94 A STUDY OF THE WAKE OF CERTAIN MODELS 
the case of Model 6. In the fine models the wake showed a slight tendency at times to de- 
crease as the speed increased. In the full models the wake was constant up to 200 feet 
per minute, but at higher speeds there was often a marked increase in the wake, due probably 
to the position of the stern wave. 
Previous papers dealing with the subject of wake have pointed out that the value of the 
wake will vary with the diameter of the wheel used, with the fore and aft position, and with 
the transverse position of the wheel. In this paper attention is called particularly to the effect 
upon the wake of variation in the immersion of the wheel, whether by changing draught 
with fixed position of wheel relative to keel or by changing the position of the wheel relative 
to the keel with the draught fixed. Attention is also called to the effect of variation in the 
form of the model. 
Results are given for a 10-foot varnished wooden plane, for a series of four wax 
models with constant length of entrance and varying length of run (see Model 1130), for 
a series of five wax models with constant length of run and varying length of entrance (see 
Model 1131), and for six wax models with no family relation (see Models 1, 2, 3, 4, 5, 6). 
The characteristics of the various models dealt with are given in Table I. 
In the 1130 series the meter wheels were 2.75 inches, 3.75 inches, and 5 inches in diam- 
eter. Tests were made at two draughts with the wheels on the center line only. 
In the 1131 series the wake was measured with wheels 3.75 inches, 4.5 inches, and 5.375 
inches diameter, at one draught only, but with the wheels on the center line and also 2.75 
inches off the center line. Certain of the models were tested with the wheel centers 1.75 
inches up from the keel, and certain others with the wheels 2.75 inches up. 
The models of the 1131 series were somewhat finer than those of the 1130 series, but 
it would appear from Figs. 2 and 4, Plate 30, that variations in the length of entrance do not 
produce as much change in the wake values as variations in the length of run. 
The lines of the 1130 and 1131 series were upon the whole quite good, especially the 
1131 series. The 1130 models had V-shaped stern sections and medium how sections. The 
1131 series was based upon the 1130 series (see Proceedings of Naval Architects and Ma- 
rine Engineers of 1921) and had the combination of bow and stern section shape which 
seemed to give the best results, namely, V-shaped bow sections and somewhat U-shaped 
stern sections. A glance at Figs. 1 and 3, Plate 30, will show the difference in section 
shape. The full lines in the body plans are stern sections and the broken lines are bow sec- 
tions. The numerals on each section indicate the number of inches from the section to the 
nearest perpendicular. 
Fig. 1 gives the location of sections for Model 1130c; the stern sections were closer to 
the aft perpendicular in Models a and 6, and more widely spaced in Model d. 
Fig. 3 gives the location of sections for Model 11316, while the bow sections of Model 
a were closer to the forward perpendicular, and in Models c, d, and e were more widely 
spaced. 
The difference in the shape of the stern sections, and the smaller beam- -draught ratio in 
the case of 1130 models probably accounts for the wake values being lower for this series than 
for the 1131 series. The sharper sections aft in Model 1130 kept the wake water with the 
greatest forward velocity farther away fromthe meter wheels than in the case of Models 
1131, even though the meter wheels were the same distance from the keel. 
Models 1, 2, 3, 4, 5, and 6 were of varying degrees of excellence as regards shape of 
