Castagneto and Maioli 



DISCUSSION 



Wm. B. Morgan 



Naval Ship Research and Development Center 



Washington, D.C. 



I would like to emphasize the authors' remarks concerning the NACA a = 1.0 

 and the NACA a = 0.8 mean lines. It is our experience at NSRDC that the theory 

 for design of moderately loaded propellers is adequate provided that certain 

 important steps are made. 



(1) The NACA a = 0.8 load distribution is used and not the constant load 

 distribution, because due to viscosity the a = 1.0 distribution cannot be realized 

 in practice. 



(2) Lifting-surface corrections from modern computer programs are 

 used. These correction factors must include a camber correction, an ideal 

 angle of attack correction, an angle correction for skew (if used), and an angle 

 of attack correction for thickness. 



A paper presenting extensive tables of correction factors will be presented 

 at the 1968 Annual Meeting of the Society of Naval Architects and Marine Engi- 

 neers. 



DISCUSSION 



C. Kruppa 



Technische Universitat 



Berlin, Germany 



I would like to supplement the data on foil section characteristics presented 

 by the authors, and refer to some hitherto unpublished work which I carried out 

 in the Vosper cavitation tunnel (Portsmouth, England), some years ago. The 

 main scope of this work was to assess the cavitation- free angle of attack (or lift 

 coefficient) ranges of two-dimensional foil sections, consisting of elliptic- 

 parabolic thickness distributions, cambered with the NACA a = 1.0 mean line. In 

 total, eight different foil sections were tested, covering thickness -chord ratios 

 0.03 < t/c < 0.12 and design lift coefficients < c^ . < 0.56. The work was 

 sponsored by the British Admiralty. Copies of the report should be obtainable 

 through AEW-Haslar by referring to Vosper Report No. 115 ("Methodical Cavita- 

 tion Tests on Blade Sections— Three Component Factors and Cavitation Pat- 

 terns"). 



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