Davis and English 



Fig. 14 - Thrust comparison — effect of thickened 

 leading edges--screw T95 



affecting the performance. These results suggest that for screws with circular - 

 arc faces, at least, there should be no difficulty in installing sufficient material 

 in the leading edges to secure structural integrity without seriously impairing 

 the efficiency. 



Since screw T95 is untypical of the Bras d'Or requirements with respect to 

 blade sweepback and hub size and shape, it was considered desirable and expe- 

 dient to confirm the effect of increasing camber and leading edge thickness on a 

 typical screw before proceeding to the final screw design. This was done by 

 simply modifying an existing screw. The blade faces were recut to provide the 

 increased camber and the backs were thickened over the leading edge region 

 with solder, giving a leading edge thickness of one-half percent chord. The ad- 

 ditional camber was provided in the form of a Johnson 3-term camber as given 



980 



