Sec. 66.18 



STEPS IN PRELIMINARY DESIGN 



483 



TABLE 66.g — First Statement op Variable Draft 

 The variations from the designed maximum service load are taken from the last column of Table 66. f. The sinkage 

 value for fresh water is reckoned constant, at its maximum value. 



(b) Extent {Lp/L) and position of any parallel 

 middlebody to be used. Normally the midlength 

 of the parallel middlebody is at the fore-and-aft 

 position selected for the maximum-area section. 



55 50 45 40 55 



Percentaqe of Ship Lenqth from FP 



Fig. 66.L Longitudinal Position of Section of 



Maximum Area LMA, or of Midlength of 



Parallel Middlebody 



(c) Forward-perpendicular area ratio /b and 

 terminal value ^e of any bulb bow to be incor- 

 porated 



(d) Area ratio f r of any submerged transom to 

 be embodied in the design. 



In 1930 S. A. Vincent published a design lane 

 giving the best location for the position of the 

 section of maximum area, or for midlength of 

 the parallel middlebody, in a range of T^ values 

 less than 1.00, F„ < 0.298 [MESA, Mar 1930, p. 

 135]. This has since been revised with his assist- 

 ance. Fig. 66.L gives the new lane, widened at 

 low C/.'s and narrowed at high Cp's. As for other 

 lanes of this type, a designer need not remain 

 between the fences if there are good and sufficient 

 reasons for going outside. 



For the ABC ship, with a Cp of 0.62, an 

 optimum position of the maximum-area section 

 is about 0.0 15L a baft midlength of the DWL. 

 The value of LMA is then 0.515L. 



66.18 Parallel Middlebody. The next step is 

 to determine whether or not any parallel middle- 

 body is to be incorporated in the hull. If so, its 

 extent (amount) and fore-and-aft position are 



