Model Tests on Contrarotating Propellers 



We agree with Dr. Morgan that for best performance the design of a contra- 

 rotating propeller set should be based on a particular application, as was still 

 the case in our contrarotating propeller investigations. However, for the deter- 

 mination of the optimum diameter or rpm of the contrarotating propeller sys- 

 tem, the results of open-water tests with a systematic series of contrarotating 

 propellers are very useful. 



With regard to Mr. Johnsson's comments it is interesting to note that for 

 the tanker and the cargo liner in the case of contrarotating propeller application 

 the relative rotative efficiencies were 1.050 and 1.065 respectively. These val- 

 ues are of the same order of magnitude as found by tests performed at the Naval 

 Ship Research and Development Center and at the Swedish State Shipbuilding Ex- 

 perimental Tank. 



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