Lesson Four
Ship Design
The design of a ship involves a selection of the features of form,size,proportions,and other factors which are open to choice,in combination with those features which are imposed by circumstances beyond the control of the design naval architect,Each new ship should do some things better than any other ship,This superiority must be developed in the evolution of the design,in the use of the most suitable materials,to the application of the best workmanship,and in the application of the basic fundamentals of naval architecture and marine engineering,
As sips have increased in size and complexity,plans for building them have became mare detailed and more varied,The intensive research since the period just prior to World War 2 has brought about many technical advances in the design of ships,These changes have been brought about principally by the development of new welding techniques,developments in main propulsion plants,advances in electronics,and changes in materials and methods of construction.
All ships have many requirements which are common to all types,whether they are naval,merchant,or special-purpose ships,The first of such requirements is that the ship must be capable of floating when carrying the load for which it was designed,A ship floats because as it sinks into the water it displaces an equal weight of water,and the pressure of the water produces an upward force,which is called the buoyancy force is equal to the weight of the water displaced by the ship and is called the displacement,Displacement is equal to the underwater volume of the ship multiplied by the density of the water in which it is gloating,When floating in still water,the weight of the ship,including everything it carries,is equal to the buoyancy or displacement,The weight of the ship itself is called the light weight,This weight includes the weight of the hull structure,fittings,equipment,propulsion machinery,piping and ventilation,cargo-handling equipment and other items required for the efficient operation of the ship,The load which the ship carries in addition to its own weight is called the deadweight,This includes cargo,passengers,crew and effects,stores,fresh water,feed water for the boilers incase of steam propelling machinery,and other weights which may be part of the ships international load,The sum of all these weights plus the lightweight of the ship gives the total displacement; that is
Displacement = lightweight + deadweight
One of the first things which a designer must do is to determine the weight and size of the ship and decide upon a suitable hull form to provide the necessary buoyancy to support the weight that has been chosen.
Owner’s requirements
Ships are designed,built,and operated to fulfill,the requirements and limitations specified by the operator and owner,These owner’s requirements denote the essential considerations which are to form the basis for the design,They may be generally stated as (1) a specified minimum deadweight carrying capacity,(2) a specified measurement tonnage limit,(3) a selected speed at sea,or a maximum speed on trial,and (4) maximum draft combined with other draft limitations.
In addition to these general requirements,there may be a specified distance of travel without refueling and maximum fuel consumption per shaft horsepower hour limitation,as well as other items which will influence the basic design,Apart from these requirements,the ship owner expects the designer to provide a thoroughly efficient ship,Such expectations include (1) minimum displacement on a specified deadweight carrying capacity,(2) maximum cargo capacity on a minimum gross tonnage,(3) appropriate strength of construction,(4) the most efficient type of propelling machinery with due consideration to weight,initial cast,and cost of operation,(5) stability and general seaworthiness,and (6) the best loading and unloading facilities and ample accommodations for stowage.
Design procedure
From the specified requirements,an approach is made to the selection of the dimensions,weight,and displacement of the new design,This is a detailed operation,but some rather direct approximations can be made to start the design process,This is usually done by analyzing data available from an existing ship which is closely similar,For example,the design displacement can be approximated from the similar ship’s known deadweight of,say,11790 tons and the known design displacement of 17600 tons,From these figures,a deadweight-displacement ratio of 0.67 is obtained,Thus,if the deadweight for the new design is,for example,10000 tons,then the approximate design displacement will 10,000/0.67 or 15000 tons,This provides a starting point for the first set of length,beam,and draft dimensions,after due consideration to other requirements such as speed,stability,and strength,Beam is defined as the extreme breath of a ship at its widest part,while draft is the depth of the lowest part of the ship below the waterline.
Length and speed
These factors are related to the hull form,the propulsion machinery,and the propeller design,The hull form is the direct concern of the naval architect,which the propulsion machinery and propeller design are concern,The naval architect has considerable influence on the final decisions regarding the efficiency,weight,and size of the propeller,as both greatly influence the design of the hull form.
