markers from offset table seen in perspective view of 33

Maxsurf

Fig. 3.5 Lines plan of designed craft 33

Fig. 3.6 Profile view 34

Fig. 3.7 Half-breadth plan 34

Fig. 3.8 Body plan view 35

vii

Figure No Figure Name Page

Fig. 3.9 Bare-hull form generated by Maxsurf, perspective view 35

Fig. 3.10 (a) General arrangement plan (Profile view) 36

Fig. 3.10 (b) General arrangement plan (Tunnel-lower deck) 36

Fig. 3.10 (c) General arrangement plan (Main deck) 36

Fig. 3.11 3D rendering (Starboard view) 38

Fig. 3.12 Internal compartments 38

Fig. 3.13 Wire mesh plan view (Top view) 38

Fig. 3.14 3D rendering (Forward-starboard view) 39

Fig. 3.15 Wire mesh (Profile view) 39

Fig. 3.16 Wire mesh (Forward-bow view) 39

Fig. 3.17 3D rendering (Aft-stern view) 40

Fig. 3.18 3D rendering (Aft-starboard view) 40

Fig. 3.19 Wire mesh (Aft-port view) 40

Fig. 3.20 3D rendering (Forward-port view) 41

Fig. 3.21 3D rendering (Forward-starboard view) 41

Fig. 3.22 Wire mesh (AutoCAD) 41

Fig. 3.23 Speed vs. Resistance graph 44

Fig. 3.24 Speed vs. Power graph 44

Fig. 3.25 Volvo Penta IPS installation layout 45

Fig. 3.26 Volvo Penta IPS propeller advantages 45

Fig. 3.27 System components, Volvo Penta IPS 46

Fig. 3.28 Joystick docking system 46

Fig. 3.29 Section showing U-Joint drive shaft arrangement 47

with counter-rotating propellers

Fig. 3.30 A complete unit of Volvo Penta IPS 48

Fig. 3.31 INCINOLET, The electric incinerating toilet 49

Fig. 3.32 Usage procedures of INCINOLET 49

Fig. 3.33 Assembly of INCINOLET 50

viii

Figure No Figure Name Page

Fig. 4.1 Two-wire insulated electrical distribution systems 59

Fig. 5.1 Hydrostatic curve 62

Fig. 5.2 Cross curve 64

Fig. 5.3 GZ curve 65

Fig. 5.4 Sectional area curve for still-water condition 66

Fig. 5.5 Sinusoidal wave condition 68

Fig. 5.6 Sectional area curve for sinusoidal wave condition 70

Fig. 5.7 Limiting KG vs. Displacement curve 70

Fig. 5.8 Tank calibration 71

Fig. 5.9 Hull form configurations of catamarans 72

Fig. 5.10 Fn4/CF vs. CT/CF curve 76

Fig. 5.11 Speed vs. Resistance curve 80

Fig. 5.12 Speed vs. Effective power curve 80

Fig. 5.13 Longitudinal strength curve 82

Fig. 5.14 Laying-up of keel when moulding hull as 85

semi-completed halves

Fig. 5.15 Laying-up of transom boundary and chine line knuckles 86

Fig. 5.16 Hull laminate for motor craft 87

Fig. 5.17 Hull laminate for motor craft 87

Fig. 5.18 Hull laminate for motor craft 87

Fig. 6.1 Stations cut out using hacksaw 90

Fig. 6.2 Tools used in making wooden mould 91

Fig. 6.3 Assembling stations and plating shells 92

Fig. 6.4 Profile view of wooden mould 92

Fig. 6.5 View from below (Fish view) 93

Fig. 6.6 View from aft (Transom) of wooden mould 93

Fig. 6.7 Profile view of fiber model 95

Fig. 6.8 View from forward-starboard side of fiber model 95

ix

Figure No Figure Name Page

Fig. 6.9 View from aft (Transom) of fiber model 96

Fig. 6.10 Underside of fiber model 96

Fig. 6.11 View from forward-port underside 96

Fig. 6.12 Fiber model placed in towing tank 97

Fig. 6.13 Assembly to towing tank carriage 97

Fig. 6.14 Dynamometer assembled in tunnel 98

Fig. 6.15 Resistance test being carried out 98

x

List of Tables

Table No Table Name Page

Table 2.1 Points score for 10-types of catamaran hull relating to

the given aspects

25

Table 3.1 Offset table of Thidar (I+II) catamaran 29

Table 3.2 Offset table of Geo-Sim 15m catamaran (Limits for our

design)

31

Table3.3 Offset table of designed 15m catamaran 32

Table 3.5 NavCad prediction data 43

Table 4.1 List of radio equipments installed 53

Table 5.1 Intact hydrostatic table 61

Table 5.2 Intact hydrostatic table (Continued) 62

Table 5.3 Cross curve table (KN values in meters) 63

Table 5.4 Load case (Weight distribution) 64

Table 5.5 Equilibrium condition (Still water) 67

Table 5.6 Equilibrium condition particulars (Sinusoidal condition) 68

Table 5.7 Tank data 71

Table 5.8 Resistance test results 74

Table 5.9 Calculation of CT/CF and Fn4/CF 75

Table 5.10 Model particulars by Molland A.F. 76

Table 5.11 Values relating to hull separation to length ratio for

each models

77

Table 5.12 Calculation of CW and 78

Table 5.13 Calculation of total resistance and effective power 79

Table 5.14 Load case (Weight distribution) 81

Table 5.15 Result of longitudinal strength calculation 82

xi

Nomenclature

b Ultimate Flexural Strength

U Ultimate Tensile Strength

Viscous Resistance Interference Factor

Wave Resistance Interference Factor

(1+k) Form Factor

A Summation of Respective Length Times Height of All Erections

above the Weather Deck which have a Length or Breadth

Greater than B/2.

B Breadth of Ship

CB Block Coefficient

Cf Frictional Resistance Coefficient

CG Center of Gravity

Cr Residual Resistance Coefficient

Ct Total Resistance Coefficient

CT CAT Total Resistance Coefficient of Catamaran

Cvol Volume Coefficient

Cw Wave Resistance Coefficient

CWCAT Wave Resistance Coefficient of Catamaran

CWDEMI Wave Resistance Coefficient of Demihull

D Depth of Ship

d Internal Diameter of Bilge

DSC Digital Selective Calling

EPIRB Emergency Position Indicating Radio Beacon

Fn Froude Number

FRP Fiber Reinforced Plastics

GA General Arrangement

GC Glass Content of Laminate (Excluding the Gelcoat

xii

GMDSS Global Maritime Distress and Safety System

GMT Metacentric Height (Transverse)

GRP Glass Reinforced Plastics

GZ Righting Arm

HSC High Speed Crafts

HySuCat Hydrofoil-Supported Catamaran

IMO International Maritime Organization

IOR International Offshore Rule

IPS Inboard Performance Systems

KB Vertical Center of Buoyancy

KG Vertical Center Gravity

KML Distance from Keel to Metacenter (Longitudinal)

KMT Distance from Keel to Metacenter (Transverse)

KN Righting Arm

KW Factor to be Multiplied for Correction of Plate Laminate

KZ Factor to be Multiplied for Correction of Stiffener

L Rule Length of Ship (LWL+LOA)/2

LBP Length Between Perpendicular

LCB Longitudinal Center of Buoyancy

LCF Longitudinal Center of Floatation

LCG Longitudinal Center of Gravity

LED Light Emitting Diode

LM Length of Model

LOA Length Overall

LPP Length Between Perpendiculars

LS Length of Ship

LWL Length on Water Line

m Index Number

MCTC Moment Change Trim One Centimeter

xiii

MSC Maritime Safety Community

NAVTEX Navigational Telex

PE total Total Effective Power

PES Effective Power of Ship

Pt bare Bare-hull Effective Power

Q Capacity of Pump

Rbare Bare-hull Resistance

Rn Reynold Number

Rr Residual Resistance

Rt m Resistance Total of Model

Rtotal Total Resistance

S Separation between Demihulls

S Wetted Surface Area

SART Search and Rescue (Radar) Transponder

SES Surface Effect Ship

SOLAS Safety of Life at Sea

T Draft

TPC Tonne per Centimeter Immersion

VCB Vertical Center of Buoyancy

Vel Velocity

VHF Very High Frequency

Vm Model Speed

VS Ship Speed

W Total Weight of Reinforcement in the Laminate

WPA Water-plane Area

WSA Wetted Surface Area

λ Scaling Factor

Submerged Volume

1

Chapter 1

Introduction

1.1 Developments

Boats are really amazing. While studying Naval Architecture, we

became more and more interested in this field. We found that boats and ships

have much more capabilities than nowadays. Moreover, we were inspired by

the possibilities of multihulls. Multihulls have many superior facts than

similar size of mono-hulls. But why aren’t they very popular in the market?

So, we decided to focus on catamaran design for our graduation project.

This project concentrates on the concept of an easy to handle pleasure

motorboat constructed as a catamaran. We decided that this craft is to be of

easy to use and with a priority in luxury and distinctive design. Seeking the

current market situations, there aren’t any places for catamarans here in

Myanmar. Catamarans are used as luxury crafts mostly in Australia, New

Zealand and can also be found in America. Very few market places can be

found here in Asia.

Another fact is that, there seems to be a gap between the design

qualities and technical superior concepts. Many engineering concepts apply

to boats and they are lacking design, style, grandeur and elegance. This

might probably be the reason why high technological inventions end up as

not practically useful and gradually lost its place for the market. What if we

took those high technological components and tried mixing them into most

stylish package providing luxury, will it fit the definition of a luxury yacht?

Is it even possible for a catamaran to bear these ideas at once?

Boats are designed with a wide diversity; no other means of

transportation is close enough to coming. Speaking of a wide diversity, there

are countless intentions for seagoing vessels. This states clearly that we can

never say any type of a boat without describing its purpose and usage. For

2

example, an oil tanker must have different characteristics from a passenger

ship/liner of the same size. Of course, there are also many sorts of oil tankers

too. Pleasure boats are like sports cars. They must define elegancy, luxury,

joy and most importantly safety.

1.2 General Definitions

1.2.1 Multihulls

Multihulls are crafts with more than one structural body, usually of

two, three or five hulls, namely catamaran for two, trimaran for three,

pentamaran for five hulls. The use of multiple hulls resulted in a vessel with

a lot of space. It is particularly well suited for carrying passengers and low-

density cargos. Multihull design produces a very stable platform, particularly

suitable for the usage in fast ferries.

Fig. 1.1 Typical sailing catamaran Fig. 1.2 Typical racing trimaran

1.2.2 Pleasure Crafts/Luxury Crafts

Pleasure crafts are vessels that are

used only for sports, fishing or

recreational purposes. They do not

operate for any financial gain to the

owner. They are generally owned by

private individuals.

Fig. 1.3 Monohull pleasure craft

3

1.3 Objectives and Scope of Project

1.3.1 Objectives

• To design a whole pleasure craft with the knowledge and the studies

that we’ve learnt.

• To use the ideas of new inventions and technologies and to apply them

into reality and to have more decent designs.

• To bring the construction of catamarans in Myanmar to a certain level.

• To point out the facts that catamarans are far more superior and a lot

better in many ways than most monohull ships.

• To build an eco-friendly, increased passenger safety and most user-

friendly, low maintenance boat.

1.3.2 Scope of the Project

In Chapter 1, the developments, general definition and objectives of

the project are reported. Picture illustrated general definition of multihulls

and luxury crafts are also included.

Chapter 2 comprises of detail definitions and histories of yachts,

luxury crafts/pleasure crafts, catamarans and classification of motor yachts,

as well as the general hull form definition and specific types of catamaran

hulls aided with sketches and figures.

In Chapter 3, creation of hull form is supported with Maxsurf Pro and

AutoCAD Software. Lines Plan, Perspective (3D-View) and General

Arrangement Plans are shown. Components to be included are also listed.

Chapter 4 provides some rules and regulations that pleasure crafts

must apply. In this chapter, SOLAS Chapter-V and Rules and Regulations

for the Classification of Yachts and Small Craft by Lloyd’s Register of

Shipping are focused.

All the designing calculations such as Stability Calculation, Resistance

and Powering Calculations, Strength Calculation by Rules are involved in

4

Chapter 5. The related tables and curves are plotted. The calculations are

done both by hand calculation and the aid of software.

Model making chapter, Chapter 6 consists of step-by-step model

making procedures, material list, photos while making model and the tests

done in towing tank.

In Chapter 7, conclusion and recommendation for the whole project of

designing a pleasure craft with catamaran hull is discussed.

5

Chapter 2

Types of Pleasure Crafts, Yachts and Catamarans

2.1 Yachts

2.1.1 Definition

A yacht (UK /jɒt/, US /jɑːt/) is a recreational boat. The term originated

from the Dutch Jacht meaning "hunt".

In modern use the term designates two rather different classes of

watercraft, sailing and power boats. Yachts are different from working ships

mainly by their leisure purpose, and it was not until the rise of the steamboat

and other types of powerboat that sailing vessels in general came to be

perceived as luxury, or recreational vessels. Later the term came to

encompass motor boats for primarily private pleasure purposes as well.

Yacht lengths generally range from 8 meters (26 ft) up to dozens of

meters (hundreds of feet). A luxury craft, smaller than 12 meters (39 ft), is

more commonly called a cabin cruiser or simply "cruisers." A mega yacht

generally refers to any yacht (sail or power) above 30 m (98 ft) and a super

yacht generally refers to any yacht over 60 meters (197 ft). In addition, there

are terms like “Maxi” and “Giga”.

There also states that above 24 meters yachts can also be called super

yachts. The problem is that these terms are not clearly defined by any size

Fig. 2.1 Yacht

6

requirements and it is even unclear whether a “super yacht” should refer to a

ship smaller or bigger than a “mega yacht”. The term maxi yacht on the

other hand can also refer to the sailing yacht class used for racing under IOR

(International Offshore Rule), around 24.4 meters to 25.6 meters long. There

might also be new yachts in dimensions probably defined as “hyper yachts”

in near future.

