zero-emission ferry

ZERO-EMISSION FERRY

Final Report of Ship Project A

Kul-24.4110

BY224051 Their Tomas467643 Ran Xiao

2014.12

Aalto University

Contents

1 Resistance Estimation & Propeller Design . . . . . . . . . . 11.1 Resistance estimation . . . . . . . . . . . . . . . . . 11.2 Rotation Speed & Propeller Design . . . . . . . . . . 71.3 Machinery . . . . . . . . . . . . . . . . . . . . . . . . 13

2 General arrangement . . . . . . . . . . . . . . . . . . . . . . 152.1 General arrangement . . . . . . . . . . . . . . . . . . 152.2 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3 Hull structure . . . . . . . . . . . . . . . . . . . . . . . . . . 263.1 Strength recalculation . . . . . . . . . . . . . . . . . 263.2 Longitudinal bending moment and strength check . . 263.3 Compatibility of the structure with general arrangement 333.4 Demands on production . . . . . . . . . . . . . . . . 363.5 Openings . . . . . . . . . . . . . . . . . . . . . . . . 37

4 Light Weight & Stability of Undamaged Ship . . . . . . . . 384.1 Wooden weight . . . . . . . . . . . . . . . . . . . . . 384.2 Connecting elements . . . . . . . . . . . . . . . . . . 434.3 Equipment weight & Gravity center calculation . . . 444.4 Stability calculation . . . . . . . . . . . . . . . . . . 50

5 Cost estimation . . . . . . . . . . . . . . . . . . . . . . . . . 555.1 Construction material . . . . . . . . . . . . . . . . . 55

2

5.2 Key components . . . . . . . . . . . . . . . . . . . . 565.3 Cost on construction workers . . . . . . . . . . . . . 605.4 Price comparison with other ships . . . . . . . . . . . 605.5 Similar capacity . . . . . . . . . . . . . . . . . . . . 605.6 Similar technology . . . . . . . . . . . . . . . . . . . 615.7 Cost calculation methods . . . . . . . . . . . . . . . 62

6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 637 Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

1. RESISTANCE ESTIMATION & PROPELLER DESIGN Zero emission ferry

1 Resistance Estimation & Propeller Design

1.1 Resistance estimation

Methodology Brief

As our ship concept is in form of catamaran, it is not proper to simply introduce the

method and diagrams of monohull model series. For catamarans, the interaction of waves

generated by twin hulls cannot be ignored, instead it affects the friction resistance as well

as wave pattern resistance.

Different from the methodology used in the previous report where Delft Series (98’)

and John Winter’s empirical resistance diagram are utilized, here we apply the method

and diagrams deduced in ’Resistance Experiments on a Systematic Series of High Speed

Displacement Catamaran Forms: Variation of Length-Displacement Ratio and Breadth-

Draught Ratio’[1].

By this method, resistance coefficient is defined as follow:

Ctcatamaran = (1 + β ∗ k))CF + ι ∗ Cw = (1 + β ∗ k))CF + CWP = CF + CR[1]

Where β is a factor related to the pressure field change and ι is wave resistance intereface

factor. By applying this equation to both models and the full scale and deducing some

mathematically transforming, the resistance coefficient of the full scale can be expressed

as:

Ctcatamaran = CFship+ CRmodel

− β ∗ k(CFmodel− CFship

)[1]

In our design, we have parameters for our ferry as below, where CB is the block coefficient,

CP is the prismatic coefficient, Cw is the waterplane coefficient, L is ferry length, ∆ is

the displacement, B is the breadth of the ferry and T is the draught.

Table 1: parameters of the design

CB Cp Cw L/ 3√∆ S/L B/T

0.495 0.62 0.7 6.34 0.3 1.8

Then we can select similar model and corresponding diagrams from ’Resistance Experi-

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ments on a Systematic Series of High Speed Displacement Catamaran Forms: Variation of

Length-Displacement Ratio and Breadth-Draught Ratio’[1] according to the parameters

listed above. Here model are classified as:

Figure 1: parameters for different models[1]

Therefore the model 3b* is the one which has the most similar parameters with our ferry’

s. We choose 3b* and its relevant parameters are:

Figure 2: parameters for model 3b* [1]

Here are some difference in term of CP . As CP stands for how full the underwater part

of hull is, a relatively larger value can make the predicted resistance larger than it should

be. But since it is a rough estimation and the difference is still limited, the influence on

the outcome is also expected to be limited.

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Determination of coefficients

Figure 3: resistance coefficients of model 3b* [1]

As mentioned previously, we know

Ctresistance = (1 + β ∗ k))CF + ι ∗ CW = (1 + β ∗ k))CF + CWP = CF + CR

and in figure above, the curves of Ctcatamaran(denoted as Ct) and (Ctcatamaran − CW )

(denoted as Ct − CW )have been given, there are also curves of CF and (1.65)�CF . Ap-

parently, illustrated in the figure, the curve for (Ctcatamaran − CWP ) matches very well

with that of (1.65)�CF outside the Froude Number zone of [0.2, 0.65], meaning outside

this zone the value of 1+��k could be estimated as 1.65. Unfortunately the resistance we

are studying is within this zone, so we have to estimate the value of 1 + β ∗ k one by one

according to the graph above, and we yield following graph:

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Figure 4: value of 1 + β ∗ k along with different speed[1]

And from the graph below we can also conclude all the CRmodel= CRship

= CR at

corresponding speed.

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Figure 5: residual resistance coefficient of model 3b*[1]

Resistance prediction

Now we have all the values needed for resistance calculation. According to the resistance

expression：

Ctcatamaran = CFship+ CRmodel

− β ∗ k(CFmodel− CFship

)

as well as formulas：

CFmodel=

0.075

(log10(Fn ∗ 5.56 ∗ 106)− 2)2

and ITTC’57 Correlation line:

CF =0.075

(log10Rn − 2)2

we have the following graph:

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Figure 6: Resistance coefficient prediction

The coefficient climbs greatly after the speed exceeds 12 knots due to the drastic increase

of CR at the corresponding speed.

Now lastly, we assume our wet surface is 180 m2, which is just a rough estimation.

Presuming that the cross sections of hulls are triangle and finding the side length of the

hull under water is around 3.2 meters for each pontoon. As the length is around 23 meters

at waterline, each hull has wet surface of 75 m2 and in total it is 150 m2. However, we

need to consider the curve of the hull shape which can increase the wet area, therefore

we assume the wet area is 180 in total for accurancy. Now we just consider one single

pontoon during the design of propeller for simplification. We are now able to calculate

the drag according to the previous formula and draw the curve in the figure below:

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Figure 7: Resistance prediction for single pontoon

1.2 Rotation Speed & Propeller Design

Propeller

The ship will be using two Azimuth thrusters, one under each hull at the rear, similar

as seen in figure 8. However, unlike the ship in the picture, our ship is catamaran. The

number of propellers was chosen because each hull contains a separate engine, and with

each engine driving one propeller we will get some control advantages, and this means

that the area between the hulls can be kept clear.

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Figure 8: A catamaran (Aluma Marine Mana’O II) with one propeller under each hull[2]

In the initial concept design we calculated that the desired speed could be achieved using

two azimuth thrusters of 100 kW (the power needed was approximately 180 kW, so to

ensure sufficient power 2 x 100 kW could be used). By checking this to available solutions

on the market we can estimate the size of the propeller in this case.

Parameters & Assumptions

According to the report and previous calculation, we can find out the following informa-

tion for each propeller:

1. Engine type: Type: Standard azimuth thrusters - type US 55P4

2. Max input power: 330 KW

3. Propeller diameter: 1050 mm

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4. Vessel design speed: 15 knots

5. Resistance at 15 knots for each pontoom: 31657 N

Now as we are going to design the propeller initially, we have to make some assumption

for further calculation.

1. t = 0.2 which is the thrust deduction

2. Ap = 0.55 which is the propeller efficient area

3. w = 0.1 which is the wake factor, it is relatively small since the utilization of Azimuth

thruster so that the affect from hulls is very small.

4. propeller is located at 3.5 meter below the water surface

5. ηHull =1−t1−w = 0.89 and ηShaft = 0, 98 (taken from empirical statistics from vessels

whose engines are located at the rear part), ηGear = 0, 96 for gear box efficiency

There are several reasons for us to make these assumptions. For the thrust deduction,

considering the azimuths is a very big appendage to our ferry, they should contribute to

a fair big t, therefore we set t as 0.2. For the wake factor, we do not have the test data,

but based on data of the range of wake factor classified by vessel types[3][26], we have a

vessel with two thrusters and they are azimuths which means they are quite far from the

hull bottom, and our ferry is quite small. According to these information we confine w

is between 0.05 to 0.1 and we take 0.1 as the final value. As for the gearbox, the speed

of motor is 3500 rpm, so the gearbox is needed, and accordingly there is a corresponding

efficiency.

