Basics of Boat Design

Basic of Boat Design

Kymenlaakso UAS / Boat Technology

Terho Halme Aug 2013

Learning OutcomesOn successful completion of the unit, students will be able to:

• explain properties and use of different boat types

• collect and compare technical data of boats

• define relative speed and select the boat type

• explain boat properties due to dimensions and parameters

• define boat dimensions and calculate boat parameters

• explain factors interacting stability

• evaluate stability of a sail boat using Dellenbaugh method

• explain and estimate elements of sail boat performance

• estimate boat speed and power requirements

• explain structure and content of lines drawing

• prepare a proposal concept design

Kymenlaakso UAS/Terho Halme 2

Content & Schedule

Mon Tue Wed Thu Fri

Learning

outcomesPlaning boats

Weight

calculation

Sailing boat

performance

Lines drawing

Relative speed

Displacement

boats Parametric

designStability

Proposal

concept

designSemi-

displacement

boats

Lines drawing


4

From the Methods

• The Methods presented in Basics of Boat Design are simplified and used only in the concept design phase of the boat.

• (Boat Design Methods are defined later in the study modules of Hydrostatics, Hydro-and Aerodynamics, Layout design and Structure engineering.)

Kymenlaakso UAS/Terho Halme

Collecting boat data

• Collect the data of boats from the boating magazines

and internet. The tests of boat magazines are good

sources, domestic and foreign magazines you will find in

the libraries.

• Boats must be representative of the entire field of the

yachting, that is, of all sizes (2.5 - 24 m), different

materials, different uses, boats for cruising, racing,

connection, etc.

• The information is later used for the boat parametric

design exercises. Save the data on an Excel table,

sailboats and motorboats on their own sheet.

• Get started now ...


Sailboat data• Length of hull (LOA, LH), [m]

• Length of waterline (LWL), [m]

• Beam of hull (BOA,BH), [m]

• Draught of hull (Tc), [m]

• Draught total (T), [m]

• Displacement fully loaded(mLDC), [kg]

• Displacement empty (mLCC), [kg]

• Ballast weight (mk), [kg]

• Sail area (As), [m2]

• Sail dimensions (P,E,I,J), [m]

• Engine power (P), [kW]

• Material of the hull and deck (glass fibre, carbon fibre, cored glass

fibre, cored carbon fibre, wood, steel, aluminium, etc.)


Motorboat data

• Length of hull (LOA, LH), [m]

• Length of waterline (LWL), [m]

• Beam of hull (BOA,BH), [m]

• Draught of hull (Tc), [m]

• Deadrise amidships (planing boat)

• Displacement fully loaded (mLDC), [kg]

• Displacement empty (mLCC), [kg]

• Engine power (P), [kW]

• Propulsion (outboard, inboard z-drive, inboard shaft, water-jet,

surface propeller, etc.)

• Material of the hull and deck (glass fibre, carbon fibre, cored glass

fibre, cored carbon fibre, wood, steel, aluminium, etc.)


Boat Hull Types

Right boat type for the purpose.

9

Relative speed

• Relative speed is

expressed by Froude

number (Fn).

• With the same Froude

number the wave

patterns are similar.

• So called “hull speed” is

when Fn = 0,40, then the

wave length and the

waterline length are equal

• Hull speed is NOT any

speed limit

s 3600

m 1852knot 1

m/s 81,9

(m)length waterline

(m/s) speedboat

2

g

L

V

Lg

VF

WL

WL

n


10

Boat types

• Displacement boats, Fn<0,45

– Fishing boats, rowboats, keelboats, trawlers,

tugs, ships

• Semi-displacement boats (semi-planing),

0,4<Fn<1,0

– Cruising boats, motor yachts, catamarans

• Planing boats, Fn>1,0

– Almost all small outboard boats, day cruisers,

runabouts, race boats


11

Speed Ranges of Boat Types

Displacement boats

Semi-displacement boats

Planing boats


12

Displacement boat


13

Displacement Boat: Keelboat


14

Displacement boat: Longkeeler


15

Exercise 1

• What is the relative speed of a keel boat, when the waterline is 9,3 m and the upwind speed is 6,7 knots?

• What is the relative speed of MS Viking XPRS when the waterline length of the ship is 180 m and cruising speed 25 knots?

• What is the relative speed of a wooden rowboat when the winner of 58 km race rowed the time of 5 h 5 min? LWL is 6,4 m.

