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Lesson One
The Naval Architect
A
naval
architect
asked
to
design
a
ship
may
receive
his
instructions
in
a
form
ranging
from
such
simple
requirements as
“an oil
tanker to carry 100 000 tons deadweight at 15
knots” to a fully detailed specification of
precisely planned requirements. He is
usually required to prepare a design for a vessel
that must carry a certain
weight of
cargo (or number of passengers ) at a specified
speed with particular reference to trade
requirement;
high-density
cargoes,
such
as
machinery,
require
little
hold
capacity,
while
the
reverse
is
true
for
low-
density
cargoes, such as grain.
Deadweight is defined as
weight of cargo plus fuel and consumable stores,
and lightweight as the weight of
the
hull, including machinery and equipment. The
designer must choose dimensions such that the
displacement of
the vessel is equal to
the sum of the dead weight and the lightweight
tonnages. The fineness of the hull must be
appropriate
to
the
speed.
The
draft------which
is
governed
by
freeboard
rules------enables
the
depth
to
be
determined to a first
approximation.
After selecting
tentative values of length, breadth, depth, draft,
and displacement, the designer must achieve a
weight balance. He must also select a
moment balance because centres of gravity in both
longitudinal and vertical
directions
must
provide
satisfactory
trim
and
stability.
Additionally,
he
must
estimate
the
shaft
horsepower
required
for
the
specified
speed;
this
determines
the
weight
of
machinery.
The
strength
of
the
hull
must
be
adequate for the service intended,
detailed scantlings (frame dimensions and plate
thicknesses ) can be obtained
from the
rules of the classification society. These
scantings determine the requisite weight of hull
steel.
The
vessel
should
possess
satisfactory
steering
characteristics,
freedom
from
troublesome
vibration,
and
should
comply
with
the
many
varied
requirements
of
international
regulations.
Possessing
an
attractive
appearance, the ship should have the
minimum net register tonnage, the factor on which
harbour and other dues
are
based.
(The
gross
tonnage
represents
the
volume
of
all
closed-in
spaces
above
the
inner
bottom.
The
net
tonnage
is
the
gross
tonnage
minus
certain
deductible
spaces
that
do
not
produce
revenue.
Net
tonnage
can
therefore be regarded as a measure of
the earning capacity of the ship, hence its use as
a basis for harbour and
docking
charges. ) Passenger vessels
must
satisfy a standard of bulkhead
subdivision that will ensure adequate
stability under specified conditions if
the hull is pierced accidentally or through
collision.
Compromise plays
a considerable part in producing a satisfactory
design. A naval architect must be a master
of approximations. If the required
design closely resembles that of a ship already
built for which full information
is
available,
the
designer
can
calculate
the
effects
of
differences
between
this
ship
and
the
projected
ship.
If,
however,
this
information
is
not
available,
he
must
first
produce
coefficients
based
upon
experience
and,
after
refining them, check
the results by calculation.
Training
There
are
four
major
requirements
for
a
good
naval
architect.
The
first
is
a
clear
understanding
of
the
fundamental
principles
of
applied
science,
particularly
those
aspects
of
science
that
have
direct
application
to
ships------mathematics,
physics,
mechanics,
fluid
mechanics,
materials,
structural
strength,
stability,
resistance,
and
propulsion.
The
second
is
a
detailed
knowledge
of
past
and
present
practice
in
shipbuilding.
The
third
is
personal experience of accepted methods
in the design, construction, and operation of
ships; and the fourth, and
perhaps most
important, is an aptitude for tackling new
technical problems and of devising practical
solutions.
The
professional
training
of
naval
architects
differs
widely
in
the
various
maritime
countries.
Unimany
universities and polytechnic schools;
such academic training must be supplemented by
practical experience in a
shipyard.
Trends in design
The introduction of calculating
machines and computers has facilitated the complex
calculations required in
naval
architecture
and
has
also
introduced
new
concepts
in
design.
There
are
many
combinations
of
length,
breadth, and draft that will give a
required displacement. Electronic computers make
it possible to prepare series
of
designs for a vessel to operate in a particular
service and to assess the economic returns to the
shipowner for
each
separate
design.
Such
a
procedure
is
best
carried
out
as
a
joint
exercise
by
owner
and
builder.
As
ships
increase
in
size
and
cost,
such
combined
technical
and
economic
studies
can
be
expected
to
become
more
common.
(From
“Encyclopedia Britannica”, Vol. 16,
1980)
Technical terms
1.
naval architect
造船工程（设计）师
naval architecture
造船（工程）学
2.
instruction
任务书、指导书
3.
oil tanker
油轮
4.
deadweight
载重量
5.
knot
节
6.
specification
规格书，设计任务书
7.
vessel
船舶
8.
cargo
货物
9.
passenger
旅客
10.
trade
贸易
11.
machinery
机械、机器
12.
hold capacity
舱容
13.
consumable store
消耗物品
14.
light weight
轻载重量、空船重量
15.
hull
船体
16.
dimension
尺度、量纲、维（数）
17.
displacement
排水量、位移、置换
18.
tonnage
吨位
19.
fineness
纤瘦度
20.
draft
吃水
21.
breadth
船宽
22.
freeboard
干舷
23.
rule
规范
24.
tentative
试用（暂行）的
25.
longitudinal direction
纵向
26.
vertical direction
垂向
27.
trim
纵倾
28.
stability
稳性
29.
shaft horse power
轴马力
30.
strength
强度
31.
service
航区、服务
32.
scantling
结构（件）尺寸
33.
frame
肋骨
34.
classification society
船级社
35.
steering
操舵、驾驶
36.
vibration
振动
37.
net register tonnage
净登记吨位
38.
harbour
港口
39.
dues
税收
40.
gross tonnage
总吨位
41.
deductible space
扣除空间
42.
revenue
收入
43.
docking
进坞
44.
charge
费用、电荷
45.
bulkhead
舱壁
46.
subdivision
分舱（隔）、细分
47.
collision
碰撞
48.
compromise
折衷、调和
49.
coefficient
系数
50.
training
培训
51.
fluid mechanics
流体力学
52.
structural strength
结构强度
53.
resistance
阻力
54.
propulsion
推进
55.
shipbuilding
造船
56.
aptitude
（特殊）才能，适应性
57.
maritime
航运，海运
58.
polytechnical school
工艺（科技）学校
59.
academic
学术的
60.
shipyard
造船厂
61.
electronic computer
电子计算机
62.
owner
船主，物主
63.
encyclop(a)edia
百科全书