Munk and Prohaska 



6ir 4'ir 2w 



RIGHT PROPELLER TURNING INWARD 



1 PROPELLER 



2 PROPELLERS 



Fig. 18 - Normal force curves for an in- 

 terlocking propeller working alone and in 

 combination with the other propeller 



6ir iir 2ir 

 NORMAL FORCE MEAN LINE 



Fig. 19 - Comparison between normal 

 force curves for the different propul- 

 sion systems 



1540 



