Munk and Prohaska 



NORMAL SINGLE SCREW P No. 6507 

 NORMAL TWIN SCREW P No. 5915 

 INTERL. PROPS. INW. DIST. 09 "0, P No 6137 



• OB «D, P No. 6137 

 . 0.7 «D, R No. 6137 



• Oj68«O.P No. 5915 



• 0.77 -D,P No. 5915 



• 0.68 «D.P No. 5915 

 MAIN PROP AUX.PROP SYSTEM P No. 6507 

 SMALLPROP • ■ • P No 6109 



Fig. 10 - Revolutions versus speed 

 for the propellers 



The rest of the difference between the wake for inward- and outward- 

 rotating interlocking propellers may be explained by the velocity diagrams for 

 a blade in the overlapping position, rotating inward and outward, as given in 

 Fig. 17. The figure shows that the induced velocity from one propeller is much 

 higher for the inward-rotating propeller and therefore the wake for the other 

 propeller is much reduced. 



This is in good accordance with the result of a comparison of the stress 

 curves for a propeller rotating inward and outward when it is working alone and 

 when the other propeller is also working. It can be seen from Fig. 18 that the 

 influence from the other propeller is much greater for an inward-rotating than 

 for an outward-rotating propeller. 



The results of the stress measurements on single- screw and on interlock- 

 ing propellers are scaled to the same mean normal force in Fig. 19 to show the 

 relative stress variations. The comparison is, however, not quite correct be- 

 cause the wake- scale effect is not taken into account and because the distance 

 between the shafts here is the smallest distance, and not the one which gave the 

 best propulsion result. 



1534 