Cavitation Calculation

As cavitation on our propeller should be always avoided, we need to find out the limitation

for propeller speed. The flow speed in far field from the ship is zero, and the flow speed

at the propeller is the advance velocity and propeller speed, where the former is VA and

the latter is 2πnD. So we have equation:

Pa + ρgh+1

2ρ(02 − (V 2

propeller + V 2A)) > PV

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In this equation, Pa is pressure of atmosphere and PV is the vapor pressure for water

which is 1200 Pa at 10 centigrade. h is the depth of propeller from the sea surface, we

have assumed it is 3.5 meters. Here we consider the cavitation problem at 0.7 of radius of

the propeller since it is the most representative section. The speed at that section can be

expressed as Vpropeller = 2 · π · n · 0.7D, where VPropeller is assumed as 15 knots. Finally

we have a maximum rotation speed as 6.5 round/s.

Propeller design

Based on the resources we have at hand, we choose Wageningen B4-55 as our propeller

type. As we already have the thrust deduction and wake factor, we can work out the

value of δ at different rotation speed for application of the B-series diagram and data

interpolation. However here comes a problem that the value of δ is too small to be

interpolated into the diagram. Moreover, it also takes too much power to keep the speed

at this level. For hydrogen and fuel cell propulsion system, it is hard to afford, especially

on such a small vessel. So we have to choose 13 knots as our service speed to design our

propeller. From now on, the resistance will be set as 17496N at the speed of 13 knots.

Table 2: parameters of the propeller at different rotation speed

Speed (knot) D(m) N(round/s) VA(m/s) δ

13 1.05 4.5 6.019 0.785014

13 1.05 5 6.019 0.872238

We interpolate the δ values that we have into the diagram below to find out the corre-

sponding values of η0, pitch ratio and BP with which we can calculate the deliver power

and effective power.

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Figure 9: B4-55 diagram[3]

Table 3: optimized parameters of the propeller at different rotation speed

N(round/s) δ P/D δ0 BP

4.5 0.785014 1.6 0.77 0.38

5 0.872238 1.3 0.755 0.39

The definition of BP is

BP =P 0.5D

DV 1.5A

As we have had the values of BP , here comes the deliver power and η0. η0 is the efficiency

of the propeller η0 = TVA

πDQ and the relationships among the deliver power PD, engine power

PS , thruster power PT and efficient power PE are as follow:

PD = PS ∗ ηShaft ∗ ηGear

PT = PD ∗ η0

PE = PT ∗ ηHull

Then the corresponding effective power and engine power are able to be listed out.

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Table 4: power at different rotation speed

N(round/s) BP PD(KW ) PS(KW ) PE(KW )

4.5 0.38 190.2 202.18 113.92

5 0.39 200.36 212.96 117.65

Since in previous calculation we have known that the needed power for our design at 13

knots is about 117 KW for each propeller, now we can make a graph to see where the

needed power and effective power meet so that we can determine the optimal pitch ratio

and RPM for our propeller as 300 r/min.

Figure 10: RPM vs Power

Also, efficiency of our propeller is also acquired

Table 5: propeller efficiency

η0 ηHull ηShaft ηGear

0.755 0.89 0.98 0.96

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1.3 Machinery

In this part, the choice of machinery will be discussed. We will try to explain why a

certain piece of machinery has been chosen, and what this means for the ship.

The power for the propulsion will be generated using hydrogen cells, and the energy

generated will be stored on on-board batteries as needed. With this system the ship

will be able to achieve the image of a green ship, which will appeal to both commuters

and tourists. Thanks to the use of fuel cells the energy can be generated only when

needed, e.g. when the power in the batteries goes under a certain amount, and if there is

sufficient power available only the batteries will drive the engines. This means that the

ship’s machinery consists of four different components have to be defined: The electric

engines, the fuel cells, the hydrogen tanks, and the batteries.

The electric engine needs to be chosen so that it can produce sufficient energy for the

propeller it is driving. When accounting for the efficiency of the propeller the power of

the engine should be at least 220 kW. Here we could use e.g. the Siemens PEM-Motor

1DB2024 – WS36, which has a power of 320 kW with a weight of 500 kg [4].

The fuel cells are hard to find information on, but there are definitely fuel cells available at

the power we wish to use. The German company proton motor, for example, manufactures

fuel cells of up to several hundred kW for maritime use [5]. The price is hard to estimate,

though, as the technology improves constantly, and the price varies greatly depending on

the product and its specifications (custom/serial production, power-weight ratio etc.).

For the hydrogen tanks we calculated that we need a capacity of 70 kg. At 350 bar

hydrogen has a density of 70kg/m3, which means that we need a total of 1000 litres of

tank space. This means that we need a total of twenty 50 litres tanks. The total weight

of these is about 1000 kg.

Finally, the batteries need to store excess energy created by the fuel cells. In the case of

the Zemships 2 concept (which is a ship of a similar size to ours), the ship has 7 x 80

V lead-gel batteries, giving 360 Ah. Since our ship uses a bit more power (the Zemships

concept only has one 48 kW fuel cell) we would probably need a bit more batteries. A

linear approximation puts the amount at roughly 20 x 80 V batteries. This can still be

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changed in the future, though, in case we e.g. want to change to lithium-ion batteries, or

get a more precise value on the needed amount of batteries.

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2. GENERAL ARRANGEMENT Zero emission ferry

2 General arrangement

2.1 General arrangement

Propulsive machinery

As our design is a kind of simple catamaran, the propulsive machinery is mainly placed

in the pontoons. There are a complete propulsion system in each hull including hydrogen

tanks, fuel cells, batteries and motors.

In the hull, every 2 meters along the longitudinal direction, there is a headbulk. So it

could be better that every part of the system can be small enough contained in a single

zone divided by the headbulks. Firstly for our motors, it is not a problem since its size is

as following.

Figure 11: moter selected[4]

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Next, batteries are quite easy to arrange since they are very small but huge in number.

It is estimated that we have 1064 batteries on each hull with specification as below.

Figure 12: information of batteries[6]

Then here comes the fuel cells. For keeping balance of our ship, it is better to lay the fuel

cell as well as the hydrogen tanks in the mid compartment of hulls. For our fuel cells,

they have the maximum size of 1600 millimeters, which means there is enough space in

the hull to settle the full cell. As for the tanks, they are all long cylinders whose height is

1450 millimeters so that it is also not a problem to place them in the hull. Consequently,

we have a rough arrangement of propulsive machinery deployed as the picture shows.

Figure 13: AFC

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Figure 14: general arrangement

A/C system & heating

In our design, the roof structure should be 3 meters high while the celling in cabin should

be around 2.2 meters above the floor, enabling the installation of A/C system between

the celling and roof possible since there is a 0.8-meter-high volume available. Meanwhile

2.2 m height is also enough for passengers to move in or out comfortably.

For the heating system, according to the similar system on trains, we place it under the

floor, making the heat spread to the whole cabin as soon as possible due to the heated

air circulation. Because there is a 0.6 meters gap between the floor and the hull in the

platform. The heating system can be easily installed beneath the floor.

Figure 15: top view

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Platform

The platform will be the largest area of the ship, and in our case the one where the cargo

(passenger) handling will take place. The general arrangement inside the area can be

seen in figure 16. The area will contain seats for 154 passengers, large spaces for e.g.

wheelchairs and pushcarts, and an area with bicycle racks in the back, as seen in figure

17. Shelves for larger bags (as seen e.g. on trains and airport buses) can also be added

to this area.

Figure 16: the arrengement of the passenger area

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Figure 17: bike rack system

The passenger handling will take place at every stop, and the plan is to use a system

similar to that used in buses. As seen in figure 18, the passengers will disembark the ship

through the two front doors, and when the area has been cleared enough new passengers

will board through the back door. This way an almost constant flow of passengers will

flow through the ship to ensure that the ship can stay on schedule.

Figure 18: the passenger flow plan

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Bridge

The bridge will be placed in front of the passenger area, with the actual bridge slightly

higher. Underneath the raised bridge will be a storage compartment which can be used

for safety equipment or electronics used on the bridge. The arrangement of this area

can be seen in figures 19 and 20. The easiest way to access the bridge, while leaving a

maximal area on the inside, is to place a door and stairs on the outside. The storage area

would be accessed through the passenger area, as electronics would most likely be placed

at the front of the compartment. Equipment like radar and radio antennas will be placed

on the roof of this structure.

