Basic Ship Theory, Combined Volume

E. C. Tupper, KJ Rawson

• Publisher: Butterworth-Heinemann
• Year: 2001
• ISBN:
  9780080523385
• Edition: 5
• Topic: Technologie et ingénierie
• Subtopic: Sciences et technologies militaires

Rawson and Tupper's Basic Ship Theory, first published in 1968, is widely known as the standard introductory text for naval architecture students, as well as being a useful reference for the more experienced designer. The fifth edition continues to provide a balance between theory and practice. Volume 1 discusses ship geometry and measurement in its more basic concepts, also covering safety issues, structural strength, flotation, trim and stability. Volume 2 expands on the material in Volume 1, covering the dynamics behaviour of marine vehicles, hydrodynamics, manoeuvrability and seakeeping. It concludes with some case studies of particular ship types and a discussion of maritime design. Both volumes feature the importance of considering the environment in design.Basic Ship Theory is an essential tool for undergraduates and national vocational students of naval architecture, maritime studies, ocean and offshore engineering, and this combined hardback version will be of great assistance to practising marine engineers and naval architects.

• Brand new edition of the leading undergraduate textbook in Naval Architecture
• Provides a basis for more advanced theory
• Over 500 examples, with answers

1

Art or science?

Many thousands of years ago when people became intelligent and adventurous, those tribes who lived near the sea ventured on to it. They built rafts or hollowed out tree trunks and soon experienced the thrill of moving across the water, propelled by tide or wind or device. They experienced, too, the first sea disasters; their boats sank or broke, capsized or rotted and lives were lost. It was natural that those builders of boats which were adjudged more successful than others, received the acclaim of their fellows and were soon regarded as craftsmen. The intelligent craftsman observed perhaps, that capsizing was less frequent when using two trunks joined together or when an outrigger was fixed, or that it could be manoeuvred better with a rudder in a suitable position. The tools were trial and error and the stimulus was pride. He was the first naval architect.

The craftsmen’s expertise developed as it was passed down the generations: the Greeks built their triremes and the Romans their galleys; the Vikings produced their beautiful craft to carry soldiers through heavy seas and on to the beaches. Several hundred years later, the craftsmen were designing and building great square rigged ships for trade and war and relying still on knowledge passed down through the generations and guarded by extreme secrecy. Still, they learned by trial and error because they had as yet no other tools and the disasters at sea persisted.

The need for a scientific approach must have been felt many hundreds of years before it was possible and it was not possible until relatively recently, despite the corner stone laid by Archimedes two thousand years ago. Until the middle of the eighteenth century the design and building of ships was wholly a craft and it was not, until the second half of the nineteenth century that science affected ships appreciably.

Isaac Newton and other great mathematicians of the seventeenth century laid the foundations for so many sciences and naval architecture was no exception. Without any doubt, however, the father of naval architecture was Pierre Bouguer who published in 1746, Traité du Navire. In his book, Bouguer laid the foundations of many aspects of naval architecture which were developed later in the eighteenth century by Bernoulli, Euler and Santacilla. Lagrange and many others made contributions but the other outstanding figure of that century was the Swede, Frederick Chapman who pioneered work on ship resistance which led up to the great work of William Froude a hundred years later. A scientific approach to naval architecture was encouraged more on the continent than in Britain where it remained until the 1850s, a craft surrounded by pride and secrecy. On 19 May 1666, Samuel Pepys wrote of a Mr Deane:

And then he fell to explain to me his manner of casting the draught of water which a ship will draw before-hand; which is a secret the King and all admire in him, and he is the first that hath come to any certainty before-hand of foretelling the draught of water of a ship before she be launched.

The second half of the nineteenth century, however, produced Scott Russell, Rankine and Froude and the development of the science, and dissemination of knowledge in Britain was rapid.

NAVAL ARCHITECTURE TODAY

It would be quite wrong to say that the art and craft built up over many thousands of years has been wholly replaced by a science. The need for a scientific approach was felt, first, because the art had proved inadequate to halt the disasters at sea or to guarantee the merchant that he or she was getting the best value for their money. Science has contributed much to alleviate these shortcomings but it continues to require the injection of experience of successful practice. Science produces the correct basis for comparison of ships but the exact value of the criteria which determine their performances must, as in other branches of engineering, continue to be dictated by previous successful practice, i.e. like most engineering, this is largely a comparative science. Where the scientific tool is less precise than one could wish, it must be heavily overlaid with craft; where a precise tool is developed, the craft must be discarded. Because complex problems encourage dogma, this has not always been easy.

The question, ‘Art or Science?’ is therefore loaded since it presupposes a choice. Naval architecture is art and science.

Basically, naval architecture is concerned with ship safety, ship performance and ship geometry, although these are not exclusive divisions.

With ship safety, the naval architect is concerned that the ship does not capsize in a seaway, or when damaged or even when maltreated. It is necessary to ensure that the ship is sufficiently strong so that it does not break up or fracture locally to let the water in. The crew must be assured that they have a good chance of survival if the ship does let water in through accident or enemy action.

The performance of the ship is dictated by the needs of trade or war. The required amount of cargo must be carried to the places which the owner specifies in the right condition and in the most economical manner; the warship must carry the maximum hitting power of the right sort and an efficient crew to the remote parts of the world. Size, tonnage, deadweight, endurance, speed, life, resistance, methods of propulsion, manoeuvrability and many other features must be matched to provide the right primary performance at the right cost. Over 90 per cent of the world’s trade is still carried by sea.

