Spc. 66.1 



STEPS IN PRELIMINARY DESIGN 



"050 Q60 0.70 080 090 TOO TiO (lo 130 i40 [50 160 ITO 

 Taylor Quotient Tt{ or Speed-Length Quotient WC 



Fig. 66.D Gkaph for Normal Values of Maximum-Section Coefficient Cv 



50 200 2 II 



they are indicated by the upper branch of the Cx 

 lane 



(2) Those designed to travel fast for their length, 

 but for which a relatively large beam is a necessity, 

 to afford stability, internal volume, deck space, 

 and the like. They are indicated by the lower 

 branch of the lane. Examples are fishing vessels, 

 ferryboats, tugs, minesweepers, yachts, and small 

 freight vessels. In fact, for these types the Cx 

 values may drop well below the lower limits of 

 the plot of Fig. 66. D, approaching 0.50 or 0.40 

 [Simpson, D. S., SNAME, 1951, p. 569]. The 

 branch lane for these low values contains no 

 optimum line, because there appears to be little 

 or nothing systematic about the Cx values in this 

 region. 



If the ship is required to have the largest 

 practicable volume for a given set of principal 

 dimensions, as for cargo vessels which must pass 

 through locks, the midsection is made as full as 

 operating clearances permit. This may give a Cx 

 of 0.995 or more, used on Great Lakes freighters. 

 Since practically all vessels are drydocked or 

 hauled out periodically, certain clearances may 

 be required for these operations. 



The best structural connection between the 

 bottom and the side along the middle portion of 

 a ship huU calls for a curved plate at the corner. 



However, these corners have been formed by 

 what may be termed large-scale chamfering, 

 using two chines with about 45-deg angles, as in 

 the straight-element section shape sketched at 1 

 in Fig. 21. k. On vessels built for some European 

 rivers, and on towed steel barges built a half- 

 century ago for service on the Erie Canal, the 

 lower hull corners are made by structural angles, 

 applied outside the side and bottom plating, with 

 a bilge radius of practically zero [Nixon, L., 

 SNAME, 1896, p. 20 and PI. 19]. 



Since the ABC ship is to give good performance 

 in the shallow and restricted waters of the Port 

 Amalo canal and the river below Port Correo, 

 there must be plenty of room for the water to 

 pass around the ship, especially under it. This 

 means that the maximum-section coefScient Cx , 

 or the midsection coefficient Cm , should not exceed 

 about 0.96, on the basis of a midsection of normal 

 form. With a displacement volume of 605,500 ft^ 

 and a waterline length of 515 ft, for the middle- 

 length ship of the three mentioned in Sec. 66.5, 

 the maximum-section area Ax for a prismatic 

 coefficient Cp of 0.62 is 



Ax = 



L(Cp) 



605,500 

 515(0.62) 



1,896 ft" 



The minimum depth of channel out of Port 

 Amalo is 28 ft but between one-third and one-half 