Figure 19: side view of the bridge

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Figure 20: top view of the bridge, the shape of the hull is simplified in the picture

The actual placement and amount of all the navigation equipment etc. may of course be

different than presented in figure 20, and there needs to be a gap if a door is placed at the

stairs as in the figure. The idea is just to give an idea of the area where the equipment

will be placed

2.2 Safety

To make sure that the ship is safe some things have to be taken into account. The ship

needs to have all necessary equipment that is needed in the case of an emergency, and extra

equipment that should make the trip safer in general (e.g. to help with the boarding).

Some of this equipment cannot be specified exactly before all the exact specifications of

the route, docks, etc. are known, but others will be determined at this point.

At the time of writing most safety equipment is still the same as specified in the conceptual

design, with some added thought given to, among others, safety during boarding and

inside the passenger area. It appears like our ship will not be specified as e.g. a high-

speed ferry (or something else that might require further safety measures), but can instead

be thought of as a ship much like the Suomenlinna ferry. However, if it later turns out

that some specification of our ship means that it will be classified differently we will take

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that into account in later reports.

Emergency equipment

From the conceptual design report [6] we can find the main safety equipment, which will

consist of things needed during an evacuation of the ship. This includes life jackets and

life rafts, as well as signaling equipment such as flares, fire extinguishers, a V-sheet and

possibly an emergency beacon for bad weather.

Finnish law requires that a ship over 124 m must carry life jackets for 110% of the

passengers. This includes special life jackets for children (10%) and infants (2,5%) with

the same safety margins. Extra-large life jackets for passengers over 140 kg should also

be kept as spares. The amounts needed for 154 passengers are specified in table 6. The

life jackets will be placed under the seats (as in airplanes), with extra life jackets placed

e.g. in boxes near the doors.

Table 6: Life jackets sizes and amounts

Life jacket size Number

Normal 120

Children 20

Infant 8

Crew 3+2

Total 213

The life rafts should be capable of carrying 125% of the passengers, and the easiest

solution for our ship is to have inflatable life rafts, that can be stored either in the same

way as the extra life jackets, or outside the ship on the front and rear decks.

Apart from the lifesaving equipment our ship will need fire extinguishers, spread over

the passenger area and the bridge for easy access. Since our ship uses hydrogen the

extinguishers must be capable of handling this sort of fire. The emergency flares should

contain normal signal flares, orange smoke flares, and a floating flare, so the ship can

signal for help during low visibility. A V-sheet should also be included although it may

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not be necessary, at least in the center of Helsinki.

Compartment division

It may be that the ship does not have enough watertight bulkheads (3 at the moment).

This gives 6 m between each watertight part, and so far we have not been able to find any

regulations saying that this is insufficient. However, a flooding of just one compartment

will lead to a lot of added weight compared to the total weight of the ship, so this

number can still change if we find a rule stating that the current one is not enough. If

the machinery installment in the hulls allows for more bulkheads these will of course be

added.

Other safety features

Apart from the obvious emergency equipment the ship may need some other equipment

to make the journey safe for the passengers. One thing that must be taken into account

is the boarding process, during which the passengers will be moving on and off the ship.

Our ship uses an automatic mooring system, as seen in figure 21, but this will still leave

a gap between the ship and the dock. This could prove especially dangerous during times

with high waves, when the ship will be moving up and down. To make the process safer

a small boarding bridge (basically a short arch with railings) should be available at the

docks. To keep the process simple it should be small enough so that one or two men on

the docks can put it into place quickly. Nevertheless, this gives the passengers something

to walk on, which should eliminate the risk of accidents.

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Figure 21: the principal idea of the docking system, with the front in the right side

picture [6]

Another thing to take into consideration are passengers standing inside the passenger

area. If the ship makes a sudden movement these passengers can fall, so the inside of the

area should contain something for the passengers to hold on to if needed. Here we can

include the same idea as seen on trains and buses, as seen in figure 22. By adding the

bars at the seats the floor area will be kept clear, so the flow of passengers does not slow

down, and if the bars are connected between the roof and the floor they will give the roof

some added stability.

Another similar safety feature is hooks or loops that will be needed to keep pushcarts and

wheelchairs secured during the crossing. These already have their own specified areas,

and the system can easily be integrated into the seats.

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Figure 22: interior of a bus with the bars for standing passengers clearly visible

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3. HULL STRUCTURE Zero emission ferry

3 Hull structure

3.1 Strength recalculation

Previous calculation check

In the conceptual design report, we already have the relevant calculation. Now we need

to check the way we used to see if it really work in our case.

In the previous calculation, it is done according to the rules of Bureau Veritas, <Rules

for the classification and certification of Yatch>, which is not our requirement of DNV.

However, it could also work by using other rules. In the calculation process, only bending

moment in still water is considered, and the one by waves is neglected, which may lead to

some great inaccuracy since wave bending moment is sometimes larger than the still water

bending moment. Furthermore, the superstructure is not taken into account because

there is not much mentioning about the superstructure’s detail in this report. But as a

continuous longitudinally structure, it contributes a lot to the moment of inertia of the

whole ship and should not been ignored. Consequently, it is necessary to redo this part

in order to make sure we have enough strength from our design.

3.2 Longitudinal bending moment and strength check

According to DNV’s rules ’HIGH SPEED, LIGHT CRAFT AND NAVAL SURFACE

CRAFT’[7], we can find the related formulas for twinhull ship bending moment in both

hogging and saging conditions.

Figure 23: bending moment

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Where the Btn is the breadth of cross structure(tunnul breadth). And after some conser-

vative approximation and calculation, we have values as below.

Table 7: factors for moment & bending momentk2 k3 Mtot hog (kNm) Mtot sag (kNm)

0.68531 0.73989 2403.4 1646.6

Having known the total moment acts on ship, we now calculate the section modulus of

the whole ship. Firstly the moment of inertia is needed. According to the report, the

thickness of hulls made of plywood is 23 mm and by assuming the shape of hull is similar

to triangles, the length of hull plates is 1.9 meters respectively.

In the course of shipyard of weight estimation, thickness of superstructure is estimat-

ed as around 10 mm with double roofs also with this thickness. Moreover the thicknesses

of platform are 5mm and 7.5 mm. in summary here comes the table with relative height

to the bottom:

Figure 24: side view of the configuration

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Table 8: areas and central heights for moment of inertiaHull

area(cm2)

H1(cm) Lower deck

layer(cm2)

H2(cm) Upper deck

layer(cm2)

H3(cm)

1748 85 433 170 649.5 190

Cabin

walls(cm2)

H4(cm) Inner

roof(cm2)

H5(cm) Exterior

roof(cm2)

H6(cm)

600 340 866 410 866 490

Neutral

axis height

(cm)

Moment

of inertia

(m4)

309.32038 1.4263

Since the values of acted moments and moment of inertia are both yield, the stress acted

on the ship is also available now according to

M

Wmin= p < σ, Wmin =

I

ymax

The result is 5.2 Mpa. As the yield strength of plywood based on the conceptual design

is 48 Mpa, which is way larger than the stress. Based on the equation provided by the

rules, 5.2 Mpa is the believable value of loads so that we do not need to consider safety

factor furthermore considering it is not mentioned in DNV’s code either. We believe our

structure is strong enough in this case.

Figure 25: property of materials

Transverse bending moment and strength check

In the regulation of DNV, the method to calculate the transverse bending moment of

twin hull ship is also provided, which is mentioned in the ’HIGH SPEED, LIGHT

CRAFT AND NAVAL SURFACE CRAFT’[7]. The rules define the moment with

related parameters in the figures below.

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Figure 26: definition of transverse moment

Figure 27: definition of acg

To calculate the moment, first we need to know the design vertical acceleration, which is

related to the significant wave height. Our ferry will operate in Kruunuvuorenselkä

water area. But unfortunately we didn’t find the sea state statistics of this area, so we

just assume it is 1.5 meter. According to the WMO sea state code, it is classified as

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moderate sea state. Considering our routing is located at somewhere very closed to

land, this assumption can be reasonable. Then we have the acceleration as:

acg = 6 ∗ 1 ∗ 9.811650

∗ ( 1.5

8.66+ 0.084) ∗ (50− 30) ∗ (15 ∗ 1.852√

23)2 ∗ (23 ∗ 8.66

2

50) = 35.4 (m/s2)

And the transverse bending moment can be

MS =50 ∗ 11.05 ∗ 6.86

8= 1517.9 (kNm)

Just like the calculation of the longitudinal, now we need to estimate our transverse

section modulus. In our case, we have two blocks that are superstructure and bridge.