• Which one does have the fastest relative speed?


16

Power of Displacement Boat

• Maximum speed of

displacement boat like

trawler, keelboat or tug

is Fn = 0,4 - 0,45

• Typical ship speeds:

– Fast ferry Fn = 0,33

– Ferry Fn = 0,25

– Cargo ship Fn = 0,21

– Tanker Fn = 0,19 2

3

3

m/s 9,81

(m)length waterline

(m/s) speed

)(mnt displaceme

(kW)power

64

:boatnt displaceme ofPower

g

L

V

Lg

VF

P

FP

WL

WL

n

n

Modified from: Gerr, Propeller Handbook


Exercise 2

• Calculate power for the boat of exercise 1

when

– The displacement of keelboat is 5 t (the

answer is for sail power)

– The displacement of XPRS is approx. 18 000 t

(the answer is for engine power)

• How much power is installed?

– The displacement of rowboat is 120 kg (the

answer is for row power)


18

Speed and Power of

Displacement Boats

• Keelboat speed upwind is approx. Fn ≈ 0,35

• Engine power for keelboat is ·4 kW/m3 and the

boat speed Fn ≈ 0,4

• Maximum speed of a heavy displacement motor

boat is Fn ≈ 0,45

• Engine power needed for a displacement motor

boat is ·8 kW/m3 (Fn ≈ 0,45 + service allowance)

Where (nabla) is the fully loaded displacement in m3


19

Exercise 3

• The mass of a small outboard boat is 120 kg. It is loaded

by 4 person (á 85 kg) and 50 kg of equipment. How

many kW’s is needed at the outboard engine?

• The hull of a fishing boat (LWL=12 m) is changed to a

pleasure craft and a new motor is needed. After the

alteration work of the boat it is weighted 5800 kg empty,

tank volumes are for water 400 l and for fuel 500 l, boat

is for 10 people and the cargo is 2300 kg. Calculate

engine power and attainable speed.


20

Semi-displacement motor boat

from 50’s


Modern semi-displacement boat


22

Semi-displacement catamaran


23

Semi-displacement

speed and power• Speed range of a semi-

displacement boat is

typically

Fn = 0,45 – 0,8

• The buttocks of boat

should be straight and

near horisontal

(transom boat) or the

boat must be light

compared to length

8,0

)(mnt displaceme

(kW)power

64

:nt)displaceme o(similar tboat

ntdisplaceme-semi ofPower

3

3

n

n

F

P

FP

Modified from: Gerr, Propeller Handbook


24

Exercise 4

• A patrol boat of Finnish Coastguard, ”VMV 11” from

1935 is in Maritime Museum Vellamo, Kotka. Her LWL =

24,7 m and displacement 35 t. During the sea test her

maximum speed was 23,5 knots and her engines were

100 hp (cruising) + 2 x 520 hp (speeding).

• What is the highest Froude number of “VMV 11”?

• What should be her engine power by Gerr?

• How many per cent is the difference? (1 hp = 0,746 kW)

• How would you describe the hull shape and performance

of “VMV 11”?


25

Planing boat 1

Spray lists

Chine


26

Planing boat 2

Chine line

Keel line

Deadrise

Cheer line Station offsets


27

Speed of Planing Boat

• At planing boat, the relative speed Fn > 1

• The narrow hull need more speed to plane than the wide one.

• Note: The narrow hull boat (like a catamaran or trimaran) can be fast even though not planing.

Inc HydroComp,

chinesbetween (m) surface

planing of Width

(m) transomfromgravity of

centre alLongitudin

2,7

:knotsin speed planingLowest

C

C

B

LCG

B

LCGV


28

Exercise 5

• The length waterline of a boat is 8,0 m and

the center of gravity (LCG) is 62% from

the bow.

– What is the lowest planing speed, if the width

between chines is 1,8 m?

– What is the lowest planing speed for a

catamaran, if the width between hull chines is

0,6 m?


29

Speed & Power of Planing Boat 1

(m) hull ofLength

)(m nt volDisplaceme

(kW)Power Engine

knotsin Speed

:viBarnaby/Le

3

25,0

2

25,0

L

P

V

kL

VP

PkLV

Coefficient k

k Propulsion:

2,35 2-shaft drive

2,43 1-shaft drive

2,51 Z-drive

2,83 Surface drive

• Usually P/ in planing

boat is 40-150.


