Performance of Partially Submerged Propellers 



Fig. 5 - Drawing of propeller 3820 



3768, a geosim of Model 3767, the most thoroughly tested of all the supercavi- 

 tating propellers available at the Center, was used. 



The experiments in this phase were carried out somewhat differently, as 

 the effect of speed of advance upon performance was an objective. Hence, the 

 tests were run at a constant forward velocity, and the rpm's were varied. This 

 limited the lowest advance coefficient to the maximum torque attainable with the 

 propulsion dynamometer and removed the problem of the wave train at low ad- 

 vance coefficients. Table 2 lists the conditions tested. During these tests visual 

 observations were made of the flow variations. 



In order to minimize the effect of the elliptical fairwater on performance, 

 it was replaced by a 60° cone. This seemed to help in reducing the thickness of 

 the film of water. 



1457 