However as the bridge does not stay continuously in the transverse direction, we

therefore neglect it and assume the form of superstructure is rectangular to simplify to

calculation. And we make a rough estimation on the length of hull considering the

shape of hulls as triangle so that we find the length of 1.92 meters in the configuration

figure below. We have such a layout on transverse cross-section on the center line:

Figure 28: front view of the configuration

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Table 9: areas and heights for moment of inertiaCabin

walls(cm2)

H1 (cm) Lower deck

layer(cm2)

H2(cm) Upper deck

layer(cm2)

H3(cm)

600 170 1250 0 1875 20

Inner

roof(cm2)

H4(cm) Exterior

roof(cm2)

H5(cm) Hull

area(cm2)

H6(cm)

2300 240 2300 320 3840 -90

Neutral

axis height

(cm)

Moment

of inertia

(m4)

89 3.21

By applying the formula,

M

Wmin= p < σ, Wmin =

I

ymax= 1.28

we find the pressure is 1.28 Mpa << 48 Mpa which is yield strength in our case.

Restriction on longitudinal spacing &plate thickness

Figure 29: configuration of U beams

Accoding to previous design, the longitudinal spacing is 500 mm, meaning every 500

mm thereis a U beam in the hull. In ’DNV’s Rules for Wooden ships’[9], there is a

limitation for the spacing defined as

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s =L

100+ 0.3 = 0.25 + 0.3 = 0.55 meter

Therefore our design fits the regulation quite well since it just within the range.

Figure 30: definition of spacing

Besides utilizing the bending moments to check strength, there are also some

requirement on thickness of bottom floor in this wooden ship regulation. The section

modulus contributed by the floor must be larger than 2.25 times of the value below.

Figure 31: definition of section modulus

Here we make some approximating estimation of the factors in the formula and have the

result as 179 cm3, meanwhile the real section value of the floor is more than 10000 cm3

proving the strength is good again.

Table 10: factors for section modulush (m) s (m) l (m) W (cm3)

4.725 0.5 0.76 79.55

Moreover, from the rules <Rules for Classification of Ships> of DNV published in 2013

Pt.3, Ch. 2, Sec. 5[8], even though the rules is aiming at steel ships, by some kind of

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truncation in the formula, we can find our required thickness for our plates.

t =15.8Kas 2

√p

2√σ

+ tk

Here for calculating the value of p, we need to specify our scenario. We are calculating

the middle point of bottom of the hull and as our stiffeners don’t have flange, s = l.

Meanwhile σ is referred to the yield strength divided by a safe factor, in this case it

should be 160. Considering that steel has the strength of 235 Mpa, we assume σ here is

divided by a factor of 1.5, thus in our case σ used in the formula should be 36 Mpa.

Apart from the value of tK , thickness should be larger than 7mm. tK is the corrosion

addition for steel ships and it is hard to define in terms of wooden ship, however, as our

design thickness is 23 mm that is way thicker than the required value, and usually tKvaries from 0 to 2 mm so that it does not affect the safety of our design which is good

and has very good redundancy.

Conclusion

Given that our design is kind of complicated and special in terms of the form and the

material, it makes strength calculation more difficult. Even though we try to exam it

according to DNV’s rules, there should still be some inaccuracy within our calculation.

But, all in all, from both the conceptual design calculation and the calculation of this

time, it shows our design has abundant redundancy on structural strength, and it proves

our design guarantees the solid strength despite of some calculative inaccuracy.

3.3 Compatibility of the structure with general arrangement

Since our ship has a relatively simple hull structure we only have a few issues that have

to be taken into consideration. The first one is to make sure that all the machinery fits

into the hull, and the other one that the HVAC system and the door engines fits into

the roof structure. Apart from these two areas there should not be any parts where

space is an issue.

Inside the hulls we need space for the engine, fuel cells, fuel tanks, and batteries. The

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hull shape and size is shown in figure 32, and each separate hull has a width of 2 m,

inside which the machinery will hopefully fit.

Figure 32: lines drawing of the hull giving the size we have to work with

Inside the hull the internal structure will be built from pieces with a width of 5 cm, so

we will lose this much around the edges

The best solution would be to fit separate parts of the machinery between bulkheads, so

the structure from the rear is e.g. engine and fuel cells – bulkhead – fuel tanks –

bulkhead – batteries with bulkhead in the middle. With this assumption we have 6 m of

the hull length available for each compartment (the height is roughly 1,7 m, although

there is not much space towards the bottom of the hull).

Figure 33: Cross section view at the location of hygrogen tanks

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The engine size is at least not a problem, although the actual size of the whole system

when connected to an azimuth thruster can be hard to estimate. A Siemens 320kW

engine (PEM-Motor 1DB2024 – WS36) has a size of 660 x 510 x 500 mm [4], which still

leaves plenty of space for the fuel cells in the same compartment. The fuel cell size will

depend greatly on the producer (the technology advances constantly, and our final

solution may already be smaller), but as an example Ballard produces a 150 kW fuel cell

module with a size of 1530 x 871 x 495 mm [10], which should easily fit in with the

engine.

Figure 34: Cross section view at the location of motors

In our conceptual design we calculated that the fuel tanks need a total capacity of 1000

liters, which gives a volume of 1 m3. Even if the volume of the entire system is twice as

much (a rack built out of several smaller tanks, which will fit the hull better) it will

have more than sufficient space.

This means that the rest of the hull can be used for the batteries. We have 12 m of hull

space available in the front, possibly room in the fuel tank compartment (because of

wiring complicity we should at least try to keep the batteries bunched together), and if

we want to increase battery capacity we can put batteries into the compartment

between the two hulls. With all this taken into consideration the total space should not

be a problem.

The other spatial problem we need to think of is the HVAC system, which will be

placed under the roof structure. The main concern is making sure that there will still be

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enough headroom in the passenger area after installing the HVAC and the inner roof.

Since the outer roof has a planned height of 3 m, the area between the roof can have a

height of up to 0.5 m, while still leaving headroom for (basically) all passengers. This

means that piping will not be a problem. The actual system (fans etc.) can probably be

placed on the outside of the ship (the rear wall is a possible solution), but after getting

an estimation of the size from a producer it might even be possible to fit this system

under the roof.

The engines that open and close the doors will also be placed inside the roof structure.

However, with the large space we currently have and the small size of the engines space

should not be a problem. The same applies for the heating system under the floor. The

heating system is basically pads with electrical wiring placed under the floor, and they

will not take up much space.

3.4 Demands on production

Since our ship is built out of wood the main demands on the production will be here.

The wooden hull will be built at the shipyard, while all other system will be ordered

from subcontractors in some form. Installing all the equipment will naturally also need

some experts.

The wooden structure will place the biggest demands on the shipyard. We need workers

who know how to build a wooden ship, which is not a big industry these days. The

working conditions may also need to be checked out, because the wood can react to

things like heat and humidity. Another problem is checking the joints and gluing in the

structure. Instead of welding seams, we need to make sure that things like longer glued

areas (e.g. with the hull sheets) and screw joints are up to standard (if it is possible for

them to be subpar).

The installation process includes a lot of equipment that is not used in many shipyards.

Therefore it is necessary to bring in experts who know how to work with e.g. fuel cells

and solar panels. These people all need place to work on their own job, and if e.g.

delays means that the shipyard runs out of space, and one person has to reschedule all

his work because he cannot work at the planned time, the entire project will be delayed

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even more. Therefore all there things must be taken into careful consideration.

3.5 Openings

Because we are only building a ferry that will operate in a small area we do not have to

worry about things like water and sewage piping. However, we have some areas in which

openings are needed.

Firstly, we need some openings in the hull structure for the hydrogen pipes, and all the

wiring from the batteries. To avoid losing strength in the structure these cannot be

pulled through openings drilled in the structural frame, but instead the openings need

to be made in the bulkheads. Since we do not have a lot of bulkheads the amount of

openings will not be high (a couple of openings for hydrogen pipes, and the same for

cable bundles at each bulkhead at most), but instead some work needs to be done to

make sure that the bulkheads stay as watertight as possible. This means that each

opening will need e.g. a plastic ring and some silicon filling to ensure a tight fit. The

placement of the openings in the bulkheads will be along the outer edge, so the pipes

and cables can be pulled along the wall of the hull between the bulkheads.

Another area that might need openings is the roof area, where the pipes of the HVAC

will run. The area between the outer and inner roof will most likely have some sort of

framework in between to ensure a strong structure, and the piping needs to be pulled

through this. However, the framework can be built out of pieces with drilled out holes

(to minimize the weight), and it should not be built out of sheets that fill the entire up

to 0,5 m high area, so separate holes for the HVAC may not be necessary.

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4. LIGHT WEIGHT & STABILITY OF UNDAMAGED SHIP Zero emission ferry

4 Light Weight & Stability of Undamaged Ship

4.1 Wooden weight

The weight of the entire wooden structure can easily be calculated from out initial plan.

