278 



THEORY OF SEAKEEPING 



FWL 



EWL 



DWL 



CWL 



BWL 



AWL 



1 WL 



2 WL 



3WL 

 35WL 



4 WL 

 45WL 



5 WL 



5iWL 



5B 



4B 3B ZB IB ^B ^B IB 2B 38 4B SB 



Fig. 27 Body plan and particulars of a destroyer model (from Sato, 1951) 



ing and heaving are similar to sinusoidal curves. The 

 amplitudes of the curves increase in proportion to wave 

 height. 



"2 The strain curves show a disturbance with in- 

 crease in ship speed. Vibrational strain is observed 

 at both ship deck and bottom in the section near amid- 

 .sliips after a heavy blow is delivered to the bottom.'' 

 It was ascertained that the frequency of the vibrational 

 strain coincided with the natural frequency of two-noded 

 fle.xural vibration." 



" Considering the sharpness of the V-bottom and the sudden- 

 ness of the flare development at the deck, the present author 

 believes that the "blows" were delivered to the flare. 



4.4 Lewis and Dalzell — Destroyer Model. Lewis 



and Dalzell (1958) reported on experiments with a 

 destroyer model. The body plan is shown in Fig. 31 

 and the particulars are given in Table 6. The model 

 arrangement was similar to the one E. V. Lewis had 

 used on the T-2 tanker and which was described in Sec- 

 tion 4.1 except that the shear force as well as the bending 

 moment was measured. The following data were re- 

 corded simultaneouslj' on an oscillograph tape: pitch, 

 heave, surge (or alternately A^ertical bow acceleration), 

 wave, bending moment, and shear force. 



The measured amplitudes of hogging and sagging 

 bending moments are plotted against speed in Fig. 32. 

 As in Sato's experiments, a pronounced increase of the 



