Panel Discussion 



In the second part of my introduction to the panel discussion, I should like 

 to emphasize some points with respect to the requirements already mentioned, 

 i.e., _ ■ .■...-.,; .^ .,,.,. ■ . .- -.^ 



1. selection of optimum diameter and rpm from the viewpoint of efficiency; 



2. cavitation criteria, based on systematic experimental data; ••-, 



3. the effect of cavitation on propeller -excited vibratory forces; 



4o data for analyzing stopping maneuvers; vj • 



5. variations of propeller load in a seaway; 



6. the effect of rpm variations on the interaction between rudder and 

 propeller. 



In Fig. 1 the effect of rpm on the efficiency has been illustrated by the re- 

 sult of a number of calculations for a 16-knot tanker with a 30,000-hp propul- 

 sion machinery. The calculations have been carried out both for conventional 

 four- and seven-bladed screw propellers and for ducted propellers. Some con- 

 clusions can be drawn from this figure: 



S 08 



< 



Ul 



K 



< 

 -I 



CD 



ai 



02 

 BAR 







20 



- 10 



SO 100 150 



NUMBER OF RPM 



Fig. 1 - Effect of rpm on screw diameter 

 and efficiency of a single -screw tanker 

 having an engine power of 30,000 DHP 

 and a speed of 16 knots 



1575 



