Sec. 60.13 



SHIP-POWERING DATA 



TABLE 60.C— (Continued) 



381 



chant vessels of normal form is represented by a 

 nearly straight meanline. It is almost certain that, 

 for the general case, including vessels of large 

 fatness ratio, there is no such simple relationship 

 between these quantities. The plot would then 

 reduce to a series of merit-factor groups for a 

 number of ship types, each of which would lie 

 within a relatively narrow range of fatness ratio. 

 One such group would cover tankers, for example; 

 another group tugs, and so on. 



Regardless of the exact nature of the plot, a 

 really useful diagram would give by inspection 

 an average value of the merit factor M for a 

 given type of ship or a certain minimum value 

 which should be bettered in any new design. 



When the quantities in Eq. (34.xxiv) are in 

 the units generally employed by English-speaking 

 marine architects the weight displacement W is 

 in long tons of 2,240 lb, the ship speed is in kt, 



and the shaft power Pg is in English horses. 

 Inserting the necessary factors in Eq. (34.xxiv) 

 to suit the pound-foot-second system, it takes 

 the dimensional form 



M 



^ [" 2,240(1.6889)' ] 

 L 550(32.174) J 



0.61 



)0(32.174) 



UW in tons)(Finkt)' "| 

 L(L in it){Ps in horses) J 



LP, 



(34.XXV) 



If the displacement weight is in kips of 1,000 

 lb, to avoid confusion as to the kind of tons 

 employed, then 



,000(1. 6889)' "|r (iy in kips)(F in kt)' ! 



M = 



'[' 



= 0.2723 



550(32.174) 



_{L in ft) (Ps in horses) J 



LPs 



