Lewis 



N 



.06 



.05 _ 



04 



)qooo 



.Ol 



O 





V 



L= 600' 



u- 3ocy 



j—L 



SvA\p 5pee"o - Knots 



25" 



Fig. 4 - Bending moment for series 60 ships in Pierson 62-knot 

 spectrum as a function of speed (highest expected value of h /L 

 in 10,000 cycles) ^ 



dominant waves, i.e., of the wind. The calculated bending moments are the re- 

 sult of superimposing the ship's response to all wave components present for 

 each heading. 



The effect on wave bending moment of ship heading is shown in Fig. 5 for 

 ships of 600-foot length in both short and long-crested seas, corresponding to 

 the 62-knot spectrum [11]. This figure indicates that maximum bending mo- 

 ments are reached in head seas, as expected, and are then less in realistic 

 short- crested than in hypothetical long-crested seas. It also shows the reduc- 

 tion in bending moments in beam seas is comparatively small when the waves 

 are short-crested, especially for fine ships. 



198 



