Page 321 - Introduction to Naval Architecture

306 SHIP DESIGN

Cargo handling
In deciding what cargo handling equipment to fit, a balance is needed
between giving a ship the ability to load and discharge its own cargo
and reliance upon the terminal port facilities. If the ship is to operate
between well defined ports the balance may be clear. If the ship is to
operate more flexibly it may not be able to rely on specialist unloading
equipment and have to carry more of its own.
The development of the container ship was closely linked to the
development of special container ports and the supporting road and
rail networks for moving the containers inland. Similarly crude oil
carriers can expect good facilities at the loading port and the refinery
terminal.

Influence of nature of goods carried
Particularly for those goods where large volumes are to be shipped, the
nature of the cargo has come to dictate the main features of the ship.
The wool clippers on the Australian run were an early example. More
recently tankers have come to the fore and with the growing demand
for oil and its by-products, the size of tanker grew rapidly. The major
influences are the possible storage methods and the means of loading
and discharging. Oil can be carried in large tanks and can be pumped
out. Some particulate cargoes can be handled similarly or by conveyor
belts and huge grabs. This has led to bulk carriers for grain, iron ore
and coal.
Mixed cargoes are often placed in containers of a range of standard
sizes. This improves the security in transit and reduces time in port. In
other cases the cargo is brought to the ship in the land transport system
units. First came the train ferries and then the roll on/roll off ships.
Cars can be driven on and off for delivery of new cars around the world
or for people taking their cars on holiday.
Perishable goods have led to the refrigerated ships, the reefers. Bulk
carriage of gas has been possible with a combination of refrigeration
and pressurized tanks.
Speed
Speed can be an emotive issue. Some authorities regard high speed as
a status symbol but it is expensive of power and fuel and if pitched too
high can lead to an inefficient ship. It is an important input to the
analysis referred to above. Faster ships can make more journeys in a
given time period. Passengers like short passage times and are often
prepared to pay a premium to get them as in the case of high speed
catamaran ferries. Some goods need to be moved relatively quickly.
They may be perishable and a balance must be struck between
refrigeration and a fast transit. For other products speed may be of little