Design of a Pleasure Craft with Catamaran Hull
Htike Aung Kyaw
Kaung Zaw Htet
Paing Hein Htet Tin
Htaik Thu Aung
Supervised by Daw Khin Khin Moe
We chose this project title because there are no
former projects from our university which
relates to this field of study.
• This type of craft has better stability and faster
speed than the other conventional types of
• It can give one’s pleasure or comfort, luxury,
attract most people.
Types of Pleasure Crafts, Yachts
Designing Concepts and Detail
Design of Pleasure Craft with
Rules and Regulations which this
Pleasure Craft Complies
Design Calculations for
Conclusions and Recommendations
This project concentrates on the concept on an
easy to handle pleasure motorboat constructed
as a catamaran.
Seeking the current market situations, there
aren’t any places for catamarans here in
Catamarans are used as luxury crafts mostly in
Australia and New Zealand, can also be found
Crafts with more than one structural body
Usually of two, three or five hulls, namely
Catamaran, Trimaran and Pentamaran
Vessels that are used for sports, fishing or
recreational purposes only
Do not operate for any financial gain to the owner
Pleasure Crafts/Luxury Crafts
Types of Catamaran Hull Forms
A recreational boat.
Maybe of sail- or
Yachts are different
from working ships
mainly by their
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
Luxury yacht (similar to the
last three types of yachts, with
• Pleasure craft includes motor
yachts, sailing yachts generally
owned by private individuals; few are
large enough to be regarded as ships.
• They provide the maximum safety,
comfort and entertainment for the
• Maintaining stability of the hull is
• No extreme of luxury can offset a
simple case of sea sickness.
• A ship consisting of two hulls,
joined by some structure, the
most basic being a frame.
• Catamarans can be of sail- or
• The twin-hulled sailing or
motor boat has since become a
popular pleasure craft, largely
because of its speed and stability.
• 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.
• Variations of hull forms exist.
AREA TWIN HULL)
A. Australian type with symmetrical sponsons*, fine entry, medium-square tunnel, low dead rise.
B. Sailing-boat type symmetrical, round-bilge and tunnel, deep forefoot, no strakes.
C. Asymmetrical sponsons with low dead-rise bottoms and no-trip chine, medium height square tunnel.
D. Split monohull with narrow, low square tunnel with high attack angle at bows.
E. Super-slim sponsons with medium-to-high tunnel, fine entry, designed to be used on protected waters.
F. SES (solid side skirt) hovercraft with low tunnel and skirts at bow and
G. Kenton cat type with low round tunnel and round bottoms, tunnel lifting at bow.
H. HySuCat with one main foil and two trim foils, high dead-rise bottoms and medium-high tunnel.
I. Bobkat with round, asymmetrical sponsons, high tunnel with tunnel-chines and bow steps.
J. Bobkat with HySuCat foils.
1. Low Vertical Acceleration – Sponsons
2. Low Vertical Acceleration – Tunnel
3. Inward banking in Turns
4. Non-broaching in Following Seas
5. Non-weaving in Quartering Seas
6. Resistance to Barrel-Rolling
7. Load Carrying Ability
8. Transverse Stability
9. Pitching Stability
10. Dry Ride in Small Chop
11. Economy at Planing Speeds
12. Economy of Construction
Length in waterline
Draught, at design waterline –
No. of Passengers
Fuel & Fresh Water Capacity –
2xVolvo Penta IPS 600
3387.131 liters, 680.045 liters
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).
The General Arrangement Plans
is adopted from a graduation
project by Juri Karinen, Lahti
University of Applied Sciences,
Finland, named as eCAT
Lines Plan of Thidar Catamaran
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.
Notice that Thidar catamaran is a round bilge hull and
our design is a chine hull catamaran. We create the chine
hull using the values of the offset table for the 15m GeoSim catamaran as the limits.
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, 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 a “.msd” format.
Markers from Offset Table seen in Perspective View in
To create Lines Plan and GA Plan, we used AutoCAD
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 know. The
export file can now be opened in AutoCAD.
Unnecessary lines are deleted and the lines from each
view is arranged in a new file after which it is saved.
A Line Plan in “.dwg” format is achieved.
GA Plan is drawn similar to eCAT hybrid.
For Calculations, we will calculate with aid of software and
verify by hand calculation wherever possible.
For the first step of powering prediction, we use the resistance
data obtained from NavCad.
It can be used both in Protected Waters and
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.
NavCad Prediction Results
using Gronslett (Catamaran)
Propulsion is by twin installation of Volvo Penta IPS 600.
Much improved efficiency, higher top speed, reduced fuel
consumption/extended range, and great acceleration
Low-speed maneuvering is easy, and high speed handling is a really fine
Onboard comfort is greatly enhanced thanks to much lower
levels of sound and vibrations
Installation is greatly
More space available for
Improved safety and quality
Ease of service, and a
complete system supported
by one supplier
• Increased blade area vs. output, smaller
propeller diameter and large gear ratio
• No side force
• Half propeller loading, means half tip losses
and minimized cavitations
• Horizontal shaft and thrust
• Counter-rotating creates no rotational
There is another interesting fact in our
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.
