Hydrofoil Motions in a Random Seaway 

 ^''ic.g. = j [^ - "'(1 + u)] dt , 



(43) 



h^ = the change in water height from datum at the foil (Note: l\^, is given 

 in space coordinates and has to be resolved into craft coordinates), 



6 = pitch angle of the boat, and 



= roll angle of the boat. 



"ttSm^ 





Note: for small angles the following assumptions can be made 

 Sin ^«( ^ radians 

 Cos jt «t \'0 



Figure (iii) 



The expression for angle of attack is basically the differential of the above 

 equation. 



a = % + (w^ - x^ + y.^ - w^ cos 0) 



= a + (w - xfii + y0 - wj 



o d 



(44) 



for fixed forward velocity. 



621 