The EU guidelines for pleasure boats define a private sports boat with

any kind of propulsion, as between 25m – 24m long. Above 24 meters,

yachts are classified under the same standards as commercial ships.

As this catamaran project is just simply a motor yacht, the size is far

away from the definition of any super yacht.

2.1.2 History

Yachts were used by the Dutch navy to pursue pirates and other

transgressors around and into the shallow waters of the Low Countries. They

were also used for non-military governmental roles such as customs duties

and delivering pilots to waiting ships. The latter use attracted the attention of

wealthy Dutch merchants who began to build private yachts so they could be

taken out to greet their returning ships. Soon wealthy individuals began to

use their 'jachts' for pleasure trips. By the start of the 17th century 'jachts'

came in two broad categories- speel-jachts for sport and oorlog-jachts for

naval duties. By the middle of the century large 'jacht' fleets were found

around the Dutch coast and the Dutch states organized large 'reviews' of

private and war yachts for special occasions, thus putting in place the

groundwork for the modern sport of yachting. Jachts of this period varied

greatly in size, from around 12 m (39 ft) in length to being equal to the lower

classes of the ship of the line. All had a form of fore/aft gaff rig with a flat

bottom and lee boards to allow operations in shallow waters. The gaff rig

7

remained the principal rig found on small European yachts for centuries until

giving way to the 'Bermudan sloop' rig in the 1960s.

Charles II of England spent part of his time in exile during the period

of the Commonwealth of England in the Netherlands and became keen on

sailing. He returned to England in 1660 aboard a Dutch yacht. During his

reign Charles commissioned 24 Royal Yachts on top of the two presented to

him by Dutch states on his restoration. As the fashion for yachting spread

throughout the English aristocracy yacht races began to become common.

Other rich individuals in Europe built yachts as the sport spread. Yachting

therefore became a purely recreational form of sailing with no commercial or

military function (see, for example, the Cox & King yachts at the beginning

of the 20th Century), which still serves a broad definition of both the sport

and of the vessel.

2.2 Motor Yachts Classification

Motor yachts generally fit into the following categories:

Day cruiser yacht (no cabin, sparse amenities such as refrigerator and

plumbing)

Weekender yacht (one or two basic cabins, basic galley appliances and

plumbing)

Cruising yacht (sufficient amenities to allow for living aboard for

extended periods)

Sport fishing yacht (yacht with living amenities and sporting fishing

equipment)

Luxury yacht (similar to the last three types of yachts, with more

luxurious finishing/amenities)

8

2.3 Luxury Crafts or Pleasure Crafts

Pleasure craft includes motor yachts, sailing yachts and dinghies

generally owned by private individuals; few are large enough to be regarded

as ships. They are usually painted white all over but other colors are also

accepted. They provide the maximum safety, comfort and entertainment for

the passengers. Isolation of machinery noise and vibration is of high

importance. Maintaining stability of the hull is even more important. No

extreme of luxury can offset a simple case of sea sickness. Electrical power

is usually of much greater magnitude, but not all crafts require that much.

2.4 Types of Hull Forms

Fig. 2.2 General hull forms

There are almost countless different forms of hulls as boats are build

for many different purposes, different operating environments and different

speed. One way to group boats into categories is by the design of the hull.

This project is about the design of a motor catamaran. Thus, the special type

of hull is basically the starting point and the main element of the whole

concept.

Basically a hull form is the result of compromising different

conflicting properties, like efficiency, payload, stability and maneuverability.

Then these properties must be optimized for the desired size, speed, of use

and operating environment. So it is the evident that the range of possibilities

is huge and there is still development going on in optimizing different hull

concepts. One recent example is the so called “displacement glider” or DG-

hull, which combines to some extend the shape of a slender displacement

9

hull with a flat bottomed gliding hull. The idea of the construction may be

around two hundred years old but could now be optimized using modern

computer aided design and hydrodynamic simulations.

As the type of boat for this design study is defined precisely, I want to

restrict the explanation to the different types of hulls and their characteristics

with focus on catamaran constructions. Basically we can define, between

three differently operating hull forms, these being:

1. Displacement hulls,

2. Semi-displacement or Semi-planing hulls, and

3. Planing hulls.

2.4.1 Displacement Hull

These are ship hulls that float by displacing their own weight in water.

The hull is supported exclusively by buoyancy. Main features of a

displacement design are good efficiency at hull speed, great payload and

good sea-going qualities. This type of hull is the conventional type for most

ships. Although it can only go with a low speed compared to other types of

hulls, it has remarkably good efficiency. Usually of deep round shaped hull

or deep rectangular shaped hull with round bilge.

These types of hull are used in crafts such as tugs and deep sea

trawlers. When viewing in profile, you will notice that the stern rises above

the waterline. The midship section of the hull is very full and is deep in the

water. Approximately, their speeds are 1.34 times the square root of the

Fig. 2.3 Hull forms

10

water line length. The V at the transom is usually fairly flat with anything

from 3 to 7 degrees from baseline.

When this type of hull is over driven, the stern will drag in water and

will create large stern and bow wave. The boat may reach such an extreme

trim angle, where water could come in over the stern and swamp the vessel.

Displacement hulls should not be driver much in excess of their "hull speed".

If higher speed is required, consider Semi-displacement or Planing hulls.

2.4.2 Semi-Displacement or Semi-Planing Hull

As stated in the name, these hulls fit neatly in between the

displacement and the planing hull types. The stern of these Semi-

displacement hulls is lower and designed to be always below the water. This

form of hull is the combine form of good qualities of a displacement hull

design with an increased range of speed. The hull can be round bilge form

but is generally of the "Hard Chine" type.

The chine line runs aft with a small curve from where it enters the

water and on back to the transom. At low speeds, the immersed strait

transom will cause turbulences of the water flow in the aft will result in

increased drag. This increase in drag will be overcome at operating speed

when the water flow at the stern continues uninterrupted. The hull form is

capable of developing a moderate amount of dynamic lift. However, most of

the vessel’s weight is still supported through buoyancy.

Semi-displacement hulls tend to have wide, flat aft sections. Usually

with Moderately-V-shape section forward and goes flat towards the stern.

These hulls are designed to partially climb on top of the bow wave and

separate the transom from the stern wave. Semi-displacement speeds are

usually in the area of 1.5 to 2.5 (square-root LWL (ft)) in knots. The flat wide

stern sections help to provide additional lift in the stern. Semi-displacement

11

hulls speed ranges up to 12 to 18 knots. Same as the displacement hull type,

the stern will tend to dig in at higher speeds.

If you are building a semi-displacement hull, you should try and keep

the weight to reasonable levels. This type of hull is a good weight carrier but

it takes additional power and fuel to get the best out of an overweight boat of

this type. For extended cruising (i.e., cruising that is of distances of over 100

miles from home base), you should plan to choose this type of hull.

2.4.3 Planing Hull

Planing is the mode of operation for a waterborne craft in which

its weight is predominantly supported by hydrodynamic lift, rather than

hydrostatic lift (buoyancy). Planing hull is supported by hydrodynamic

pressure developed under the hull at high speeds. The hull is usually of V-

Shaped or flat type shape. Commonly used in pleasure boats, patrol boats,

missile boats and racing boats, etc. It has limited load carrying capacity and

high power requirements. Planing hulls are designed with straight sections

aft. A typical deep-V bottom hull has the same angle to the ‘V’ (the same

“deadrise” angle) from midship to transom. The angle between the baseline

and the bottom of the V will be in the range of 12 to 20 degrees at the

transom.

They are designed to climb completely out of the water at high speed

and “hydroplane” on top of the water. When it is at rest, its weight is carried

entirely by the buoyant force. At low speeds every hull acts as a

displacement hull, meaning that the buoyant force is mainly responsible for

supporting the craft. When the speed increases, hydrodynamic lift increases

as well. In contrast, the buoyant force decreases as the hull lifts out of the

water, decreasing the displaced volume. At some speed, lift becomes the

predominant upward force on the hull and the vessel is planing.

12

Due to the hull shape with the characteristic straight cut transom a

hydrodynamic disturbance is created with an effective low pressure at the

stern pulling the vessel against its direction of movement through the water.

This makes the hull shape very energy consuming at speeds below the

planning threshold. At planing speeds, water is breaking cleanly from the

transom and the hull is riding on its straight aft sections. The greatest

resistance at planing speeds is frictional resistance. It takes more power to

climb out of the water over the bow wave than it does to maintain planing

speed once this is achieved.

To plane, the power-to-weight ratio must be high, since the planing

mode of operation is quite inefficient; sailing boats need a good sail area and

powerboats need a high-power engine. They should not be used as long

distance or passage making cruising powerboat. Depending on the particular

design, they can be driven at speeds in excess of 50 knots; however most are

designed to cruise at speeds between 30 to 35 knots. Its disadvantage is

mainly the high cost of operation.

2.4.4 Monohull and Multihulls

The hull types mentioned above are the three basic forms of hull and

they can be constructed in various ways, most commonly being a mono-hull.

A mono-hull is one type of boat having only a single hull, unlike multi-hull

boats: which have two or more individual hulls; most commonly, two, three,

five hulls; namely catamaran, trimaran and pentamaran. There are countless

types and designs of mono-hulls, which is why we will not explain them at

this point, but to go straight ahead to the design of catamarans.

2.5 Catamaran

2.5.1 Definition, History, Advantages and Disadvantages

2.5.1.1 Definition

A catamaran is a type of multihulled boat or ship consisting of two

hulls, joined by some structure, the most basic being a frame. Catamarans

13

can be of sail- or engine-powered. The word “catamaran” comes from the

Polynesian Languages meaning “tied up trees”.

Catamarans are a relatively recent introduction to the design of boats

for both leisure and sport sailing, although they have been used since time

immemorial among the paravas, a fishing community in the southern coast

of Tamil Nadu, India, and independently in Oceania, where Polynesian

catamarans and outrigger canoes allowed seafaring Polynesians to settle the

world's most far-flung islands.

In recreational sailing, catamarans and multihulls in general, had been

met by a degree of skepticism from Western sailors accustomed to more

“traditional” monohull designs, mainly because multihulls were based on, to

them, completely alien and strange concepts, with balance based on

geometry rather than weight distribution. However, the catamaran has

arguably become the best design for fast ferries, because their speed,

stability and large capacity are valuable.

The twin-hulled sailing or motor boat has since become a popular

pleasure craft, largely because of its speed and stability. High-speed

catamaran ferries can exceed 40 knots (74 km/h). Catamarans range typically

from 15 ft to 330 ft in length and are among the world’s fastest sailing and

motor craft.

2.5.1.2 History, Advantages and Disadvantages

Catamarans were developed to perfection and enabled the Polynesians

to spread their civilization over the Pacific Sea. Thus, the approval of the

catamaran hull for seagoing craft was actually established long before our

time.

The design of catamaran remained relatively unknown in the West for

almost 200 years; in the 1870s when the catamaran design first was

introduced in America by Nathanael Herreshoff, they sailed so successfully

14

against mono-hulled boats that they were barred from racing till 1970s. In

1947, the first modern ocean-going catamaran was built and designed in

Hawaii by the surfing legend, Woodbridge "Woody" Brown and Alfred

Kumalae.

As a constructive characteristic, they cannot achieve the high pay load

of mono-hulls with a square-like cross-section. Also the advantage of low

resistance and a higher cruise speed is lost with the growing size of a

catamaran, as the hull-speed increases in proportion to the length of a mono-

hull. At the same time propulsion power needed to use a possible efficiency

benefit of a catamaran grows exponentially.

So there is a size range and boat type where the constructional

advantage of a catamaran comes to best effect. What makes it interesting is

that this range covers well the areas where a mono-hull has its most

drawbacks.

2.5.2 Types of Catamaran Hulls

When talking about catamarans, we are not speaking of just one type

of hull, but merely a whole hull category with many different types of

constructions and optimization for different purposes. As the catamaran hull

is basically the starting point of this study it is necessary to understand the

basic constructional differences and types. Variations of hull forms exist.

Fig. 2.4 General catamaran hull types

15

“Power catamarans come in many shapes, and in different parts of the

world preference is given to specific types.

This is an effort to analyze the 10 hull shapes of medium- and high-

speed existing boats.

Racing boats have deliberately been excluded, because comfort, safety

and a low-cost construction takes a poor second place to outright speed in

that type of boat.”

2.5.2.1 Characteristics of Type-A. Australian type with symmetrical

sponsons*, fine entry, medium-square tunnel, low deadrise.

This Type-A catamaran hulls are popular in Australia when it is found

that two identical symmetrical sponsons reduced costs and gave a beamy

boat with lots of deck space. Lateral stability at rest is very good. If wavelet

heights are less than half of the tunnel height, the fine, deep forefoot passes

through without much trouble while giving comfort and economy.

A severely warped bottom, i.e., twisting the bottom from almost

vertical at the bow to almost horizontal at the stern, resistance in calm water

(on rivers and in large harbors) is kept low with a small wetted area & low

wave-making resistance. Problems start when it ventures out to sea where

conditions are not as favorable. Even on calm day, there can be large rollers,

flowing in clear for thousands of miles at 24 knots.

Fig. 2.5 Type-A catamaran hull

16

If the water is deep enough, they have a sinusoidal shape with the

steepest gradient always less than 20° and mostly 10° or less. When Type-A

runs straight into these rollers, it will try to act like a wavepiercer with its

fine, low-lift bows until buoyancy lifts the bows with the help of the tunnel

roof, if necessary. In the process it will slow down a fair amount because of

the increased resistance caused by the extra wetted area and, of course, the

gradient. No vehicle or vessel will go faster up a hill than down. And talking

about the downward run, after cresting a head sea it is usually an exhilarating

feeling, the acceleration and the higher speed.

If the wave length is long enough, say six times the boat’s length then

nothing strange should happen when you arrive at that trough and start up

the next wave. Running beam-on to the big swells, either on top or in the

bottom, is no problem. Quartering the head seas without wind and chop may

make the passengers feel a small uneasiness when the cat leans away from

the higher water, but there is no real chance of overturning.

