96 A STUDY OF THE WAKE OF CERTAIN MODELS 
TABLE II. 
Total resist. = Frict. resist. | 
Length | Draught 
Naked With bossing 
V V V V 
Ft. Ins. = 5 | = =_8 | = |= =, 
Nr NL NL NL § 
Model aera 10.0 6.96 1.21 ae WA eee ciine alles SO 
Pere ere tcc 10.0 pr) L321 IBADAN PO le nerntey ee 
Ossie heer 10.4 6.81 1.25 1.29 1.25 1.32 
PO Fas ey 10.5 6.58 1.31 1.41 1.31 1.41 
Osa ete 10.0 7.07 1.35 1.40 1.32 1.38 
Gn: 10.1 7.0 1.75 1.83 1.61 1.69 
longitudinal distribution of displacement. Model 6 (see Fig. 24) was more or less of a 
monstrosity; the shape of sections was bad and the length of run was so short that the driv- 
ing qualities of the model were materially improved by the addition of bossing. This was true 
to a less degree of Model 5, while Model 4 was on the ragged edge. 
The results of wake tests upon Model 1 are shown in Figs. 6, 7, 8, and 9, Plate 31. 
The wake was searched with a 2.75-inch wheel at three different heights and at three trans- 
verse positions, and the results are shown in Fig. 6. This figure shows the line which the 
center of the meter wheel must follow for constant wake value. The horizontal and vertical 
scales are not the same, so that the lines appear flatter than they should. The lines rise 
at an angle of about 45 degrees. The wake of Model 1130c was searched in the same way 
and the results for this fuller model were of the same general character, the lines of constant 
wake values rising a little more sharply. 
Figs. 11, 12, and 13, Plate 32, give the reults of tests upon Model 2. Models 1 and 2 
were not tested with bossing. 
Model 3 was tested with three sizes of meter wheels at three draughts and three heights 
of meter wheel above keel for the single-screw condition, but at only two heights above keel 
for the bossed condition. It will be noticed in Figs. 15, 16, and 17, Plate 33, that for 
the same immersion of center of meter wheel the wake will vary, depending upon whether the 
draught is constant with position of meter wheel varied vertically relative to keel, or whether 
the draught is varied with the meter wheel at a fixed height above the keel. The wake is 
much more constant in the latter case. The full lines are for the single-screw condition, and 
the broken lines are for the twin-screw condition with bossing. When the meter wheel is 
on the center line the general effect of bossing is to decrease the wake, the decrease being 
considerable in the case of the small wheel, but it does not-amount to much in the case of the 
large wheel. 
When the wheel is out from the center line the wake in the bossed condition is greater 
than when there is no bossing, and the difference is not affected much by the change of 
diameter. 
In general the effect of bossing seems to be to even up the wake, making it less at the 
center line than in the single-screw condition and greater in the way of the bossing. 
