470 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 66.7 



of the fuel will have been consumed by then, 

 bringing the ship up in the water by the order of a 

 foot or so. The ship drops to a deeper draft in 

 the fresh water of the river at Port Correo, and 

 ample clearance must be left over the river bed, 

 which has a minimum depth of 30 ft. It appears 

 necessary, at least at this stage of the design, to 

 limit the draft in salt water to a maximum of 26 ft. 

 This draft then corresponds to the maximum 

 designed service load being carried when leaving 

 Port Correo. From Table 66.d, first hne, and from 

 the first weight estimate, the consumable-store 

 weight is only 400 t at this time, compared to the 

 700 t which the ship must carry when fully 

 stocked at Port Amalo. 



For the 515-ft ship the beam Bx at the maxi- 

 mum-area section is then 



£x = 



Ax ^ 1,896 

 Cx{Hx) " (0.96)26 



= 75.96 ft. 



is not too large but it increases as fuel is consumed 

 during the voyage. 



The large beam will undoubtedly give all the 

 square moment of area required in the designed 

 waterplane for transverse metacentric stability. 

 Indeed, it may give too much for easy rolling. 

 Almost certainly it will involve additional pressure 

 resistance from wavemaking, due to the cor- 

 respondingly large waterline slopes and the pres- 

 sure disturbances set up around the wide ship. 

 This matter is brought up again, a little later in 

 the design. 



Working through the procedure described, for a 

 ship 525 ft long on the waterline, with a Cp of 0.62, 



Ax = 



Br = 



¥ 



_ 605,500 

 L{Cp) 525(0.62) 



= 1,860 ft' 



CxiHx) 



1,860 

 (0.96)26 



= 74.52 ft 



= 7.05 Bx/Hx = 



= 2.866 



This is quite large for a seagoing ship only 515 ft 



long. The length-beam ratio is small, namely L/Bx = 



515/75.96 = 6.78. The beam-draft ratio is rather 



large, equal to 75.96/26 = 2.92. The latter ratio This 525-ft length gives considerably better pro- 



525 

 74.52 



74.52 

 26 



400 500 600 700 



Waterline Length, ft 



100 125 150 175 200 225 



800 



Waterline Lenalh, meters 

 Fig. 66.E Plot of Length-Beam Ratio and Beam on Ship Length 



275 300 325 350 



