4 Wilson and VVestov, Torpedo-Boat Deslroyers. 



correct, and a continuous variation is secured between 

 them. The authors have, therefore, assumed that the 

 wave surface may be represented by a curve of sines, 

 and the boat is supposed to cross this surface at right 

 angles to the crest line of each wave, with a relative 

 velocity of v feet per second. 



It appears that the effect of the wave surface will be 

 worst when the wave-length is about the same as the 

 length of the boat, otherwise the vibration or deflection 

 of the boat from its horizontal centre line will be less, 

 although the pitching and tossing may or may not be 

 greater. When the wave-length is equal to the length of 

 the vessel and its depth equal to the (draught + free- 

 board) the maximum stress in the plates, at the middle 

 section of the vessel is given by the following expression : 



{ . nl . . nl \ 



„ . sin— + sinh 



/ ^^'J^A I ^^ 2 2 I _ 



dE Att'^ EI w'v- 1 . , «/ nl nl . hI\ ' 



,., sinh — cos— + cosh —sin — 



L- K ^ 2 2 2 2 J 



where 



\/\gEI U J 

 and 



/= maximum stress in the frame of the vessel. 



^= draught or freeboard. 



E = Young's modulus of elasticity for the structure. 

 7v ^- density of sea water. 

 w' = weight of the vessel per foot run. 

 /= maximum moment of inertia of cross section. 

 L - length of vessel. 



*When — is small, as it usually is for velocities up to 6o miles per hour. 

 2 



the term in the brackets reduces to 





24 . ■ 96.^ 