2.5.2.2 Characteristics of Type-B. Sailing-boat type symmetrical

sponsons*, round-bilge and tunnel, deep forefoot, no strakes.

Type-B Catamaran Hull has symmetrical round bilge sponsons and

wide lowish tunnel. After French proved that a catamaran can out sail any

monohull of the same size, power-boaters started to look at this hull

configuration for medium speed cruisers without sails. This type of hull has

no lift rails and chines, amount of lift at speed is negligible, thus no

Fig. 2.6 Type-B catamaran hull

17

reduction of wetted area. Long, slim sponsons with fine entry have very little

wave-making resistance.

The speed range is approximately between 15 to 25 knots, to give

reasonable economy. This speed is a lot quicker than normal displacement

speed for a hull of same length. Round-bilge shape gives a soft ride and can't

slam but short flat tunnel does that with vengeance when trying to go

directly into a head sea. The fine entry and deep forefoot slice through the

chop nicely, but it lacks the buoyancy or lifting surfaces to save it from some

stuffing into the back of the next wave.

Type-B has a relatively small water plane area so it can carry light

loads and when overloaded to the extent where the tunnel roof stays in

contact with the sea, there will be a large increase in resistance. Type-B can

benefit from some new patented idea such as the HySuCat to lift it at speed

and improve the top speed.

2.5.2.3 Characteristics of Type-G. Kenton Cat type with low round

tunnel and round bottoms, tunnel lifting at bow

Let us skip to Type-G from Type-B as there are some common

features such as round-bilge sponsons and symmetrical bows sections. But

Type-G has a lower, full-length, rounded tunnel and a lot less beam to

change its sea-behavior completely.

That soft entry and landing of the rounded bottom of the sponsons are

completely overshadowed by the bang that occurs when solid water hits that

Fig. 2.7 Type-G catamaran hull

18

low, round-tunnel roof and finds that it has nowhere to go. As a matter of

interest, it is our conviction that the well-known spitting (sneezing) of a

bucketful of water forward, out of the tunnel mouth at speed, is caused by

the speed of sound in the two phase medium being exceeded. This happens

when aerated water is suddenly compressed.

Type-G usually uses chines on the outside and, together with the

tunnel which is submerged at rest, has considerable lift at speed. As a matter

of fact it probably is the best load carrier of all catamarans, providing it can

get over the hump, another big difference from Type-B which has no real

hump in its resistance curve.

2.5.2.4 Characteristics of Type-C. Asymmetrical sponsons with low

deadrise bottoms and no-trip chine, medium height square

tunnel.

This catamaran hull type has good directional stability in head seas

and following seas but, in quartering seas it weaves as the seaward-curved

bow, causes it to "steer". A steering correction to the opposite side gets

worse when the other bow enters the same wave and does the same, resulting

in an uncomfortable yawing motion which is highly encouraging to motion

sickness.

Medium-height tunnel has a limit on wave heights that it can handle at

speed without severe slamming. Depending on the deadrise angles of the

Fig. 2.8 Type-C catamaran hull

19

bottoms, it can have a good ride even in rough seas and will react safely

when sliding sideways off large swells. In following seas, it behaves well

because of the full bows, but at an angle, a broaching action may be felt

when the leading bow hits the bottom of the trough and then veers off.

Lateral stability is excellent and it will need abnormal loads to make it

roll too far. Ride wetness will depend on the detail shape of the forward

chines and the amount of flare in the bows, but it should be much better than

the Type-A. It can carry reasonable loads and its CG is not critical, within

bounds, of course.

2.5.2.5 Characteristics of Type-D. Split monohull with narrow, low

square tunnel with high attack angle at bows.

Strictly speaking, this should not be called a catamaran because its

parent was a monohull that got split down the middle, and the halves were

moved apart by a small amount and the gap covered over.

The result is a hybrid which inherited the worst characteristics of both

monohull and a bad catamaran. It slams and bangs in any kind of head sea or

even chops and does it with a noise like a thunderclap.

The transverse stability has been improved from that of its original

monohull, but not to the extent that would match any decent catamaran.

Load capacity is good and the economy in smooth water is reasonable.

Fig. 2.9 Type-D catamaran hull

20

2.5.2.6 Characteristics of Type-E. Super-slim sponsons with medium-

to-high-tunnel, fine entry, designed to be used on protected

waters.

This type has high aspect-ratio sponsons that have very little wave-

making resistance. At certain speeds, there is an advantage for the super-

slim. However, in doing this, a large area is running wet, and skin friction

resistance has increased over that of a similar sized planing craft. Because of

the minimal bow lift there is no dynamic lift and almost no buoyant lift.

Therefore Type-E is fine in small chop and wave lengths of less than

half the boat length, but it urgently needs a helping hand in the way of a

third sponson or tunnel roof extension to prevent stuffing. Vertical

acceleration from the sponsons is very low, but the tunnel roof will slam if it

is flat and not high enough for the sea state.

Because of the low water plane area, Type-E is sensitive to load shifts

and it becomes important to control people movement and other factors that

can offset the critical center of gravity. Because of its wave penetrating

action, it cannot be used offshore or where large waves and rollers occur.

In other words, this is a protected-water boat similar to Type-A and

Type-G. The narrow sponsons pose problems in installing wide engines and

long cardan-shafts, such as those used in SWATHs and SES may be needed

and that adds to the cost. Lateral stability will depend on aspect ratio, but is

less than on other, more normal types of catamarans. Construction is not

difficult but speeds (for economy) are within a narrow range.

Fig. 2.10 Type-E catamaran hull

21

2.5.2.7 Characteristics of Type-F. SES (Solid Side Skirt) hovercraft

with low tunnel and skirts at bow and stern.

The solid side skirt hovercraft is not considered a catamaran by many,

but it does have two long, slim sponsons almost like Type-E, but with the

addition of flexible skirts fore and aft. The skirts are there to contain the

cushion – air that is pumped into the big empty space between the sponsons,

skirts and tunnel roof to lift the craft up to where it has minimal draft and

wetted area.

The SES was developed by people who were unhappy with the normal

hovercraft where air-propulsion is needed. They thought that these slim

sponsons would allow propulsion by water jet or propeller and so make it

more efficient. Another handicap of a pure hovercraft is its susceptibility to

cross winds and its consequent need to weathercock to counter them. So

don’t be surprised if you see one traveling almost sideways to go along a

certain course. Having slim hulls in the water helps offset this to a

considerable extent but it is costly to build and maintain and its ride

characteristics are not acceptable to many.

It is load-sensitive and the CG has to be dead right. The ride is wet and

becomes hard when the waves hit the relatively low tunnel. On the upside, it

is capable of good speeds in calm conditions. As an afterthought, it is

probably unfair to compare it with normal cats.

Fig. 2.11 Type-F catamaran hull

22

2.5.2.8 Characteristics of Type-H. HySuCat with one main foil and

two trim foils, high deadrise bottoms and medium-high tunnel.

HySuCat means Hydrofoil-Supported-Catamaran. Professor Günther

Hoppe was testing one of the early Bobkat Catamaran models in the

circulating tank at Stellenbosch University when he decided that the

resistance-to-weight ratio was too high and needed improvement. Firstly, he

changed the cross section of the sponsons by introducing a wide, and low-

deadrise bottom with no non-trip chines. This immediately reduced their

resistance, but not enough for Hoppe and he continued experimenting until

he hit on the novel idea of fitting a foil between the sponsons to carry part of

the load and, in so doing, reduced the wetted area.

It is a proven fact that long and narrow wings of aeroplanes produce

more lift at low and medium speeds than short, wide ones. The same goes for

hydrofoils. The Russians developed hydrofoil craft for use on their rivers

where a low wash was needed, together with economy at high speeds. Many

configurations were tried out but all lifted the hull completely clear of the

water which gave them the best speed, but introduced other problems.

Among these were deep draft at rest and wide foils extending beyond

the sides of the boat to make docking difficult, and sometimes downright

Fig. 2.12 Type-H catamaran hull Fig. 2.13 HySuCat working principle

23

dangerous. It was also very expensive to produce, and large shaft angles

made propulsion inefficient.

The Hoppe solution, registered as HySuCat, is a low-cost compromise

that has been developed to give excellent results within its effective speed

range. The foils between the sponsons are positioned to not only lift the boat

when planing speed is reached, but also to adjust the trim for optimal main

foil and sponson attack angles. In the early HySuCat designs the main foil

was placed just forward of the Center of Gravity and small trim foils were

mounted near the transom, all of them above the bottoms of the sponsons.

However, the world patent covers many other possible configurations.

Production models of the HySuCat had a higher deadrise to improve the ride

in rough water and help the vertical tunnel sides for banking less in turns.

Without the non-trips, the lateral stability – in Extreme conditions – could

lead to tripping and flipping if the Center of Gravity is too high.

The sweeping bow with the chine going right up to the gunwales has

poor buoyancy and dynamic lift with all the problems previously mentioned

for asymmetrical hulls. At low speeds the tunnel may slam a bit, but once the

foils come into action at about 14-18 knots, and lift the whole boat a

considerable amount, the tunnel clearance is also increased and very much

larger waves are needed to create an uncomfortable slamming. We have

found that the foils also dampen action such as heaving and pitching, which

improves the ride even further.

The main advantage of the foil system is the dramatic reduction in the

resistance, resulting in a higher top speed and improved economy. Recent

applications of the HySuCat system on other hull shapes such as Type-A

improved the speed and lifted the tunnel a bit but it could not cure the other

inherent bad habits in the basic design.

24

2.5.2.9 Characteristics of Type-I. Bobkat with round, asymmetrical

sponsons*, high tunnel with tunnel-chines and bow steps.

Fig. 2.14 Type-I catamaran hull (Bobkat)

2.5.2.10 Characteristics of Type-J. Bobkat with HySuCat foils.

The registered trademark Bobkat covers a range of power catamarans

from 2.5m-33m that have similar looking hull shapes, but with detailed

changes for different sizes and speeds. The convex shape incorporates the

equally important non-trip below the wide chines to further improve safety

in beam seas and quartering swells in a large following sea.

The rounded section does not slam and gives a comfortable ride in

rough water, even when jumping the large waves at high speed. The 20m

patrol boat, for instance, can take 3m high head seas at 26 knots without

discomfort. The tunnel is also the highest of the boats listed and when the

foils are fitted on the Type-J the effective tunnel height allows high-speed

travel in severe sea states.

The tunnel chines lift up in a flattened S-shape near the stern as does

the tunnel roof, to provide an increased tunnel area for waves to enter when

traveling at speeds below 20 knots in following seas. For the sports

fisherman this feature also allows for backing down at speed when fighting a

large fish without any danger of swamping. The overall aspect ratio of 3:1

with a sponson ratio of 10:1 reduces wave making resistance, especially on

the foil, while giving excellent lateral stability.

25

Fig. 2.15 Type-J catamaran hull (Bobkat with HySuCat foils)

2.5.2.11 Summary and Comparison of the above (10-Types) of Hull

The rest of the world is starting to realize that a tiny country at the

southern tip of Africa is one of the leaders in the design of safe, fast, low-

cost and seaworthy offshore craft with this foil-assisted catamaran concept.

There is also ongoing research we expect to lead to further improvements in

the near future. Points are scored relating to the following aspects and with

the rating of 1 to 9.

Table 2.1 Point score for 10-types of catamaran hull relating to the given

aspects

Aspects A B C D E F G H I J

1. Low Vertical Acceleration (Sponsons) 2 7 5 4 9 9 5 6 7 8

2. Low Vertical Acceleration (Tunnel) 3 3 3 1 5 9 1 6 7 9

3. Inward banking in Turns 1 1 9 7 6 4 5 7 9 9

4. Non-broaching in Following Seas 2 3 6 7 4 6 7 5 8 8

5. Non-weaving in Quartering Seas 8 8 2 3 4 7 7 3 8 8

6. Resistance to Barrel-Rolling 1 5 9 3 7 7 7 5 9 9

7. Load Carrying Ability 5 5 6 7 2 3 8 5 6 7

26

8. Transverse Stability 6 6 7 3 4 3 4 7 7 7

9. Pitching Stability 4 5 6 7 4 3 6 7 7 8

10. Dry Ride in Small Chop 6 6 6 3 7 2 2 7 7 7

11. Economy at Planing Speeds 8 4 7 4 2 9 7 9 6 8

12. Economy of Construction 8 9 8 7 5 1 6 7 9 7

Total Score 54 62 74 56 59 57 65 74 90 95

27

Chapter 3

Designing Concepts and Detail Design of Pleasure Craft with

Catamaran Hull

3.1 Principal Particulars

Maxsurf, AutoCAD and related software are used to create the hull

form. The principal particulars of our ship’s hull form are as follows:

Length overall – 15 m

Breadth (maximum) – 6.75 m

Depth – 2.1 m

Draught, at design waterline – 0.7 m

Speed – 15 knots (Maximum 20 knots)

No. of Passengers – 6

Propulsion – 2xVolvo Penta IPS 600, 2x320kW

(2x435hp)

Fuel & Fresh Water Capacity – 3387.131 liter, 680.045 liter

Classification – Lloyd’s Register of Shipping

3.2 Reference Ship Data and Contents

The principle dimensions of this design ship are derived from Thidar

Catamaran (a 23.837m Catamaran, the only two catamarans built in

Myanmar as Thidar I & Thidar II) and the general arrangement plan is

adopted from a graduation project by Juri Karinen, Lahti University of

Applied Sciences, Finland, named as eCAT hybrid.

In this chapter, detail lines plan, general arrangement, step-by-step

designing procedures, offset tables, marker data, power prediction by Hull

Speed software, perspective 3-D view, propulsion systems and integrated

equipments will be listed. Both the mothership data and the design ship data

will be included wherever available.

28

Fig

. 3.2

Tec

hnic

al l

ayou

t d

esig

n o

f eC

at h

yb

rid c

atam

aran

Fig

. 3.1

Lin

es p

lan o

f T

hid

ar c

atam

aran

29

Tab

le 3

.1 O

ffse

t ta

ble

of

Thid

ar (

I+II

) ca

tam

aran

s

30

Fig. 3.3 Body plan of designed hull

3.3 Step-by-Step Designing Procedures

From the Lines Plan of Thidar catamaran, we collect data to create the

offset table. (Note that there may be errors up to 20 millimeters in full

scale).From this offset table, we use Geo-Sim Method to create an offset

table for a 15m Catamaran.

