Page 40 - Practical Ship Design

Introduction. Methods and Datu 11

Whilst it is still early days in the development of expert systems, a 1990
R.I.N.A. paper “The application of an expert system to ship concept design
investigations” by Welsh, Buxton and Hills gives a good idea both of the way to set
up such a system and of the advantages that can stem from its use. In the paper, the
design of a container ship was taken as an example and it is interesting to note the
wealth of information about containers that was assembled from shipping company
experts, going well beyond what a naval architect could expect to know and which
could in principle have major design implications. It was salutary to note that the
knowledge base contained around 7000 lines of statements.
The author thinks he would have enjoyed writing, or contributing to the writing
of an expert system but unfortunately has never had the opportunity to do so. He
believes that this book contains data and formulae that can provide a substantial
contribution to ship design expert systems for a variety of ship types.

1.2.3 Use of spreadsheets

Although the use of programs in which all the data is input by the user, and all the
formulae involved are standard naval architecture (like most of the programs
discussed in $1.2.4.) can be unreservedly recommended, it may be wise to have
some reservations about programs which use stored data and algorithms that are
not known and approved by the user.
Spreadsheets present an easy way of using a computer for a wide variety of tasks
without having to write or purchase special-purpose programs. One advantage of
using a spreadsheet is that a user will generally write the program himself and will
therefore know exactly what formulae are included in his calculations and what
confidence can be given to the answers.
In writing this book, the author made considerable use of spreadsheets, a
number of which are included in the text.

1. In the next section of this chapter spreadsheets have been used to marshal
data on dimensional relationships, deadweightldisplacement ratios and
capacity/volume relationships, all of which are required in Chapter 3.
2. In Chapter 4 a spreadsheet format is used for a calculation sheet for initial
design.
3. In Chapters 6 and 7 spreadsheets are used for various aspects of powering:
to convert Ci F or C ITTC to Ct ITTC57 or Ct ITTC78;
to calculate (1 + K) using Holtrop and Mennen’s formula;
to calculate (1 + K) using a modified Prohaska method.
4. In Chapter 12 a sheet for dredger spill-out calculations is given.