Speed has an important influence on the length selected for the ship,The speed of the ship is related to the length in term of the ratio V/,where V is the speed in knots and L is the effective waterline length of the ship,As the speed-length ratio increases,the resistance of the ship increases,Therefore,in order to obtain an efficient hull form from a resistance standpoint,a suitable length must be selected for minimum resistance,Length in relation to the cross-sectional area of the underwater form (the prismatic coefficient),is also very important insofar as resistance is concerned,Fast ships require fine (slender) forms or relatively low fullness coefficients as compared with relatively slow ships which may be designed with fuller hull forms.
Beam and stability
A ship must be stable under all normal conditions of loading and performance at sea,This means that when the ship is inclined from the vertical by some external force,it must return to the vertical when the external force is removed,Stability may be considered in the transverse or in the longitudinal direction,In surface ship,longitudinal stability is much less concern than transverse stability,Submarines,however,are concerned with longitudinal stability in the submerged condition.
The transverse stability of a surface ship must be considered in two ways,first at all small angles of inclination,called initial stability,and second at large angles of inclination,Initial stability depends upon two factors,(1) the height of the center gravity of the ship above the base line and (2) the underwater form of the ship,The center of gravity is the point at which the total weight of the ship may be considered to be concentrated,The hull form factor governing stability depends on the beam B,draft T,and the proportions of the underwater and waterline shape,For a given location of the center of gravity,the initial stability of the ship is proportional to B2/T,Beam,therefore,is a primary factor in transeverse stability,
At large angles of heel (transeverse inclination ) freeboard is also an important factor,Freeboard is the amount the ship projects above the waterline of the ship to certain specified decks (in this case,to the weatherdeck to which the watertight sides extend ),Freeboard affects both the size of the maximum righting arm and the range of the stability,that is the angle of inclination at which the ship would capsize if it were inclined beyond that angle.5
Depth an strength
A ship at sea is subjected to many forces because of the action of the waves,the motion of the ship,and the cargo and other weights,which are distributed throughout the length of the ship,These forces produces stresses in the structure,and the structure must be of suitable strength to withstand the action,The determination of the minimum amount of material required for adequate strength is essential to attaining the minimum weight of the hull,The types of structural stress experienced by a ship riding waves at sea are caused by the unequal distribution of the weight and buoyancy throughout the length of ship,The structure as a whole bends in a longitudinal plane,with the maximum bending stresses being found in the bottom and top of the hull girder.
Therefore,depth is important because as it is increased,less material is required in the deck and bottom shell,However,there are limits which control the maximum depth in terms of practical arrangement and efficiency of design.
(From,McGraw-Hill Encyclopedia of science and Technology”,Vol.12,1982)
Technical Terms
form 船型，形状，格式
proportion 尺度比，比例
workmanship 工艺质量
basic fundamentals 基本原理
marine engineering 轮机工程
intensive 精致的
propulsion plants 推进装置
naval ship 军舰
special-purpose ship 特殊用途船
buoyancy 浮力
fittings 配/附件
piping 管路
ventilation 通风
cargo-handing equipment 货物装卸装置
crew and effects 船员及自身物品
stores 储藏物
fresh water 淡水
feed water 给水
boiler 锅炉
measurement (吨位)丈量，测量
trial 试航，试验
distance of travel 航行距离
refueling 添加燃料
consumption 消耗
initial cost 造价
26,cost of operation 营运成本
27,unloading facility 卸货设备
28,cross sectional area 横剖面面积
29,fineness 纤瘦度
30,prismatic coefficient 菱形系数
31.slender 瘦长（型）
32.beam 船宽
33.inclined 倾斜的
34.external force 外力
35.surface ship 水面船舶
36.submarine 潜水艇
37,submerged condition 潜水状态
38.initial stability 初稳性
39.weather deck 楼天甲板
40,righting arm 复原力臂
41,capsize 倾复
42.stress 应力
43.unequal distribution 分布不相等
44.longitudinal plane 纵向平面
45,hull girder 船体梁
AdditionalTerms and Expressions
1,tentative design 方案设计
2,preliminary design 初步设计
3.technical design 技术设计
4.working design 施工设计
5.basic design 基本设计
6,conceptual design 概念设计
7.inquire design 咨询设计
8.contract design 合同设计
9,detailed design 详细设计
10.finished plan 完工图
11.hull specification 船体说明书
12.general specification 全船说明书
13.steel weight 钢料重量
14.outfit weight（木作）舾装重量
15.machinery weight 机械重量
16,weight curve重量曲线
17,weight estimation 重量估计
18.cargo capacity 货舱容积
19.bale cargo capacity 包装舱容积
20.bulk cargo capacity 散装货容积
21.bunker capacity 燃料舱容积
22,capacity curve 容积曲线
23,capacity plan 容量（积）图
24.stowage factor 积载系数
25.homogenuous cargo 均质货物
26.gross tonnage 总吨位
27.net tonnage 净吨位
28,tonnage capacity 量吨容积
29,tonnage certificate 吨位证书
30.displacement length ratio 排水量长度比
31.accommodation 居住舱室
32.ice strengthening 冰区加强
33.drawing office 制图室
34.drafting room 制图室
Notes to the Text
1.A ship floats because as it sinks into the water it displace an equal weight of water,and pressure of the water produces an upward force which is called buoyancy.
