megayacht design 2006 vassilios zagkas

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Megayacht Design & The Modular Concept Chapter1

4.The Modular Concept and its Application.Modular Design is a design methodology that aims at developing a product architecture

consisting of distinct sub-systems in order to achieve pre-defined benefits.

In order to achieve modularity and design integrated products, the designer needs to depart

from the current design procedure. A modular product has its components clustered into well

defined modules, so that everything can be designed, manufactured and assembled

separately. Modules should be able to be physically detached from the overall product to be

repaired, recycled or upgraded. Another characteristic of modules is that they may be used in

other similar products, or can be arranged in different configurations to obtain several

functions and solve different problems.Classifying product as modular or not can be very tricky, because modularity can exist in

various levels in the construction of the product. According to [Ulrich 1991] good modular

designs usually exhibit some common characteristics.

1. A modular product is constructed by a set of compatible basic modules which can beused to construct a variety of other products.

2. The interface among units must allow for simple assembly and disassembly.3. It is a two phase product. First phase the design and production of basic modules.

Second phase is the design of complete modular products using the basic modules.

It is therefore revealed from the above that the development of modules the interfaces amongst

them and their hierarchical structure are fundamental issues of modular design.

4.1Platform DesignConsumer needs and expectations have been rising rapidly the last decade. The industry in

order to respond to that has developed a production paradigm called mass customization. This

is very different from the conventional way of mass production, which basically is the

manufacture of many identical products by the use of large production lines.

Platform Design is used in this project as a specific objective with the modular design.

Nevertheless platform design is a specific type of modular design in which the objectives of

modularization relate to multiple products that are considered members of the same family.

According to Simpson the key to a successful product family is the product platform from

which it is derived, either by adding, removing, or substituting modules to the platform or by

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scaling the platform in one or more dimensions to target specific market niches [Simpson

2003]

The concept of modular design and more specifically Platform design is used in this project

in order to create an increased product variety at less cost for the manufacturer in a highly

competitive marketplace. Furthermore the main expectation in this project and generally by

designers/engineers is to design and develop a family of products with as much commonality

between products as possible with minimal compromise in quality and performance.

Platform design and product families are widely used in several industries with success. The

difficult task and main goal is to introduce that in the mega-yacht industry. In order to that

several constraints have to be taken into account. Before defining the introduction of the

common platform in the mega-yacht design it would be useful to explore and investigate the

already tested case of automobiles. Here the underbody structure is the product platform. One

of the main purposes of the underbody is to provide support to the rest of the automobile. It

compromises of metal components either bolted or welded together in order to support the

structure. The variety in the underbody comes from the need of manufacturers to

accommodate different car models. The underbody needs to accommodate different engine,

transmission, suspension, and varying body lengths to name a few.

Fig.8: Typical car underbody platform.

Typical platforms are composed of three main sections:

1. Front Structure (Engine Compartment)2. Front Underbody (Floor of passenger compartment)3. Rear Structure (Trunk area)

The joints between these three sections above are called the weld lines. Ideally a common

platform would be one that can accommodate different variations required for different car

models without requiring changes in weld-lines and assembly process.

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Fig.9: VW cars sharing the Golf IV platform.

In the picture above we can se a range of well established cars in the market that share the

same platform. An example that can be widely understood is that the VW Golf IV shares the

same platform with the Audi TT. However those cars are intended for completely different

customer profiles.

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Chapter2:Design MethodsIn this Chapter, Section 1 reviews some of the theoretical research in engineering design and

Section 2 identifies the most appropriate methods for our case and how these can be used in

Mega-yacht design. Finally by adapting these methods to our needs we can obtain a sequence

which identifies the preliminary particulars for our parent hullforms.

1. Defining DesignIn contradiction with natural sciences that study the existing laws and phenomena of nature,

the design sciences are related to human intent and the attainment of goals. Herbert Simon

has called that the sciences of the artificial [Simon 1969]. Simon states that the term

artificial refers to man-made artefacts, and that the distinguishing feature of man-made

artefacts is that they are created to serve human purpose.

Nowadays there is still a lack of understanding design. It is a highly manipulative activity in

which the designer has to simultaneously balance several factors that influence the design

outcome. Design is very closely related to inventing and making tough decisions. Most

designers and engineers/researchers would agree that design is an iterative process. The

incompleteness of knowledge at each stage where decision have to be taken, forces the

designer to assume and then re-examine when additional knowledge is developed.

