van Manen and Oosterveld 



Fig. 1 - Arrangement of contrarotating propellers 

 for a cargo liner model 



the cavitation characteristics, the propeller induced vibratory forces, and the 

 stopping abilities were dealt with. 



The investigations on contrarotating propellers were given in detail in Refs. 

 4 through 8; a recapitulation of the results is given here. 



TEST RESULTS WITH SYSTEMATIC SERIES 

 OF CONTRAROTATING PROPELLERS 



An important method of screw design is that which is based on the results 

 of open-water tests with systematically varied series of screw models [9,10]. 



According to the lifting line theory, as described in Ref. 11, a systematic 

 series of contrarotating propellers, consisting of a four-bladed forward propel- 

 ler and a five-bladed aft propeller, was designed. A problem which may occur 

 on contrarotating propellers is that the cavitating tip vortices generated by the 

 blades of the forward propeller may impinge on the blades of the aft propeller 



136 



