* 



0.5 

 0.4 

 0.3 

 0.2 

 0.1 





 0.6 



0.5 



0.4 



0.3 



0.2 



0.1 





















Wave Length = 360"- 















































































Wove Length =480". 

























■v 







/^" 









— - 



















15 20 5 



Ship Speed in knots 



20 





















Wave Length = 600 ft. 



















^** "" 



--" 



'" 









^sf 























































s 





Wave Length = 720" 



• 











^.-"'^ 











- 























L 



Without F 

 With Fins 



1 



egend 











1 1 



15 20 5 



Ship Speed in knots 



10 



20 



Figure 9 - Experimental Heave Amplitude Asa Function of Wave Height 



POINT OF MINIMUM VERTICAL MOTION (Figure 11) 



The location of the point of minimum vertical motion, (apparent pitching axis), 2 was 

 computed from experimental values of heave, pitch, and their phase relationship. In such 

 computations sinusoidal ship motion was assumed. Sinusoidal motion was verified to the ex- 

 tent that the pitch and heave amplitudes obtained directly from the gyroscope and potenti- 

 ometer were within 5 percent of the values computed from the sum and differences of the 

 instantaneous accelerations of two equi-distant points fore and aft of the LCG. As the pitch 

 and heave amplitudes are linear with wave height, the point of minimum motion is independent 

 of wave steepness within the range of the tests. 



VERTICAL MOTION AND ACCELERATION (Figures 12a through 13d) 



The amplitude of the vertical motion and the acceleration of any point along the length 

 of the ship were computed from experimental values of heave, pitch, and their phase relation- 

 ship. Sinusoidal ship motion was assumed. The amplitude of the vertical motion or accel- 

 eration of any given point along the length of the ship is linear with wave height at constant 



speed and wave iength. 



(Text continued on page 23.) 



13 



