Johns son and Stfntvedt 



DISCUSSION 



Edmund V. Telfer 

 R.I.N. A. 



Ewellj, Surrey , U.K. 



I had the privilege in the spring of discussing Mr Johnsson's 

 paper before the Institution of Naval Architects and I went into the 

 history of such fins, and there is no need for me to go into that again. 

 All I would like to ask on this occasion is this : granted that the real 

 effect of the fins in minimising cavitation vibration must emanate from 

 the starboard fin and not the port fin, has the author tested everything 

 he has done so far for both fins also only with the starboard fin in po- 

 sition ? I feel that is where the progress is to be made, and I would 

 suggest that the port fin is quite unnecessary. I should like to have 

 the author's reaction to that suggestion. 



REPLY TO DISCUSSION 



Carl-Anders Johns son 



Statens Skeppsprovningsanstalt 

 Goteborg, Sweden 



In connection with the project, no single fin version has been 

 tested and I do not think we have ever used that concept. Of course it 

 is an interesting idea, but maybe we will lose one of the merits of the 

 fin, that is the propulsion merit. Of course, the main effect of the 

 fins, in this case at least, was that they reduced separation and accor 

 dingly, in the model test at least, more than compensated for the in- 

 crease in frictional resistance. Probably that effect will not be so 

 complete if we have only one fin, but from the research point of view 

 it is a good idea and should be tried. 



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