98 * A STUDY OF THE WAKE OF CERTAIN MODELS 
of floor and will be connected more or less intimately with the height of center of gravity of 
wetted surface. 
The lower the center of gravity of the wetted surface the stronger will be the wake near 
the keel. A large part of the wetted surface is below the upper turn of the bilge. In full 
vessels this portion of the wetted surface may constitute from 0.5 to 0.65 of the total. In 
the dead flat alone the surface will be from 0.25 to 0.33 of the total. 
The curve for Model 6 in Fig. 27 shows that as the stern gets more box-like there will 
be a region of high wake near the keel. As the virtual rise of floor increases this point of 
maximum wake is higher. In Model 6 a maximum occurs at about 0.2 of the draught, in 
Model 5 at about 0.48 of the draught, in Model 3 at about 0.55 of the draught. 
While this variation of wake along a vertical plane through the center line of the model 
is most marked when the small meter wheel is used, it also exists when the larger wheels 
are used. The curves of wake values for Models 1, 2, 3, and 5 are sufficiently complete to 
enable the wake to be obtained for identical conditions in the above models. 
Let B = breadth of model. 
H = draught of model. 
E = elevation of center of meter wheel above keel. 
D = diameter of wheel. 
Let the identical conditions be: 
= 2.31. = 0.76. = 0:39. 
These are close approximations to the conditions that will exist in ordinary cargo vessels 
when loaded. 
Table IV shows the results obtained from cross curves. 
TABLE IV. 
B DE PO ea 
H = 2.31 WT 8:48 H 7 9:39- 
= : 5 
Diam Elev. of | 
of meter | : 
Draught area above Wake | Run | G, Prism. 
H keel ESSE | Cs coef. of 
D E engt after body 
Ins Ins. Ins %o | 
Model 1....... 6.94 5.28 2.7 18.7 50 728 616 
2 7.74 5.88 3.02 21.5 47 835 712 
3 7.34 5.58 2.85 31.7 376 904 792 
5 jae ec 5.375 2.75 | 88.0 30 -919 .807 
| gation on 6.81 5.18 PATS, |e 2G o77 Nee SPY 967 .818 
| | | 
Fig. 26 shows the wake values given in Table IV plotted upon the longitudinal pris- 
matic coefficients of the whole body, and of the after body, and also upon the vertical pris- 
Cs 
WL 
use for plotting the wake values for single-screw vessels of full form. 
matic coefficient of the whole body, * The latter seems to be a better quantity to 
