Unusual Two-Propeller Arrangements 



which may be assumed to be nearly constant. The stress, consequently, in the 

 first approximation is proportional to the normal force. The normal force is a 

 function of the inflow velocity vector, which is the vector sum of the ship speed, 

 the circumferential velocity, and the wake speed. Only the last is not constant. 

 Therefore, the variation of the curves gives an impression of the variation of 

 the wake during one revolution. 



TEST RESULTS 



The results of the test series are given graphically in Figs. 5 through 12. 



Figures 5 through 9 give the required propeller horsepower for the tested 

 propulsion systems as a fimction of the ship speed, and the corresponding num- 

 bers of revolutions are given in Fig. 10. 



NORMAL SINGIE SCREW P No. 6507 



— "- NORMAL TWIN SCREW P No.5915 ,/ J 



- • — INTERL.PROPSOUTW. DIST 077- D.P Na5915 /f / 



AUXPROP SYSTEM TOTAL PHP P Nos. 6507,6109 /// 



Fig. 5 - Comparison between the required 

 propeller horsepowers for the different 

 propeller arrangements 



1529 



