Munk and Prohaska 



PHP Propeller horsepower 



C. Additional resistance coefficient 



A 



REFERENCES 



1. Pien, P.C., and Str^im-Tejsen, J., "A Proposed New Stern Arrangement," 

 Naval Ship Research and Development Center, Washington, D.C., Report 

 2410, May 1967 



2. Prohaska, C.W., "Analysis of Ship Model Experiments and Prediction of 

 Ship Performance," Hydro- and Aerodynamics Laboratory, Lyngby, 

 Denmark, Report Hy-1, Dec. 1960 



APPENDIX A 

 FURTHER TESTS WITH INTERLOCKING PROPELLERS 



A supplementary test with outward- rotating interlocking propellers with a 

 distance between the shafts of about 0.9 • D was carried out after the comple- 

 tion of the paper, and the results are given in Fig. Al (refer to Fig. 7). 



The results confirm that a distance between the shafts of about 0.8 -D 

 still gives the lowest propeller horsepower at the service speed. 



Supplementary stress measurements were also carried out for outward- 

 rotating propellers with a distance between the shafts of about 0.8 • D and 0.9 • D. 

 The results at service speed were nearly the same as earlier found for a dis- 

 tance of 0.7 • D. At zero speed, the stress variations proved to be smaller, and 

 thus can be judged as of no importance. 



APPENDIX B 

 OVERLAPPING PROPELLERS 



Test No. 18 with interlocking propellers, which gave the lowest propeller 

 horsepower, was repeated with the propellers placed clear of each other, in 

 longitudinal direction. The distance between the propeller shafts was about 

 0.8 • D and the longitudinal distance about 0.2 • D. The shafts were still coupled 

 together and the propellers therefore ran at the same number of revolutions. 



This modification of the arrangement did not give rise to any measurable 

 difference in the total horsepower. The wake coefficient for the forward pro- 

 peller was increased by 0.06, and for the aft propeller decreased by 0.04. The 



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