Panel Discussion 



shapes were different, showed that there was practically no change in hull effi- 

 ciency as the LCB moved forward, while in a third model the hull efficiency 

 decreased slightly. All these models were analyzed in the same way and 

 Lackenby believed that the changes are essentially an effect of the ship form 

 and the propeller interaction. 



Dr. Todd recalled that in the analysis of the Series- 60 models some pe- 

 culiar shapes were found for some of these propulsion factor curves, which it 

 was not possible to explain in a logical way. 



J. Leaper (Admiralty Research Laboratory, Teddington, England) said that 

 this propeller-hull interaction was not his specialty, but until Dr. Morgan spoke 

 he had been very surprised by the complete absence of any mention of attempts 

 to predict these factors theoretically, because it would seem that such a capa- 

 bility would be useful in itself and could possibly give an understanding of scale 

 effects at the same time. The panel would be interested to know that at ARL 

 one of his colleagues had started a program to compare theoretical predictions 

 of hull efficiency elements with experimental measurements. Initially these 

 experiments deal with a series of axisymmetrical hulls and behind the hull he 

 has a simulated propulsion unit. He can also vary the actual spacing between 

 hull and propulsor. This work is going to be done in a large wind tunnel, and 

 he is going to measure drag, pressure distribution on the hull, pressure distri- 

 bution on his simulated propulsor, and the mass flow through the propulsor. 

 The measurements will be made on quite a series of hull shapes that have been 

 theoretically derived. Some account will also be taken of the viscous effects 

 and the boundary layer. The hope is that if these experiments on a wide range 

 of body shapes give good agreement with theory, then an effort will be made to 

 extend the theory to the case of the nonaxisymmetric body. Even if the theory 

 is not confirmed, the work should show in what respect it is deficient, and in 

 any case it will give a fairly large amount of systematic data. 



Dr. Schmiechen said that the last speaker mentioned that naval architects 

 had never considered the case of the theoretical prediction of t. He disagreed, 

 and pointed out that a lot of work in this field had been done by the Berlin School 

 under Professor Horn and Professor Dickman, and then by Professor Amtsberg 

 and his pupils, the last work appearing from this school being that by Novaki. 

 This research has covered a great many of the problems previously mentioned. 

 Dr. Todd also pointed out that a great deal of work had been done on this sub- 

 ject by many people. A number of problems had been uncovered in the discus- 

 sion, and a number of suggestions had been made as to what might be done to 

 solve some of them in the future. He believed that at the ATTC Meeting in 

 Ottawa in June a proposal was discussed to build an 80-ft craft ~ call it a model 

 or a ship — in order to get some line on the scale effect on wake and thrust de- 

 duction and other propulsion factors. Such a proposal has been discussed many 

 times at Taylor Model Basin and by BSRA, but it has never got far because of 

 expense. Dr. Todd said he had been one of the people who have for years advo- 

 cated such full-scale trials, but he did not feel enthusiastic about an 80-ft model 

 because he believed at the end it would still be necessary to run a fairly large 

 ship. A 72 -ft Victory model had been made at Wageningen and a 75-ft model of 

 a tanker in Germany, and although they extended the geosim range quite appre- 

 ciably, they probably created as many or more problems than they solved. In 

 the Wageningen work, for instance, considering the range from the small models 



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