High-Speed Planing Hull for Rough Water 



The length L is load waterline length and is taken to be 

 equal to 1. 10 L^ . It has been found that this relation between L 

 and Lfc is most satisfactory. If L is less than 10% greater than 

 L^ , there is substantial bow immersion at high speed resulting in a 

 significant increase in smooth water resistance. When L is much 

 larger than 1. 10 L^ , the excessive hull length forward of L^ pro- 

 vides additional impact area when running in a seaway with resultant 

 increasing impact loads. 



Also included in the previous tabulation are the correspond- 

 ing values of block coefficient C-o and slenderness ratio L/v 1 / 3 

 These will be subsequently discussed. 



Smooth Water Operation (Low Speeds) 



Since one of the operational objectives for the craft is to 

 cruise at 12 knots for extended periods, the hydrodynamic resist- 

 ance should be minimized. For a displacement of 150, 000 lbs. , the 

 volume Froude number 



gv 



20.4 



v4 



32.2 x(2350) 



173 



= 1.0 



From a basic study of the resistance of planing hulls in the 

 prehump speed region (Reference 6 ), it has been found that low 

 speed resistance is primarily dependent upon slenderness ratio 

 L/v 1 /3 . Figure 7 of this report shows the variation of resistance- 

 weight ratio of the Series 62 hull form (Reference 7 ) as a function 

 of L/v 1 / 3 for F = 1. 0. It is seen that, although the data points 

 represent a wide range of hull loadings and length-beam ratios, they 



429 



