846 



HYDRODYNAMICS IN SHIP DESIGN 



Sec. 77.25 



77.25 Design Check on a Basis of Chine Di- 

 mensions. Despite the logical nature of the pro- 

 cedure and the various design data given in 

 Sec. 77.17, based upon the chine dimensions, 

 proportions, and position, there are insufficient 

 background and reference data to enable a new 

 planing craft to be laid out on a basis solely of 

 the chine dimensions and characteristics. It is 

 nevertheless useful at this point to ascertain how 

 the characteristics already determined for the 

 ABC tender compare ^\'ith the available chine 

 data plotted by E. P. Clement ["Hull Form of 

 Stepless Planing Boats," SNAME, Ches. Sect., 

 12 Jan 1955; also TMB Rep. 1093, Nov 1956]. 



There are listed in Table 77. f the principal 

 dimensions and characteristics of the ABC 

 planing-form tender, derived by the methods 

 described in the sections preceding. Included in 

 the table are some of the ratios used as parameters 

 by Clement, based upon the actual dimensions 

 of the craft whose lines are depicted in Fig. 77. K. 



As a check of these dimensions and ratios with 

 the data given by Clement in the reference cited. 

 Figs. 77. M and 77. N have been adapted from his 

 Plates 12 and 13, with necessary changes to 

 standard notation. Using the tentative total 

 weight of 19,000 lb for the full-planing tender, 

 Fig. 77. M is entered along the bottom scale and 

 a value of the ratio Lc/Bc of 3.86 is taken from 

 the meanline shown. With a fore-and-aft chine 

 length Lc of 36.35 ft from Table 77.f, the mean 

 chine beam Be = 36.35/3.86 = 9.417 ft. 



With the Lc/Bc ratio of 3.86, Fig. 77.N is 

 entered along the bottom scale and a ratio of 



12 16 20 24 28 32 36 40 44 48 52 56 



I I I I I I.I I I I I 



D.iaplocement, met 



Adopted from 

 E.P Clement,' Hull 

 Form of Stepless 

 Ploninc) Boats,* 

 5NAME, Ches.Sect 

 l2Jan I955,PI. 12 



^1 



1000 to 



:t 



o Motor Yachts 

 • PT Boots, 



World Worll 



10 20 30 40 50 60 70 80 90 100 110 120 

 Bisplocement, l<ip», or thousands cff pounds 



Fig. 77. M Vaeiation op Chine Ratio Lc/Bc 

 With Displacement 

 The dimension Lc is the projeoted length of the chine 

 and Be is the mean width of the projected chine planform. 

 The displacement corresponds to the buoyancy volume 

 with the boat at rest. The solid line represents a tentative 

 meanline for the data plotted here. 



Ac/V^^^ of 0.3 is taken from the meanline. The 

 value of ¥''' from Table 77.f is 44.484 ft'; Ac is 

 found to be 413.7 ft'. This is considerably larger 

 than the projected area of the chine, 334.6 ft', 

 of the actual boat of Fig. 77. K. If this larger 

 value of A c is divided by the actual chine length, 

 the mean chine beam Be is found to be 413.7/36.65 

 or 11.29 ft. If, on the other hand, this larger area 

 is used in combination with the Lc/Bc ratio of 

 3.86, the fore-and-aft chine length comes out as 

 39.96 ft. 



TABLE 77.f Chine Chabacteristics and Other Features of Proposed Fuli^Planing Tender fob ABC Ship 

 The principal dimensions, characteristics, and other data listed here are for the craft whose lines are shown in Fig. 77.K. 



V = 296.7 ft' in standard salt water 



Ax = 10.56 ft" 



Le = 0.57LwL , from FP to section of maximum area 



LoA = 38.0 ft 



LwL = 35.0 ft 



Lc of chine = 36.35 ft 



W = 19,000 lb 



A = 8.482 long tons 



T, = V/VL = 24/V35 



= 4.057 

 A/(0.010L)' = 197.8 



Ratios Based upon the Chine Dimensions: 

 Ac/Vi' = 334.6/44.484 = 7.522 



Be mean, over chines, = Ac/Lc = 334.6/36.35 = 9.205 ft 

 Ratio of Weight W /{Brake Power Pb at designed speed) = 19,000/430(est.) 

 Weight TF/(Brake Power Pb) = 19,000/450 (to be installed) = 42.22 

 Center of projected area of chine, Ac , Ues at 0.532LirL abaft the FP 

 Rise of floor at midlength of Lwl = 18.25 deg; at AP = 3.75 deg 

 LCB = 0.5ML^L or 20.79 ft abaft the FP 



LCG is assumed to be in the same fore-and-aft position, corresponding to 3.29 ft abaft midlength of the designed waterline 

 or 14.21 ft forward of the AP. 



4jf of at-rest waterline = 281.9 ft- 

 Ac of chine, projeoted, = 334.6 ft^ 

 ¥'!' = 6.6696 ft 

 F2/3 = 44.484 ft^ 



Le/Be = 36.35/9.205 = 3.949 



44.19 



