Page 36 - Ship Construction.DJ Eyres 6Ed

Ch03-H8070.fm Page 25 Wednesday, October 18, 2006 6:52 AM
Development of Ship Types 25

BRIDGE
ACCOMDT.
8
7
6
5 DECK
4
3
2
1
STERN RAMP
--- ใช้เพื่อการศึกษาเท่านั้น---
DOWN
3,2
UP 5,4
งานห้องสมุด ศูนย์ฝกพาณิชย์นาวี
QUARTER RAMP Deck No. 4
FIGURE 3.5 Car carrier

weather deck. Propulsion machinery is situated aft with bow thruster/s
forward to aid mooring/manoeuvring.
The ship shown in Fig. 3.5 has an overall length of 148 metres, a beam of
25 metres and a speed of 19 knots on a 7.2 metre draft. It can carry some
2140 units. A unit being an overall stowage area of 8.5 square metres per car
and representing a vehicle 4.125 metres in length and 1.55 metres wide plus
an all round stowage margin. ึ

Oil Tankers

Until 1990 the form of vessels specifically designed for the carriage of oil
cargoes had not undergone a great deal of change since 1880 when the ves-
sel illustrated in Figure 3.6(a) was constructed. The expansion trunk and
double bottom within the cargo space having been eliminated much earlier.
The greatest changes in that period were the growth in ship size and nature
of the structure (see Figure 3.6(b)).
The growth in size of ocean-going vessels from 1880 to the end of the
Second World War was gradual, the average deadweight rising from 1500
tonnes to about 12000 tonnes. Since then the average deadweight increased
rapidly to about 20000 tonnes in 1953 and about 30000 tonnes in 1959.
Today there are afloat tankers ranging from 100000 tonnes deadweight to
500000 tonnes deadweight. It should be made clear that the larger size of
vessel is the crude oil carrier, and fuel oil carriers tend to remain within the
smaller deadweights.
Service speeds of oil tankers have shown an increase since the late 1940’s,
going from 12 knots to 17 knots. The service speed is related to the opti-
mum economic operation of the tanker. Also the optimum size of the
tanker is very much related to current market economics. The tanker fleet