van Manen and Oosterveld 



9, Manen, J.D. van, "Fundamentals of Ship Resistance and Propulsion; Part B, 

 Propulsion," Intern. Shipb. Progr., 1967 



10. "Principles of Naval Architecture," Society of Naval Architects and Marine 

 Engineers, New York, 1967 



11. Manen, J.D. van, and Sentie, A., "Contra-rotating Propellers," Trans. I.N.A., 

 1956; Intern, Shipb. Progr., 1956 



12. Manen, J.D. van, "The Choice of the Propeller," Marine Technology, 1966 



13. Lammeren, W.P.A. van, "Testing Screw Propellers in a Cavitation Tunnel 

 with Controllable Velocity Distribution over the Screw Disc," Trans. SNAME, 

 1955; Intern. Shipb. Progr., 1955 



14. Manen, J.D. van, "On the Usefulness of a Test with a Propeller Model in a 

 Cavitation Tunnel with a Simulated Non-uniform Flow," Symposium on Test- 

 ing Techniques in Ship Cavitation Research, Trondheim 1967; Intern. Shipb. 

 Progr., 1967 



15. Wereldsma, J., "Some Aspects of the Research on Propeller-Induced Vibra- 

 tions," Intern. Shipb. Progr., 1967 



16. Jaeger, H.E., "Le freinage de grands navires (V) correlation entre navire 

 et modele en ce qui concerne 1' arret par le propulseur," ATMA, 1967 



DISCUSSION 



Hans B. Lindgren 



Swedish State Shipbuilding Experimental Tank 



G'dteborg, Sweden 



This paper is very similar to the paper I will present in the final session on 

 Friday with C. A. Johnson and G. Dyne as coauthors. Unfortunately the paper 

 has not been available in printed version so that we could have made any quanti- 

 tative comparisons. As our paper has been available for a long time, it would 

 be interesting to know if the authors have made such a comparison. With regard 

 to Mr. Oosterveld's presentation I should like to ask two questions. 



First, Mr. Oosterveld mentioned that there is a danger that the tip vortex 

 cavity of the forward propeller causes erosion on the aft propeller. He also 

 mentioned that this could be avoided by decreasing the diameter of the aft pro- 

 peller in relation to the forward. I should like to know how big a decrease has 

 been adopted and if the result was satisfying. At the Swedish State Shipbuilding 

 Experimental Tank we use in our theoretical design method the hypothesis that 



162 



