Some very good articles appeared in
the short-lived magazine Steamboats and Modern Steam Launches, in particular "Balance is the Magic
Word", which appeared in the September/October 1961 issue. Its
wisdom is well worth repeating here.
have noted that 1/2 horsepower will move a fine (length to beam ration
of 4 to 5) 1000 pound hull, at hull speed. A broad (length to
beam ratio of 2 to 3) hull of 1000 pounds will require one horsepower.
Hull speed is defined as 1.3 times the square root of the waterline
length of the boat's hull.
Beyond this speed, excessive amounts of energy are required to move the
to ten square feet of boiler heat transfer surface will be required for
each horsepower. A good water tube boiler will be close to five,
while a poor fire tube boiler will be more like ten. Common usage
to describe the quantity of steam produced in a boiler is the actual
weight of water from which the steam was evaporated. Forty pounds
of steam per hour per horsepower should supply a good single engine or
a typically worn compound.
To replace this water in the boiler, which is converted to steam, 5
gallons of water per horsepower will have to be replaced each hour,
thus determining the capacity of the feed water pump. It should
always be borne in mind that getting water into the boiler under all
conditions and at all times is extremely important. For
that reason we always recommend at least three means of getting water
into the boiler. Common methods are a piston force pump driven by
the engine, a hand piston force pump, and an injector. The latter
two being used when the engine cannot be turned.
condenser should be about one sq. ft. per horsepower if mounted inside
the hull and 1/2 sq. ft. per hp. If mounted outside the hull.
Note that there is a distinct disadvantage in using a condenser which
is more than one- third larger in diameter than the engine
exhaust. In the case of a large condenser pipe diameter, the
steam will pass right down the center of the condenser and make little
or no contact with the cooling surface. Of course , the use of a
small condenser pipe size will increase back pressure and choke the
exhaust. The choking effect of many elbows, bends, and other
obstructions in the engine exhaust line is also to be avoided.
Using a piece of high quality heater hose leaving the engine exhaust in
a nice smooth sweep to the condenser is a plus.
newcomers to steam are surprised to learn about the large amount of
required to run a steam engine--40,000 Btu per hour for each
horsepower. That means that a typical 3 hp (120,000Btu) engine
requires a fire that would heat a home quite nicely