You will notice that Thidar catamaran is a round bilge hull and our

design is a chine hull catamaran. We create the chine hull which has the limit

values of the offset table for the 15m Catamaran which we calculated earlier.

In creating a chine hull, first we draw it by hand, adjusting the limits.

Again, we collect offset data from the hand drawing and create a 3D marker

data which will later be imported to Maxsurf Pro software.

Marker data is created using Microsoft Excel Spread Sheet and saved

in a “.txt” format. On markers window in Maxsurf Pro, Open the saved “.txt”

marker data. Prefit software is not used as it will give and undesirable result

while importing catamaran hull marker data.

Create multiple surfaces, bond them and trim them as necessary.

Transverse stiffness is set to 2 as we are creating a chine hull form. After

quite enough fairing is done, the required hull form is obtained in “.msd”

format.

31

To create Lines Plan and GA Plan, we used AutoCAD software. It is

easy to bridge Maxsurf and AutoCAD software. The hull form that we

created in Maxsurf can be exported as a “.dxf” format. This is a data

exchange format that most CAD modeling software knows. The export file

can now be opened in AutoCAD.

Unnecessary lines are deleted and the lines from each view are

arranged in a new file after which it is saved. A Line Plan in “.dwg” format

is achieved. GA Plan is drawn is drawn similar to eCAT hybrid.

The drawn GA Plan is snipped into image file, “.jpg” and is then used

as background image back in Maxsurf Pro. Once the image zero point and

image reference point has been set in Display->Background menu, we are

now ready to fit bulkheads, decks, stairs and superstructures using new

surfaces. After quite a lot of work has been done, the final 3-D Perspective

View of our designed catamaran is obtained.

For Calculations, we will calculate with both hands and with aid of

software where possible. For powering prediction, we will use the resistance

data obtained from Hull Speed for this instance.

Table 3.2 Offset table of Geo-Sim 15m catamaran (Limits for our design)

32

Tab

le 3

.3 O

ffse

t ta

ble

of

des

igned

15m

cat

amar

an

33

Fig. 3.4 Markers from offset table seen in perspective view of Maxsurf

Fig. 3.5 Lines plan of designed craft

3.4 Intended Voyage of the Designed Catamaran

It can be used both in Protected Waters and Sea-going. As it has a low

draft, it has no problems in going shallow water, but it is designed mainly to

go offshore, coastal area around Myanmar.

34

3.5 Lines Plan and Bare-Hull Form Generation

Fig

. 3.6

Pro

file

vie

w

Fig

. 3.7

Hal

f-b

read

th p

lan

35

Fig. 3.8 Body plan view

Fig. 3.9 Bare-hull form generated by Maxsurf, perspective view

3.6 General Arrangement Plan

Below are the pictures of general arrangement plan adopted from eCat

Hybrid. These plans are drawn with AutoCAD software, thus might have a

little difference with the drawings from Maxsurf. Most common errors are

corrected.

In this catamaran, there will be main deck-bridge deck, sundeck, and

tunnel-lower deck. The sun deck is located on forward side of the craft, in

front of the bridge deck windshield. The sun deck is accessible from the

main deck. There are altogether seven emergency exit hatches. The aft part

36

of the main deck is formed by stairs where the passengers can swim, dive or

just simply sit, putting the feet into the pleasant sea.

(c) Main deck

Fig. 3.10 General arrangement plan

(a) Profile view

(b) Tunnel-lower deck

37

The aft part of bridge deck formed a sea view area with luxurious

settees where you can sip a cold drink while enjoying the view of the sea.

The mid portion of the bridge deck forms a small home theatre where you

can spend your time with your family, laughing and smiling while having

surround sounds of a home theatre. In the forward part of the ship, there is a

navigation deck with less complicated but efficient systems which are user

friendly.

The bridge deck then declines to the tunnel deck with the series of

circular stairs. You will arrive to the dining room. The bridge deck

windshield formed a sky light for the dining room. The compartment in front

the dining room is the master bedroom with bathroom attached. The

bathroom is located on the tunnel deck so it kind of needs to go down the

few steps of stairs. The aft part of the tunnel consists of the life boat and two

tanks containing fuel and fresh water.

Lower deck is reachable by the stairs from the dining room. The

forward port side is the galley while the starboard side contains the bathroom

from master bedroom. There is also a small bathroom on the after part of the

port side. Two compartments near the midship section are the bedrooms for

4 persons. The aft-most part of the lower deck is the engine room.

As this catamaran is a six passenger capable pleasure craft, there will

be six beddings. The maximum limit for the no. of passenger boarding this

boat is eleven. If twelve, there will be more rules and regulations that must

be applied and approved. For the same dimension of ship, if used as the ferry

boat, it can carry about 30-50 persons but must be approved by the

authorities. As this is a pleasure craft design, it is only designed for a family

size of 6 persons.

The lifeboat is of rigid inflatable boat type, also called ribs, with a

capacity of 11 passengers just for safety, although only 6 persons is to board

in case of emergency. The outboard motor is mounted in the aft part of the

38

lifeboat. The lifejackets are located below the beds and the extra ones are

located in the stair case cabinet. A total number of eleven lifejackets are

placed on the boat. The lifejackets are to be of approved type.

3.7 Designed Ship’s 3D Image Renderings Including Superstructure

Fig. 3.11 3D rendering (Starboard view)

Fig. 3.12 Internal compartments

Fig. 3.13 Wire mesh plan view (Top view)

39

Fig. 3.14 3D rendering (Forward-starboard view)

Fig. 3.15 Wire mesh (Profile view)

Fig. 3.16 Wire mesh (Forward-bow view)

40

Fig. 3.17 3D rendering (Aft-stern view)

Fig. 3.18 3D rendering (Aft-starboard view)

Fig. 3.19 Wire mesh (Aft-port view)

41

Fig. 3.20 3D rendering (Fwd-port view)

Fig. 3.21 3D rendering (Fwd-starboard view)

Fig. 3.22 Wire mesh (AutoCAD)

42

3.8 Power Prediction by NavCad

It is not easy for the catamaran to predict power and resistance. It can’t

be done directly. It is most complicated as the interference effects of the

waves between the two hulls need to be considered.

To use NavCad, there are certain limitations on the use of methods as

the algorithms are designed for specific hull types. For this craft, Gronslett

Method (Catamaran) is the most appropriate. The limitations of for this

method are:

Requirements Design

0.6 < Fn (LWL) < 1.6 0.64

0.6 < Fn-high < 1.6 0.88

7.3 < Cvol (hLpp) < 9.5 7.4

NavCad has one algorithm for catamarans [Gronnslett, 1991]. The

algorithm utilizes a set of curves for residuary resistance. A random

collection of full-scale and model tests of high-speed displacement

catamarans with slender symmetric demi-hulls is the basis of this algorithm.

The method does not take differences in hull separation into account.

Differences in interference drag are averaged to produce a generic result.

This algorithm exhibits surprisingly good accuracy, however. We surmise

that this is due to two characteristics of these types of vessels.

First, the hulls are long and slender operating in a high speed range (Fn

from 0.6 to 1.6). A good portion of this resistance will be frictional, which is

directly calculated. Second, hull spacing has shown to have the most effect

on interference resistance in the lower speed ranges near the principal wave-

making hump speed (Fn from 0.3 to 0.7). Above this speed regime, there is

little difference in added interference drag due to different hull spacing

[Insel, 1991].

43

Using Gronslett Method, we get Table 3.4 corresponding to Fig. 3.23

and Fig. 3.24. Thus we get the predicted power of approximately 336 kW for

the speed of 15knots, 439 kW for the speed of 18 knots and 630 kW for the

speed of 20 knots. Assume 450kW is needed to be on save side, since we are

installing two engines, one on each side of the hull, we will need estimate of

225kW per engine.

So, we chose two Volvo Penta IPS 600 Propulsion Units (Inboard

Performance Systems), which can give propeller shaft power of 307kW

(418hp). Details of Volvo Penta IPS 600 will be stated below and detail

powering calculations will be shown in Chapter-5.

Table 3.4 NavCad prediction data

44

Fig. 3.23 Speed vs. Resistance graph

Fig. 3.24 Speed vs. Power graph

3.9 Propulsion System with Volvo Penta IPS 600 (Inboard

Performance System)

Propulsion is by twin installation of Volvo Penta IPS 600. It has much

improved efficiency, higher top speed, reduced fuel consumption/extended

range, and great acceleration. Low-speed maneuvering is easy, and high

45

speed handling is a really fine. Onboard comfort is greatly enhanced thanks

to much lower levels of sound and vibrations.

Installation is greatly simplified. Compact propulsion design gives

more space available for accommodation. It has improved safety and quality.

It is also very easy to service, and a complete system is supported by one

supplier. It is designed to reduce pollution and to improve environmental

care.

The Volvo Penta IPS system can be installed in various ways, either as

a compact system or with an extended jackshaft, giving opportunities for

different boat designs. The system is always installed in a twin or multiple

engine configurations. A special mounting collar is integrated in the hull

construction. The propulsion unit is lifted in place from beneath the hull,

with the combined rubber suspension and sealing in place. The clamp ring is

positioned and attached with standard bolts. No time-consuming alignment is

Fig. 3.26 Volvo Penta IPS propeller advantages

Fig. 3.25 Volvo Penta IPS installation layout

46

needed. Steering, shift and throttle plus instrumentation are connected in the

simplest way possible.

Volvo Penta IPS systems do not need shaft alignments. With the

Volvo Penta IPS 600 propulsion units placed under the hull, and all

components exposed to seawater made of either nickel-aluminum-bronze or

stainless steel, excellent corrosion resistance is achieved, and marine growth

is minimized.

Volvo Penta IPS patented propellers means increased blade area, half

the load on each propeller, and smaller propeller diameter with minimized

tip losses and cavitation. Furthermore, the propeller system prevents

rotational losses and does not create any side forces. The thrust the

Fig. 3.28 Joystick docking system

Fig. 3.27 System components, Volvo Penta IPS

47

propellers produce is horizontal with all the force driving the boat forward.

The propellers are at the front of the propulsion unit, working in undisturbed

water with a minimum of pressure pulses affecting the hull.

A conventional shaft system loses efficiency with the thrust angled

downward and the propellers working in water disturbed by the propeller

bracket and shaft. Selecting propellers is also very easy, since Volvo Penta

provides optimized gear ratios and a complete and systematic series of

propellers developed for the Volvo Penta IPS system.

Onboard comfort is one of the main factors for a pleasure craft design.

Minimal amounts of sound, vibration and exhaust fumes make life aboard

that much more pleasant. Volvo Penta IPS new technology leads to major

improvements for all comfort enhancing factors. The propulsion forces and

vibrations are absorbed by the combined rubber suspension and sealing.

Engine vibrations are reduced thanks to a U-joint drive shaft, which makes it

possible to have the engine soft suspended.

The propellers are working in undisturbed water with no cavitation,

and have good clearance from the hull. There is an increased number of

propeller blades to distribute the forces. This means that the pressure pulses

created by the propellers have very little effect on the hull. Exhaust fumes

Fig. 3.29 Section showing U-Joint drive shaft arrangement with

counter-rotating propellers

48

are truly minimized. First of all, the new engines have very low exhaust

emissions, and secondly, the exhausts are emitted through the propulsion

unit into the prop-wash and carried well behind the boat.

Crankshaft power, kW (hp)@3500 rpm - 320 (435)

Prop-shaft power, kW (hp)@3500 rpm - 307 (418)

Aspiration - Turbo, after-cooler, compressor

Package weight, kg (lb) - 901 (1986)

Voltage - 12 V or 24V

Application - Twin/multiple engine installation

in planing hulls

Driveshaft - Compact (standard), jackshaft as

option

Fig. 3.30 A complete unit of Volvo Penta IPS system

49

3.10 Sewage System

There is another interesting fact in our designed ship. It is no other

than the sewage system. There are two toilet bowls in our designed ship but

there is neither retention tank nor a sewage treatment plant. This is because

we use INCINOLET, the electric incinerating toilets.

The working principle of INCINOLET toilet is easy.

INCINOLET uses electric heat to reduce human waste (urine, solids, paper)

to a small amount of clean ash, which is dumped periodically into the

garbage. INCINOLET remains clean because waste never touches the bowl

surface. A bowl liner, dropped into the bowl prior to use, captures the waste,

then both liner and its content drop into the incinerator chamber when the

foot pedal is pushed. You can use INCINOLET at any time-even while it is

in cycle.

Fig. 3.32 Usage procedures of INCINOLET

Fig. 3.31 INCINOLET, The electric incinerating toilet.

50

Incineration cycle is started with the push button. Both heater and

blower come on when button is pushed. Heater alternates off and on for a

preset period of time, blower continues on until unit has cooled. Several

people may use the toilet in rapid succession. Push the start button after each

use to reset the timer.

The main advantages of this system is that it requires no plumbing,

uses no water and drains nothing out, easy to be used at sea. There are still

Fig. 3.33 Assembly of INCINOLET

51

many advantages such as cleanliness, odor, residue and low electrical

requirements compare to other conventional composting toilets. Maintenance

has to be done only once a year but the ash pan must be emptied at least once

every week. This can be easily done because our catamaran is only designed

to cruise a week at most.

The price of this product is around $1800. Two units are installed so,

it will cost around $3600. Installing INCINOLET is really easy. All it need

is an electric power and a vent pipe. This appliance uses around 20 amps,

either 120 volts or 240 volts is your choice. Here we will use 240volts unit.

The only disadvantage of this product is the need to use a bowl liner

every time you use toilet and the need to clean the ash pan weekly.

