86 THE APPLICATION OF DYSON’S METHOD 
The various problems may be divided into three groups: (1) Single-screw vessels; (2) 
vessels fitted with two or more screws, the wing screws being carried in struts; (3) vessels 
fitted with two or more screws, the wing screws being carried in bosses or spectacle frames. 
GRoupP l. 
Problem 1, Plate 20.—The ship used in this problem is the S. S. Gulfprince, the trials 
of which were described by Mr. H. A. Everett in his paper entitled “Power and Speed 
Trials of Ten Thousand Deadweight-Ton Tanker,” which was published in last year’s volume 
of the transactions of this society. It will be noticed that the actual power is less than the 
calculated at the higher speeds, while at the lower speeds the reverse is the case. As the 
after body is quite long, the value of K is probably less than that shown on the chart, while 
the increase in actual power of the lower speeds in relation to that calculated is undoubtedly 
due to the falling off of the mechanical efficiency of the engine at the lower powers. 
Problem 2, Plate 20.—As this model had never been tested in the tank, no effective horse- 
power curves were available. The revolutions estimated (by using the indicated horse-power 
developed on the trial) compare favorably with those obtained on the trial. Calculations 
were then made for the effective horse-power which also compare favorably with an esti- 
mated effective horse-power obtained by using Taylor’s method. The resistance per ton of 
displacement was taken from a ship of the following dimensions: L. B. P., 380; beam, 53; 
draught, 24; displacement, 10,900 tons; block coefficient, 0.79; M. S. coefficient, 0.988. 
Problem 3, Plate 21.—This ship was fitted with geared turbines. Unfortunately, no 
torsion meter was installed, but the shaft horse-power was estimated from curves supplied 
by the manufacturer of the turbine. The vessel was first run on a twelve-hour trial, during 
which the following were the average pressures and temperatures: 
Pressurevat throttles. 3 suey micysaciencls seer eer Torn 186 lbs. gauge. 
Pressurerat MoZZlesh asst a thay caguionns eee ence ee ae nner 182 lbs. gauge. 
Stipenlicat ts Beye caters ave hobo ese: scence cutie icc che eee as Not given. 
Wemperature at exhaustys sae accsn miss aches Gack c Qa eene ee Oe Oo IR 
Wacuumrcorrespondinento GO: Sekar srt els a ee ere 28.3. 
SHA PS Er Ome neve see eta gees oo Aste Maas latin blew taps aie eae 2,500. 
Progressive runs were then made over the Provincetown course with the following 
results : 
Speed in Knots R. P. M. 
6.355 50, 075 
8.055 64.05 
9.511 74.00 
11.447 89.37 
From this the speed on the twelve-hour run was estimated to be 11.38 knots. 
It will be noticed that while the R. P. M. on the trial practically agree with the analysis, 
there is quite some difference in the horse-power. This might be explained by the fact that, 
the propeller being a cast-iron wheel, the roughness of its surface added at least 2 to 3 per 
cent to the power, while the remainder may be due to a slight inaccuracy of the gauges and 