Speed & Power of Planing Boat 2

Coefficient C150 Heavy runabouts, cruisers,

passenger vessels

175 Average, ordinary boats

190 High-speed runabouts, very

light high speed cruisers

210 Race boat types

220 Three point hydroplanes,

stepped hydroplanes

230 Racing power catamarans

Note: Can be used, when Fn > 0,8

30

Terho)by (adapted

SI imp 0,78

(kW)Power

(kg)nt Displaceme

(knots) Speed

)78,0(

78,0

:Formula sCrouch'

2

2

P

m

V

C

mVP

m

PCV


Fuel Tanks

• For a displacement boat, the volume of tank is approx. 5 l/kW, in which case you can cruise over a day.

• For a planing boat approx. 1 l/kW, in which case you can cruise over two hours by a 2-stroke and over three hours by a 4-stroke engine.

• Rules of thumb (1 hp = 0,746 kW): – An old 2-stroke engine burns approx. 1/2 l/hp/h

– A new 2-stroke electronic controlled and 4-stroke petrol engine burns approx. 1/3 l/hp/h

– A Diesel engine burns approx. 1/4 l/hp/h.

31Kymenlaakso UAS/Terho Halme

32

Exercise 6

• How much should the Froude number of 8,0 m

long smuggler boat be to escape ”VMV 11” in

1930’s?

• How much should the engine power be, when

the mass of the boat was 1900 kg, the crew of

three smugglers and 1000 liters of spirits as a

cargo?

• Where could you find such an engine in 1930’s?


33

Exercise 7

• Based on the boat data table you collected:

– Calculate the speed for planing boats by Barnaby/Levi and

Grouch’s formula and compare it to speed measured or informed

by manufacturer. Note:

• One crew member is 85 kg

• Add outboard engine to the mass of outboard boat (normally

exclused)

• Add fuel tank (1 kW of power ~ 1 kg of fuel)

– Calculate the speed and power for displacement boats by Gerr’s

formula.

– Calculate power to displacement ratios to the table.

– Compare and comment.


Parametric Design

Dimensions and coefficients

35

Boat Dimensions 1


36

Boat Dimensions 2


37

Boat Symbols

LH = Length of hull

LWL = Length waterline

BH = Beam of hull

BWL = Beam waterline

Tc = Draft of hull

T = Draft of boat

D = Depth of hull

FM = Freeboard mid

FF = Freeboard fore

B = Center of buoyancy

LCB = Longitudinal center of buoyancy

VCB = Vertical center of buoyancy

LCF = Longitudinal center of flotation


38

Exercise 8

• Find the lines drawing of a sailboat enclosed. The scale of the lines drawing is 1:40. Determine and measure:

– Hull length LH

– Waterline length LWL

– Hull draft Tc

– Hull depth D

– Hull beam BH

– Waterline beam BWL


40

Displacement

• Displacement volume =

Volume of water displaced

by the craft

• The symbol is (nabla)

• In the boat standards the

symbol is VD

• The unit of displacement

volume is cubic meter (m3)• 1 m3 of sea water weight in 1025 kg

• 1 m3 of fresh water weight in 1000 kg

• Displacement =

Mass of water displaced

by the craft

• The symbol is D (delta)

• In the boat standards the

symbol is m (mass)

• The unit of displacement is

kilogram (kg) or tonne (t)

• 1 t = 1000 kg


41

Longitudinal Center of Displacement

W L

W L

LLCB

LLCB

%100

2(%)

= Center of Bouyancy

Longitudinal center of displacement

(LCB) is typically 0-6 % backwards

of amidships (LWL/2).

By modern racers LCB % is -3...-4%


42

CW LW L

bTBL

C

Block Coefficient Cb


43

xW L

PAL

C

Prismatic Coefficient Cp

Modern sailboats

Cp = 0,55 - 0,56

Displacement motor boats

Cp = 0,60


44

Midship Coefficient Cm

pmb

cW L

xm

CCC

TB

AC

:Note


45

Waterplane Coefficient Cw

W LW L

w

wBL

AC

Modern sailboats typically

Cw = 0,69 – 0,71

= Longitudinal Center of Flotation


46

Exercise 9

• The sailboat enclosed has the prismatic

coefficient 0,55, the block coefficient 0,41 and

the waterline coefficient 0,70. Calculate

– Displacement volume

– Maximum section area Ax

– Water plane area Aw

– Midship coefficient Cm

– LCB is 5,10 m. What is LCB %?