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.
Rules and Regulations for the Classification of Yachts
and Small Craft (Lloyd’s Register of Shipping)
Our design ship will go in Sea Area A1 only.
Below, we will define basic ship requirements
(equipments required to be fitted onboard) by
Chapter IV, Part C &
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.
DSC (Digital Selective Calling) is a technique using digital codes which enables a
radio station to establish contact with and transfer information to another
VHF with DSC
VHF with DSC receiver
Float-free satellite EPIRB
Radar Transponder (SART)
Hand-Held GMDSS VHF Transceiver
Very High Frequency
Emergency Position-Indicating Radio Beacon
Search and Rescue ( Radar ) Transponder
Global Maritime Distress and Safety System
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 that the users have not applied the basic
principles outlined here, they could be prosecuted.
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
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.
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 on-board (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.
If the yachts and small crafts are to be registered under the Lloyd’s Register of Shipping class,
the rules and regulations must be applicable.
Some of the main important factors to consider are listed below.
For constructional safety arrangements,
Hatches and Doors
Portlights and Windows
Chains, Anchors and Mooring are to be considered.
For machinery and electrical installations,
Pumps and Piping Systems
Electrical Distribution Systems
Hydrostatic Curve Calculation
The density of water used is 1.0252 tonnes/m3
The hydrostatic particulars at the draft of 0.7 m are:
1.105 m (aft of midship)
1.344 m (aft of midship)
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.
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 multi-hulls which have only small heel angles,
maximum GZ might occur on angles less than 30.
For our design ship, Max GZ of 2.127m occurs at the
angle of 21.9 degree.
HSC Code states that multi-hulled vessels must have
Max GZ at the angles greater than 10 degree.
In still water condition, we can see that the boat is trimming by
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
The deck has a maximum inclination of 0.6 degree. This isn’t
This deck inclination is cause by the trim of the boat, having the
same trim angle of 0.6 degree.
Trim is by stern.
Sectional area curve for still water condition
Resistance Calculation/Prediction in catamaran is more
difficult and complicated than most conventional mono-hull.
Generally saying, catamaran resistance is twice the individual
hull resistance, plus an added drag due to the interference of
the hulls with each other.
Solutions cannot be generalized by one simple formula but
varied in accordance with specific configurations of
catamaran hull forms and their separation.
Due to asymmetric
water flow around
Due to interaction of
the two separate wave
systems in the tunnel
between the hulls.
Insel and Molland (1992) proposed that the total
resistance of a catamaran should be expressed as:
CT CAT = (1+ ϕk) σCF + τCw
They also state that for the practical purposes, σ
and ϕ can be combined into a viscous resistance
interference factor β, where
(1+ ϕk) σ = (1+ βk).
Thus, total Resistance Coefficient;
CT = CF + CR = (1 + βk)CF + τCw
Frictional Resistance Coefficient can be calculated by
the formula of C F = (log R − 2)2
Viscous Resistance Interference Factor
Residuary Resistance Coefficient (Residuary resistance
coefficient is found by using Froude – CR diagrams)
Wave Resistance Coefficient
Wave Resistance Interference Factor
It may be noted that for demi-hull in isolation, β = 1 and τ = 1, and
for a catamaran, τ can CWCAT [CT − (1 + βk )as:]CAT
be calculated CF
[C − (1 + k )C ]
Form factor (1+k) is obtained using regression method, plotting
Fn4/CF vs. CT/CF, using an index of m=4.
Myanmar Maritime University
Marine Hydrodynamics Centre
of Model (knots)
of Model (m/sec)
Compare principle particulars of our
model to the models tested by
L/ 1/3 5.110
The model 4b shows the most
nearest values, thus the related
values of 4b will be chosen.
Calculation can now be done using the 8 procedures shown in the book.
The results are as follows:
Effective power for the ship speed of 15 knots is
Assume QPC = 65% or more
QPC = PE/PD
Delivered Power Required = 595 kW.
One Volvo Penta IPS 600 engine could deliver a
power of 307 kW.
Since two units are installed, Delivered Power
Installed = 614 kW.
Other way of saying, Volvo Penta IPS 600 gives
out a total of 614 kW delivered power.
QPC = 65%
Thus the effective power of 399.1 kW can be
Effective Power for 15 knots = 387.25 kW.
Power Installed > Power Required.
Longitudinal Strength Calculation
Load Case (Weight Distribution with Forward and Aft Limits)
Materials used for fiber boat building, polyester resin, catalyst,
accelerator, color pigments, gelcoat, wood and plywood, are to be of
approved type by the Society for marine construction purposes.
Production of the craft can be either by hand lay-up or spray lay-up
contact moulding techniques, and either of single-skin or sandwich
construction or the combination of both.
Recommended that the sandwich construction for hull and singleskin construction for deck and other structures.
Moulds are constructed of suitable material and adequately
stiffened to maintain their overall shape and fairness of form.
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 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/mm2, Flexural modulus = 5206 N/mm2,
Ultimate compressive strength = 117.2 N/mm2, Compressive
modulus = 6000 N/mm2, Ultimate shear strength = 62.0 N/mm2,
Shear modulus = 2750 N/mm2, 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 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 Speed to Length ratio.
