By raising the center of gravity and/or lowering the center of buoyancy, 

 we can make this difference negative and thereby possibly decrease this 

 natural frequency. However, in general, the exact amount by which such 

 adjustments will affect the natural frequency is not certain, since the de- 

 nominator in Equation [17b] will also be affected. In any case, reductions 

 in S(0) (for lo-wering the heave frequency) will also lower the pitch-surge 

 frequency. 



REFERENCES 



1. Newman, J.N., "The Motions of a Spar Buoy in Regular Waves, " 

 David Taylor Model Basin Report 1499 (in preparation). 



2 . Cummins, W . E. , "The Force and Moment on a Body in a Time- 

 Varying Potential Flow, " Journal of Ship Research, Vol. 1, No. 1 

 (Apr 1957), pp. 7-18. 



30 



