70 DESCRIPTION AND TRIAL OF THE 
DISCUSSION. 
Mr. Ernest H. B. ANpErson, Member:—I should like to make a few remarks regard- 
ing the design of this yacht. As Secretary Cox points out, she is a remarkable vessel in 
‘many ways, and the designers and builders deserve the greatest praise. 
As regards the machinery, the aim of the builders was to produce an installation com- 
bining extreme simplicity and ruggedness without sacrificing, in any way, essential features. 
Few auxiliaries are actually needed for propelling the vessel; the circulating water from 
the sea for condensing the exhaust steam is forced through the condenser by scoop circula- 
tion, which eliminates this pump and its engine when the vessel is under way. The two forced 
draft blowers are arranged in series which effects a considerable saving in steam consump- 
tion; the usual practice in vessels of similar type is to have live steam connections to each 
blower, so the saving in steam is approximately one-half. 
The reason for the two-hour trial run in the open sea at approximately 20 knots was 
to determine the cruising radius of the vessel at this speed, and I think the result showed that 
she could steam about 2,000 knots at this speed with the quantity of oil fuel which the 
tanks hold. 
The simplicity of the machinery design has also resulted in a large saving in weight, 
and I think the value of the paper would be greatly enhanced if these figures are available, 
for it would then be possible to give figures of shaft horse-power developed per ton of ma- 
chinery. Again, a plan view in outline showing the arrangement of the engine and boiler 
rooms would also be of much value, as the general arrangement plan of the vessel shows no 
machinery in these compartments. 
LizuTENANT S. M. Rosrnson, U. S. Navy, Member (Communicated) :—The following 
table has been made out for the Winchester using the data given by Mr. Stevens, and in it the 
revolutions have been calculated by using the ac ual instead of the estimated horse-powers. This 
table shows that up to 28 knots there is practically no error in the revolutions. From 28 
knots on up to the highest power reached, the error is constantly increasing. If the values 
f e.h.p. 
E.H.P. 
in cavitation after the 28-knot point was reached. At 3114 knots the cavitation was consid- 
erable. 
The equation for the revolutions will not hold with the same accuracy for a propeller 
cavitating that it will for a propeller working under normal conditions. In fact, if cavita- 
tion is serious, the equation will not hold within the reasonable limit desired. 
As regards the difference in estimated and actual horse-power, the same phenomenon 
is found in this high-speed boat that has been found in some of the destroyers. They seem 
to have an abnormal wake which increases the effective horse-power of the hull when it is 
being towed, but also increases the propulsive coefficient and consequently reduces the neces- 
sary shaft horse-power when the boat is being propelled by its screws. 
0 
and = are plotted on the cavitation chart, it will be seen that the propeller was 