Now the process of designing is the methodology of putting together a series of actions or

operations in order to complete an activity. Procedures are structured usually by a step by

step template in order to help in decision making. Structuring the design process is the most

distinguished feature of solving design problems, it can save time and can be used to create

innovative ideas. Many different design models have been created in order to capture the

perfect structure of the design process. This has resulted to an overcapacity of design modelsthat can however be described by some generic rules.

1.1Generic Design ApproachesSome of the most important design models will be roughly described below, in order to assist

the reader understand the evolution of generic design models and how and comprehend their

use in the project when it is necessary.

Documented design processes usually have developed over time by trial and error and the

best have survived with evolution.

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Prescriptive Models of DesignPrescriptive models embrace a systematic approach that has at its core a general design

methodology which mainly compromises of three main activities: Analysis, synthesis and

evaluation. It is beyond of the scope of this project to discuss the all of the prescriptive

models that have been proposed and used. However it is essential to refer at significant

such models as the Pahl and Beitz. This model compromises of a number of steps

wherein the main phases include clarifying the task (Conceptual design, embodiment

design and detailed design). At every step a decision must be made as to whether the next

step can be taken or whether it needs to be repeated.

Fig.10: G. Pahl and W. Beitz, Engineering Design, 1984, The Design Council.

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With the emergence of hybrid models the model proposed by Pahl and Beitz has been

taken further by the Verein Deutcher Ingenieure publication with the contribution of

Beitz and Cross. Crosses model had played significant role on the emergence and

development of hybrid models also characterized as the third generation models. This

model compromises of seven stages which are placed with purpose within the

symmetrical problem/solution model.

Fig.11: N.Cross, Engineering Design Methods, 1989.

Procedures are integrated with structural aspects of design problems. The procedural

aspects are represented by the larger arrows showing the commutative relationships

between problem and solution and the hierarchical relationships between problem/sub

problems and between sub solution/solution.

Prescriptive models have the tendency to lead the designer into what to do, instead of

describing the process. However most of the prescriptive models heavily rely on

assimilation and iteration which resembles the traditional approach to ship design as it

has developed until now. This relation with the ship design approach and how it is

integrated will be explored further below.

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Descriptive Models of DesignIn contrast to prescriptive models, descriptive models exemplify how design is done by a

designer and not what should be done to arrive at a solution. Descriptive models can be

considered a product of architectural design practice.

The Hillier and Darke model is considered to be one of the primary efforts to create

descriptive models. The basis of this model is that the designer starts with a variety of

potential solutions that are gradually reduced to a small manageable group. This requires

certain objectives to be set and close interaction with the client.

PRIMARY

GENERATORCONJECTURE ANALYSIS/SOLUTION

Fig.12: Graphical Representation of the Hillier/Darke model.

Overall it is a simple model, which uses many potential solutions at the early stages in

order to elicit more information about the problem of a client.

Continuing with the descriptive models we should not fail to mention that Pahl and Beitz

together with Cross have identified four basic activities for the descriptive models of

design:

1. Problem analysis:A problem statement is developed.2. Conceptual Design: The statement of the problem is used to generate a collection of

broad solutions.

3. Embodiment design: Solutions are refined in order to eliminate the least satisfactoryones.

4. Detail Design: Final design is specified with all its details, while complete drawingsand specifications produced.

Concluding descriptive models have a significant contribution and application in ship design

practice. Especially in our case, where the luxury vessels market is highly client orientated

and descriptive models provide us with useful steps to interact well with the client and

understanding his true request.

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1.2Ship Design ApproachesThe first significant contribution into visualizing and modeling the process of ship design

was made in 1959 by Evans. His general design diagram looking like the example in the

picture below has captured the basic beliefs of good practice and has developed to what is

now known as the Ship Design Spiral.

There could be infinite variations of the

ship design spiral. Design spiral should not

be though of as showing the exact order in

which the different aspects of the ship

design should be tackled, because this will

depend strictly on the type of ship being

designed. Some identifying characteristics

of the spiral approach are: firstly that the

design process is sequential and iterative,

which makes it also more laborious.

F

ig.13: Ship Design Spiral [Evans, 1959].

everal refinements have been made since the spiral concept was introduced. The mostS

significant ones were when Buxton introduced economic issues into the spiral and when

time was added as the third dimension by Andrews.

Fig.14: Enhanced Design Spiral [Andrews, 1981].

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The representation of the ship design procedure by Andrews looks like a corkscrew as it is

2. eveloping the Design Process

Having explored above, firstly the some generic design approaches and secondly some

process can follow there are three other paths

: In naval architecture, original design occurs when only the mission

e

rts or subsystems of a basis vessel are

xploring the modular

.1Database Driven Preliminary Designtive design method in order to retrieve the

The owner will usually

shown below in fig. 14. The model still relies on sequential activity and iteration but the

author claims that the shape has the advantage of showing many functions and constraints to

be fundamental for the whole process.