The entire structure for the hull can be seen in figure 35, and when adding the weights

of the super structure, rood structure, and the entire outer “shell”of the ship we will

get the total wood weight.

Figure 35: the wooden structure of the hull

Structural parts of the hull

The wooden structure will be built from wood with a density of 450 kg/m3 (550 kg/m3

for the bulkheads). By using the amounts and sizes of all parts we can calculate the

approximate weight for the hull structure found below.

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Table 11: weight approximation for the wooden structure

Part Dimensions(l*h*w),[mm] Density[kg/m3] Amount Mass[kg]

Longitudinal beams 25000 x 45 x 45 450 6 x 2 275

U-shaped frames 9000 x 85 x 85 450 50 x 2 2925

Bulkhead 7 m2 x 5 550 3 x 2 115

Platform9000 x 165 x 85 450 42 2385

　　　　　 22000 x 45 x 45 450 8 320

Total - - - 6020

Some errors are possible in this calculation, mainly the length of the U-shaped frames,

since they are not of a completely equal size through the entire ship. Another problem

could come from the bulkheads, since the final value could change with some regulations

we are not aware of at the moment

Hull shell mass estimation

By numerical modeling of the hull we have gotten an approximate surface area of 445

m2. The shell itself will consist of a three-layered structure; an 18 mm pine plywood, a

linen/epoxy composite, and a final gel coat and paint. The final properties, as well as

the weight estimation can be found in table below. In the table we can also find the

thicknesses of the separate layers, which add up to a total hull thickness of 25 mm.

Table 12: properties and weight estimation of the hull shell

Material Density[kg/m3] Thickness[mm] Mass[kg]

Pine plywood 500 18 3785

Linen/epoxy composite 1600 5 3560

Coating(gel+paint) 1400 2 1245

Total - - 8590

In this case the largest possibility for error would come from the area estimation. If this

value is wrong all the calculations will be off. However, correcting the values would be

very easy if a new value came up.

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Roof structure

The roof structure, which is defined as the superstructure apart from the bridge block,

will be a sandwich structure, consisting of two layers made from natural fibre

composites (7,5 and 5 mm thick), separated by a 190 mm thick polyurethane insulation.

The area of the roof structure can be approximated as

Aroof structure = 2Awall + 2Aback/front wall +Aroof = 2 ∗ 21 ∗ 2.5 + 2 ∗ 9 ∗ 21 = 329 m2

To make the calculation of the center of gravity easier we will calculate the masses of

the walls and the roof separately. This will be done using Awalls = 150 m2, and

Aroof = 189 m2. The final masses can be found in the following two tables.

This is a very rough estimation, the actual value would probably be smaller because of

e.g. rounded corners, but this will still give an idea of the total weight.

Table 13: weight estimation of the walls of the roof structure

Part Density[kg/m3] Thickness[mm] Mass[kg]

Outer composite layer 1600 7.5 1800

Insulation 30 190 850

Inner composite layer 1600 5 1200

Total - 202.5 3850

Table 14: weight estimation of the roof of the roof structure

Part Density[kg/m3] Thickness[mm] Mass[kg]

Outer composite layer 1600 7.5 2268

Insulation 30 190 1077

Inner composite layer 1600 5 1512

Total - 202.5 4857

This estimation is most likely a bit higher than the final mass, but the estimation does

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not take any possible strengthening structures into consideration, so this value should

do for now.

Superstructure

The superstructure, which in our case is defined as the bridge block, will be built in a

similar way as the hull, but with an outer shell more like the roof structure. The inner

structure will have vertical and horizontal beams, and the outer shell can be like a

lightweight version of the roof structure (it does not actually support itself this time).

The roof structure weighs a little less than 26,5 kg/m2, so here we will assume 20 kg/m2.

The inner structure will have a height of 3 m, with 20 vertical beams, and 7 horizontal

ones. The horizontal beams will have an approximate length of 10.3 m, while the area of

the outer shell will be approximately 37,1 m2 (Once again, to simplify further

calculation we use Awalls = 30.8 m2 and Aroof = 6.3 m2). The estimations of the

masses can be found in the table below.

Table 15: weight estimation of the superstructure

Part Dimensions(l*h*w),[mm] Density[kg/m3] Amount Mass[kg]

Structure3000 x 85 x 85

4507 68

　　　　　 10300 x 45 x 45 20 188

Shell,walls/roof 30.8/6.3 20 1 616/126

Total - - - 998

The largest error in this case comes from the outer shell. The final weight depends on

e.g. the total amount of isolation in the walls, and the need of the walls to actually give

the entire structure some strength.

Deck weight

The final elements to be included in the wood weights are the main deck (i.e. the entire

deck on platform level + the raised deck for the bridge). The density for these will not

need to be high, as the actual strength comes mainly from the frame structure. The

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floors only provide a smooth walking surface.

The area for the deck would be

Adeck = Aplatform level +Abridge = 9 ∗ 23 + 1

2π22 = 207 m2 + 6.3 m2 = 213.3 m2

If the deck are considered to be built out of a plywood layer similar to that in the hull

shell, and a layer of material to protect the surface (e.g. PVC, for which the mass is 3,2

kg/m2 for a 2 mm thick material) we get the mass in the table.

Table 16: weight estimation of the roof of the roof structure

Element Density[kg/m3] Thickness[mm] Mass[kg]

Plywood 500 10 1067

PVC 1600 2 683

Total - 12 1750

Final wood weight

In the previous report[6] and reports of other courses, we have discussed the most of the

equipment of our design. Here we just list them along with their corresponding gravity

center. In previous chapter <wood weight> we have discussed the weight of hulls,

platform, etc. Now the gravity center calculation is applicable. In the table below, the

figures of gravity center is the vertical distance from the hull bottom to the center. Roof

block corresponds to roof structure in last chapter. And attention should be paid that

the sum of weight of structural mesh and platform structure is equals to the weight of

wooden structure in last chapter, since the two parts they have different gravity center,

calculating them separately could make the estimation more accurate.

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Table 17: total weight of all the wooden parts

Element Mass[kg]

Hull structure 6020

Hull shell 8590

Roof structure 8705

Superstructure 998

Deck 1750

Total 26063

4.2 Connecting elements

In the Shipyard Engineering course we defined the amount of connecting elements

needed for the basic structure of the ship (i.e. not including connecting elements used for

installing various outfitting components). These amounts can be found in table below.

Table 18: amounts of connecting elements

Screws Glue meters

Hull 845 500

Deck 123 700

Superstructure 140 132

Total 1113 1332

An exact weight of screws is difficult to find anyway, but we can try finding the weight

of a pack containing several screws, and estimate the weight through this. One example

of large structural screws is Simpsons’structural screws. The weight of 1000 of these

would be roughly 322 kg (although the weight is estimated from a pack of 10, so the

weight without the package can be different) [21]. This weight will, however, depend

greatly on the actual screws chosen, so the final weight can probably be anywhere

between 200-500 kg.

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The glue weight depends greatly on the glue, how it reacts when drying, the application

process, etc. A manufacturer with plenty of specifications for their glue is Titebond, and

using the information provided on their site we can estimate the glue weight. The glue

area will be approximated as 5 cm x 1332 m (5 cm to accommodate for not completely

straight glue lines) giving an area of 66.6 m2 = 716.9 ft2. This would require 3 gallons

of glue, with a total weight of 27.6 lbs = 12.5 kg. This weight is so small that some

errors in the approximation still will not affect the total weight of the ship notably.

4.3 Equipment weight & Gravity center calculation

Vertical location of Gravity center

As we the weight of screws is distributed all over the ferry, and the weight is quite

limited compared to other equipment or structure, we think it is not necessary to apply

this weight into the gravity center calculation. Of course, the weight of glue is also

neglected as well.

In the previous report and reports of other courses, we have discussed the most of the

equipment of our design. Here we just list them out with their vertical height attached.

The weight estimation of equipment and passengers is based on data given by

conceptual design, which we believe is reliable.

Here is something needs to be specified in this table. In our case, the shape of hull shell

is regarded as straight plate for simplification so that the gravity center can be located

at the middle of hull. Actually the real gravity center should be a little lower since the

plate has curve meaning more weight is concentrated around the lower area, but for

safety reason, it is reasonable to assume the point locates at a relatively higher location.

The same works on the structure mesh center. For the superstructure term, we also

consider in this way to put it in a higher position. In fact as most of the supports may

be installed around the roof area, it is also reasonable to assume its gravity center is at

two thirds of the cabin height. And for the location of HVAC system, Air conditioning

system is set between the roofs of the roof structure while the heating system is set

between the decks of the roof structure.