52

Chapter 4

Rules and Regulations which this Pleasure Craft Complies

4.1 SOLAS

The International Convention for the Safety of Life at Sea (SOLAS),

1974, currently in force, was adopted on 1 November 1974 by the

International Conference on Safety of Life at Sea, which was convened by

the International Maritime Organization (IMO), and entered into force on 25

May 1980. It has been amended and consolidated since then.

In SOLAS it is stated that “unless expressly provided otherwise, the

present regulations apply only to ships engaged on international voyages.”

As our catamaran is only designed to go within coastal regions or shallow

water inland, it doesn’t matter whether it comply all the rules but it will be

best if it obeys all.

In this chapter, we will only focus on the fundamental equipments

required by SOLAS. We will emphasize on SOLAS Chapter-4 Part C and

SOLAS Chapter -5. Chapter-4 Part C points out the required Radio

Communication Equipments and Chapter-5 focuses mainly for pleasure craft

users.

Our designed ship will be going in sea area A1. That is “Sea Area A1

is between 30~40 nautical miles from land, i.e., an area within the

radiotelephone coverage of at least one VHF coast station in which

continuous DSC alerting is available.” Where DSC here means “DSC

(Digital Selective Calling) is a technique using digital codes which enables a

radio station to establish contact with and transfer information to another

station or vessels.”

4.1.1 SOLAS Chapter IV, Part C (Ship Requirements)

Radio installation is located away from harmful interference of

mechanical, electrical equipments and systems. It is protected against

53

harmful effects of water, extremes of temperature and adverse environmental

conditions. A distress panel is installed at the navigation deck, the panel

containing only one single button which when pressed, initiates a distress

alert using all radio communication installations. This panel is provided to

prevent inadvertent activation of the button.

Below is the list of radio equipments installed on this craft:

Table 4.1 List of radio equipments installed

Equipments No. Installed

VHF with DSC x1

VHF with DSC receiver x1

NAVTEX receiver x1

Float-free satellite EPIRB x1

Radar Transponder (SART) x2

Hand-Held GMDSS VHF Transceiver x1

VHF - Very High Frequency

NAVTEX - Navigational Telex

EPIRB - Emergency Position-Indicating Radio Beacon

SART - Search and Rescue (Radar) Transponder

GMDSS - Global Maritime Distress and Safety System

4.1.2 SOLAS V for Pleasure Craft

On 1st July 2002, some new regulations came into force, which

directly affect the pleasure boat users. These regulations are part of Chapter

V of the International Convention for the Safety of Life at Sea, otherwise

known as SOLAS V. Most of the SOLAS convention only applies to large

commercial ships, but parts of Chapter V apply to small, privately owned

pleasure craft. If a boating accident is involved and it is subsequently shown

54

that the users have not applied the basic principles outlined here, they could

be prosecuted.

4.1.2.1 Radar Reflectors

Many large ships rely on radar for navigation and for spotting other

vessels in their vicinity. So, whatever size of the boat is, it’s important to

make sure that it can be seen by radar. Regulation V/19 requires all small

craft to fit a radar reflector ‘if practicable’. If the boat is more than 15m in

length, it should be able to fit a radar reflector that meets the IMO

requirements of 10m2. If the boat is less than 15m in length, it should be

fitted with the largest radar reflector possible. Whatever size of the boat is,

the radar reflector should be fitted according to the manufacturer’s

instructions and as high as possible to maximize its effectiveness. Our

designed craft is fitted with a 10m2 radar reflector.

4.1.2.2 Life Saving Signals

Regulation V/29 requires the pleasure boat users to have access to an

illustrated table of the recognized life saving signals, so that they can

communicate with the search and rescue services or the other boats if they

get into trouble. If the boat is not suitable for carrying a copy of the table

onboard (because it’s small or very exposed), they must make sure that they

have studied the table before they go boating. Larger boats should keep a

copy on-board. Our designed craft have a copy onboard in the tunnel deck,

near the navigation bridge.

4.2 Rules and Regulations for the Classification of Yachts and Small

Craft, (Lloyd’s Register of Shipping)

If the yachts and small crafts want to be registered under the Lloyd’s

Register of Shipping class, the rules and regulations must be applicable.

Some of the important facts are listed below for our designed craft.

55

4.2.1 Requirements from Part 2

4.2.1.1 Bulkheads

According to Part 2, Chapter 6, Section 1.2, a watertight collision

bulkhead is to be fitted only if the length of the craft exceeds 15m. As our

craft is 15m, it is on the margin, so we installed a collision bulkhead at the

longitudinal position of 13.25m which is approximately 750mm (0.05L,

Required by the rule) abaft the fore end of the design waterline.

As required, the machinery bulkheads are extended to the upper deck

and the space is made to be gastight, whilst the accommodation spaces are

protected from gas and vapour fumes from machinery, exhaust and fuel

systems.

The doors fitted in watertight bulkheads are capable of being closed

watertight. Both hinged and sliding types are used wherever they suit most.

They are also capable of being operated from both sides of the bulkhead.

4.2.1.2 Hatches and Doors

Hatches and doors have adequate securing arrangements. Hatches on

weather decks are watertight with the cover permanently attached. Where

intended for escape purposes, they are to be operable from both sides. There

are altogether 7 escape hatches in this craft.

Exposed doors in superstructures are weathertight and the sill height is

about 160mm above the deck surface. The rule (Part 2, Chapter 6, Section

1.4) requires a sill height of not less than 150mm.

4.2.1.3 Portlights and Windows

The portlights have a minimum sill height of 500mm above the

waterline and are watertight. All glass installed have a thickness of 12mm.

Storm shutters are required for all windows in the front of the deck house on

the weather deck and the sides. (Part 2, Chapter 6, Section 1.5)

56

4.2.1.4 Guard Rails

Hand rails are installed on exposed decks.

(Part 2, Chapter 6, Section 1.6)

4.2.1.5 Ventilations

Adequate ventilation is provided throughout the craft.

(Part 2, Chapter 6, Section 1.9)

4.2.1.6 Fire Protection

The machinery space is separated from adjacent compartments by

bulkheads. Fire pumps required by the rule (Part 2, Chapter 6, Section 2)

states for a craft of 9m to 21m with less than 150 tons gross, a hand pump is

required and its permanent sea connection is to be situated outside the

machinery space. The minimum nozzle size must be 9.5mm and the

minimum jet throw must be 6m. For this craft, two hand pumps are located

in midship section of the ship embedded in the stair case wall on both sides

of the ship and they are also operable from the main deck.

Fire hoses are made of approved material. The hoses are of 8m length

to project a jet of water to any of the spaces. The rule states the hose length

must not exceed 9m. 5x1.4kg dry powder portable fire extinguishers are

provided. Four extinguishers are of “B” type, i.e., suitable for extinguishing

fires involving flammable liquids, grease, etc., and the remaining are to be of

“C” type, where butane gas installations for cooking or heating. “C” type is

capable of extinguishing fires involving gases.

Two buckets with ropes attached (lanyards) are stowed near the stair

case. A fire blanket is provided and stowed in the store room which is

adjacent to the galley space. A fireman’s axe with insulated handle is an

option. It is only required for craft over 20m overall length. Cooking

appliances are suitable for marine use and secured permanently in position

and must be well ventilated.

57

4.2.1.7 Chains, Anchors and Mooring

The equipment of anchors, chain cables, hawsers and warps required

is based on an “Equipment Number” which can be calculated as:

Equipment Number = 10.76L ((B/L) + D) + 5.38 A

Where,

A= the summation of the respective length times height, in m2, of

all erections above the weather deck which have a length or breadth greater

than B/2.

The equipment number for our designed craft is approximately 885.

The anchors fitted here are stockless. The weights of the anchors are around

45kg. Two anchors are to be fitted. The length of the chain cable must be at

least 95m and the diameter of the short link cable must be at least 10.25mm.

For hawsers and warps they must be 65m long and the breaking loads

required in KN are, for hawsers, 42.2 and for warps, 19.5. These are the

values interpolated from the table given in Part 2, Chapter 6, Section 5.

4.2.2 Requirements from Part 3

4.2.2.1 Engine Seatings

Rigid engine seatings are constructed integral with the hull and permit

easy access to any fitting. Means are provided for removing leakage of oil

fuel or lubricating oil using drip trays fitted around the engine.

A sufficient number of bolts are fitted as required by the engine

manufacturer and are tightened and secured using locking arrangements.

Engine mountings of wood from approved FRP are provided with steel

plates under the engine feet. (Part 3, Chapter 1, Section 4)

4.2.2.2 Pumps and Piping Systems

Pipes are properly secured in position to minimize vibration.

Sufficient joints are provided to enable the pipes to be readily removed. All

sea inlet and overboard discharges are provided with shut off valves located

58

in positions readily accessible at all times. The valves, cocks, inlet chests are

made of corrosion resistance material.

The openings in the shell have suitable pads, which the attached

fittings are spigotted. The fittings are secured with an external ring under the

bolts made of brass.

Bilge pumping system is fitted, arranged that any green water entering

any compartment can be pumped overboard. The diameter of bilge suctions

is to be in accordance with the following formula:

d = (L/1.2) +25mm

Where,

d = internal diameter of the bilge line, in mm,

L = Rule length of the craft, in m.

Thus, the required size of bilge suctions is approximately 3.7cm.

At least two pumps, one power pump and one manual pump is to be

fitted. The capacity of the pump must not be less than 180 l/min for this

craft, which is calculated by the equation:

Q = 25 (d-25) – 112 l/min

Where,

d = the internal diameter of the bilge line

The bilge pumps are connected to a bilge line with a branch

connection to each compartment. Each branch bilge suctions, from the main

bilge line and each separate pump suction is controlled by a non-return

valve.

The power pump is driven by an electric motor. The manual bilge

pump is accessible from the deck, above the waterline. (Part 3, Chapter 3)

4.2.2.3 Electrical Installations

The insulation resistance of the electrical systems, circuits and

apparatus must exceed 100000 ohms. Electrical equipments are located clear

59

of flammable material, in well ventilated spaces in which flammable gases

are not likely to accumulate, and where they are not exposed to risk of

mechanical damage, or damage from water, steam or oil. Where necessarily

exposed to such risks, the equipments are suitably constructed or enclosed.

Equipments are installed in the way that it is easy to access for maintenance.

(Part 3, Chapter 4, Section 1)

4.2.2.4 Electrical Distribution Systems

The electrical distribution system used in this craft is two wire

insulated. 12V system is used. Two wire insulated system is a perfect but a

bit costly. It is best for hulls constructed with FRP too. Earthing connection

in FRP hull (if needed) is made to the generator frame, engine bedplate and

earthing plate (if fitted).

Short circuit protection is fitted wherever necessary. LED lighting

system is used in this craft.

Following points should be noted in the figure.

1. A double pole switch is fitted so that the battery can be completely

isolated from the system (Switch No.1).

2. An ammeter and voltmeter are fitted; the voltmeter (if fitted) is

protected by fuses.

Fig. 4.1 Two-wire insulated electrical distribution systems

60

3. All outgoing circuits from the main switchboard can be isolated

(Switch No.2).

4. Final sub-circuits have single pole switches (Switch No. 3).

5. Each individual circuit is protected by fuses or circuit breakers in each

non-earthed pole (Marked 4). (Part 3, Chapter 4, Section 2)

4.2.2.5 Batteries

Batteries are located in the starboard side compartment which is

adjacent to the engine room. Drip trays are provided, resistant to the effects

of spilled electrolyte. Cable entries to battery compartments and enclosures

are to be effectively sealed. Switches, fuses and other equipment liable to

cause an arc are not located within the compartment.

Battery compartment is well ventilated to remove the hydrogen

evolved during charging and is constructed so that pockets of hydrogen

cannot accumulate. Ventilating systems for battery compartment is made

independent from other spaces. Although mechanical ventilation is used, the

fan motors are kept away from the air stream and it is arranged that the

charging of the battery cannot start unless the ventilation fan is on and

running. Inlet air level is located below the level of the battery and the outlet

vent is at the highest point of the compartment. (Part 3, Chapter 4, Section 4)

4.2.2.6 Lightning Conductors

A copper strip of 150mm2 cross-section is secured to the copper spike

of 12mm diameter is projected 200mm above the top mast. The lower end of

the conductor is earthed to the copper earthing plate. As the hull is

constructed with FRP, a copper earthing plate of 0.2m2 is fitted beneath the

lowest part of the hull, which is always below the waterline, immersed under

all conditions of heel. (Part 3, Chapter 4, Section 5)

61

Chapter 5

Design Calculations for Pleasure Craft

5.1 Stability Calculation

5.1.1 Hydrostatic Curve Calculation

The draft, displacement, wetted surface area, water plane area,

longitudinal center of buoyancy, vertical center of buoyancy, LCF, KMT,

KML, TPC and MCTC are calculated using Hydromax Software and are

checked by hand calculation. The results are as shown in table. The

following results are obtained by using the water density of 1.0252

tonnes/m3.

Table 5.1 Intact hydrostatic table

Draft

(m)

Displacement

(t)

LCB

(m)

VCB, KB

(m)

WPA

(m2)

LCF

(m)

0.1 0.3296 -0.530 0.069 7.464 -0.520

0.2 1.6090 -0.577 0.139 18.192 -0.678

0.3 4.0500 -0.721 0.208 30.395 -0.933

0.4 7.5180 -0.851 0.275 37.422 -1.066

0.5 11.5200 -0.950 0.336 41.692 -1.214

0.6 15.8800 -1.039 0.395 44.306 -1.322

0.7 20.4200 -1.105 0.451 45.362 -1.344

Longitudinal Center of Buoyancy (LCB) and Longitudinal Center of

Floatation (LCF) are measured from midship (¤), taking forward of the

midship as positive (+).

