The record-union., 1895-07-16

| iatSU ~ DO thS &IoSI
| Useful Warships Belonging TO the
United States Government.
WASHINGTON, July 15.-SiX magnifi-
cent steam yachts, such as could be
owned only by the lucky possessors of
many millions OF dollars, will be built by
the navy during the current fiscal year.
and although they are to be finer than
similar vessels of their class, they prom
! ise to be all-around the most useful ships
belonging to the United States Govern
! menL
by Act Of Congress, approved March 2,
1895. provision was made for tho con-
struction of six iight-dratt, composite
gun boats, the individual, constructive
| limit of cost being $780, exclusive OF
! the cost OF armament From this au-
thori.y the Chief Constructor Hichborn
and Engineer-in-C Chief Melville have
drawn designs for entirely novel types of
war ships involving Tor the first time In
| Government vessels the principle or COM
| poslte construction, the framing being oil
steel and the hull OF wood.
| The essential reasons tor the cOnStruc
ton OF vessels of the composite type are
that they are largely independent of
| docking facilities and economical in the
use OF fuel. The extoliation OF the copper
causes the barnacles, grass, ETC., to be re-
| leased Just as soon as the vessel Is put in
| motion, and The bottom is made COM
paratively clean, thus permitting the
vessel to maintain her designed speed
| with minimum consumption Of coal.
The docking expenses, whether al home
or abroad. and the cost of fuel are two
very serious outlays that these vessels are
counted upon TO minimize, while their
| activity, range OF action and general el1i-
cheney are greatly increased. The six
vessels will be of two radically different
| types. one type carrying full sail power
and propelled by single screw, the other
one having steadying sails only and pro-
! PEELED by twin screws actuated by two
separate engines.
The siugle-screw vessels, Nos. 10, ii, II
and IL, have finer lines than the other two,
and carry spread of IL 900 square feet Of
canvas. Under sail alone they will make
| ten knots with stiff wind and fairly
smooth sea, while in the trade winds for
| long voyages they can be relied upon 10
make long cruises at the rate Of six or
eight knots. When going under sail
alone, the engines OF the singie-screw
boat will be uncoupled, allowing the
shafting and screw to revolve simply by
| the action OF the passing water; and so
| slight Is the retarding influence OF the
screw tnus disengaged that there is every
reason to expect d sailing speed fully
equal to the steam power conditions.
The engines in each type are designed
to develop the same horsepower, and to
induce the same speed, that of twelve
knots. differing only as regards shatting,
number OF screws and the Incidental
division OF motive force.
For the twin-screw gunb0ats, the en-
gines will be rights and let's, each in II
| separate water-tight compartment, and
Will be of the usual vertical, direct-act
ing, triple-expanslOn type, with high
pressure cylinder OF y, ISL and 2S inches
respectively, having a common stroke of
| Is inches, capable OF developing 500 horse
power with 200 revolutions minute.
The engine Of the single-screw boats
will also be Of the triple-ex pansion type,
| with cylinders of the following dame
ters: l5i. z34 and 80 inches, with COM
mon stroke OF 80 inches, aud to run at $50
revolutions "a minute When developing
the required 800 horsepower.
Each boat Will have two Slngle-ended
! "Scotcho boilers, with two corrugated
| furnaces each three feet in diameter.
| Each boiler will have a diameter of l0l
| feet, a length OF 10! feet, with 50 square
feet OF CRATE surface and l ,250 feet OF heat
face of 2,5O0 square feet and d total CRATE
! surface of rs square feet. They will nave
| moderate forced draught induced by two
| blowers Tor each boat, applied directly to
| the ash pit. The boilers will be placed
side by side in the same compartment,
with common flre-rOom. The normal
| coal supply of the single-screW boat will
| be 100 tons, with total bunker ca Dacity OF
23S; the normal coal supply Of the twin
screw boats will be l20 tons, with total
| bunker capacity Of $50 tons.
| These gunbOatS have been given much
| less speed and only about half the power
which it lately has been the practice to
put in boats of their displacement. The
great advantage of this idea consists in
allowing a boat of a given size to carry
moro coal, since the machinery weighs
less, and drives the boats much more
economically at Il slow speed. Thus at
eight knots these boats Will require about
350 horsepower, whether tho maximum
power of the engines be 500 or l.600.
In one case the engine would be work.
ing at about one-quarter OF its designed
power, which is within the limit OF rea-
sonable economy; and in the other case
the engine is working at only One-eighth
its actual power. AS the power required
to drive vessel varies as the cube of the
speed the coal burned per knot will vary
as the square of the speed. or in other
words, with two engines OF equal econy
omy one of which would drive the boat
ten knots and the other eight knots per
hour, the first would burn 100 tons OF
coal in going the same distance as the
other would run in burning SiXtyfOur
tons. This illustrates the advantage of
having engines which are economical at
slow speeds. This was the, principal roa-
son why low-powered machinery was
put in the ships.
| hOatc will r0nI1ira al I ftyn va I'm
| their maximum speed, 800 indicated
! horsepower; at ten knots, 450 indicated
! horse power, and at eight knots, 80 in
| dicated horsepower. The capacity of the
| bunkers will be about $50 tons. The coal
| consumption for all purposes at full
! power will be about twenty-five tons per
! day. giving steaming radius in smooth
water of 3, ,150 knots. at ten knots tho
local consumption will be about twelve
/ tons per day, and the Steaming radius
will be about 500 knots. At eight knots
speed the coal consumption would be
/ about eight and one-halt tons per day,
and the steaining radius Will be about
/ $500 miles, making 1t posi- bic to run
/ them at that speed from San ranclsco TO
! New Zealand.
The steamng radius of small ships Is
greatly affected by wind and weather.
i The large Atlantic liners plow through
ali kinds OF weather, ami only the hardest
storms affect their speed, and then only
/ to limited extent. These boats, when
sieaning against moderate hard wind
and sea, will have their speed decreased
;yo or three knots. The single-serew
boat will he affected much more III this
respect than the other one, since her
/ spars and rigging will catch more wind.
She VIII also be troubled more By her
engines racing. since her screw will not
| be SO deeply immersed as that of her
rival.
! The great gain in the twin-screw ship
will be the ease with which she can steam
/ In and Out OF narhnrs and I'D narrnu nd