LOADS ACTING ON A SHIP AND THE ELASTIC RESPONSE OF A SHIP 



281 



2 3 4 



Speed of Model (m/sec) 



Wave Length 7.GG7m. Height 200mm 



Location of Strain Meter SS 



( 150 mm Forward from Midship) 



' Bending Moment 

 • Heaving 



o On Upper Deck (Center Line) 



n On Upper Deck (Starboard) 



A On Keel (Right Side of Center Girder) 



— — — Pitching 

 Fig. 30 An example of results of ships moving in waves showing effect of speed; wave height and length constant (from Sato, 1951) 



Table 8 



Measured Computed 



BM, BM, 



ft-lb ft-lb 



At zero speed 4.15 3.40 



At 2.53 fps (ship 



12.2 knots) 4.27 3.80 



Ratio: 



measured 



computed 



1.22 



1.12 



realize that this practice may give an unrealistic picture 

 of a ship's behavior within practically attainable operat- 

 ing conditions. It can be recommended that in all ship- 

 model tests in waves a clear distinction be made between 

 the conditions practically attainable and the exaggerated 

 conditions. 



The difficulty in following the foregoing recommenda- 

 tion lies in the scarcity of information on the limiting 

 speed of ships at sea in adverse conditions, lor the 

 particular case of destroyers, considered in the two 

 preceding sections, some information is available from 

 the trials of three destroyers of the Royal Netherlands 

 Navy described by Szebehely (195G) and Warnsinck and 

 St. Denis (3-1957). These are preliminary and very in- 

 complete descriptions. Sea conditions unfortunately 

 were recorded only by visual observations. However, 



Fig. 31 



Destroyer body plan, ETT Model 1723 (from Lewis 

 and Dalzell, 1957) 