62

Table 5.2 Intact hydrostatic table (Continued)

Draft

(m)

KML

(m)

KMT

(m)

WSA

(m2)

TPC

(t/cm)

MTC

(t-m/cm)

0.1 82.989 45.123 8.864 0.075 0.021

0.2 62.749 32.824 21.786 0.184 0.078

0.3 50.492 30.443 36.431 0.307 0.157

0.4 42.211 21.987 46.870 0.378 0.244

0.5 36.681 16.428 54.973 0.421 0.325

0.6 31.460 12.977 61.960 0.447 0.384

0.7 26.071 10.564 67.691 0.458 0.409

Fig. 5. 1 Hydrostatic curve

63

5.1.2 Cross Curve Calculation

Cross Curve is plotted as displacement versus KN values with various

angles as shown in Fig. 5.2

Table 5.3 Cross curve table (KN values in meters)

Displacement

(t) 0 deg 5 deg 10 deg 15 deg 20 deg 30 deg 40 deg 50 deg

0.300 0 1.517 2.258 2.734 2.797 2.729 2.540 2.267

2.933 0 1.871 2.113 2.271 2.411 2.525 2.459 2.301

5.567 0 1.704 2.112 2.210 2.296 2.424 2.420 2.318

8.200 0 1.526 2.108 2.193 2.257 2.354 2.390 2.331

10.83 0 1.367 2.046 2.190 2.243 2.320 2.365 2.340

13.47 0 1.221 1.955 2.193 2.241 2.306 2.345 2.341

16.10 0 1.088 1.855 2.185 2.246 2.304 2.336 2.334

18.73 0 0.974 1.751 2.152 2.256 2.310 2.337 2.320

21.37 0 0.880 1.648 2.102 2.269 2.322 2.341 2.302

24.00 0 0.802 1.548 2.042 2.272 2.338 2.346 2.284

64

Fig. 5.2 Cross curve

5.1.3 Large Angle Stability (GZ Curve)

As our design ship is small, every single loads acting on it can cause

serious stability issues. Thus, even small loads like chairs and accessories

aren’t neglected. The following load case is used to determine large angle

stability.

Table 5.4 Load case (Weight distribution)

65

The following GZ Curve is obtained. For most vessels, the GZ Curve

must satisfy the criteria stating that the angle where maximum GZ occurs

must be above 30 degrees. But for multihulls which have only small heel

angles, maximum GZ might occur on angles less than 30.

For our design ship, Max GZ of 1.966m occurs at the angle of 20

degrees. HSC Code states that multihulled vessels must have Max GZ at the

angles greater than 10 degree. Thus, our design satisfies this. The following

are the criteria tested and passed.

IMO A.749 (18) 3.1.2.1 Area from 0 to 30, Area from 0 to 40, Area

from 30 to 40 (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.)

IMO A.749 (18) 3.1.2.4 Initial GMt (Finds the value of GMt at either

a specified heel angle or the equilibrium angle. The criterion is passed

Fig. 5.3 GZ curve

66

if the value of GMt is greater than the required value. GMt is

computed from water-plane inertia and immersed volume.)

MSC.36 (63) HSC Code, Annex 7, Multihulls, HSC multi, Intact. 1.1

Area from 0 to 30 (The area under the GZ curve is integrated

between the specified limits. However the required minimum area

depends on the upper integration limit ( ).The criterion is

passed if the computed area under the graph is greater than the

required value.)

MSC.36 (63) HSC Code, Annex 7, Multihulls, HSC multi, Intact. 1.2

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 down-flooding angle. The criterion is passed if

the angle is greater than the required value.)

MSC.36 (63) HSC Code, Annex 7, Multihulls, HSC multi, Intact. 1.5

HTL: Area between GZ and HA (Checks the area under the heel

angle as per “Heel: Area between GZ and heeling arm curves”)

MSC.36 (63) HSC Code, Annex 7, Multihulls, HSC multi, Intact.

3.2.1 HL1: Angle of equilibrium (Checks the equilibrium heel angle

as per “Angle of equilibrium - general heeling arm”)

5.1.4 Equilibrium Condition (Still Water)

max11 /A

Fig. 5.4 Sectional area curve for still water condition

67

The sectional area curve is obtained as shown in figure. This sectional

area curve is for still water condition (flat/no waves). The following

particulars are achieved.

In still water condition, we can see that the boat is trimming by aft.

The draft at AP is 0.06m more than the average draft. Both LCB and LCF

are located aft of the midship. The immersion is 0.468 LT/cm. This is

because the boat is relatively small. The deck has a maximum inclination of

0.6 degree. This isn’t much. This deck inclination is cause by the trim of the

boat, having the same trim angle of 0.6 degree. Trim is by stern.

Table 5.5 Equilibrium condition (Still water)

68

5.1.5 Equilibrium Condition (Sinusoidal Wave)

The sectional area curve is obtained as shown in figure. This sectional

area curve is for sinusoidal water condition. The sinusoidal wave condition

has the following wave characteristics: Wave Length = 13m, Wave Height =

0.986m, Phase Offset = 0.95.

Table 5.6 Equilibrium condition particulars (Sinusoidal condition)

Ph

ase

0.0

0

Ph

ase

0.1

5

Ph

ase

0.3

0

Ph

ase

0.4

5

Ph

ase

0.6

0

Ph

ase

0.7

5

Ph

ase

0.9

0

Ph

ase

0.9

5

Draft

Midship. (m) 0.759 0.702 0.615 0.527 0.593 0.718 0.767 0.766

Displacement

(Long Ton) 21.09 21.09 21.09 21.1 21.1 21.09 21.1 21.1

Heel to

Starboard

(deg)

0 0 0 0 0 0 0 0

Draft at FP

(m) 0.921 0.444 0.012 -0.08 0.579 1.167 1.14 1.049

Draft at AP

(m) 0.597 0.961 1.218 1.138 0.608 0.269 0.394 0.482

Draft at LCF

(m) 0.734 0.755 0.756 0.702 0.596 0.677 0.71 0.725

Trim (+ive by

stern) (m) -0.33 0.517 1.206 1.221 0.03 -0.9 -0.75 -0.57

WL Length

(m) 14.1 13.63 12.48 11.84 13.83 13.02 13.59 13.96

WL Beam

(m) 6.292 6.253 6.352 6.434 6.467 6.434 6.355 6.322

Wetted Area

(m2)

74.46 73.54 68.1 62.44 56.28 66.8 75.08 75.77

Waterpl.

Area (m2)

46.17 48.7 45.52 41.12 35.31 42.09 47.16 47.44

Prismatic

Coeff. 0.553 0.474 0.613 0.518 0.394 0.465 0.531 0.545

Fig. 5.5 Sinusoidal wave condition

69

Block Coeff. 0.304 0.276 0.329 0.423 0.329 0.385 0.303 0.293

Midship Area

Coeff. 0.837 0.618 0.778 0.819 0.836 0.83 0.833 0.834

Waterpl.

Area Coeff. 0.81 0.604 0.638 0.83 0.605 0.772 0.845 0.835

LCB from

Amidsh. (+ve

fwd) (m)

-1.26 -1.25 -1.25 -1.25 -1.26 -1.26 -1.26 -1.27

LCF from

Amidsh. (+ve

fwd) (m)

-1 -1.32 -1.52 -1.86 -1.21 -0.6 -0.99 -0.93

KB (m) 0.579 0.576 0.506 0.504 0.539 0.505 0.538 0.56

KG solid (m) 0.445 0.445 0.445 0.445 0.445 0.445 0.445 0.445

BMT (m) 9.518 9.755 9.601 9.093 7.861 8.891 9.854 9.73

BML (m) 29.47 31.21 24.76 17.66 10.92 21.12 29.91 31.24

GMT

corrected (m) 9.653 9.886 9.663 9.153 7.955 8.951 9.947 9.846

GML

corrected (m) 29.6 31.34 24.82 17.72 11.02 21.18 30 31.36

KMT (m) 10.1 10.33 10.11 9.597 8.4 9.396 10.39 10.29

KML m 30.05 31.79 25.27 18.16 11.46 21.63 30.45 31.8

Immersion

(TPc) (Long

Ton/cm)

0.466 0.491 0.459 0.415 0.356 0.425 0.476 0.479

MTc (Long

Ton.m) 0.48 0.509 0.403 0.287 0.179 0.344 0.487 0.509

RM at 1deg =

GMt.Disp.sin

(1) Long

Ton.m

3.554 3.639 3.557 3.37 2.929 3.295 3.662 3.625

Max deck

inclination

(deg)

1.4 2.3 5.3 5.4 0.1 4 3.3 2.5

Trim angle

(+ve by stern)

(deg)

-1.4 2.3 5.3 5.4 0.1 -4 -3.3 -2.5

70

5.1.6 Limiting KG

The following figure shows the limiting KG values of our design ship.

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

Fig. 5.6 Sectional area curve for sinusoidal wave condition

Fig. 5.7 Limiting KG vs. Displacement curve

71

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

criteria fails.

5.1.7 Tank Calibration

The following tank data is used for tank calibration. The result of tank

calibration is shown in the following graph.

Table 5.7 Tank data

Fig. 5.8 Tank calibration

72

5.2 Resistance and Powering Calculation

Resistance Calculation/Prediction in catamarans is more difficult and

complicated than most conventional mono-hulls. Generally saying,

catamaran resistance is twice the individual hull resistance, plus an added

drag due to the interference of the hulls with each other.

Calm water resistance of catamarans is in general attributed to two

major components namely, frictional resistance and calm water wave

resistance. The former has been acceptably determined from ITTC-1957 line

whilst the latter still remains to be a stimulating question to the researchers.

It is understood that the solutions cannot be generalized by one simple

formula but varied in accordance with specific configurations of catamarans.

Fig. 5.9 Hull form configurations of catamarans

5.2.1 Viscous and Wave Interference Effects

When the hulls of a catamaran are widely (infinitely) separated the

total catamaran resistance is equal to the sum of the resistance of the two

single hulls. With reduced hull separation two kinds of interference effects

influence the resistance characteristics:

1. Viscous interference due to asymmetric water flow around each hull:

The decreasing area between the hulls leads to an increase of the water flow

velocity which increases the skin friction.

2. Wave interference due to interaction of the two separate wave systems

in the tunnel between the hulls: Wave interference usually increases the

resistance and in particular at Froude numbers (Fn) about 0.45 - 0.5.

73

However, at lower speeds, when Fn is less than 0.42, the two separate wave

systems may have some cancelling effects on each other, resulting in a

relative decrease of the wave resistance. The total wave energy generated by

a catamaran may be measured behind the hull and is analogous to the wave

resistance. The wave resistance can also be assessed by integrating the

pressure field around the hulls (ideal fluid). The wave interference at

relatively low speed disturbs the pressure field on the hulls, however, at

higher speeds the wave interaction occurs behind the hulls and thus no

pressure field disturbance acts directly on the hulls.

5.2.2 Insel and Molland (1992)

Insel and Molland (1992) proposed that the total resistance of a

catamaran should be expressed as:

CT CAT = (1+ ϕk) σCF + Cw

They also state that for the practical purposes, σ and ϕ can be

combined into a viscous resistance interference factor where (1+ ϕk) σ = (1

+ k). Thus the equation becomes:

Total Resitance Coefficient; CT = CF + CR = (1 + k)CF + Cw

Where,

CF = Frictional Resistance Coefficient can be calculated by the

formula of

2)2(log

075.0

n

FR

C

CR = Residuary Resistance Coefficient (Residuary resistance

coefficient is found by using Froude – CR diagrams)

CW = Wave Resistance Coefficient

= Viscous Resistance Interference Factor

= Wave Resistance Interference Factor

74

It may be noted that for demi-hull in isolation, = 1 and = 1, and for

a catamaran, can be calculated as:

DEMIFT

CATFT

WDEMI

WCAT

CkC

CkC

C

C

])1([

])1([

To be able to determine the form factor (1+k), we plotted Fn4/CF vs.

CT/CF graph with an index of m=4.

5.2.3 Resistance Test Results of Ship Model, Carried Out in Towing

Tank

The resistance test is carried out in the towing tank of Myanmar

Maritime University. The details of model particulars will be shown in

Chapter-6. The calculations from these results are shown in next section. The

results from the towing tank are as follows:

Table 5.8 Resistance test results

Myanmar Maritime University

Marine Hydrodynamics Centre

Lm

1.364

Ls

15

Length Ratio

11

Correspondin

g Speed

Vm=Vs*(Lm/Ls)^

0.5

(Lm/Ls)^0.5 0.301551543

Ship

Speed

(Knots)

Ship Speed

(m/sec)

Corresponding

Speed

of Model (knots)

Corresponding

Speed

of Model (m/sec)

Rtm

6 3.09 1.81 0.93 1.422920

7 3.60 2.11 1.09 2.794620

8 4.12 2.41 1.24 5.095257

9 4.63 2.71 1.40 7.714650

10 5.15 3.02 1.55 13.159010

75

11 5.66 3.32 1.71 19.839000

12 6.18 3.62 1.86 30.511650

13 6.69 3.92 2.02 39.184440

14 7.21 4.22 2.17 39.221220

15 7.72 4.52 2.33 39.553480

5.2.4 Calculation from Towing Tank Results

The following data obtained from the towing tank is used.

Lwl= 1.27272727 m, S = 0.58761157 m2, ν = 8.4305x10

-07 m

2/sec,

ρ = 996.3507 kg/m3, Temperature = 27.59°C

Table 5.9 Calculation of CT/CF and Fn4/CF

v (m/s) RT (N) Rn = vL/ν CT=RT/(0.5

ρSv2)

CF=0.075/

(log Rn -

2)2

Fn=v/(gL)0.5 CT/CF Fn

4/CF

0.931 1.423 1406099.799 0.0056 0.0044 0.264 1.285 1.108

1.087 2.795 1640449.765 0.0081 0.0042 0.308 1.915 2.119

1.242 5.095 1874799.731 0.0113 0.0041 0.351 2.748 3.714

1.397 7.715 2109149.698 0.0135 0.0040 0.395 3.366 6.093

1.552 13.159 2343499.664 0.0187 0.0039 0.439 4.750 9.484

1.708 19.839 2577849.631 0.0232 0.0038 0.483 6.031 14.150

1.863 30.512 2812199.597 0.0300 0.0038 0.527 7.928 20.385

2.018 39.184 3046549.564 0.0328 0.0037 0.571 8.811 28.519

2.173 39.221 3280899.53 0.0284 0.0037 0.615 7.714 38.912

2.328 39.553 3515249.497 0.0249 0.0036 0.659 6.867 51.961

76

Fig. 5.10 Fn4/CF vs. CT/CF curve

From this graph, when x=0, y =(1+k) = 1.1344. Therefore k = 0.1344

can be obtained. The form factor (1+k) = 1.1344.