47

Linear Ratios

cruisers 5

:Ratio Beam/Draft

or

:Ratioft Length/Dra

or

:Ratio mLength/Bea

c

W Lc

c

W Lc

W L

H

H

W L

W L

T

BBTR

T

LLTR

T

LLTR

B

LLBR

B

LLBR

boatempty of mass is

keel theof mass is

:ratioBallast

LCC

LCC

m

Q

m

QBR


48

Length/Displacement Ratio

• ”Slenderness ratio”

• LDR of sailboat > 5,7,

to outrun Fn = 0,45

– Heavy boats <4,6

– Average 4,6 - 5,2

– Light boats 5,2 - 6,6

– Ultra light boats >6,6

• Used for motor boats

and sail boatsLDRFn

L

LLDR

WL

WL

09,0

:speednt displaceme Max.

)(mnt Displaceme

(m)length Waterline

ratio) ss(Slenderne

:ratioplacement Length/dis

max

3

3



Effects of Length-Displacement Ratio LDR= LWL/^(1/3)

Displacement 1.0 m3

Beam-Draft Ratio BTR 5.0

Block Coefficient Cb 0.50

Length-

Displacement

Ratio

Length

Waterline

Beam

Waterline

Draft

Canoe

Body

Length-

Beam

Ratio

Metacentric

Radius

Metacentric

Height

Hull

Speed

LDR LWL/m BWL/m Tc/m LBR BM/m GM/m V/knots

4 4.0 1.58 0.32 2.5 0.791 0.664 4.86

5 5.0 1.41 0.28 3.5 0.707 0.594 5.43

6 6.0 1.29 0.26 4.6 0.645 0.542 5.95

7 7.0 1.20 0.24 5.9 0.598 0.502 6.43

8 8.0 1.12 0.22 7.2 0.559 0.470 6.87


0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

9,0

4,0 5,0 6,0 7,0 8,0

LWL,

BW

L, T

c, K

no

ts

Length-Displacement Ratio (LDR)

Effects of Length-Displacement Ratio

LWL/m

BWL/m

V/knots

Tc/m

GM/m

51

Displacement/Length Ratio

(m)length Waterline

)(mnt Displaceme

5,30

(ft)length Waterline

tons)(longnt Displaceme

01,0

:ratiolength nt Displaceme

3

3

3

WL

WL

WL

WL

L

LDLR

L

LDLR

• Widely used in boat

literature (am, br)

• Classify boats:

<50 super ultra light

50-100 ultra light

100-200 light

200-300 average

300-400 heavy

>400 very heavy

for motor and sail boats


Typical parameters of planing hull


8,0

55,0

74,0

42,0

6,0

5,35,2

85,0

w

m

p

b

W L

W L

H

W L

C

C

C

C

LCB

B

L

L

L

53

Exercise 10

• Calculate ratios for our sailboat.

– LBR, LTR, BTR, LDR, DLR

– BR, when keel mass is 1980 kg and

draft 1,8 m.

• Calculate to your table of sailboat data new

columns of above.

• Classify your sailboats.

• Calculate to your table of motorboat data new

columns for LBR, LTR, BTR, LDR and DLR


Weight, Mass and Center of

Gravity

Guesstimate or estimate?

Moment method calculation

55

m

Ma

mamamama

amM

mmmmmm

ii

i

Distance

Moment

Mass

44332211

4321


56

Center of Gravity

KGVCG

m

zmVCG

m

ymTCG

m

xmLCG

i

ii

i

ii

i

ii

:nscalculatiostability In

:Vertical

:lTransversa

:alLongitudin

The mass of a single part is mi

and it’s center of longitudinal

gravity is xi. Reference point is at

0-station.

The transversal center of gravity of

a part is yi. Reference point is at

centerline

The vertical center of gravity of a

part is zi. Reference point usually is

the lowest keel point of the hull.


57

Weight calculation table

Part m x y z mx my mz

1

2

3

…

n

mLCG =

mx/m

TCG =

my/m

VCG =

mz/mmx my mz


58

Exercise 11

• Calculate the weight table when:

part; mass; x; y; z

hull; 3000 kg; 5,20 m; 0 m; 0,93 m

keel; 1980 kg; 4,90 m; 0 m; -0,85 m

mast; 150 kg; 3,98 m; 0 m; 8,1 m

engine; 170 kg; 6,50 m; 0 m; 0,40 m

batteries; 80 kg; 6,0 m; -0,60 m; 0,30 m

water tank; 200 kg; 3,6 m; 0,40 m; 0,35 m


Stability

Capsize or not?