这是一个复合句。
从because开始至句末均属原因状语从句，它本身也是一个复合句，包含有以下从句：
as it sinks into the water 为整个原因状语从句中的时间状语从句;
it displaces an equal weight of water,and pressure of the water produces an upward 为整个原因状语从句中的两个并列的主要句子；
which is called buoyancy 为定语从句，修饰an upward force.
2,In addition to 除……以外（还包括……）
例：In addition to these general requirements,… 除了这些一般要求外，还有……
而在The load which the ship carries in addition to its own weight is called the deadweight中的in addition to 应理解成“外加在它本身重量上的”，故应译为“本身重量除外（不包括本身重量）。
3,插入语，相当于 for example,一般在口语中用得比较多。
4,注意,ton”,“tonne”,和,tonnage” 三个词的区别。ton和tonne一般用来表示船舶的排水量和载重量，指重量单位。其中ton可分long ton (英吨)和 short ton (美吨),而tonne为公吨；tonnage 是登记吨，表征船舶容积的一种单位。
5,…the angle of inclination at which the ship would capsize if it were inclined beyond that angle.
从at 开始至句末是一定语从句，修饰angle,而该从句本身又由一个带虚拟语气的主从复合句所构成。因为假设的条件不会发生，或发生的可能性非常小，所以主句和从句中的谓语动词都采用虚拟语气。
Ship Design
The design of a ship involves a selection of the features of form,size,proportions,and other factors which are open to choice,in combination with those features which are imposed by circumstances beyond the control of the design naval architect,Each new ship should do some things better than any other ship,This superiority must be developed in the evolution of the design,in the use of the most suitable materials,to the application of the best workmanship,and in the application of the basic fundamentals of naval architecture and marine engineering,
As sips have increased in size and complexity,plans for building them have became mare detailed and more varied,The intensive research since the period just prior to World War 2 has brought about many technical advances in the design of ships,These changes have been brought about principally by the development of new welding techniques,developments in main propulsion plants,advances in electronics,and changes in materials and methods of construction.
All ships have many requirements which are common to all types,whether they are naval,merchant,or special-purpose ships,The first of such requirements is that the ship must be capable of floating when carrying the load for which it was designed,A ship floats because as it sinks into the water it displaces an equal weight of water,and the pressure of the water produces an upward force,which is called the buoyancy force is equal to the weight of the water displaced by the ship and is called the displacement,Displacement is equal to the underwater volume of the ship multiplied by the density of the water in which it is gloating,When floating in still water,the weight of the ship,including everything it carries,is equal to the buoyancy or displacement,The weight of the ship itself is called the light weight,This weight includes the weight of the hull structure,fittings,equipment,propulsion machinery,piping and ventilation,cargo-handling equipment and other items required for the efficient operation of the ship,The load which the ship carries in addition to its own weight is called the deadweight,This includes cargo,passengers,crew and effects,stores,fresh water,feed water for the boilers incase of steam propelling machinery,and other weights which may be part of the ships international load,The sum of all these weights plus the lightweight of the ship gives the total displacement; that is
Displacement = lightweight + deadweight
One of the first things which a designer must do is to determine the weight and size of the ship and decide upon a suitable hull form to provide the necessary buoyancy to support the weight that has been chosen.
Owner’s requirements
Ships are designed,built,and operated to fulfill,the requirements and limitations specified by the operator and owner,These owner’s requirements denote the essential considerations which are to form the basis for the design,They may be generally stated as (1) a specified minimum deadweight carrying capacity,(2) a specified measurement tonnage limit,(3) a selected speed at sea,or a maximum speed on trial,and (4) maximum draft combined with other draft limitations.
