Introduction

In their young days the authors performed the calculations outlined in this work manually aided only by slide rule and, luxuriously, calculators. The arduous nature of such endeavours detracted from the creative aspects and affected the enjoyment of designing ships. Today, while it would be possible, such prolonged calculation is unthinkable because the chores have been removed to the care of the computer, which has greatly enriched the design process by giving time for reflection, trial and innovation, allowing the effects of changes to be examined rapidly.

It would be equally nonsensical to plunge into computer manipulation without knowledge of the basic theories, their strengths and limitations, which allow judgement to be quantified and interactions to be acknowledged. A simple change in dimensions of an embryo ship, for example, will affect flotation, stability, protection, powering, strength, manoeuvring and many sub-systems within, that affect a land architect to much less an extent. For this reason, the authors have decided to leave computer system design to those qualified to provide such important tools and to ensure that the student recognizes the fundamental theory on which they are based so that he or she may understand what consequences the designer’s actions will have, as they feel their way towards the best solution to an owner’s economic aims or military demands.

Manipulation of the elements of a ship is greatly strengthened by such a ‘feel’ and experience provided by personal involvement. Virtually every ship’s characteristic and system affects every other ship so that some form of holistic approach is essential.

A crude representation of the process of creating a ship is outlined in the figure.

This is, of course, only a beginning. Moreover, the arrows should really be pointing in both directions; for example, the choice of machinery to serve speed and endurance reflects back on the volume required and the architecture of the ship which affects safety and structure. And so on. Quantification of the changes is effected by the choice of suitable computer programs. Downstream of this process lies design of systems to support each function but this, for the moment, is enough to distinguish between knowledge and application.

The authors have had to limit their work to presentation of the fundamentals of naval architecture and would expect readers to adopt whatever computer systems are available to them with a sound knowledge of their basis and frailties. The sequence of the chapters which follow has been chosen to build knowledge in a logical progression. The first thirteen chapters address elements of ship response to the environments likely to be met; Chapter 14 adds some of the major systems needed within the ship and Chapter 15 provides some discipline to the design process. The final chapter reflects upon some particular ship types showing how the application of the same general principles can lead to significantly different responses to an owner’s needs. A few worked examples are included to demonstrate that there is real purpose in understanding theoretical naval architecture.

The opportunity, afforded by the publication of a fifth edition, has been taken to extend the use of SI units throughout. The relationships between them and the old Imperial units, however, have been retained in the Introduction to assist those who have to deal with older ships whose particulars remain in the old units.

Care has been taken to avoid duplicating, as far as is possible, work that students will cover in other parts of the course; indeed, it is necessary to assume that knowledge in all subjects advances with progress through the book. The authors have tried to stimulate and hold the interest of students by careful arrangement of subject matter. Chapter 1 and the opening paragraphs of each succeeding chapter have been presented in somewhat lyrical terms in the hope that they convey to students some of the enthusiasm which the authors themselves feel for this fascinating subject. Naval architects need never fear that they will, during their careers, have to face the same problems, day after day. They will experience as wide a variety of sciences as are touched upon by any profession.

Before embarking on the book proper, it is necessary to comment on the units employed.

UNITS

In May 1965, the UK Government, in common with other governments, announced that Industry should move to the use of the metric system. At the same time, a rationalized set of metric units has been adopted internationally, following endorsement by the International Organization for Standardization using the Systême International d’Unitês (SI).

The adoption of SI units has been patchy in many countries while some have yet to change from their traditional positions.

In the following notes, the SI system of units is presented briefly; a fuller treatment appears in British Standard 5555. This book is written using SI units.

The SI is a rationalized selection of units in the metric system. It is a coherent system, i.e. the product or quotient of any two unit quantities in the system is the unit of the resultant quantity. The basic units are as follows:

Special names have been adopted for some of the derived SI units and these are listed below together with their unit symbols:

The following two tables list other derived units and the equivalent values of some UK units, respectively: