Performance of Partially Submerged Propellers 



J = 0.75 



•*iil#fj 



Fig. 26 - Photographs of propeller 

 3768 partially submerged 



submergence tested, and that for estimating purposes it would be possible to 

 make a tentative prediction of the performance at any submergence based upon 

 the results of tests at one submergence. 



It was noted in comparing the efficiency curve of Propellers 3767 and 3768 at 

 the semisubmerged condition that the efficiency of 3768 was somewhat higher. 

 This was because the test speeds of 3767 were quite low; thus, the base drag of 

 the blade sections was relatively high. 



The collapse for the two tests conducted on Propeller 3820 is not as good 

 but the region of greatest variation is the low Cj' 's where the small amount of 

 data that exist are of questionable accuracy and where there is a fairly large 

 base-drag component. The coincidences demonstrated from Propellers 3767, 

 3768, and 3820 do not hold for 4002. It may be noted that the test data are 



1477 



