Lang 



MOTION IN WAVES 



During the 1969 towing tests, various S 3 model configurat- 

 ions were tested in 4-inch X 80-inch waves in head and following 

 seas. The non-dimensional pitch and heave amplitudes for two S 3 

 models in head seas are shown in Figure 12 together with the pitch 

 and heave amplitudes of a 5 -foot model of a C-4 monohull ship. 

 Note that the motion of the S 3 models is significantly less than that 

 of the monohull model. The S models were also tested in a 

 variety of wave lengths, and no resonance was found in head seas. 



The test results in following waves showed significantly more 

 motion, as seen in Figure 13. The monohull was not tested in follow- 

 ing waves. The wave height was equal to the hull diameters, so the 

 waves were relatively high. Tests in 2-inch waves showed consi- 

 derably less motion. Data taken on the lift force and pitching moment 

 indicated that small control surfaces and an automatic control sys- 

 tem would significantly reduce motion in following seas. 



Tests at rest in beam seas showed that the roll of the S 

 models was significantly less than that of the monohull model, and 

 no resonance occurred at any of the wavelengths tested. 



AUTOMATIC CONTROL SYSTEM 



The combined use of horizontal canard control fins near the 

 noses of the hulls, and controllable stabilizing fins near the aft end 

 of the hulls, provides motion control over heave, pitch and roll in 

 high sea states. 



Figure 14 presents computer results obtained by Dr D. T. 

 Higdon of NUC showing the reduction of heave and pitch in head 

 waves which is achievable by automatic stabilization of an S 

 ship similar in shape to the radio-controlled model of Figure 10. 

 The already small motions are reduced by a factor of four or more. 



Figure 15 shows the computer results for motion reduction 

 in following waves. In this case, the result is much more dramatic. 

 Heave is reduced by factors of twenty or more, and pitch is reduced 

 by factors of five to ten. 



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