Comparing the principle particulars of our model to the models tested

by Molland A.F.

Length (m) 1.273

L/1/3

5.110

L/B 6.816

B/T 2.935

CB 0.5108

WSA (m2) 0.588

S/L 0.16

The model 4b shows the most nearest values. So, we will choose the

related values of 4b.

y = 7E-06x4 - 0.0006x3 + 0.0101x2 + 0.3285x + 1.1344

0

1

2

3

4

5

6

7

8

9

10

0 10 20 30 40 50 60

Fn4/CF Vs. CT/CF

Fn4/CF Vs CT/CF

Poly. (Fn4/CF Vs CT/CF)

Table 5.10 Model particulars by Molland

A.F.

77

Table 5.11 -Values relating to hull separation to length ratio for each model

The Value of 4b Model at S/L=0.2 is 1.57 and at S/L=0.3 is 1.43.

Extrapolating the value for S/L=0.16 gives =1.626. Thus the form factor

value (1+k) = 1.219.

Thus the calculation procedures are as follows:

1. The model particulars of LM= 1.2727 m, WSAM = 0.5876 m2,

νM = 8.4305x10-07

m2/sec, ρM = 996.3507 kg/m

3, Temperature =

27.59°C are used.

2. From the towing tank data, RTM with their related VM, the values of

CTM, RnM, CFM are calculated as usual.

2

2

2Relog

075.0

2

1

nM

FM

M

MMnM

M

TMTM

C

LvR

Sv

RC

3. The values (1+k) and are obtained, (1+k) from previous model

test datas and values from the equation.

DEMIFT

CATFT

WDEMI

WCAT

CkC

CkC

C

C

])1([

])1([

78

4. Thus CW is achieved.

FMTM

W

CkCC

1

Table 5.12 Calculation of Cw and

vM (m/s) RTM (N) RnM CTM CFM Cw

0.931 1.423 1406099.80 0.0056 0.0044 0.440 0.0007

1.087 2.795 1640449.77 0.0081 0.0042 0.892 0.0033

1.242 5.095 1874799.73 0.0113 0.0041 0.948 0.0066

1.397 7.715 2109149.70 0.0135 0.0040 0.962 0.0090

1.552 13.159 2343499.66 0.0187 0.0039 0.977 0.0142

1.708 19.839 2577849.63 0.0232 0.0039 0.983 0.0189

1.863 30.512 2812199.60 0.0300 0.0038 0.988 0.0257

2.018 39.184 3046549.56 0.0329 0.0037 0.989 0.0286

2.173 39.221 3280899.53 0.0284 0.0037 0.987 0.0242

2.329 39.554 3515249.50 0.0249 0.0036 0.985 0.0208

The design ship particulars of LS=14m, WSAS=71.101m2, νS = 9.3713x10

-7

m2/sec, ρS = 1023.3873 kg/m

3, Temperature = 25°C are used.

5. Similar to calculation for model, the RnS and CFS are found. CW is

assumed to be the same for both model and design ship.

6. CTS is calculated from the equation, CT = CF + CR = (1 + k)CF + Cw.

Substituting related values, and using (1 + k)=1.219 and

(1+k)=1.1344, the equation becomes:

CTS2 + CTS [ 0.0846 CFS + CW ] = 1.219 CF CW - 1.3828 CF

2

7. Thus the CTS values are acquired.

8. From these values RTS and the PES are established.

79

STE

SSTSTS

vRP

vSCR

2

2

1

We predicted that we could test up to 3.1m/sec model speed in the

towing tank but we only got permission to test up to 2.33 m/sec. Thus the

design ship speed only up to 15 knots can be tested. We designed the ship

speed of 20 knots but only up to 15 knots can be verified. Thus the power

requirement for 20 knots is extrapolated linearly from the graph data. This

value might deviate from the actual power requirement.

Power requirement for 20 knots of ship speed = 631.42 kW

Table 5.13 Calculation of total resistance and effective power

vS

(knots)

vS

(m/s) RnS Cw CFS CTS RTS (N)

PES

(kW)

6 3.089 46142462.43 0.0007 0.0023 0.0033 1148.30 3.55

7 3.604 53832872.83 0.0033 0.0023 0.0059 2780.78 10.02

8 4.118 61523283.24 0.0066 0.0022 0.0092 5655.08 23.29

9 4.633 69213693.64 0.0090 0.0022 0.0167 13006.32 60.26

10 5.148 76904104.05 0.0142 0.0022 0.0167 16057.18 82.66

11 5.663 84594514.45 0.0189 0.0021 0.0213 24839.44 140.66

12 6.177 92284924.86 0.0257 0.0021 0.0281 39054.01 241.25

13 6.692 99975335.26 0.0286 0.0021 0.0312 50877.41 340.48

14 7.207 107665745.67 0.0242 0.0021 0.0265 50140.95 361.36

15 7.722 115356156.07 0.0208 0.0020 0.0231 50151.29 387.25

Thus the effective power for the ship speed of 15 knots is 387.25kW.

In this design, we used Volvo Penta IPS 600, which could deliver the power

PD of 307kW for each engine. Since two units are installed, PD of 614kW is

achieved. Assuming Quasi-Propulsive Efficiency of 65% or more is

obtained, the PE provided by the engines can be above 399.1kW. This power

is enough for our design to archieve the speed of 15 knots or more. Volvo

80

Penta IPS 600 gives out the shaft power PS of 320kW and deliver power PD

of 307kW, thus only 4% of shaft transmission is lost.

In other words, for 15 knots of ship speed, the PD needed will be below

595.77 kW.

Fig. 5.11 Speed vs. Resistance curve

Fig. 5.12 Speed vs. Effective power curve

Some general conclusions for catamarans relating to resistance are as

follows:

Catamarans have larger resistance than monohulls in the low speed

range (Fn<0.4) when length and displacement are kept constant.

y = 6579.3x - 43712

-10000.00

0.00

10000.00

20000.00

30000.00

40000.00

50000.00

60000.00

0 2 4 6 8 10 12 14 16

Speed (knots) vs. Resistance (N)

Speed (knots) vs. Resistance (N)

y = 49.089x - 350.36

-100.00

0.00

100.00

200.00

300.00

400.00

500.00

0 5 10 15 20

Speed (knots) vs. Power (kN)

Speed (knots) vs. Power (kN)

81

A catamaran with asymmetric single hulls and conventional hull form

has lower resistance than a catamaran with symmetric single hulls in the

traditional low speed range. (FN<0,36)

A catamaran fishing vessel with a well designed hull form can obtain a

higher speed than a traditional high displacement monohull vessel. In order

to obtain high speed with acceptable power the displacement has to be kept

low.

5.3 Strength Calculation

5.3.1 Longitudinal Strength

Using the load case following load case data shown below, the

longitudinal strength can be calculated in Hydromax.

Table 5.14 Load case (Weight distribution)

82

Table 5.15 Result of longitudinal strength calculation

Fig 5.13 Longitudinal strength curve

83

5.3.2 Hull Construction by Glass Reinforced Plastics (GRP/FRP),

Requirements by Rules and Regulations for the Classification of

Yachts and Small Crafts, Lloyd’s Register of Shipping

Our design ship uses an unsaturated polyester resin system with glass

fibre reinforcement. The polyester resins used are of a type which have been

approved by the Society for marine construction purposes. The type and

amount of the catalyst and accelerator are to be those recommended by the

resin manufacturer for the particular application, so that the resin will cure in

the required time, without the application of local heat.

The amount of colour pigments added does not to exceed 5 percent of

the weight of the resin. No pigments are used in gel coat or laminating resins

used in the underwater portion of the hull laminate or in laminates forming

fuel and water tanks.

Core materials for sandwich construction are of types approved by the

Society. Rigid expanded foam plastics are closed-cell types and are

impervious to water, fuel and oils, and are compatible with the polyester

resin. Balsa wood is end-grain and have a mositure content not exceeding 12

percent. Plywood is of a marine grade manufactured to an ISO or national

standard.

The production of the craft can be either by hand lay-up or spray lay-

up contact moulding techniques, and on the use of either single-skin or

sandwich construction or a combination of both. For the hull construction, it

is recommended that the sandwich construction is to be used and for deck

and other structures, single-skin construction is recommended.

Moulds are constructed of a suitable material and adequately stiffened

to maintain their overall shape and fairness of form. The materials used for

the construction of moulds should not affect the resin cure. Gelcoat resin is

applied to a thoroughly cleaned mould by brush, roller or spraying device to

give a uniform film thickness of between 0.4 and 0.6 mm.

84

Gelcoats are not to be left exposed longer than necessary after

gelation, and in no case overnight, before the application of the first layer of

reinforcement. The hull gel coat is to be backed up by a lightweight

reinforcement, not exceeding 300g/m2 in weight, with a resin-to-glass ratio

of not less than 2.5 to 1.

The scantlings are to be determined by interpolation of the values

given in tables in the Rule Book with respect to the dimensions of the craft.

The interpolated values will be shown later in this section.

The mechanical properties of a laminate, at a glass content by weight

per layer of reinforcement of 0.3 are: Ultimate tensile strength = 85N/mm2,

Tensile modulus = 6350 N/mm2, Ultimate flexural strength = 152 N/mm

2,

Flexural modulus = 5206 N/mm2, Ultimate compressive strength = 117.2

N/mm2, Compressive modulus = 6000 N/mm

2, Ultimate shear strength =

62.0 N/mm2, Shear modulus = 2750 N/mm

2, Interlaminar shear strength =

17.25 N/mm2 and Nominal laminate thickness per weight of reinforcement =

0.7mm per 300 g/m2.

The reinforcements are to be thoroughly impregnated with resin, and

consolidated to give a maximum glass content by weight of reinforcement as

follows: Chopped strand mat or sprayed fibres = 0.34, Woven rovings = 0.5,

Unidirectional rovings = 0.54 and Cloth fabrics = 0.5

The scantling values interpoled from the tables are based on the

mechanical properties and glass content of the laminate mentioned above. If

the properties and glass content differs:

1. For the plate laminates, the corrected weight obtained from the table is

to be multiplied by the factor KW,

36.13072

56.2

16.08.2152

88.1

27.5

W

TG

GKORG

GK

C

CW

bC

C

W

85

Where,

b = ultimate flexural strength, in N/mm2

GC = glass content of laminate (excluding the gel coat)

T = the measured laminate thickness (excluding the

gelcoat)

W = the total weight of reinforcement in the laminate, in

g/m2

2. For the stiffner sections, the corrected section modulus obtained from

the table is to be multiplied by the factor KZ,

45.1615

1)(

852

C

Z

U

ZGG

KORK

C

Where,

U = ultimate tensile strength, in N/mm2

GC = glass content of laminate (excluding the gel coat)

The frame spacing in the design is (350+5L) = 1075 mm, L=14.5m

( .2

WLOA LLL

). The hull laminate is initially moulded as two halves joined

Fig. 5.14 Laying-up of keel when moulding

hull as semi-completed halves

86

together. The outside hulls have gel coat. Where changes in hull form

occurs, such as at the transom boundary or chine, the reinforcement is to be

carried through and past the knuckle, the ends of various layers staggered.

The hull is to be locally increased in thickness in way of fittings for

propulsion units, etc. The increased laminate weight is to be gradually

reduced to the normal laminate weight, and the exposed edges of any

openings in the hull laminate are to be sealed with resin.

The scantling of hull laminate is to be determined by the type of the

craft, length and stiffener spacing. The values required are interpolated with

respect to Length and WLL

v. Thus the required values for our craft are:

Basic Stiffener Spacing = 422.5 mm

Bottom Shell Weight = 4988.7 g/m2

Side Shell Weight = 3756.9 g/m2

Keel Width = 662.5 mm

Keel Shell Weight = 7483.05 g/m2

The bottom shell weight determined is to be maintained throughout

the length of the craft and is to extend to 150mm above the waterline. The

keel is extended from transom to stem head. The side shell weight is to be

Fig. 5.15 Laying-up of transom boundary and chine line knuckles

87

maintained throughout the length of craft. The stern or transom is to be the

same weight as the side shell as our designed craft is not carrying an

outboard propulsion motor.

Fig. 5.17 Hull laminate for motor craft

Fig. 5.18 Hull laminate for motor craft

The hull is to be provided with an efficient system of side and bottom

framing in conjuction with girders, bulkheads or web frames to provide

transverse rigidity. The framing used in this craft is longitudinal framing.

Fig. 5.16 Hull laminate for motor craft

88

The modulus of longitudinals can be obtained by interpolation. For this craft,

we will need a modulus of 172.93 cm3

for the bottom longitudinals and

112.19 cm3 for the side longitudinals. The stiffener spacing is the same as the

scanling required by hull laminate, 422.5 mm.

The longitudinals are to be supported by bulkheads and transverse web

frames, spaced not more than 2 m apart. Additional transverse floors or webs

are to be fitted in way of engine seatings and the bottom of the craft forward,

modulus of floors and frames being 166.8 cm3 and 52.345 cm

3 respectively.

Modulus of web frames at center is 951.25 cm3 and at side is 393.17 cm

3.

Floors and bulkheads are to be connected to adjacent structure by double

angles, where they are manufactured from plywood of 12.5mm thickness,

the weight of laminate forming each angle is 1800g/m2.

The scantlings of the deck of single skin construction are: Basic Beam

Spacing = 422.5 mm, Deck Weight = 2275 g/m2. The openings in the upper

and weather deck for access hatches are properly framed and the coaming is

to be effectively connected to deck structure. Working areas of the weather

deck have an anti-slip surface. The decks are sheathed with wood.

The deck to hull connection is watertight and is constructed by

bonding and mechanical fastenings. Watertight integrity and strength of the

connection is not to be impaired by the attachment of the hull fender.