60

Floating PositionA floating object always takes up a balance where

the center of gravity (G) and the center of

buoyancy (B) align vertical.

G = Center of Gravity

B = Center of Buoyancy


What is stability?

• Ability of a vessel to resist heeling from

level = initial stability, form stability

• Ability of a vessel to resist capsizing =

ultimate stability, weight stability

• Ability of a vessel to damp accelerations

induced by outside (waves) or inside

(steering) forces= dynamic stability


Two Main Factories of Stability:

• Metacentre M– Depends on boat

geometry

– The wider the boat the

higher the metacentre,

M ~ BWL2

– The lower the draft the

higher the metacentre,

M ~ 1/TC

– The higher the

metacentre, the higher the

initial stability

• Centre of gravity G– Vertical centre of gravity

– Decreasing centre of gravity:

• Inboard motor

• Ballast keel

• Tanks near the keel

– Increasing centre of gravity:

• High superstructure

• Cargo on high deck

– The lower the centre of

gravity, the higher the

ultimate stability


63

Metacentre M


Swedish shipbuilder Fredrik

Henrik af Chapman validated in

his famous ”Architectura Navalis

Mercatoria” (1768) that stability of

a ship can be calculated if the

second moment of waterplane I,

the displacement and the

centre of gravity G are known. )(mnt displaceme

)(m e waterplanofmoment second

:(m) radius cMetacentri

3

4

I

IBM

Metacentre M is always

straight above the centre

of buoyancy B.

Metacentre can be

imagined to be a heeling

centre in small angles.

64

Second Moment of Waterplane I

hullssailboat modern on

shape aneon waterpl depends

12

2

3

w

WLWL

Ck

k

kBL

I


65

Vertical Center of Buoyancy VCB

KBBMKM

ATVCBKB

w

c

:line keel from Metacentre

2

5

3

1

:ionapproximat sMorrish'


Metacentric Height GM

• Centre of gravity G (or KG) comes

from weight calculation or heel test

• Difference between centre of gravity

G and metacentre M is called

metacentric height GM, and is a

fundamental measurement of

stability

• If G is above M, the vessel will

capsize

• High GM in motor boats leads to

jerky motions

• Low GM leads to wide, slow rolling

• GM > 0,15 m (IMO)

• Typically on sailboats

1 m < GM < 2 m


KGKMGM

:height cMetacentri

When a vessel heels to angle• Centre of buoyancy B

moves sideways to B’

• Metacentre M is always

straight above B’ and

on the centre line of the

vessel (on small heel

angles)

• In between centre of

gravity G and buoyancy

B’ is a horizontal

distance GZ, called

righting arm


g

Small angle heeling

g = Buoyant force

mg = Gravitational force

= Heel Angle

Z = Perpendicular to G

B’ = new buoyancy centre

68

GZmgRM

GMGZ

:Moment Righting

sin

:Arm Righting


g

69

Large angle heeling

mg

g

• When the boat heels,

metacentric radius will

decrease by cos, until

the gunwale sinks

(approx. 35°).

30cos30sin30

:degrees 30at moment Righting

cossin

:30 heel angle Large

GMmgRM

GMGZ


70

Exercise 12

• Calculate in our sail boat

– Second moment of waterplane, I

– Metacentric radius, BM

– Metacentric height GM, when the center of

gravity is 100 mm above design waterline

• Calculate righting moment at

– 1 degree heel RM1

– 30 degrees heel RM30


Instant estimate of metacentric radius

71

T

BBM

C

C

CT

CB

CTBL

CBLIBM

)(C

C

BL

AC

CBLI

CTBL

b

w

b

w

b

w

w

w

ww

w

b

10 so 2,1

4,0

7,0 while

:simplistic more hulls,boat sailmodern in

1212 radius cMetacentri

21,0 usesimilar or canoesin

enough, accurate is sailboatsmodern In

and , 12

e waterplanofmoment Second

and nt volumeDisplaceme

222

2223

2

23


Estimation of Instant Stability

72

gmGZRM

GMGZ

KGBMTGM

KG

TKB

moment Righting

)30( cossin arm Righting

64,0height cMetacentri

ncalculatio weight from is gravity ofCenter

64,0 sailboatsmodern In


Exercise 12aRecalculate exercise 12 using estimation above.

Compare the results and write your findings down.

