The models tested were a 6.42-ft model of a destroyer escort, a 5-ft model of the Series 

 60 parent form of 0.60 block coefficient,^ and a 5-ft model of the cargo ship M/S SAN 

 FRANCISCO. The ship lines are shown in Figures 1 through 3 and the form characteristics 

 are listed in Table 1. 



TABLE 1 

 Characteristics of Ship Forms 



Characteristics 



Destroyer Escort 



Series 60 



M/S SAN FRANCISCO 



Model Number 



4369 



4509 



3572-5A 



Length L^p, ft 



308 



400 



429 



Beam B, ft 



36.7 



53.33 



59 



Full Load 









Draft Amidships, 









//, ft 



11.5 



21.33 



24.37 



Corresponding 









Displacement A, tons 



1802 



7807 



13,264.4 



Block Coefficient, C^ 



0.50 



0.60 



0.75 



Design Speed, knots 



25 



17 



14 



The lines of the ships selected for the work represent a considerable range in ship form. The 

 destroyer escort has fine lines and a low block coefficient (Cj, = 0.50), the SAN FRANCISCO 

 has full lines with a block coefficient of 0.75, and the Series 60 is between the above two 

 extremes with a block coefficient of 0.60. 



The models were ballasted for displacement and draft conditions corresponding to that 

 listed in Table 1 for the ships. The radius of gyration determined by the bifilar method was 

 25 percent of the length for each of the models. The dimensionless natural periods associated 

 with these radii of gyration are listed in Table 2. 



TABLE 2 



T 

 Dimensionless Natural Periods t = — t — 



Ship 



Natural Pitching 

 Period 



Natural Heaving 

 Period 



Destroyer Escort 



Series 60 



M/S SAN FRANCISCO 



1.39 

 1.77 

 1.93 



1.34 

 1.77 

 1.88 