Ship geometry concerns the correct interrelation of compartments which the architect of a house considers on a smaller scale. In an aircraft carrier, the naval architect has 2000 rooms to relate, one with another, and must provide up to fifty different piping and ducting systems to all parts of the ship. It is necessary to provide comfort for the crew and facilities to enable each member to perform his or her correct function. The ship must load and unload in harbour with the utmost speed and perhaps replenish at sea. The architecture of the ship must be such that it can be economically built, and aesthetically pleasing. The naval architect is being held increasingly responsible for ensuring that the environmental impact of the product is minimal both in normal operation and following any foreseeable accident. There is a duty to the public at large for the safety of marine transport. In common with other professionals the naval architect is expected to abide by a stringent code of conduct.

It must be clear that naval architecture involves complex compromises of many of these features. The art is, perhaps, the blending in the right proportions. There can be few other pursuits which draw on such a variety of sciences to blend them into an acceptable whole. There can be few pursuits as fascinating.

SHIPS

Ships are designed to meet the requirements of owners or of war and their features are dictated by these requirements. The purpose of a merchant ship has been described as conveying passengers or cargo from one port to another in the most efficient manner. This was interpreted by the owners of Cutty Sark as the conveyance of relatively small quantities of tea in the shortest possible time, because this was what the tea market demanded at that time. The market might well have required twice the quantity of tea per voyage in a voyage of twice the length of time, when a fundamentally different design of ship would have resulted. The economics of any particular market have a profound effect on merchant ship design. Thus, the change in the oil market following the second world war resulted in the disappearance of the 12,000 tonf deadweight tankers and the appearance of the 400,000 tonf deadweight supertankers. The economics of the trading of the ship itself have an effect on its design; the desire, for example, for small tonnage (and therefore small harbour dues) with large cargo-carrying capacity brought about the three island and shelter deck ships where cargo could be stowed in spaces not counted towards the tonnage on which insurance rates and harbour dues were based. Such trends have not always been compatible with safety and requirements of safety now also vitally influence ship design. Specialized demands of trade have produced the great passenger liners and bulk carriers, the natural-gas carriers, the trawlers and many other interesting ships. Indeed, the trend is towards more and more specialization in merchant ship design (see Chapter 16).

Specialization applies equally to warships. Basically, the warship is designed to meet a country’s defence policy. Because the design and building of warships takes several years, it is an advantage if a particular defence policy persists for at least ten years and the task of long term defence planning is an onerous and responsible one. The Defence Staff interprets the general Government policy into the needs for meeting particular threats in particular parts of the world and the scientists and technologists produce weapons for defensive and offensive use. The naval architect then designs ships to carry the weapons and the men to use them to the correct part of the world. Thus, nations like Britain and the USA with commitments the other side of the world, would be expected to expend more of the available space in their ships on facilities for getting the weapons and crew in a satisfactory state to a remote, perhaps hot, area than a nation which expects to make short harrying excursions from its home ports. It is important, therefore, to regard the ship as a complete weapon system and weapon and ship designers must work in the closest possible contact.

Nowhere, probably, was this more important than in the aircraft carrier. The type of aircraft carried so vitally affects an aircraft carrier that the ship is virtually designed around it; only by exceeding all the minimum demands of an aircraft and producing monster carriers, can any appreciable degree of flexibility be introduced. The guided missile destroyer results directly from the Defence Staff’s assessment of likely enemy aircraft and guided weapons and their concept of how and where they would be used; submarine design is profoundly affected by diving depth and weapon systems which are determined by offensive and defensive considerations. The invention of the torpedo led to the motor torpedo boat which in turn led to the torpedo boat destroyer; the submarine, as an alternative carrier of the torpedo, led to the design of the anti-submarine frigate; the missile carrying nuclear submarine led to the hunter killer nuclear submarine. Thus, the particular demand of war, as is natural, produces a particular warship.

Particular demands of the sea have resulted in many other interesting and important ships: the self-righting lifeboats, surface effect vessels, container ships, cargo drones, hydrofoil craft and a host of others. All are governed by the basic rules and tools of naval architecture which this book seeks to explore. Precision in the use of these tools must continue to be inspired by knowledge of sea disasters; Liberty ships of the second world war, the loss of the Royal George, the loss of HMS Captain, and the loss of the Vasa:

In 1628, the Vasa set out on a maiden voyage which lasted little more than two hours. She sank in good weather through capsizing while still in view of the people of Stockholm.

That disasters remain an influence upon design and operation has been tragically illustrated by the losses of the Herald of Free Enterprise and Estonia in the 1990s, while ferry losses continue at an alarming rate, often in nations which cannot afford the level of safety that they would like.

Authorities

CLASSIFICATION SOCIETIES

The authorities with the most profound influence on shipbuilding, merchant ship design and ship safety are the classification societies. Among the most dominant are Lloyd’s Register of Shipping, det Norske Veritas, the American Bureau of Shipping, Bureau Veritas, Registro Italiano, Germanische Lloyd and Nippon Kaiji Kyokai. These meet to discuss standards under the auspices of the International Association of Classification Societies (IACS).

It is odd that the two most influential bodies in the shipbuilding and shipping industries should both derive their names from the same owner of a coffee shop, Edward Lloyd, at the end of the seventeenth century. Yet the two organizations are entirely independent with quite separate histories. Lloyd’s Insurance Corporation is concerned with mercantile and other insurance. Lloyd’s Register of Shipping is concerned with the maintenance of proper technical standards in ship construction and the classification of ships, i.e. the record of all relevant technical details and the assurance that these meet the required standards. Vessels so registered with Lloyd’s Register are said to be cla...