73

Angle of Heel 0°

g

mg

G

B


74

Angle of Heel 30°

B

gG

mg


75

Angle of Heel 60°

mg

g

B

G


76

Angle of Heel 90°

mg B

G g


77

Angle of Heel 120°

mg B

G g


78

Angle of Heel 150°

B mg

g G


79

Angle of Heel 180°

B

mg

g

G


80

Stability curve

GZ from Hydrostatics

GZ=GM*sin*cos


Sailing Boat Performance

Well, is it any good?

82

Sail Area

sfsms

sf

sm

AAA

JIA

EPA

:area Sail

2

:area triangleFore

2

:area sailMain


83

Heeling Arm

LPCE

LDCLP

s

sffsmm

CE

f

m

HHHA

mH

A

ACEACEH

FFICE

FMBASPCE

boat of arm Heeling

04,0

waterlinebelow centre Lateral

area sail of arm Heeling

33,0

sail head of arm Heeling

33,0

sail mail of arm Heeling

3


84

Dellenbaugh angle

• Dellenbaugh angle is estimated heeling while sailing upwind at wind force 4 (approx. 8 m/s)

• Value of DA is compared to “stiff” or “tender” boat.

• Can be used for sail area estimation. (m)height

cMetacentri

(kg)nt Displaceme

(m) arm Heeling

)(m area Sail

279

2

GM

m

HA

A

GMm

HAADA

s

s


85

Dellenbaugh compare


86

Exercise 13

• Dimension the sails of our sail boat to

have Dellenbaugh angle 17-18 degrees.

– BAS = 1,5 m. (Boom Above Sheer line)

– It will get easier if you take P = 2,6*E ja I =

3*J.

– 2,6 is the geometric aspect ratio of main sail

and 3 is the geometric aspect ratio of fore

triangle.

– You can use Excel’s target search to help


87

Sail Area/Displacement Ratio

)(mnt displaceme

)(m area sail

3

2

3/2

s

s

A

ASDR

• Indicates Power to

weight ratio

• <7 Motorsailor

• 14-20 Cruiser

• 20-22 Cruiser/Racer

• 22-25 Racer/Cruiser

• >25 Racer

• In old, narrow sailboats

SDR is 1-2 smaller


Sail Area/Wetted Surface Ratio

W Lw

c

cW Lw

rkw

s

LS

TTLS

SSS

ASWR

8,2

or 2

• Sail area/wetted

surface ratio indicates

performance in light

wind.

• SWR < 2,0 slow

• SWR > 2,5 fast

88

)(m hull of surface Wetted

%2 )(mrudder of surface Wetted

%5 )(m keel of surface Wetted

2

2

2

w

srr

skk

S

ASS

ASS


89

Exercise 14

• Determine sail area/displacement ratio of

our sail boat.

• Determine sail area/wetted surface ratio.

• Write an analysis of the performance of

our sailboat (use speed upwind, DA, SDR,

SWR etc.)


90

Measured Rating of Keel Boat

purpose various

for t coefficien

)(mnt Displaceme

)(m area Sail

(m) Waterline

3

2

4

3

k

A

L

ALkMR

s

W L

sW L

• Just comparing boats coefficient k can be 1. Then MR can be imagined as a speed in knots over similar conditions.

• If used as a yard stick, first calculate MRref of a reference boat when k = 1 and then replace k = 1/MRref.

• Sailing times are then divided by RM


Exercise 15

• Calculate to your Excel table of sail boats

SDR, SWR and MR for all boats.

• Arrange the boat in order of performance

a) in light wind (1-3 knots)

b) in fresh breeze (17-21 knots)

• What is the fastest boat in your table (in

average)?

• What is the slowest boat in your table?


Guesstimated Price, €/kg?

• Cost of materials and installed parts(1,4*LDR) €/kg (2008)

• One-off boat can be built approx. (LDR/5) kg/h. The heavier the faster (=easier material, bigger parts).

• In small production a boat can be built approx. 2 kg/h

• In highly module-based mass production 2-10 kg/h

• General costs are approx. 15-20% of production costs

• Design cost of a one-off boat is 5-10% of production costs


Exercise 16

• Estimate building costs of our sail boat as a one-

off boat. Note labour cost, margin and taxes too.

• If they were built in small production, what are

the building cost then?

• If they were built in mass production, what are

the building costs?

• Compare your cost estimation to real prices in

boat market.