In addition to these general requirements,there may be a specified distance of travel without refueling and maximum fuel consumption per shaft horsepower hour limitation,as well as other items which will influence the basic design,Apart from these requirements,the ship owner expects the designer to provide a thoroughly efficient ship,Such expectations include (1) minimum displacement on a specified deadweight carrying capacity,(2) maximum cargo capacity on a minimum gross tonnage,(3) appropriate strength of construction,(4) the most efficient type of propelling machinery with due consideration to weight,initial cast,and cost of operation,(5) stability and general seaworthiness,and (6) the best loading and unloading facilities and ample accommodations for stowage.
Design procedure
From the specified requirements,an approach is made to the selection of the dimensions,weight,and displacement of the new design,This is a detailed operation,but some rather direct approximations can be made to start the design process,This is usually done by analyzing data available from an existing ship which is closely similar,For example,the design displacement can be approximated from the similar ship’s known deadweight of,say,11790 tons and the known design displacement of 17600 tons,From these figures,a deadweight-displacement ratio of 0.67 is obtained,Thus,if the deadweight for the new design is,for example,10000 tons,then the approximate design displacement will 10,000/0.67 or 15000 tons,This provides a starting point for the first set of length,beam,and draft dimensions,after due consideration to other requirements such as speed,stability,and strength,Beam is defined as the extreme breath of a ship at its widest part,while draft is the depth of the lowest part of the ship below the waterline.
Length and speed
These factors are related to the hull form,the propulsion machinery,and the propeller design,The hull form is the direct concern of the naval architect,which the propulsion machinery and propeller design are concern,The naval architect has considerable influence on the final decisions regarding the efficiency,weight,and size of the propeller,as both greatly influence the design of the hull form.
Speed has an important influence on the length selected for the ship,The speed of the ship is related to the length in term of the ratio V/,where V is the speed in knots and L is the effective waterline length of the ship,As the speed-length ratio increases,the resistance of the ship increases,Therefore,in order to obtain an efficient hull form from a resistance standpoint,a suitable length must be selected for minimum resistance,Length in relation to the cross-sectional area of the underwater form (the prismatic coefficient),is also very important insofar as resistance is concerned,Fast ships require fine (slender) forms or relatively low fullness coefficients as compared with relatively slow ships which may be designed with fuller hull forms.
Beam and stability
A ship must be stable under all normal conditions of loading and performance at sea,This means that when the ship is inclined from the vertical by some external force,it must return to the vertical when the external force is removed,Stability may be considered in the transverse or in the longitudinal direction,In surface ship,longitudinal stability is much less concern than transverse stability,Submarines,however,are concerned with longitudinal stability in the submerged condition.
The transverse stability of a surface ship must be considered in two ways,first at all small angles of inclination,called initial stability,and second at large angles of inclination,Initial stability depends upon two factors,(1) the height of the center gravity of the ship above the base line and (2) the underwater form of the ship,The center of gravity is the point at which the total weight of the ship may be considered to be concentrated,The hull form factor governing stability depends on the beam B,draft T,and the proportions of the underwater and waterline shape,For a given location of the center of gravity,the initial stability of the ship is proportional to B2/T,Beam,therefore,is a primary factor in transeverse stability,
At large angles of heel (transeverse inclination ) freeboard is also an important factor,Freeboard is the amount the ship projects above the waterline of the ship to certain specified decks (in this case,to the weatherdeck to which the watertight sides extend ),Freeboard affects both the size of the maximum righting arm and the range of the stability,that is the angle of inclination at which the ship would capsize if it were inclined beyond that angle.5
Depth an strength
A ship at sea is subjected to many forces because of the action of the waves,the motion of the ship,and the cargo and other weights,which are distributed throughout the length of the ship,These forces produces stresses in the structure,and the structure must be of suitable strength to withstand the action,The determination of the minimum amount of material required for adequate strength is essential to attaining the minimum weight of the hull,The types of structural stress experienced by a ship riding waves at sea are caused by the unequal distribution of the weight and buoyancy throughout the length of ship,The structure as a whole bends in a longitudinal plane,with the maximum bending stresses being found in the bottom and top of the hull girder.
