It can be seen that at very low and very high frequencies the nonlinearities can be 

 neglected. At low frequencies this is due to the smallness of B^, while at high frequencies 

 the magnification factor is insensitive to large changes in damping. However, in the vicinity 

 of resonance, the neglect of the nonlinear damping could result in a serious over-estimate of 

 the motions particularly if the amplitudes of heaving motion are large. 



Thus it is apparent that the neglect of nonlinear features of the equations of motion 

 may lead to erroneous motion predictions. Furthermore, this is far from the complete picture 

 since pitching experiments may indicate additional significant nonlinear elements. 



28 



