Propeller-Hull Interaction 



of (l/50)-th scale of the Victory ship up to the size normally used in a towing 

 tank — say, 23 ft — there is not too much wrong with the pattern. In fact, it is the 

 75-ft craft that really leads things astray. So he did not know whether a model 

 of that length would really solve the problems. We had a feeling that, if we built 

 it and spent a lot of money in testing it, when we were finished the experiments 

 we would feel the need to extend them to a full-scale ship. It's a question of 

 whether such an intermediate one is really worth the money. It is a remarkable 

 fact that in all the history of ship research there has never been a good and 

 comprehensive set of full-scale data. The nearest approach was the BSRA tests 

 on the Lucy Ashton, but although they gave probably the most reliable resistance 

 measurements ever made on a ship, the fact that the ship could not be propelled 

 meant that no information was obtained about scale effects on the propulsion 

 factors. The money that BSRA put into the Lucy Ashton provided an end spot on 

 a geosim series, but in fact all that was really obtained was a roughness allow- 

 ance for the Lucy Ashton with different hull surfaces, without any information on 

 propulsion problems. This is in strange contrast to the money that is spent on 

 other forms of transport, such as aircraft or hovercraft. It is strange that ever 

 since powered ships were built there has never been a single vessel devoted 

 solely to research, in which all the model tests could be repeated full scale. In- 

 stead, we have to put up with a few odd hours that some generous and forward- 

 looking shipowner is willing to provide. Perhaps the main lesson to be learned 

 from this panel discussion is the need for full-scale trials to investigate the 

 problems of propeller-hull interaction. 



Rader mentioned that in Germany they were in the fortunate position of hav- 

 ing a large research vessel, the Meteor. The ship is about 90 m long and, this 

 summer, wake surveys have been done, the ship being propelled by aircraft jet 

 engines on deck. The data will be presented at the autumn meeting of the S.T.G. 

 in Germany. Unfortunately, the vessel is relatively slow, but the trials should 

 provide some data about wake scale effect, thrust deduction, etc. Unfortunately, 

 the ship is mostly used by oceanographers. 



Dr. Todd said that again the tests were restricted to what can be done in the 

 time that is made available from the ship's other duties. Rader agreed, and said 

 that sometimes they had to wait two years before time was allocated to do trials 

 on the ship. Dr. Todd welcomed the good news that a research ship was avail- 

 able, even on an intermittent basis. Rader had said that if the panel had any sug- 

 gestions as to work that could be done with the Meteor, the people concerned 

 would be glad to see if they could be worked into the program. 



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