CYGNET SAIL PLAN—DESIGNED BY TAMS, LEMOJNE & CRANE FOR ARNOLD LAWSON, 1901. 
expansion engines at corresponding speeds, for in the 
case of a reciprocating engine efficiency is very slightly 
affected by changes of speed. 
This loss of efficiency at low speeds is admitted eyen 
by Parsons himself, and it is stated that in the design 
of the newest torpedo boat destroyer to be fitted with 
turbines, supplementary reciprocating engines are to be in- 
stalled for driving the boat at low speeds. 
There is one point on which there is absolutely no com- 
;parison between turbine and engine, and that is the mat- 
■ter of vibration. With a turbine there is no vibration 
whatever, and, as in place of the fifty or more different 
ibearings on a reciprocating engine, we have only two in 
the turbine; the cost of repairs and maintenance is as i to 
25 in favor of the turbine. 
Having made this brief comparison, it will be interest- 
ing to see how the fundamental differences affect the ap- 
plication of turbines to marine propulsion. To sum up: 
Our turbine must revolve certainly five times as fast as a 
reciprocating engine of the same power. It is inefficient 
except at one speed. It cannot reverse. 
In its favor: There is practically no vibration. There 
is a very marked saving in weight and space. 
Let us briefly analyze the advantages : 
The saving in weight is from 5 to 7lbs. per indicated 
horse-power, but this is a saving which applies to the 
engine alone. The boiler and auxiliary machinery, such 
as pumps, piping, condenser, etc., in the case of the very 
high speed boats would weigh about 3olbs. per indicated 
horse-power. This would be the same whether we used 
turbine or engine. The coal to be carried would be the 
same, or nearly the same, in case both, boats were always 
run at their full designed speed. At the slower speeds we 
.should need to carry 10 to 25 per cent, more coal on a 
l)oat driven by turbines than one driven by reciprocating 
^engines in order to go the same distance. 
In the case of the high-speed boat, the machinery would 
weigh probably 50 per cent, of the total weight of boat 
and machinery. 
In the case of the slower yachts or passenger boat, the 
boiler and auxiliaries would probably weigh golbs. per 
indicated horse-power, and the weight of machinery 
would be only 12 per cent, of the total weight of yacht 
and machinery. 
Now, let us sum up these facts : In the case of a high- 
speed boat, we could save 5 per cent, of our total weight 
of hull aiid engines by using turbines. This would mean 
greater speed. We should eliminate two-thirds of the 
vibration, as one-third is certainly due to the vibration 
of the screws. We should cut down our repair bill to the 
smallest dimensions. At slow speeds we should require 
a greater amount of coal than with ordinary engines ; but 
this is not a matter of vital importance on a boat of this 
character. In the case of a cruising yacht the total sav- 
ing in weight would be about 2 per cent, on the whole 
boat. This would mean practically no difference in speed. 
At slow speeds we should have to carry more coal, and as 
a cruising yacht rarely steams at top speed, this would be 
an important consideration. We would make a very small 
saving in room, and we should probably need more space 
for coal and would lose nearly all we gained from the 
small size of the turbines. 
Repairs and vibration are small in vessels of this char- 
acter with slow-moving reciprocating engines. 
To sum up : Turbines are eminently suitable to high- 
speed vessels, and are of the greatest advantage in cutting 
down- vibration and cost of repairs. In slower types of 
vessels they are also of advantage, though to a less de- 
gree, except where the vessels run at constant speed. So 
far as first cost is concerned, the turbine and reciprocat- 
ing engine are practically on a par. 
Turbines are now being so generally built for electrical 
purposes in this country and abroad that it is only a 
question of months when some of our best contractors 
will be willing to take up the matter of marine turbines. 
Since compiling the foregoing the Writer has had the 
pleasure of a trial trip on the new turbine-driven boat 
Revolution. The turbines on this boat are designed by 
Mr. Charles G. Curtis, and seemed to the writer to be 
the best turbines for marine propulsion yet placed before 
the public. The one drawback to the equipment seemed 
to be the noise either from the propellers or the roaring 
of steam, which was apparent in the after quarters. 
This, although less than is usual on boats of the same 
power driven by the ordinary type of engine, was ap- 
CYGNET MIDSHIP SECTION. 
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