further movement forward would result in excessively full entrance waterlines and probably 

 poor behavior and heavy speed loss in a seaway. 



It can be concluded that if the LCB location is chosen to give minimurri (c) values 

 and so minimum ehp, the dhp also will be practically a minimum except for the very fullest 

 models of the series. The charts given in Figures 31 and 32 can thus be used by the designer 

 with the knowledge tJiat, within practical limits, they will- lead to ship forms having both 

 minimum ehp and dhp in smooth water. 



The detailed results of the self-propelled experiments are given in Tables 27 to 31. 

 Cross plots of these data show a general waviness of character, associated with changes in 

 wake fraction w;^ consequent upon changes in wave formation with speed, but for a given full- 

 ness, both wake fraction and thrust deduction fraction tend to decrease as the LCB moves 

 forward, due to the progressive fining of the afterbody. As a result, the hull efficiency 

 remains fairly constant, although showing considerable variation due to the interplay of the 

 changes in w and t. The one exception to this pattern is the set of models of 0.80 Co, 

 where the value of w remains fairly constant with LCB m.ovement, but t decreases rapidly as 

 the LCB m.oves forward. As a result, the hull efficiency increases continually, and the 

 resultant increase in propulsive efficiency and decrease in dhp is the reason why this set 

 shows no optimum LCB location for minimum dhp within the range tested. 



VII-9 



