Page 13 - Introduction to Naval Architecture

2 INTRODUCTION

energy sources, gas and oil, and extraction of minerals. There are oil
tankers, ranging from small coastal vessels to giant supertankers. Other
huge ships carry bulk cargoes such as grain, coal or ore. There are
ferries for carrying passengers between ports which may be only a few
kilometres or a hundred apart. There are the tugs for shepherding
ships in port or for trans-ocean towing. Then there are the dredgers,
lighters and pilot boats without which the port could not function. In
a naval port, there will be warships from huge aircraft carriers through
cruisers and destroyers to frigates, patrol boats, mine countermeasure
vessels and submarines.
Besides the variety of function there is variety in hull form. The vast
majority of ships are single hull and rely upon their displacement to
support their weight. In some applications multiple hulls are preferred
because they provide large deck areas without excessive length. In
other cases higher speeds may be achieved by using dynamic forces to
support part of the weight when under way. Planing craft, surface effect
ships and hydrofoil craft are examples. Air cushion craft enable shallow
water to be negotiated and provide an amphibious capability. Some
craft will be combinations of these specialist forms.
The variety is not limited to appearance and function. Different
materials are used - steel, wood, aluminium and reinforced plastics of
various types. The propulsion system used to drive the craft through the
water may be the wind, but for most large craft is some form of
mechanical propulsion. The driving power may be generated by
diesels, steam turbine, gas turbine, some form of fuel cell or a
combination of these. The power will be transmitted to the propulsion
device through mechanical or hydraulic gearing or by using electric
generators and motors as intermediaries. The propulsor itself will
usually be some form of propeller, perhaps ducted, but may be water or
air jet. There will be many other systems on board - means of
manoeuvring the ship, electric power generation, hydraulic power for
winches and other cargo handling systems.
A ship can be a veritable floating township with several thousand
people on board and remaining at sea for several weeks. It needs
electrics, air conditioning, sewage treatment plant, galleys, bakeries,
shops, restaurants, cinemas, dance halls, concert halls and swimming
pools. All these, and the general layout must be arranged so that the
ship can carry out its intended tasks efficiently and economically. The
naval architect has not only the problems of the building and town
designer but a ship must float, move, be capable of surviving in a very
rough environment and withstand a reasonable level of accident. It is
the naval architect who 'orchestrates' the design, calling upon the
expertise of many other professions in achieving the best compromise
between many, often conflicting, requirements. The profession of naval