Therefore,depth is important because as it is increased,less material is required in the deck and bottom shell,However,there are limits which control the maximum depth in terms of practical arrangement and efficiency of design.
(From,McGraw-Hill Encyclopedia of science and Technology”,Vol.12,1982)
Technical Terms
form 船型，形状，格式
proportion 尺度比，比例
workmanship 工艺质量
basic fundamentals 基本原理
marine engineering 轮机工程
intensive 精致的
propulsion plants 推进装置
naval ship 军舰
special-purpose ship 特殊用途船
buoyancy 浮力
fittings 配/附件
piping 管路
ventilation 通风
cargo-handing equipment 货物装卸装置
crew and effects 船员及自身物品
stores 储藏物
fresh water 淡水
feed water 给水
boiler 锅炉
measurement (吨位)丈量，测量
trial 试航，试验
distance of travel 航行距离
refueling 添加燃料
consumption 消耗
initial cost 造价
26,cost of operation 营运成本
27,unloading facility 卸货设备
28,cross sectional area 横剖面面积
29,fineness 纤瘦度
30,prismatic coefficient 菱形系数
31.slender 瘦长（型）
32.beam 船宽
33.inclined 倾斜的
34.external force 外力
35.surface ship 水面船舶
36.submarine 潜水艇
37,submerged condition 潜水状态
38.initial stability 初稳性
39.weather deck 楼天甲板
40,righting arm 复原力臂
41,capsize 倾复
42.stress 应力
43.unequal distribution 分布不相等
44.longitudinal plane 纵向平面
45,hull girder 船体梁
AdditionalTerms and Expressions
1,tentative design 方案设计
2,preliminary design 初步设计
3.technical design 技术设计
4.working design 施工设计
5.basic design 基本设计
6,conceptual design 概念设计
7.inquire design 咨询设计
8.contract design 合同设计
9,detailed design 详细设计
10.finished plan 完工图
11.hull specification 船体说明书
12.general specification 全船说明书
13.steel weight 钢料重量
14.outfit weight（木作）舾装重量
15.machinery weight 机械重量
16,weight curve重量曲线
17,weight estimation 重量估计
18.cargo capacity 货舱容积
19.bale cargo capacity 包装舱容积
20.bulk cargo capacity 散装货容积
21.bunker capacity 燃料舱容积
22,capacity curve 容积曲线
23,capacity plan 容量（积）图
24.stowage factor 积载系数
25.homogenuous cargo 均质货物
26.gross tonnage 总吨位
27.net tonnage 净吨位
28,tonnage capacity 量吨容积
29,tonnage certificate 吨位证书
30.displacement length ratio 排水量长度比
31.accommodation 居住舱室
32.ice strengthening 冰区加强
33.drawing office 制图室
34.drafting room 制图室
Notes to the Text
1.A ship floats because as it sinks into the water it displace an equal weight of water,and pressure of the water produces an upward force which is called buoyancy.
这是一个复合句。
从because开始至句末均属原因状语从句，它本身也是一个复合句，包含有以下从句：
as it sinks into the water 为整个原因状语从句中的时间状语从句;
it displaces an equal weight of water,and pressure of the water produces an upward 为整个原因状语从句中的两个并列的主要句子；
which is called buoyancy 为定语从句，修饰an upward force.
2,In addition to 除……以外（还包括……）
例：In addition to these general requirements,… 除了这些一般要求外，还有……
而在The load which the ship carries in addition to its own weight is called the deadweight中的in addition to 应理解成“外加在它本身重量上的”，故应译为“本身重量除外（不包括本身重量）。
3,插入语，相当于 for example,一般在口语中用得比较多。
4,注意,ton”,“tonne”,和,tonnage” 三个词的区别。ton和tonne一般用来表示船舶的排水量和载重量，指重量单位。其中ton可分long ton (英吨)和 short ton (美吨),而tonne为公吨；tonnage 是登记吨，表征船舶容积的一种单位。
5,…the angle of inclination at which the ship would capsize if it were inclined beyond that angle.
从at 开始至句末是一定语从句，修饰angle,而该从句本身又由一个带虚拟语气的主从复合句所构成。因为假设的条件不会发生，或发生的可能性非常小，所以主句和从句中的谓语动词都采用虚拟语气。
