Hadler and He eke r 



Denny Ship Model Basin was going to reactivate this system for a specific pro- 

 posal for India in 1963 and commence a new series of experiments in the light 

 of modern propeller design, when the firm's liquidation put an end to this pro- 

 posed program. 



DISCUSSION 



S. G. Bindel 



Bassin d'Essais des Carenes 



Paris, France 



When the submergence of a propeller is not sufficiently large, a ventilation 

 may occur when the ship is stopping, since the rotation of the propeller is re- 

 versed while the motion of the ship is still forward. This ventilation leads to a 

 decrease of the thrust, and thus to an increase in the stopping length. It is 

 speculated that this unfavorable effect may also be severe on the partially sub- 

 merged propeller. 



I should like to ask Mr. Hadler if tests were carried out to investigate these 

 unusual working conditions. 



DISCUSSION 



C. Kruppa 



Technische Universitdt 



Berlin, Germany 



I would like to congratulate the authors on the presentation of a paper that 

 undoubtedly will have to be looked upon as the first piece of fundamental informa- 

 tion on the performance of partially submerged high-speed propellers. I think 

 we all are aware of the fact that partially submerged propellers have been used 

 for some time in racing craft and record-breakers, and have performed more or 

 less successfully, due largely, no doubt, to the reduction of appendage drag. How- 

 ever, nobody has so far been able to quote efficiencies or account, on a rational 

 basis, for possible advantages that this type of propulsion device may offer under 

 certain circumstances. 



The authors have already outlined what they think should be done in the 

 future on a theoretical basis and experimentally, in order to arrive at a better 

 understanding of the hydrodynamic phenomena in partially submerged propellers 

 and to derive the basis for a design method, if possible. To their 10 recommen- 

 dations for future investigations, however, I would like to add a further one, which 



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