Chryssostomidis 
present study is lower (0.69 vs. 0.75) than the one suggested in 
Reference 5 . The reason is that in the present analysis the design 
point for the propeller corresponds to a heavier load condition than 
the one used in Reference 5 . It is also of interest to point out that 
because the design point of both propellers of this study is well to the 
left of the peak of the efficiency curve, there was no need to make 
any special provisions to assure efficient operation in light loads as 
this is achieved automatically. 
11.4. Analysis of the Results. Conclusions and Recommendations 
From the results of the previous section it can be seen that 
seakeeping considerations should be incorporated in preliminary 
design as they affect the ship's speed and hence its profit earning ca- 
pability and/or ability to perform its mission, It is recommended that 
seakeeping considerations be included when speed (SHP,) is a va- 
riable in the optimization scheme. This is not so much because of the 
variation of added resistance with speed for a given ship but because 
of the importance of motion limitations above a certain speed, Itis 
also recommended that seakeeping considerations be incorporated in 
preliminary design optimization schemes when large differences 
exist among the alternatives investigated, as is the case with ships 
A and B of the previous section, because their seakeeping perfor- 
mance is different. 
The results also suggest that when optimization does not in- 
volve large changes in the principal characteristics of the different 
alternatives considered, as in the case of ships with constant payload, 
then seakeeping considerations should not be included in the optimiza - 
tion scheme because they are not expected to influence the final de- 
cision, It should be emphasized however, that this is not to be inter- 
preted that seakeeping considerations are not to be included in preli- 
minary design of such ships. On the contrary they should be included 
because it is only then that the designer can predict with confidence 
the speed (and hence profit) of his ship in the actual operating environ- 
ment, 
The optimization criterion to be used in conjunction with the 
model proposed in the present study must include profit considerations. 
This is so because speed and payload are variable and therefore mi- 
nimum cost solutions are not necessarily synonymous with the ''best" 
solution, 
Comparison with published results show that the speed re- 
duction from motion considerations is underpredicted, see Ref. 14. 
This is not because unrealistic motion indices were adopted but rather 
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