Smith and Cummins 



Similarly the forward speed cases were good over the same frequency 

 range. There was, however, some evidence that coupling of surge into heave 

 and pitch was significant at forward speeds and indicates the desirability of a 

 three mode (pitch, heave and surge) analysis. The damping and added mass 

 terms are shown along with those reported by Gerritsma. 



CONCLUSIONS 



It is apparent from the preliminary results that good experimental results 

 can be obtained even at zero speed in a 240 by 360 ft tank. While wall effects do 

 occur, they appear only as one or two sharply defined discontinuities in the re- 

 sponse date.. The results also indicate that, while a two mode pitch and heave 

 test can be conducted, a further increase in accuracy should be obtained by an 

 extension to the three mode analysis. While there is much to be done, especially 

 in such areas as increasing the dynamic range of the instrumentation system 

 and an extension to a 3 or 4 mode analysis, it is felt that these preliminary re- 

 sults demonstrate not only the validity of the pulse testing technique but further 

 show that satisfactory results are witiiin the capability of modern instrumenta- 

 tion and measurement systems. 



! 



MODEL DETAILS 

 Series 60 Parent Form 



L Length between perpendiculars 10.0 ft 

 B Beam 1.35 ft 



H Draft 0.53 ft 



A Displacement 239.3 lb 

 Cb Block coefficient 0.60 



A Area of waterline plane 9.39 ft^ 



C^i Waterline coefficient 0.71 



Iq Mass moment of inertia for pitch (in air) 557.89 lb in. /sec ^ 

 r^ Radius of gyration 0.25 L 



m„ Mass of model 7.439 slugs 



456 