Lines Drawing

How to draw a 3D hull shape

onto 2D paper?

95

Cuttings of Lines Drawing

3D-surface is sliced up from three directions:

1.Stations

– Transversal and vertical cuts

2.Waterlines

– Longitudinal and horizontal cuts

3.Buttocks

– Longitudinal and vertical cuts


96

Stations

Vertical cuts

Transversal cuts

Station curves


97

Waterlines

Horizontal cuts

Waterline curves

Horizontal cuts


98

Buttocks

Vertical cutsButtock curves

Longitudinal cuts


99

Views in Lines Drawing

• 3D-surface of the hull is projected in three

orthogonal views:

• Profile

– View straight from side

• Body

– View straight from bow (or stern)

• Plan

– View straight from bottom (or top)


100

Profile (side view)

10 9 8 7 6 5 4 3 2 1 0

DWL

Amidships

Buttocks

Waterlines

Sheer line

Keel line

Stations


101

Body (stern & bow view)

2 3 4 5

0 1

DWL

109876

Stations BowStations SternCenter Line

CL


102

Plan (bottom or top view)

DWL

012345678910

Waterlines

Buttocks Stations Center line

Sheer line


103

Lines Drawing

012345678910

Station nr 0 is at the

intersection of keel line

and design waterline

Station nr 10 is at the intersection of keel line and design waterline

BodyProfile

Plan

Design Waterline


104

Directions of dimensions

012345

Body viewProfile view

Plan view

Wid

thH

eig

ht

Length

WidthWidth


105

Equivalent points

0123

Every intersection of lines has an equivalent point in another view. The

point has equivalent length, width and height in every view.


Typical V-bottom lines


107

Lines drawing exercise 1

Add stations to the body view.

(Ask an A3 copy)


108


Add waterlines and buttocks.

(Ask an A3 copy)



This sailboat has design waterline and stations 0, 5

and 10 done. Complete drawing up to 11 stations, 3 buttocks and 5 waterlines

(Ask an A3 copy)


Proposal Concept Design

Time to have some practice fun!

111

Concept Design Process

• Design brief

• Operating speed -> Froude number, Fn -> boat type

• Parametric design– Existing boats-> data

collection

– Analysis -> parameters L/B, L/, P/, SA/ etc.

– Synthesis ->choose of L, B, D, T, P, SA, etc.

– Form coefficients Cb, Cw, Cm, Cp

• Sketching lines drawing– profile: sheer, keel, DWL

– plan: (sheer, DWL)

– body: amidships, transom

• Concept drawings– Profile (sail plan), deck

plan, accommodation

• Check:– Displacement

– Weight calculation

– Stability

– Performance

• Cost estimation


112

Design Brief

• Use of the boat

• Operational conditions

• Propulsion

• Operational speed

• Size of the boat

• Displacement

• Crew

• Cargo, loading

• Range

• Equipment

• One off / production

• Building cost

• Operating cost

• Accommodation

• Arrangements

• etc.


Why Concept Design?

• Improves possibilities to success

• You can get almost there at the first step,

only some fine tuning left

• You can be quite sure of performance,

stability and safety

• Still, you can do better (or worse) than

existing boats

• You can get paid



HULL TYPE SELECTION

Sail Cp ~ 0,55

Motor Cp > 0,6

LCG = 0...-8%

Transom above DWL

Fn < 0,45

Displacement Hull

Transom immersed

LCG = 0...-10%

Direct buttock lines

(can rise few deg aft)

0,45 < Fn < 1

Semi-displacement Hull

Avoid curves in chine

at aft body

Deadrise 15 - 26

LCG = -10...-25%

Direct buttock lines

parallel to keel

Fn > 1

Planing Hull

Check LWL

Check Speed

Calculate Fn

Design office Exercise (will be graded)

1. Make two-people design offices (one three-people, if odd number of

students)

2. Give them names like: Jan & Kalev Yacht Design

3. Every design office is also the customer to the next office in class.

(an unbroken chain of offices…)

4. As a customer, write down the design brief of your dream boat (LH 8

– 24 m)

5. Order the Concept Design of your dream boat from the previous

office of the chain. So, you are not going to design it yourself.

6. As a design office, go through the concept design process and make

all the documents for the customer.

7. Have some meetings with your customer to be sure of the demands.

8. Do teamwork inside your office as much as necessary.

9. Still, every student returns his/hers own Concept Design which will

be graded.


Basics of Boat Design

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