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Figure 36: general arrangement

Table 19: All the equipment & structure of the ferry

Equipment & structure Weight(ton) Gravity center(meter)

Azimuth thrusters 3.8 -0.75

Motors 1 0

Batteries 1.47 0

AFC 1 0

Hydrogen tanks 1.08 0

Other machinery 1.7 0

Hull shell 8.59 0.9

Structural mesh 3.3 0.9

Deck structure 2.7 1.7

Decks 1.75 1.9

Cargo and passengers 12 2

Equipment on deck 2.24 2

Walls of the roof block 3.85 3.4

Walls of superstructure 0.87 3.4

HVAC 2 3.4

Lower roof of roof block 4.86 4.1

Upper roof of roof block 4.86 4.9

Roof of superstructure 0.13 4.9

Total 57.2 1.934

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The total weight is 57.2t which is a bit larger than our previous prediction of 50t, but

not that much larger. We can slightly revise our design hull shape to increase the

buoyancy. And for the gravity center, due to safety consideration, this location is just a

rough estimation and cannot be very precise, therefore we keep some redundancy in the

height of gravity center and set it as 2 meters not 1.972 meters. The calculation

afterwards all based on the assumption that vertical location of gravity center is 2

meters.

Horizontal location of Gravity center

Here we are discussing the horizontal location. Similar to the vertical location

calculation, we list out the weight and horizontal location of equipment and structure

parts of the ferry. The horizontal location is the distance from the stern of the ferry to

the location, and as the length at waterline is 23 meters, so we presume that the

location of buoyancy center is somewhere in the middle around 11.5 meters, which is the

gravity center should be close to.

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Table 20: All the equipment & structure of the ferry

Equipment & structure Weight(ton) Gravity center(meter)

Azimuth thrusters 3.8 1.5

Motors 1 3

Batteries 1.47 6

AFC 1 15

Hydrogen tanks 1.08 18

Other machinery 1.7 21

Hull shell 8.59 12

Structural mesh 3.3 12

Platform structure 2.7 12

Decks 1.75 12

Cargo and passengers 12 10

Equipment on deck 2.24 22

Walls of the roof block 3.85 10

Walls of superstructure 0.87 12

HVAC 2 12

Lower roof of roof block 4.86 11

Upper roof of roof block 4.86 11

Roof of superstructure 0.13 20

Total 57.2 11.11

In this table, we place our heating system pretty closed to the fore part, and we think

the anchoring system is located in the very front of the fore part, which is counted

within the equipment on deck. We see that the location of gravity center is 11.11 meters

which is acceptable in term of longitudinal floating position.

Division of weight components

According to SFI system[26], classification of the equipment and structure zones is made

accordingly. we define 611 represents the machinery main components-propulsion

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system-thruster component, 612 represents the machinery main components-propulsion

system-engine component, 613 stands for the machinery main components-propulsion

system-electricity generation system and 621 stands for machinery main

components-other machinery system-other machinery; 511 means equipment for crew

and passengers-HVAC-A/C system; 411 stands for ship equipment-ship equipment; 211

means hull-structure-supporting structure, 212 stands for hull-structure-shell, 213

represents hull-structure-superstructure and 214 is hull-structure-deck. Therefore we

have folloing table.

Table 21: classification for equipment &structure

Equipment & structure SFI number

Azimuth thrusters 611.001

Motors 612.001

Batteries 613.001

AFC 613.002

Hydrogen tanks 613.003

Other machinery 621.001

A/C system 511.001

Equipment on deck 411.001

Hull structure 211.100

Hull shell 212.100

Roof structure 213.100

Superstructure 213.101

Decks 214.100

For those huge vessels like tankers or cruises, there might be thousands of equipment

and components to manage, and the SFI system can help classify them with quite sound

order. However, as our ferry is kind of small and simple, using SFI system here may be a

bit unsuitable and awkward since the system and components onboard are very limited.

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Comparison with other ships

Since our ship has a very unconventional design it is very difficult to get any useful

information from comparisons with other ships. We have not been able to find a ship

with both a similar size and construction method. Wooden catamarans are available on

the market, but these are mostly smaller ships or sailing boats, which means that a

comparison would not give us much interesting. Steel ships, on the other hand, are

available with both the right size and weight, but unfortunately not both at once. A

steel ship of a similar size as ours is heavier, while one with a similar weight is clearly

smaller.

One comparison we can make, though, is with the Ar Vag Tredan passenger ferry in

Lorient. The ship is a 22 m long catamaran ferry, with a draught of 1.5 m. These values

are very close to ours (as are many other specifications), so we can at least assume that

our initial specifications are not completely wrong. It is important to remember that

there still are many differences between the ships when it comes to e.g. hull design (and

the weight seems to be unavailable), but the similarities are encouraging nevertheless.

[11]

Displacement and draught recheck

As we calculate the weight of the ferry as 49 tons in conceptual design report, we find

out the corresponding draught is 1.15 metets in the case. But now since the result has

been changed according to the recalculation we have done in this chapter, we need to

see how much the draught also changed accordingly.

We still apply the same method we used in conceptual design to estimate the draught:

T =W

2×B × L× Cb × ρ=

57200kg

2× 1.8× 23m× 0.495× 1025kg/m3= 1.35m

This means that draught increased 20 centimeters and we still have a freeboard as 0.54

meters.

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4.4 Stability calculation

First of all, our design is a catamaran ferry with a very limited freeboard, which means

that the allowed angle for the roll movement is very small because the situation of water

on deck should be always avoided. Consequently, we assume that the extreme situation

is there is only 0.1 meter freeboard left where the roll angle is closed to 9 degree.

Typically if the roll movement is confined within 9 degree, we can consider that the

intersection point of water plane and the central line of ship stays at the same location

as showing in the figure.

Figure 37: configuration assumed at small angle[3]

However, in our case, it is not the same thing. Given that our twin hulls locate at both

of sides of the ship which are distant to the gravity center, any small roll movement can

lead to a horizontal displacement of buoyancy center which cannot be ignored, which is

illustrated as figure below.

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Figure 38: configuration assumed at large angle[3]

Please note that this is a very essential figure. All the parameters in equations[3] that

will be mentioned later are based on the configuration.

This kind of scenario usually happens when the roll angle is pretty large like 20 or 30

degree. But as our design is not the traditional hull shape, we have to consider this

situation in this report. Assuming the increased and decreased volumes that provide

buoyance in the figure are defined as V1 and V2, it is easy to see they are not the same

in the above figure.

According to some rough estimation, which is actually manually to find out the

intersection of water planes where V1 and V2 are equal, we find that displacement

(which is c in the last figure) is at around 0.44 meters when the angle is 9 degree. We

assume that the displacement varies linearly with the change of degree from 0 to 9

degree. Therefore we can know how the OO’ changes in the figure above.

Then, to calculate the stability, we applied the method used for stability at large

inclination angle. Basically the used formula are written below.

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lϕ = OE =Mϕ

∇ϕ=V1OA+ V2OB −∇0OF

∇0 + V1 − V2[3]

δ∇ϕ = V1 − V2 [3]

M ′′ϕ = V1OA+ V2OB [3]

M ′ϕ = −∇0OF [3]

lϕ =M ′′

ϕ +M ′ϕ

∇0 + δ∇ϕ[3]

M ′ϕ = −∇0OF = −∇0[(d0 −KB)sinϕ+ c · cosϕ] [3]

lS = lϕ + c · cosϕ+ (d0 −KS)sinϕ[3]

Equations above are for monohull stability.

Where the lS is the restoring arm at inclination angle of ϕ, and lϕ is a part of the

former restoring arm and is caused by the change of displacement. M ′ϕ and M ′′

ϕ are

restoring moment by changed displacement. δV is the displacement difference after

inclination. V0 is the original displacement. L is the length of the vessel.

If our ship is monohull vessel, then we can find out the distance from O to both edges of

the hull, however we cannot in this case. For catamaran, a lot volume within V1 and V2is empty (obvious in the figure below), which is not part of hull and do not provide

buoyancy ever, we have to modify the formula to let them make sense in our case. We

introduce two more distance parameters defined in the figure below so that we can

calculate how much volume we need to exclude in order to match the reality by

applying c and d into the formula.

Figure 39: definition of a,b,c and d

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Here a and b are defined the same as in previous equations and figure. As we need to

exclude the empty volume, formula for changed submerged volume should be modified.

Figure 40: original equation for calculating changed displacement

It will be transformed into

δVϕ =1

2L

∫ ϕ

0

(a2 − c2)− (b2 − d2) dψ.