Basic Stiffener Spacing
Bottom Shell Weight
Side Shell Weight
Keel Shell Weight
In order to test resistance in towing tank, we need a fiber model.
Fiberglass making is managed mostly by a couple dozens of companies.
Rare for individuals to make their own fiberglass products as there is a
difficulty to buy material required.
For this project, a fiber model of approximately 1.5m in length is required.
We chose a scale ratio of 11. Model dimensions are shown below.
2.33 m/sec for 15 knots of ship speed
Tools used in making wooden mould
Stations cut out using hacksaw
Assembling stations and plating shells
View from aft (Transom) of wooden mould
View from below (Fish view)
Profile view of wooden mould
Cost of Timber mould is about 35,000 kyats.
The usual way of fiber model making requires the female
fiber mould to be made first out of wooden primary mould.
Usually made with 6 laminates of chopped strand mat.
Primary mould (Wooden) must first be sanded, applied with
poly putty and again sanded starting from the sandpaper no.
of 40 to 1800.
For sandpapers of no. 400 and above, mould surface must be
first sprayed with water before rubbing.
Gelcoat is painted or sprayed on this finished surface,
lamination starting about an hour after.
Chopped strand mat and polyester resin is used for
Mat laid, Resin applied, Rollers coated, avoided air gaps,
released excessive resin.
6 layers of laminate, Female mould is ready.
Final male model is made similarly using the female mould as
base, of 4 layers of laminate.
This usual way can cost extra money if we make only one
model, leaving the female mould an exces.
For a 4.5’x2’x7” model, could cost 250,000 Kyats or more.
As one model is only needed and best if final male model can
be obtained without making a female fiber mould.
We want the cost to be minimum as we only want one model
for our project.
The company named Fusion Fiberglass agreed to make a final
male model, costing only around 140,000 Kyats, where we
won’t be able to get back the wooden primary mould.
The way they make isn’t usual. Although we couldn’t see the
making of it with our eyes, they explained us how they made.
First, they put a tape fully around the primary mould. Then
applied a really thick putty around it and let it dry.
They destroyed the wooden mould which is lying inside the
putty, taking care not to harm the putty.
After peeling the tapes off, the putty now forms a female
mould. Care must be taken in all stages afterwards. The male
model is made just the same as the steps mentioned above.
The required fiber model will be shown below.
When Fusion Fiberglass delivered the model, they said they
have tested that the model is watertight. But we need to verify
it. No lake or tank to test the model immediately. So, filled the
model with water and see if there were leaks. None.
Finally, we got our model for just around 18000 Kyats.
Fit wooden pieces for seating of dynamometer and guiding
arms, to test in towing tank.
Dynamo must be fitted at CG both longitudinally and
LCG position calculated by Maxsurf and verified by putting
the model subjected to a tripping point, most likely to be edge
of chair and seen balanced and stabled.
Carriage Moving at a Speed of 2.33 m/sec, Related Ship Speed = 15 knots
In our project, detail definition 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.
This project will help the development of using catamaran hull forms in
ship industry in our country.
Chine hull form is used, intended to design a semi-displacement/semiplaning craft.
Displacement hull forms, useful for load carrying but slow speed.
Planing hulls, designed for speed but power requirements are too high.
Thus semi-displacement/semi-planing craft is selected for our design,
Maxsurf, easy to use and fast calculation. Required catamaran hull
form is created by bonding and trimming surfaces in Maxsurf. GA plan
and Lines plan are drawn in AutoCAD.
Stability calculations by Hydromax. Freeboard and
Tonnage calculations are not necessary for this type of craft.
Resistance test in towing tank of MMU. Calculation by Insel
and Molland Theory. Viscous and Wave Interferences
present for catamaran resistance calculation.
Strength and Section Modulus by Lloyd’s Rules,
interpolated linearly from given tables w.r.t length and
speed to length ratio.
Model making chapter help understand basic model
making and fiberglass technology.
FRP boat building, not widely used here.
Locally manufactured boats are cheaper than imported
In mass production of same design, fiber boat building is
more beneficial and less costly compared to conventional
boat building but if built only a few, the cost of making
fiber mould is expensive and unprofitable.
Project points out superior facts of catamarans compared to
Further developments necessary.
Fast ferries should be designed as catamarans.
In depth study in this field would give stable, fast and more
profitable catamaran design.
No mother ship. Best if there is one.
Calm water wave resistance, estimated by using theories and previous
test data by others.
Preferred if all separation to length ratio of specific type of hull form is
tested. Resistance due to appendages neglected.
Strength calculation incomplete. More rules and theories to study for
strength calculation of FRP crafts.
Projects that can be derived using this as a base:
Change GA Plan to design a ferry boat of same size with a capacity of
35 to 50 passengers, more rules and regulations required.
Study resistance. Verify wave resistance w.r.t hull separation.
Fit hydrofoils to form HySuCat arrangement.
Install solar panels to form either electric only or diesel-electric hybrid
system or hydrogen fuel hybrid system.
“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. Took 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.