Fully Cavitating Propeller for a Hydrofoil Ship 



> 20,000 



10,000 



0-6 0-7 08 



RADIUS FRACTfON 



Fig. 33 - Values of maximum and minimum tensile prin- 

 cipal stresses, typical takeoff conditions — screw T95 



stress at the 20 percent chord position and that the 65 to 70 percent propeller 

 radius arises primarily because of the local bending of the leading edge, then in 

 accordance with the simple beam theory the stress may be taken as inversely 

 proportional to the blade thickness squared. A correction to account for the 

 difference in the thickness of the two blades can then be made by multiplying the 

 T95 stresses by a value of 0.7. This then approximates to the stresses that 

 would be experienced in the T95 blades if the thickness at 20 percent chord 

 were made the same as that used in the De Havilland test. Applying this cor- 

 rection reduces the T95 stress to about 19,000 lbf/in2 compared with 22,000 

 Ibf/in^ from the static loading tests. 



In a similar manner, if the takeoff condition is taken as that occurring at an 

 advance coefficient of 0.4 in Fig. 33, then a stress of 33,000 Ibf/in^ results when 



1001 