And for formula to calculate the moment by changed displacement

Figure 41: original equation for calculating moment by changed displacement

It shoulb be

M ′′ϕ =

1

3L

∫ ϕ

0

(a3 + b3)− (c3 + d3) cos(ϕ− ψ) dψ.

By applying lS = lϕ + c cos(phi) + (T − ygravity) sin(ϕ), where T stands for the draught

and yGravity stands for gravity center of the ferry, and picking the angles of 3, 6 and 9

degree, we can calculate and plot the restoring moment arm under the angles.

Table 22: Calculation parameters

ϕ in degree a b c d

0 0 0 0 0

3 4.15 4.33 1.87 2.34

6 4 4.4 1.58 2.52

9 3.8 4.4 1.58 2.81

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Table 23: Calculation results

ϕ in degree M ′ϕ M ′′

ϕ δV lϕ lϕ

0 0 0 0 0

3 8.640503 53.48721 0.272347 1.186269 1.287584

6 17.24156 103.5683 0.5949129 2.292629 2.494677

9 25.76331 136.6321 0.866538 3.066001 3.367615

Figure 42: Curve of restoring moment arm of rolling movement

According to the regulation of DNV[27] on stability for the ferry, it gives the equation

for calculating the heeling moment with a roll angle smaller than 10 degrees:

MR = 0.02V 2OD(KG− d/2)/L

where the V 2O stands for the service speed, L is length at waterline, D and d represent

for displacement and draught respectively and KG is the height of COG above keel.

The heeling moment is 2.89 ton*meter which is far smaller than our stability

performance. But we are not sure if this equation is also suitable for catamaran.

Therefore this question needs to be further studied.

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5. COST ESTIMATION Zero emission ferry

5 Cost estimation

5.1 Construction material

To estimate the total cost for our designed ferry, firstly we need to know how much

material we will need to construct the hull.

According to last assignment, for the wood beam, we have a weight of 6020 kg from

structural parts of hulls. And there is another 256 kg from the superstructure. So we

have 6276 kg of wood beams

For the plywood, we have 3785 kg from the hull shell and 1067 kg from the floor weight.

The gross weight is 4852 kg.

In our case, the outer and inner layers of walls and ceilings are made of fiber, also, the

coating of the hull shell is composed by fiber. So we have the weight of fiber where 1245

kg from hull shell, 10560 kg from roof structure (two ceilings are counted) and 578 kg

from the superstructure. Attention should be paid that for the walls and ceilings, there

is always 12.5 mm thickness of fiber and 190 mm of insulation so that the weight

between them is fixed and we apply this ratio finding the fiber weight contributed by

superstructure. In all the weight is 12383 kg.

As for epoxy resin, it mainly composes the hull shell with the weight of 3560 kg.

Then it comes to the Fastenings, which does not change throughout our design, so we

pick the value give in the conceptual design [6] which is 500 kg.

And the cost on insulation, which is not considered in conceptual design, can be

estimated by the information of ‘acoustic & thermal Insulation mineral fiber best

thermal insulation material’[17]. The weight is the sum of 3004 kg from roof structure

and 164 kg from superstructure, which is 3168 kg. The price for insulation material is

around 0.4 Euro/kg.

Meanwhile the price of PVC is around 0.7 Euro/kg in American market [12]. Finally we

can estimate the cost for the raw material. The rest of the prices for materials are in

accordance with the conceptual design.

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Table 24: Evaluation of the raw material costMaterial Quantity(kg) Unit price(Euro/kg) Loss Price(Euro)

Wood beam 6276 1.5 15% 10826

Marine plywood 4852 1.05 10% 5604

Linen fibre 12353 2.5 5% 32505

Epaxy resin 3500 1.65 2% 5991

Fastening 500 6.35 2% 3240

PVC 683 0.7 5% 502

Insulation 3168 0.4 10% 1394

Total - - - 60062

After all these above, we also need to count the electronics like wires and insulation

measurement which we believe can be 20% of the cost calculated above. Therefore the

total cost should be 60062 x 120%=72074 Euros.

5.2 Key components

Here we have some big items and key equipment onboard and they take a lion’s share

of the total cost. Specifically they are: thrusters, motors, AFC, batteries, anchoring

equipment, solar panels, passenger seats, docking system, HVAC, fuel tanks,

navigation/radar/AIS equipment, power management system, hydraulic system, access

doors and bilge pump.

Thrusters

For an azimuth thruster with a power of approximately 100KW[6], it costs between

12000 Euros to 25000 Euros. And here we just take the middle value of 17 000 Euros,

and in our case the power is tripled for each[13], therefore we assume it takes 50000

Euros for each thrust and in total the cost could be 100000 Euros. This is just a rough

estimation, however, as it is difficult to find the price from the suppliers. So even we

have known what the thruster is, we still cannot give a precise estimation.

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Motors & AFC

As we have calculated previously, we have two induction engines with around 300 kW

power from each. We are not able to find the exact price for our selected engines, but

we do find some motors with the similar power. We find the engine made by ABB with

300 kW power[23] has an original price as 70000 dollars. Considering the dollar has

depreciated to some extent and our exact power is 320 kW, so we think it is plausible to

assume the price for our motor is around 100000 dollars each, which transfers to Euros

is 80000 Euros and in total 160000 Euros.

And for the AFC, from ’The Fuel Cell Industry Review 2013’[24], we presume the ratio

is around 1.8 dollar/W. Therefore the cost in our case for AFC is 936335 Euros, along

with motors it is 1096335 Euros.

Batteries

Based on the power-to-cost ratio assumption, in the conceptual design [1] we found the

ratio is 2.13 Euro/watt for batteries, however, we now think this could too much. We

find some other materials[25] and find the practical price for a 12 V*600Ah battery is

600 pounds, which is 750 Euros. Therefore we find a new ratio as 0.1 Euro/W, which is

quite different with the ratio we get from conceptual design. We then check the battery

for electric cars, and the ratio is around 0.5 Euro/W. We consider that the bigger

capacity is, the cheaper the battery is. So we take the ratio as 0.3 Euro/W and the total

cost is 192000 Euros.

Hydrogen tanks, Seats, Hydraulic system & Navigation and Safety system

As solid information and estimation are provided in the conceptual design report, we

just list out the prices.

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Table 25: Cost for some key equipment

Equipment Price(Euro)

Hydrogen tanks 18000

Seats 3500

Anchoring system 1600

Gyrocompass 2000

EPIRB system 500

GPS 600

Radar equipment 6000

Total 32200

Solar panels

In our design, we assume that we have solar panels with an area of 90 m2. According to

solar panel market, we choose ‘Power Solar panel SCHUTTEN Poly 300Wp’[14].

Each pallet has an area of 2 m2, and in total there is 45 pallets where the price is 7650

Euros.

Figure 43: solar panels

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Bilge pump

As we didn’t specify how much the power the pump should have, according to the

information from the market, WEST MARINE 2000gph Bilge Pump should work well

in our case [15]. Considering it is related to the safety of the ferry, we place 4 pumps

onboard and each of them cost nearly 100 Euros, in all it is 400 Euros.

Figure 44: Bilge pump

Automatic sliding doors

As we don’t have the needed size of the automatic sliding doors, and some details still

need to be engineered, we can only give an estimation on the cost. Based on the sliding

doors applied on the hotels [16], we find the usual price for a set of the door is around

800 dollars which in Euro is 650 Euros.

Total cost of key equipment

As the economic information of power management system, docking system and HVAC

is hard to acquire, we just assume them account for 15% of the cost that we have

calculated. The sum of cost at this stage can be calculated as:

Cost = (72074+1096335+192000+32000+32200+7650+400+650)∗115% = 1801570 Euros

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5.3 Cost on construction workers

According to our report of shipyard engineering, it takes 9 workers working for 21 weeks

to complete a ferry of our design. Given that the workers in shipyard is paid by 12

Euros per hour, assuming every worker work 35 hours every week, then we can find the

expense of human resource to build the ferry is 79380 Euros. Therefore the building

expense including everything should be 1880951 Euros which is nearly 1.88 million

Euros.

5.4 Price comparison with other ships

Since our ship has a very unorthodox design we will not be able to find a completely

similar ship that we can compare our price to. Instead we will need to find different

ships in various key areas, and see how the price for each of these compares to ours.

Possible comparisons could be made e.g. with ships with a

- Similar size - Similar capacity - Similar wooden structure - Similar machinery

None of these will give an absolute comparison, but if our ship is roughly in the same

price range we can at least say that our ship would be able to compete in the market.

One problem we encounter here is that ship costs are very hard to find, especially for

not very conventional designs, or new ships. Any price we can find will help, though,

and already showing that we are in more or less the same price class will go a long way.

