Variety

Naval architecture is a fascinating and demanding discipline. It is fascinating because of the variety of floating structures and the many compromises necessary to achieve the most effective product. It is demanding because a ship is a very large capital investment and because of the need to protect the people on board and the marine environment.

A visit to a busy port reveals the variety of forms a ship may take. This is due to the different demands on them and the conditions under which they operate. There are fishing vessels ranging from the small local boat operating by day to the ocean going ships with facilities to deep freeze their catches. There are vessels for exploitation of undersea 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 iron ore. Ferries carry passengers between ports which may be only a few kilometres or a hundred

4 INTRODUCTION

apart. There are tugs for shepherding ships in port or for trans-ocean towing. Then there are dredgers, lighters and pilot boats without which a port could not function. In a naval port there will be warships ranging from huge aircraft carriers through cruisers and destroyers to frigates, patrol boats, mine countermeasure vessels and submarines.

Increasingly naval architects are involved in the design of small craft such as yachts and motor cruisers. This reflects partly the much greater number of small craft, mostly for leisure activities; partly the increased regulation to which they are subject requiring a professional input and partly the increasingly advanced methods used in their design and new materials in their construction. However, in spite of the increasingly scientific approach the design of small craft still involves a great deal of 'art'. Many of the craft are beautiful with graceful lines and lavishly appointed interiors. The craftsmanship needed for their construction is of the highest order.

Over the last half century many naval architects have become involved in offshore engineering - the exploration for, and production of, oil and gas. Their expertise has been needed for the design of the rigs and the many supporting vessels, including manned and unmanned submersibles which are increasingly used for maintenance. This involvement will continue as the riches of the ocean and ocean bed are exploited more in the future.

For ships themselves there is considerable variety in hull form. Much of this book is devoted to single hull, displacement forms which rely upon displacing water to support their full weight. In some applications, particularly for fast ferries, multiple hulls are preferred because they provide large deck areas with good stability without excessive length. Catamarans have been built in large numbers. The idea is far from new as many societies have made use of outriggers to provide increased safety. As early as the 1870s two twin hull ships of 90 m length were used on the cross channel route between Dover and Calais. Although overtaken by other developments both ships had good reputations for seakeeping. More recently trimaran and pentamaran designs have been proposed and the Triton, a trimaran demonstrator, has been very successful on trials.

In planing craft high speeds may be achieved by using dynamic forces to support part of the weight when under way. Surface effect ships use air cushions to support the weight of the craft, lifting it clear of the water. This is particularly useful in navigating areas with sand banks and in providing an amphibious capability. Hydrofoil craft rely on hydrodynamic forces on submerged foils under the hull to lift the main part of the craft above the waves. Other craft, particularly on rivers in Russia, lift is gained by the so-called wing-in-ground effect (WIG). There are, of course, many examples of hybrid craft incorporating several of the above features.

Some of the more specialized craft are dealt with in a little more detail in the chapter on ship types.

Variety is not limited to appearance and function. Different materials are used - steel, wood, aluminium, reinforced plastics of various types and concrete. 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 or gas turbine, some form of fuel cell or a combination of these. 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 is usually some form of propeller, perhaps ducted, but may be water or air jet. There will be many other systems on board, such as means of manoeuvring the ship, electric power generation, hydraulic power for winches and other cargo handling systems, and so on.

A ship can be a veritable floating township of several thousand people remaining at sea for several weeks. It needs electrics, air conditioning, sewage treatment plant, galleys, bakeries, shops, restaurants, cinemas and other leisure facilities. All these, and the general layout must be arranged so that the ship can carry out its intended tasks efficiently. 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 architecture is not only engineering, it is an art as well. The art is in getting a design that is aesthetically pleasing and able to carry out its function with maximum effectiveness, efficiency and economy. The naval architect's task is not limited to the design of ships but extends into their building and upkeep. These latter aspects are not covered in any detail in this book.

Naval architecture is a demanding profession because a ship is a major capital investment taking many years to create and expected to remain in service for 25 years or more. It is usually part of a larger transport system and must be properly integrated with the other elements of the overall system. A prime example of this is the container ship. Goods are placed in containers at the factory. These containers are of standard dimensions and are taken by road, or rail, to a port with specialized handling equipment where they are loaded on board. At the port of destination they are off-loaded on to land transport. The use of containers means that ships need spend far less time in port loading and unloading and the cargoes are more secure. Port fees are reduced and the ship is used more productively.

Most important is the safety of ship, crew and, increasingly nowadays, the environment. The design must be safe for normal operations and

6 INTRODUCTION

not be unduly vulnerable to mishandling or accident. No ship can be absolutely safe and a designer must take conscious decisions as to the level of risk judged acceptable in the full range of scenarios in which the ship can expect to find itself. There will always be a possibility that the conditions catered for will be exceeded. The risk of this and the potential consequences must be assessed and only accepted if they are judged unavoidable or acceptable. Acceptable, that is, by the owner, operator and the general public and not least by the designer who has ultimate responsibility. Even where errors on the part of others have caused an accident the designer should have considered such a possibility and taken steps to minimize the consequences. For instance, in the event of collision the ship must have a good chance of surviving or, at least, of remaining afloat long enough for passengers to be taken off safely. This brings with it the need for a whole range of life saving equipment. The heavy loss of life in the sinking of several ferries in the closing years of the 20th Century show what can happen when things go wrong.

Cargo ships may carry materials which would damage the environment if released. The consequences of large oil spillages are reported all too often. Other chemicals pose even greater threats. In the case of ferries, the lorries on board may carry dangerous loads. Clearly those who design, construct and operate ships have a great responsibility to the community at large. If they fail to live up to the standards expected of them they are likely to be called to account. Over the years the safety of life and cargo has prompted governments to lay down certain conditions that must be met by ships flying their flag, or using their ports. Because shipping is world wide there are also international rules to be obeyed.

It will be clear from what has been said above, that naval architects must work closely with those who build, maintain and operate the ships they design. This need for teamwork and the need for each player to understand the others' needs and problems, are the themes of a book published by The Nautical Institute in 1999.

How To Have A Perfect Boating Experience

How To Have A Perfect Boating Experience

Lets start by identifying what exactly certain boats are. Sometimes the terminology can get lost on beginners, so well look at some of the most common boats and what theyre called. These boats are exactly what the name implies. They are meant to be used for fishing. Most fishing boats are powered by outboard motors, and many also have a trolling motor mounted on the bow. Bass boats can be made of aluminium or fibreglass.

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