Page 31 - Practical Ship Design

2 Chapter I

a number of other factors in his mind at one time so that he can synthesise a ship
concept which both in its main dimensions and in its general arrangement satisfies
or comes close to satisfying all these requirements.
If he can do this successfully from the start of a project, he will greatly reduce the
time and effort required to produce a design. If he fails to do so the design is likely to
require major changes as it is developed and detailed calculations can be made.
Once an initial design has been completed, each facet of it must of course be
tested using the appropriate rigorous scientific naval architectural methods, but in
the author’s view it is ponderous and time wasting to apply these methods whilst
the initial design is still being developed, although it must be admitted that the use
of computers has opened the door to the possibility of making detailed calculations
much earlier in the design process than used to be possible.
To give one example of the way in which thinking ahead can greatly reduce
design effort: the development of an outline design in which the stability is
satisfactory, or nearly so, need not necessitate detailed stability calculations at the
initial design stage (when the all-important weights are in any case likely to have a
considerable margin of error) but can instead be reasonably assured by choosing a
ratio of beaddepth which experience has shown will result in satisfactory stability.
Similar thinking can ensure that a design, almost from its inception, is such that
no really nasty surprises in strength or powering will be found when it is subjected
to the detailed scientific examination that comes at a later stage.

1.1.2 Reader’s background knowledge

This book makes no attempt to teach scientific naval architecture and it is assumed
that professional naval architects will bring a well developed background know-
ledge of naval architecture to their reading and use of the book.
Ships are, however, a fascinating subject and reading this book should not be
too difficult for anyone interested in learning how they are designed. Lay readers
will want to skip those parts that invoke terms with which they are unfamiliar, but
should still find much that is intelligible to them and be able to see why ship
designers find their profession so absorbingly interesting.

1.1.3 Scope in terms of ship types

This book covers the design of a wide range of monohull displacement ship types,
but this needs to be set in the context of the even wider range of marine vehicles
shown in Fig. 1.1. These range from surface skimming vessels, through displace-
ment ships and semi-submersibles, whose main buoyancy is well under the water
surface, to wholly submerged submarines.