D

important ship design methods, now we have the background to organize a design process

which will fit our own needs for this project.

Except from the various models that a design

that a designer can follow during his design, depending on the nature of the product. These

three paths are:

Original Design

requirements are known and the famous basis-ship design procedure cannot be employed.

Adaptive Design: An existing design is adapted to different conditions. The solution principl

remains the same, but the product will differ in order to meet new requirements. The basis-

ship approach is considered to be adaptive design.

Variant Design: Here the size/arrangements of pavaried, but the design tasks and the solution principle are not changed.

This project will employ all three of the above paths. Since we are e

concept within our design, several subsystems will emerge. Some subsystems can be of

original design or others of variant of adaptive design.

2

In this stage of the design process we use the adapmain particulars of the vessels needed. This is succeeded by the generating a tabular data-

base of basis vessels. However, before we jump into the data-base process we need to how

the right decisions are taken in order to select the appropriate data.

In the superyacht market, owners drive the design requirements.

contact the designer of his preference and explain to him his dream boat. This is the

customers brief, which can be detail or even a broad description of requirements. It is then

the designers work to generate a design brief, which is the functional description of the

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owners dream. This projects customers brief is generated by the designer, after a market

research and in order to cover most of the variant customers requirements.

In order to cover the market need size-wise, the decision was to employ three key sizes that

cover a significant range. The first size range selected is the 50-70m. For that 51 basis vessel

where selected in a data-base. Then the second size range is the 70-90m, where 18 basis

vessels where selected for processing. Lastly the third size range is the 90-130m where only

11 basis vessels could be considered appropriate for processing.

The selection of the basis vessels was based on some significant constraints that guide our

design objectives. The constraints were the vessels to be:

1. Used as private or chartered yachts (Small cruise ships were not considered in thedata-base).

2. The yacht to be constrained in size by each size category (50-70, 70-90, 90-130).3. The yachts to be build after 1970. (The oldest yacht in the data-base is build on 1973).4. The yacht to be displacement monohulls.5. To be constructed by steel (Except from superstructure which usually is aluminium).6. The yachts selected are considered successful in the market and aesthetically pleasing.

After selecting all the vessels satisfying the above constraints for each size category, then the

data were processed according to their importance. In this step our main objective is to

retrieve the main particulars of the vessel, which mean the length, the beam and the draught.

For this task we employed to important ratios the L/B ratio and the B/T ratio. For each vessel

on each category we derived the L/B ratio and the B/T ratios and then an average was

calculated for each size category. The results are the following:

For 50-70m:

Average L/B = 5.56, Average B/T = 3.2

For 70-90m:


For 90-130m:


The data-base in detail and the above results can be found in Appendix 1.

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The premium ratio used in order to derive a trend in dimensions is the L/B ratio. Although we

have to consider that the L/B ratio also has implications in the resistance and propulsion of

the vessel, the hull construction costs and the directional stability.

Considering that mega-yacht design is length driven, by specifying the desired length, we can

derive form the above ratios the Beam and Draught of the vessels. As mentioned previously

we have three categories to investigate in this project (50-70, 70-90, 90-130), therefore we

will derive a parent hullform for each category.

For the 50-70 category:

The desired parent hullform is taken to be 60m long. Therefore from the ratios we can derive:

60

5.5610.791=

L

B = 5.5 and if L = 60 then B m=

B

T

10.791

3.23.372= and then we have that: = 3.2 so we have mT =


The desired parent hullform is taken to be 80m long. Therefore from the ratios we can derive:

Bthen = 80

6.2012.903=

L

B and if= 6.2 L = 80 m

12.903

3.243.982=

B

T= 3.24 so we haveand then we have that: mT =


The desired parent hullform is taken to be 110m long. Therefore from the ratios we can

derive:

L

B

110

6.6316.591= and if= 6.6 L = 110 then B m=

BT

16.5913.38

4.909= and then we have that: = 3.38 so we have mT =

This is a rough estimation of the preliminary dimensions, based on a statistical analysis from

carefully chosen basis vessels. When retrieving results from processing collected data, great

care should be given on the validity of the data and the relevant constraint that should be

imposed.

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Some other valuable trend can be identified from the collected data-base as well. Data

considering such luxury vessels are usually kept hidden. Therefore due to the lack of data, we

will try and draw significant conclusion from the available dimensions: L, B, T and their

ratios.

We can therefore produce the following graph:

L/B v T

0

1

2

3

4

5

6

7

8

9

0 1 2 3 4 5 6 7

T (Draught)

L/BR

atio

90-130

70-90

50-70

Linear (50-70)

Linear (70-90)

Linear (90-130)

Fig.15: L/B ratio versus T. Own processing.

The above graph is not of usual practise in ship design. However it will be used as a

preliminary tool in order to trace some trends of how the volume of the vessels moves in each

size category. It should be mentioned that not significant decisions can be drawn from this

graph since each size category has different amount of data and particularly the 90-130m

category suffers from lack of data, due to the limited construction of such vessels.

Starting to analyse the graph with the 90-130 category we can see the trend line leaning

downwards, which indicates that draught (T) is decreasing as the L/B ratio increases.

Someone can observe in the vessels database Appendix 1, that the speeds of vessels in

category 90-130m are on average higher that in other categories. This is due to higher Froude

numbers that results from increased waterline length. Coming back to our first observation

the draught is decreasing while L/B is increasing, in order to keep the CB in the order of 0.53

0.54 and at the same time the required speed. People who end up in this length category are

possibly driven by speed or the prestige of owning a very large yacht.

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Furthermore for the 70-90 m category we observe that the draught (T) increases together with

increasing L/B. Another observation on the graph is that vessels in this category share similar

regions with the 90-130m data. The reason for the increasing L/B together with T in this

category is due to the need of constraining the length of the vessels but at the same time

maintaining sufficient volume for the needs of the owner. Constraining the length of the

vessel can be some times very important. Usually it happens in order to reduce the first cost

of the vessel, but other reasons can be: Avoiding regulations for over 90m vessels (Structural

and Stability rules), Practicality in harbouring, avoiding taxes and harbour payments that are

related to the length of the vessel, reducing crew members needed and many more practical

reasons. Since the length is constraint somewhere along the 70-90 m category then its logical

that, as the L/B ratio rises volume is lost, therefore draught (T) needs to rise as well in order

to compensate the lost volume.

Lastly for the 50-70 m category we can observe again that the trend line presents a small

declination, however someone could even consider it almost as a straight line. That means

that in such lower L/B ratios where designers try to squeeze as much volume as they can

between the 50-70 m, the draught (T) would have to decrease slightly in order to maintain a

fine block coefficient and consequently an acceptable speed.

Fig.16: L/B ratio versus T significant region. Own processing.

Exploiting further the generated graph, it was easy to observe and mark as shown above, a

significant region where a big population of all three categories data are found, for a wide

range of draughts. This essentially means that there can be found a common design pattern

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for all the categories as far as it concerns L/B, but obviously for a wide range of T since it is

highly depended on length and beam. The common L/B region can be identified as the L/B =

5.7 6.9 for the range of T = 2.2 6.2 m.

2.2Hullform Selection and Final DimensionsIn the data-base used to derive the results above, which is listed in Appendix 1, only full

displacement vessels have been gathered. This section will throw some light onto the

selection of this type of hullform over the semi-displacement hullform. Furthermore some

other aspects of choosing the significant hullform will be defined.

The Full Displacement Hullform

The load carrying capacity of such vessels is entirely supported by static lift. They are

generally much fuller and bigger ships. A reason for that is because, displacement hull are

used for speeds corresponding to Froude numbers up to 0.5. That means that to achieve a

high speed we need a big water line length, which will give us a bigger ship.

The full displacement mega-yachts that have been build the last ten years have a L/B ratio

not less than 5.5 and some even well above 6. Another important characteristic is their Block

coefficient which is varying between 0.40 and 0.50 with 0.45 being a typical value. As

mentioned above length is increased and length is restricted to get block coefficient down and

improve the Froude number.

Fast Semi-Displacement Vessel

Monohull vessels of this category usually use Deep-V hullforms or Hard-Chine Planning

hulls. Those are configured to develop positive dynamic bottom pressures at high speeds.

Theses positive pressures actually lift the hull and thereby reduce the buoyant component.

Obviously then these kind of hullforms support their load carrying capacity not entirely with

dynamic lift. These hulls are designed to avoid the large squat and trim angles associated

with displacement hulls operating at high speeds. Continuing from above semi-displacement

vessels can be planning as well as semi-planning. The last ones have hullforms that develop

positive dynamic pressures that tend to lift the stern and raise the hull. Although these

positive dynamic bottom pressure are not as large as they appear in a Hard-Chine planning

hull. Moreover it is used this kind of vessels to be fitted with submerged wings, T-foils and

big stabilizers that create another dynamic lift. Concluding high speed semi-displacement

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megayacht design 2006 vassilios zagkas

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