Seakeeptng Constderattons tn a Total Destgn Methodology 
The computer programs described in References 12 and 15 
employ a two parameter conformal representation for the hull sections. 
This has been found to be very satisfactory when compared to the 
close fit representation. Figure 7 from Reference 18 shows that the 
close fit representation approaches the results of the two parameter 
representation when the number of points employed in the close fit 
representation is increased (i.e. its accuracy is increased). However 
as the number of points is increased in the close fit representation 
the expense also increases and for 40 points it is prohibitive. The 
limitation of the two parameter fit is that all calculations are perform- 
ed with the transformed sections and not with the original sections. 
This however is not considered important because good two parameter 
description of regular sections and of sections with moderate bulbs is 
presently available. In addition moderate geometrical changes in the 
section shape do not affect the seakeeping results. In any case ifa 
section is to be described accurately in the close fit representation, 
especially bulb sections, a large number of points is necessary which 
make it prohibitively expensive. 
The expense for the use of seakeeping programs can be con- 
siderable especially if a complete investigation is to be made, In an 
attempt to overcome this limitation the authors of Reference 3 are 
extending the notion developed therein and are currently working ona 
scheme in which the Hydrodynamic properties of a section is stored 
in a matrix as a function of the two parameters describing the section, 
A and o , and the non-dimensional frequency 6 . Although the 
work is still underway, it is expected that a sparsely populated matrix 
will provide all the accuracy necessary in the second iteration of the 
proposed design methodology. This will permit the designer to perform 
the analysis suggested above at almost no cost at all. 
Before concluding this discussion the author wishes to take 
this opportunity to suggest research in the area of viscous roll damp- 
ing under speed and with bilge keels because the state of the art in this 
area is not satisfactory. 
fice hind Iteration 
In the final iteration the author suggests the use of seakeep- 
ing experiments for the selection of these parameters whose effect 
cannot be predicted by either models described above such as for 
example the above water hull shape. In addition these experiments can 
serve as a confirmation of the prediction made with the seakeeping 
computer programs especially in the areas where the theory is weak, 
for example in the prediction of power. The author recognises that 
seakeeping experiments are time consuming and expensive and there- 
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