Prediction of Ship Slamming at Sea 



jPi/3 = J P f(P) dp. (A.22) 



Pl/3 



From Eqs. (A. 19), (A.21) and (A.22) the average of the highest one-third 

 values becomes 



Pi/ 3 = p, + 2CR: (l - log |-) 



= 2C Ir^ + 2.10 R:\ . (A.23) 



Similarly, the average of the highest one-tenth values is 

 Pi/ 10 = P* + 2CR: (l - log ^ 



2C fr' + 3.30 r: ] . (A.24) 



DISCUSSION 



G. Aertssen 



University of Gent 



Gent, Belgium 



The first look at this paper gives the impression that it is a remarkable 

 example of the truncated exponential probability law applied to the study of 

 slamming and deck wetness from model results. Were it not that there is much 

 more in it for the naval architect it would not have deserved much attention. 



There is a difficulty in carrying out slamming experiments on models be- 

 cause the rigidity of the model cannot be easily scaled up to the rigidity of the 

 ship. Giving the relation impact pressure, relative velocity, the author however 

 gives — I think for the first time — the means to correlate his model results with 

 full scale. His threshold velocity is 12 ft/sec and if I modify this value, ac- 

 cording to the Froude scaling law, to a cargo ship of 480 ft I obtain a threshold 

 velocity of 11.5 ft/sec which according to the author's relation transforms to 

 our impact pressure of 11 psi. I am interested in this cargo ship of 480 ft be- 

 cause last winter 1 made a westbound crossing of the North Atlantic in very se- 

 vere weather on board such a ship which was instrumented by the Centre Beige 

 de Recherches Navales. There were on board a shipborne wave recorder, 

 strain gages, ship motion recorders, 2 pressure transducers in the keelplate, 



589 