We can probably also allow a somewhat higher price for our ship because of the

expensive technology implemented in our design.

5.5 Similar capacity

This comparison is the most interesting one from a marketing standpoint. Ships with a

similar capacity are the ones that our ship would be competing with, so a reasonable

price in comparison to these is important.

One example that we have been able to find is from a purchasing plan in Connecticut in

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2001. The plan was to purchase ferries with a capacity for 150 passengers. Two possible

ships were presented in the report, and the prices of these, along with the conversion to

modern day prices, can be found in table 1. [18]

Table 26: ships and prices in the 2001 report [6]

Shipyard Model 2001

Price(dollar)

2014

Price(dollar)

2014

Price(Euro)

Gladding-

Hearn Ship-

building

InCat 22 me-

ters

1.3 - 1.6 M 1.75 - 2.15 M 1.4 -1.72 M

Westport

Shipyard

Super Express

95

1.8 M 2.42 M 1.94 M

Comparing these prices, our own estimation of 10.7 million Euros seems too much.

However, in our case, a large portion of the cost comes from the propulsive system,

which is composed of hydrogen tanks, AFC, batteries which are complex advanced and

expensive equipment. Therefor the estimation may be a bit too large but still makes

sense to some extent.

5.6 Similar technology

Finding similar ships in this category is difficult, but one example worth mentioning is

the STX-France built Ar Vag Tredan, seen in figure 45. The ferry has many

specifications similar to ours, and a very similar look. The difference is that the ferry

has electric engines driven by supercapacitors that are recharged at every stop. This

ship was built a couple of years ago at a price of 3.2 million Euros [19], which means

that our ship would be roughly 30% cheaper to build (or at least our final cost could be

higher, and the ship would still be able to compete within the same class). Another

interesting point is that this ship, apart from being of a similar size, also offers the same

zero-emission appeal as our ship.

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Figure 45: the supercapacitor driven Ar Vag Tredan [20]

5.7 Cost calculation methods

Finding a method for calculating the price in a similar way as with big ships is very

difficult. Most methods appear to be made for larger ships, and because of the small

lightweight of our ship these methods will not work. Add in the fact that our ship

includes things like fuel cells and solar panels, and there is really no applicable method.

However, the small size also works in our favor, because this allows for us to calculate

the price of all parts separately quite quickly. This is also why we think this estimation

is better than anything we can get from a cost estimation method. The price

comparisons also seem to indicate that our cost calculations are in the right area, so at

this point we can be quite happy with our approximation.

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6. SUMMARY Zero emission ferry

6 Summary

Throughout this project, we made quite a lot of improvement on our conceptual design

and worked out many new details for our design. Finally it is now a relatively completed

and plausible ferry design. As quite many unusual technology and design features are

applied, we encounter quite a lot of difficulty during this project. The best endeavor has

been done to ensure this ferry is designed according to the related regulations and code.

This ferry uses hydrogen-AFC as the source of its power, enabling the idea of green and

non-emission realized. The final standard service speed is 13 knots, which considers

both the energy efficiency and necessary time spent on trips. Wood, as a sustainable

material, is used for the hull material for this ferry to fulfill the green idea. Design of

catamaran is utilized to acquire the large cabin space and low resistance. We believe, at

last, we come up with a reliable and innovative design of wooden ferry with

non-emission. And people would benefit from it if it was realized.

We also have learned a lot while doing this project. Information and understanding of

the new energy and now propulsion system is needed and we now do have gained some

insight of it. Also, we try to go deeper about hydrodynamics and do learn knowledge of

it like resistance prediction for catamaran. The old knowledge is consolidated as well

like the propeller design and so on. Moreover, we learned more about the insight of ship

design as a whole, and we learned what we should consider and what should be given

priority due to the mistakes we made. This is a somewhat tough project and we are

pretty glad we made it.

This final report may still exist flaws here or there due to our immature knowledge or

lack of experience on ship design, and we are pleased to hear your comments to help the

report and us to be better.

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6. SUMMARY Zero emission ferry

Table 27: Main technical details

Details Value

Displacement 57.2 tons

Main engine power 640 kW

Service speed 13 knots

Propulsion system power 426 kW

Resistance 34992 N

RPM 300 r/min

Draught 1.35 m

Freeboard 0.55 m

Vertical COG 2 m above bottom

Horizontal COG 11.11 m from the stern

Waterline length 23 m

Building cost 1.88M Euros

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7. REFERENCE Zero emission ferry

7 Reference

[1]Molland, A.F., Wellicome, J.F. and Couser, P.R. (1994) Resistance experiments on a

systematic series of high speed displacement catamaran forms: variation of

length-displacement ratio and breadth-draught ratio. Southampton, UK, University of

Southampton, 84pp.

[2]Custom aluminum work boats, crew boats, rib boats, deck boats, response vessels

marine fabrication;

http://www.alumamarine.com/workboat_files/alumcatamaran/2.jpg;

[3]盛振邦, 刘应中, Shanghai Transportation University, <Ship Principal>, 2003.

[4]Induction motors; https://www.industry.usa.siemens.com/drives/us/en/electric-

drives/hybrid-drives/Documents/elfa-components-data-sheets.pdf;

[5]Proton Motor Fuel Cell GmbH;

http://www.eurosfaire.prd.fr/7pc/documents/1374147913_sebastian_dirk___proton_motor.pdf

[6]Their Tomas, Armando Junior and Guilhem Grimaud, ”2A Zero-Emission Ship final

report”, 2013

[7]DNV, ”Rules for Classification of HIGH SPEED, LIGHT CRAFT AND NAVAL

SURFACE CRAFT”, Pt.3, Ch.1, Jan of 2011

[8]DNV, ”Rules for Classificantion of Ships”, Pt. 1, Pt. 3, July of 2012

[9]DNV, ”RULES FOR THE CONSTRUCTION AND CLASSIFICATION OF

WOODEN SHIPS”, 1970

[10]Fuel Cell Products | FC Velocity Motive Power | FC Velocity HD 6 | Ballard Power

Systems; http://www.ballard.com/fuel-cell-products/fc-velocity-hd6.aspx;

[11]Commuter craft prototype creates no emissions; Passenger Ship Technology; 2012;

http://www.stirlingdesign.fr/presses/articles/stirling_design_lorient_passenger-ship-

technology_10_2012.pdf;

[12]Polymerscan;

http://www.platts.com/IM.Platts.Content/ProductsServices/Products/polymerscan.pdf;

[13]Azimuth thruster; http://www.rolls-

royce.com/marine/products/propulsors/azimuth_thrusters/standard_type_us.jsp;

[14]Solar panel; http://www.ev-power.eu/Solar-Panels/Solar-panel-EUFREE-Poly-

300Wp-72-cells-Schutten-MPPT-35V.html?cur=1;

[15]Bilge pump;

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7. REFERENCE Zero emission ferry

http://www.westmarine.com/buy/west-marine–2000gph-bilge-pump–15003833;

[16]Automatic sliding door; http://www.alibaba.com/product-detail/ES200G-

Automatic-door_299737360.html?s=p;

[17]Insulation material; http://www.alibaba.com/product-detail/Acoustc-thermal-

Insulation-mineral-fiber-best_1881467903.html?s=p;

[18]Intrastate passenger sommuter ferry study;

http://ntl.bts.gov/lib/24000/24300/24368/FerryReport.pdf;

[19]New Eco-friendly Ferry Uses Supercapacitor Technology;

http://www.marineinsight.com/sports-luxury/cruise-industry/new-eco-friendly-ferry-

uses-supercapacitor-technology/;

[20]Zero emission ferry;

http://www.motorship.com/news101/industry-news/zero-emission-ferry;

[21]Home Depot - 6 in. Strong-Drive SDS Structural Wood Screws (10-Pack);

http://www.homedepot.com/p/Simpson-Strong-Tie-6-in-Strong-Drive-SDS-Structural-

Wood-Screws-10-Pack-SDS25600-R10/203302238#specifications;

30.11.2014

[22]Titebond Original Wood Glue;

http://www.titebond.com/product.aspx?id=d4d28015-603f-4dfc-a7d9-f684acc71207;

30.11.2014

[23]http://www.salvex.com/listings/listing_detail.cfm?aucID=182944666; 03.12.2014

[24]The Fuel Cell Industry Review 2013, p.27;

http://www.fuelcelltoday.com/media/1889744/fct_review_2013.pdf

[25]Hybrid Marine; http://www.hybrid-marine.co.uk/14.htm; 03.12.2014

[26]XANTIC, ”SFI GROUP SYSTEM”, 05-2001 Version

[27]DNV, ”Rules for Classification of Ships”, Pt.5, Ch.2, July of 2012

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