The laminate weight of deckhouse of single-skin construction in g/m2

is 2275 and the basic stiffener spacing in mm is 422.5. Openings for doors

and windows are to be adequately framed.

89

Chapter 6

Model Making

In order to test resistance in a towing tank located in the

Hydrodynamic Center of Myanmar Maritime University, we need to make a

fiber model. In this chapter, we will include the step-by-step model making

and approximate cost.

Making ship models, tanks, boats and seats out of fiberglass here in

Myanmar is managed mostly by a couple dozens of companies. The

ingredients for fiberglass making can’t be bought that easily here. So, it is

rare that individuals make their own fiberglass products.

Since there are only a few dozens of companies, they tend to raise the

prices so high. The companies play the fiberglass market here. For us

students with no income, we found it difficult to deal with the prices. The

companies took a large sum of money just to make a mould. Mould making

is not really that difficult but it is time consuming and much effort must be

made to get a perfect mould.

So, for our project, we need a fiber model of approximately 1.5m in

length in order to test in a towing tank. Our design is a catamaran of 15m in

length. This is what we find trouble. The linear scale ratio, scaling factor (λ)

is only 10. Our designed ship speed is 20 knots. Thus, when the ratio is 10,

the model speed must be, 3.3 m/s. That is near upper speed limit of the

towing tank. The upper speed limit for the towing tank in Myanmar

Maritime University is 4 m/s.

M

S

V

V

Thus we choose the ratio λ =11 in order to reduce the model speed

(carriage speed) to 3.1 m/s. Reduction in 0.2 m/s doesn’t seem to be much if

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you look at the magnitude but what if you look in inches per sec. It would be

about 8 in/sec. But there was more trouble. Only after we made the fiber

model, we did not get permission to test with 3.1m/s. We only got the

permission to test up to 2.33m/s. Thus, the designed ship speed of 15 knots

can only be achieved.

So, the model dimensions and speed were as follows:

LOA = 1.364 m

LBP = 1.812 m

LWL = 1.268 m

B = 0.614 m

T = 0.064 m

D = 0.191 m

VM = 3.106 m/s (expected), 2.33 m/s (reality)

Once we got the main dimensions and the scale factors we needed,

we started making a mould. We needed sheets of 3-plywood and 2"x1"

timber blocks. Firstly, as we have a Maxsurf design file, we printed out the

stations that we’ve created. As the breadth of the model is about 2 feet

maximum, Half-breadth is only around 12 inches. Actually, we needed to

print out the stations with A3, B4 or papers of larger size using a plotter. The

only things we have was legal papers and a printer. So we only printed out

half the stations.

Fig. 6.1 Stations cut out using hacksaw

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The printed out papers are cut using a small paper knife and are

drawn on the 3-plywood. After which they are sawed out using a hacksaw.

For this model, we used 18 stations. The more stations or frame you include,

the more precise your model will be.

The stations are joined using 2"x1" wooden blocks which are sawed

out according to the station spacing calculated. Just before this, some small

wooden blocks are nailed to the station to enable the shell plating to attach

the stations. All blocks and stations are joined with ½" nails. Following this

you will get a fish-bone like structure, which all the stations are erected and

connected.

Similarly, the shell plating is printed out but as we don’t have a

plotter, we had to redraw on the plywood scaling it to the desired size. Here

we found a huge problem. Maxsurf doesn’t give the shell plating for the

whole structure. It only gives out up to designed waterline. And the

development plan given by Workshop Pro gives us really a hard time. The

shell can’t be plated. We have to redraw nearly everything for the side shell

Fig. 6.2 Tools used in making wooden mould

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plating. The shell plating of the tunnel and the inner side of the demi-hull

wasn’t of any trouble but the side shell plating really does.

Because of this shell plating error, there were some little gaps

between the plates which we have to fill it up using the general purpose

silicone sealant. We used two tubes of Silicone, each costing 2000 Kyat.

While applying Silicone sealants, we use a masking tape to obtain a smooth

and neat finish. First apply the silicone, then apply the masking tape, wait for

a few seconds and then remove before the sealant cures. Thus, we got a

smooth finish. Silicone is a bit more expensive than other adhesives but it is

really easy to use.

Fig. 6.4 Profile view of wooden mould

Fig. 6.3 Assembling stations and plating shells

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So, we have finished cutting out the stations, erecting and joining

them, shell plated them and the gaps are filled with sealant. After all these,

the only thing left is to sand the plywood to obtain a smooth finish. First, we

used a No. 3, P: 36 sandpaper, following with a No. 0, P: 120 sandpaper.

Wipe out all the dust and finally, we get a primary male mould made of

plywood.

Fig. 6.6 View from aft (Transom) of wooden mould

Fig. 6.5 View from below (Fish view)

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For this primary mould, we used 4 sheets of 3'x6' 3-plywood, about 7

feet of 2"x1" wood, 2 tubes of silicone sealant, ½" nails, ¾" nails and some

screws. The tools we used here are a hacksaw, masking tape, pliers, caulking

gun, sand papers, screw drivers, scissors, knife, rulers, pen, pencils,

permanent markers, hand saw, printed out papers, tee and set-squares

(triangular rulers). The estimate cost of this timber mould is about 35,000

Kyat.

For the fiber model, we let Fusion Fiberglass to take care of the job.

Usually, to get the fiber model with the neat outside finish, the female mould

must be made out of the wooden primary mould. This female mould is

usually made of fiberglass having 6 laminates. The primary mould sanded, is

applied with ATM poly putty, which was then again sanded using

sandpapers of number 40, 60, 80, 100, 120, 180 and so on up to 1800. For

the sandpapers of No. 400 and above, the mould surface must be sprayed

with water before rubbing.

Gelcoat is painted or sprayed on this primary mould with putty

applied. Lamination started about 1 hour after. Chopped strand mat and

polyester resin is used for lamination. About 6 layers of lamination are made.

The mat is laid, resin is applied as adhesive solution, rollers are used to coat,

avoid air gaps, release excessive resin, etc. Sheets of mat layers are applied

with unsaturated polyester resin between each other. After 6 layers of

laminate and it had been dried, the female mould is obtained.

The required final male model is made similarly using the female

mould as a base, usually of 3 to 4 layers of laminate. This is the usual way of

making fiberglass models. But the female mould would be an excess if we

made only one model and the female mould could cost extra money. Even

for our model of around 4.5'x 2'x 7" it could cost 220,000 Kyat or more. We

only needed 1 model and we could only spend a few. Thus, it would better if

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we could get a final male model without making a female mould out of

fiberglass.

Fusion Fiberglass had agreed us to make a final male model which

would cost only around 140,000 Kyat but we would not be able to get back

the wooden primary mould. The way they make the model sounds

interesting. Although we couldn’t see the making with our eyes, they

explained us how they made it. First, they put a tape fully around the primary

mould. They then applied really thick putty around it and let it dry. After

which they destroyed the wooden primary mould, which is lying inside the

putty, taking care not to harm the putty. After peeling of the tapes, the putty

now forms as a female mould. Care must be taken in all stages afterwards.

The male model is made just the same as the steps mentioned above.

Finally, we get the required fiber model as shown below.

Fig. 6.8 View from forward-starboard side of fiber model

Fig. 6.7 Profile view of fiber model

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Fig. 6.11 View from forward-port underside

Fig. 6.10 Underside of fiber model

Fig. 6.9 View from aft (Transom) of fiber model

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When Fusion Fiberglass delivered us the model, they said they have

tested that the model is watertight. But we have to see it for ourselves. There

is no lake or tank where we could test the model immediately, so what we

did was we filled up the model with water and see if there were any leaks.

Luckily there were none. So, finally we got our model which we wanted for

just around 175,000 Kyat, saving between 45,000 Kyat to 1 lakh.

To test in a towing tank, we needed to fit wooden pieces on the fiber

model so that the dynamo can be seated properly and the guiding arms be

fitted. The dynamo must be fitted at the center of gravity both longitudinally

and transversely. So it is fitted in the tunnel where CG is located. The design

waterline is drawn around the model. The LCG position is calculated from

Maxsurf and is verified by putting the model, subjected to a tipping point,

most likely to be a chair and is seen whether it is balanced and stabled.

The instruments were fitted and the model was now in place for a

resistance test. The results were shown in Chapter-5.

Fig. 6.12 Fiber model placed in

towing tank Fig. 6.13 Assembly to towing tank

carriage

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Fig. 6.14 Dynamometer assembled in tunnel

Fig. 6.15 Resistance test being carried out

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Chapter 7

Conclusion and Recommendations

7.1 Conclusion

In our project, detail definitions relating to catamaran hull forms and

pleasure crafts, designed hull, drawn with Maxsurf and its calculations, rules

and regulations required and model making are included. Our project will

help the development of using catamaran hull forms in ship industry in our

country.

The fact that we chose a chine hull form is because we intended to

design a semi-displacement/semi-planing craft. Thidar Catamaran which we

used as a reference is a round bilge craft, meaning which it is a displacement

hull form. Displacement hull forms are useful for load carrying but they have

very slow speeds. As our design is a pleasure craft, speed is a factor that is

needed to be considered. Planing hulls are designed for speed but they need

more power to plane. So, we chose a semi-displacement/semi-planing hull

form.

Maxsurf software is easy to use and calculations are fast compared

with other types of software. We used Maxsurf Pro Software to initially

create required catamaran hull form, bonding and trimming surfaces as

necessary. From the hull form obtained, we designed general arrangement

plan using AutoCAD and creating complete 3D design back in Maxsurf.

Stability calculations are calculated using Hydromax Software and the

result of curves and table are plotted. Intact Hydrostatics, Large Angle

Stability, KN values, cross curve, Longitudinal Strength, etc. are also

calculated using Hydromax. Freeboard and Tonnage calculations are not

required by this type of craft.

Resistance test is carried out in towing tank located in Myanmar

Maritime University compound. Calculation is done with Insel & Molland

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Theory. Here we can notice that the viscous resistance interference and wave

resistance interference factors are needed to be considered in calculation of

resistance for catamaran. Strength and Section Modulus required by Rules

and Regulations for the Classification of Yachts and Small Crafts, Lloyd’s

Register of Shipping are interpolated linearly from the given tables with

respect to length and speed to length ratio. Model making chapter will help

understand the basic model making and fiberglass technology.

In Myanmar, FRP boat building is not widely used yet and is not well

developed. Development in this technology is necessary as this will help

production of locally manufactured boats which could be definitely cheaper

than the imported ones. In mass production of the same design, fiber boat

building is more beneficial and less costly compared to conventional boat

building but if built only a few numbers, the cost of making a fiber mould is

expensive and unprofitable.

Catamaran is another technology that our country need to

development. This project states the superior facts of catamarans compared

to monohull. We have Thidar Catamaran, Japanese technology which we

could base on but it is rather old. Further developments are necessary. Fast

ferries should be designed as catamarans. In other countries, the Research

and Development Centers of their universities studies and research for

improvement of catamaran design. We don’t have this in our university, so

this technology could not be studied widely.

If we could study this technology, we can have stable, fast and

profitable catamaran designs. Our project could be a revolution to catamaran

development in our country.

8.2 Recommendations

We used the principle dimensions limiting the boundaries of 15m

catamaran offset derived from Thidar Craft using GEOSIM method. Simply

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speaking, we could say that our craft does not have a mother ship. It is a new

design with the set of limitations using a similar length catamaran. It would

be better if we have a mother ship of this hull form. Calm water wave

resistance is estimated by using theories and previous test data. It would be

better if all separation to length ratio for specific type of hull form is tested.

In this project, the resistance due to appendages is neglected when

calculating resistance. It will be more accurate, if these data are considered.

Strength calculation is incomplete. More theory and rules must be

studied for strength calculation of FRP boats and crafts. Most people use

AutoCAD software to design a full ship with all superstructures and

appendages but we found using Maxsurf when drawing a 3D design hull is a

bit more easy and less time consuming. But AutoCAD is necessary software

for all engineering students.

From this project, we can change the general arrangement form to

change the design to a ferry boat of same size with the capacity of 30-50

passengers but more rules and regulations would be required. Or we could

head to resistance, verifying the wave resistance with respect to hull

separation. Or fit hydrofoils to form a HySuCat arrangement. Or making use

of this boat and install solar panel to form either electric only or diesel-

electric hybrid system or hydrogen fuel hybrid system. Many new directions

can be made using this project as a base.

“Design of a Pleasure Craft with Catamaran Hull” is just a graduation

project which we approached design aspects with the availability of data and

resources all we could get. It takes a lot of hard work to gather data as there

is no former project to rely on and most data from the internet are incomplete

and costly. We really hope this project could be the start or foundation of

many projects relating this field of study for students in our country.

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References

1. eCat Hybrid – Power Catamaran Design Study, Juri Karinen, 2011

2. Insel, M. and Molland, A.F (1992), An Investigation into Resistance

Components of High-Speed Displacement Catamarans. Trans. of

Royal Institute of Naval Architects, Vol.134, pp 1-20.

3. International Convention for Safety of Life at Sea, SOLAS, November

2000

4. ITTC-Recommended Procedures, Fresh Water and Seawater

Properties, 7.5-02-01-03, Effective Date – 2011, Revision – 02.

5. Recent Applications of Hydrofoil-Supported-Catamarans, K.G.W

Hoppe, 2001

6. Resistance experiments on a systematic series of high speed

displacement monohull and catamaran forms in shallow water. A.F.

Molland, P.A. Wilson and D.J.Taunton. Ship Science Report No.127

University of Southampton, 2003.

7. Rules and Regulations for the Classification of Yachts and Small Craft

(Lloyd’ Register of Shipping), 1994

8. Ship Resistance and Propulsion, Anthony F. Molland, Stephen R.

Turnock, Dominic A. Hudson, 2011.

9. The Spring 2000 Issue of Power Multihulls Magazine by Prof. Jacob

van Renen van Niekerk

10. Volvo Penta IPS and INCINOLET Manuals

11. http://en.wikipedia.org

12. http://www.thaiboating.com

APPENDIX

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Chopped Strand Mat Used in Fiber Making