Fully Cavitating Propeller for a Hydrofoil Ship 



Fig. 15 



Torque comparison — effect of thickened 

 leading edges — screw T95 



in Ref. 11, such that the section cambers comprised about one-third circular- 

 arc camber and two-thirds 3-term camber. Since the geometric incidence of 

 the chord of the two-dimensional 3-term section is close to zero, no pitch ad- 

 justment was made when installing this camber. The modified screw was desig- 

 nated W264 and is shown in Fig. 17, while the results obtained with it are given 

 in Figs. 18, 19, and 20. The improvements obtained with the W264 as compared 

 with the W257 are quite large, giving approximately 17 percent more thrust at a 

 considerably higher efficiency in the flying condition, with attendant improve- 

 ments in the takeoff condition. 



The ship will be fully operational in the 200-ton load condition with screws 

 made to the W257 design. A speed of 60 knots will be attainable in the calm 

 water condition, while adequate thrusts are also available in the higher resist- 

 ance conditions when operating in high sea states at speeds up to 50 knots, and 

 with a towing load at lower speeds. The improvements offered by screws ac- 

 cording to the W264 design are mainly in additional thrust margins at the higher 

 loads and increased range through the higher efficiency. 



A typical fully cavitating propeller model of the type fitted to the Bras d'Or 

 is shown in Fig, 21 operating at simulated high speed in the No. 2 water tunnel 

 at NPL. 



981 



