Chryssostomtdts 
not think this can be done, or done very easily. To remain with series 
60, the work of Vosser on the motions of this series is totally ignored, 
In fact, if I study the references I find something strange : a prepon- 
derance of them are from authors at M.I. T. Now 1am an alumnus of 
M.I. T. and am very proud of the work that is being done there but I 
think that the paper is a bit parochial and I have the feeling that it is 
essentially an advertising brochure for the work done there, 
DISCUSSION 
Raymond Vermter 
Naval Shtp Research and Development Center 
Bethesda, Maryland, U.S.A. 
This interesting paper represents a rather ambitious exten- 
sion of our normal ship design process and I should like to discuss 
several points made by the author and to advise some caution in the 
use of the procedure. First, the author states that for the particular 
example given in the paper, fully developed long crested sea spectra 
are used and that this simplification is not considered unrealistic, It 
would appear from some of yesterday's discussion regarding sea spec- 
tra, however, that this assumption is unrealistic, that the fully risen 
case is rarely realised and that swell forms an important component 
of most seaway forcing functions. That the consideration of swell is 
an important factor for the successful accomplishment of naval mis- 
sions has been painfully demonstrated to us at the Naval Ship Research 
and Development Center several times in the recent past and it is 
never accounted for through the use of standard spectra. It is suggest- 
ed that multi parameter direction spectral considerations are neces- 
sary for a valid design study of this type. 
One might also question the suggested number of iterations 
concerning the establishment of an EHP value for propeller selection 
and, even more generally, the real importance of power limitations 
as regards ship operation ina seaway. It has been our experience that 
naval ships are never power limited, but that power is voluntarily li- 
mited from a fear on the part of the captain that he will cause either 
personnel injury or structural damage if he drives his ship harder. 
Propeller design considerations for the Naval ship case involve pro- 
per blade stressing and vibration considerations for maximum power 
and cavitation free operations to as high a speed as possible, trading 
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