THE INFLUENCE OF FREEBOARD 

 ON WETNESS 



G. J. Goodrich 



National Physical Laboratory 

 Teddington, England 



ABSTRACT 



Model experiments in regular waves and probability theory have been 

 used to predict the probability of occurrence of wetness at the fore- 

 end of a ship of given type. Calculations made for ships of different 

 fullness have suggested that the frequency of occurrence of wetness 

 varies with block coefficient as well as with length for a given free- 

 board ratio. 



INTRODUCTION 



The prediction of the probability of occurrence of wetness from model ex- 

 periments in regular waves has been attempted by Newton [1] using statistical 

 sea data to represent full scale conditions. Newton's work suggested that for a 

 given freeboard ratio a 200 ft ship would be drier than say a 400 ft ship under 

 North Atlantic conditions. This general conclusion seemed contrary to what 

 would be expected and consideration was given to the possibility of using model 

 data and probability theory to predict the probability of occurrence of wetness 

 for ships of different fullness and length. 



The intention of the present paper is not to provide detailed design informa- 

 tion but to indicate a method of analysis which could be used for specific design 

 studies and to show the trend of the variation of wetness with ship length and 

 block coefficient. 



WETNESS DEFINITION 



When considering the prediction of the probability of occurrence of wetness 

 it is sufficient to say that if the motion of the bow relative to the water surface 

 is such that the water rises above the deck level at the fore end, then the prob- 

 ability of wetness exists. No attempt is made to say how wet the deck will be, 

 nor to what height the water will rise above the deck. 



597 



