Savitsky 3 Roper 3 and Benen 



Effect of Trim Angle on Hydrodynamic Impact : 



The hydrodynamic impact load is linearly dependent upon trim 

 angl& so that, within the range of data acquisition, a 50% reduction 

 in trim angle (from 4° to 2°) results in a 50% reduction in hydro- 

 dynamic impact load. The reference trim angle is the smooth water 

 running trim of the craft for the considered hull dimensions, loadings, 

 and speed. 



Effect of Deadrise Angle on Hydrodynamic Impact : 



The accelerations decrease linearly with increasing deadrise 

 so that a 50% reduction is achieved by increasing the deadrise from 

 10° to 30°. 



In order of importance, then, impact loads in a seaway can 

 be reduced by providing a hull having a narrow beam, a low running 

 trim angle, and a high deadrise. As will be subsequently developed, 

 this results in as long and narrow a hull as can be accepted without 

 seriously compromising other essential operational conditions. 



Relation Between Beam and Trim Angle to Achieve (v nr .)~ = 0. 4g : 



v>(^r av g 



Considering an initial deadrise angle of 20°, the relations 

 between beam and trim angle to achieve ( ^ qq) av „ = 0. 4g can be 

 established. The following tabulation follows from TTigure 4. 



(1) Average value for range of L/B as given in Figure 4. 



426 



