The morning news. [volume] (Savannah, Ga.) 1887-1900, 1897-12-09
TANK TRIALS OF MODELS.
NO MORE GOVERNMENT PREMIUMS
FOR SPEED IN SHIPS.

The Tank at the Navy Yard in WASH
iDgton Nearly Completed, Where
the Possibilities of the Heaviest
Ships May he Predetermined to "a
Nicety-HOv the Plant Works.
From the New York Sun
1t has cost the government over $3OOO,-
600 in speed premiums to verify by per-
Torrance the calculations of the designing
bureaus of the navy department but here
after, by means of the experimental model
tank at the navy yard, Washington, and
upon an original outlay of hardly more
than $10qN the possibilities Of the heaviest
of our ships may be determined to a nice
ty. The last regular session of congress
completed a total provision of 100000 for
the construction of this experimental
plant, and by industrious work the es-
tablishment has already been fastened
half way to completion Easily within a
year the place will be ready for practical
application.
For years such a place has been recog-
nized by the principal European naval
worthy performance of our ship reflects
all the more credit upon our designers,
handicapped by the absence of such prac-
teal facilities. Much as mathematical sci
ence has done in other directions. 1t still is
unequal to the solutions of all the difficult
questions involved in the motion of a body
in water, and it is only by practical eX-
periments that the forces at work can be
rightly measured and divided among the
elements of wave motion, surface friction,
and mechanical propulsion.
Rased uDon the inVes legations of the late
DR.. William Froude of England, 1t is
known that the performance of a model
bears a mathematical ratio to the perform
ance of a full-sized ship, and by multiply
ing thASnown functions of the miniature
by itS 10 to the proposed craft the pos
sibiities and pecularites OF the contem-
plated vessel are predetermined beyond
question What this may mean when per
culiar forms of hull or exceptional speeds
are involved is easily grasped, even by
the lavrnan. and the discovery of what
must be expected of a ship built upon
those lines may mean the success or rum
of a vast enterprise. The application OF
the model tank applies as well to mer-
chant craft as to naval vessels, ana IL IS
the purpose of the navy department 10
Mace the establishment at the disposal
Of civilian and commercial undertakings.
The present tank may be said truly to
no the result of the persistent efforts OF
Chief Constructor Hichborn and, folioW-
ing out his direction, the plant VIII be at
once upon a scale and of character con-
siderably in advance of anything now eX-
tent abroad The completed structure wall
consist primarily of a concrete-lined basin
surrounded by one-story brick building,
which is surmounted by steel-trussed
roof of an approved pattern. The build
ing is so feet long and 30 feet wide, with
two small extensions for the installation
Of the ventilating heating, pumping i'll
tering. and power plants. BY TINS means
T, the main body of the structure Is lelt I'M
hampered for the experimental work.
The main basin Is go feet long and az
feet wide and will have au inform depth
of IA feet At one end will be narrow
shoal extension, 70 feet long and feet
wide from which the trial runs Will be
started. and at the other end, one "a feet
long and 8 feet wide, into which the mod
els will be carried upon the completion of
fine runs The latter extension will have
no sDecial features; but at the starting end
there will be pit on each side ana at the
rear for the purpose of providing conVen-
lent means for measuring the models as
they float in the basin preparatory to the
trials. There. too, will be a standard
Weighing apparatus for adjusting ana
standardizing the dynamometer which
measures the resistance of the models or
the correlative, the power required to tow
them at their several speeds.
on the inner lip, so to speak or the
main foundation of concrete, will rest the
tracks upon which the carriage will travel
during the runs. These tracks, of wrich
there are two on each side of the basin,
extend from end to end of the building,
and are so fastened 10 the foundation as
to make them as nearly rigid as possible.
The object of this is to obtain surface
over which the carriage-which spans the
basin and lows the modeIs-may be run at
high speeds and with the least amount of
jar. This is essential to the proper work
ing of the necessary delicate instruments
that register and record accurately the
various elements of the trials
The towing carriage is also rigidly con-
structed, and is driven by electric motors
run on the trolley system. There are four
of these motors Two will be needed for
runs at speeds from one to twelve knots,
while all four will be required from that
up to the maximum of twenty knots. II
may be stated here that a twentyknot
run on the part of a model is the correla-
tive of a speed of perhaps forty knots or
more in the contemplated craft.
In starting the experimental runs II will
be needful, in utilizing the whole length
Of the deep main basin, that the carriage
with the model shall attain the full speed
Of the intended test by the time Is emerges
from the extension at the starting end
Otherwise the length Of the runs, especial
ly at high speeds, would be materially re-
duced To this end ample power will be
provided to vercome the inertia of the
heavy carriage. which. when once in mo
ton, will be kept at a uniform speed by
the expenditure OF very little power-its
own weight contributing to that end while
absorbing whatever slight vibration may
be present.
The dynanometer for measuring the re-
sistance of the models, together with thu
apparatus for recording the results and IL,
necessary fixtures and electrical arrange
ments required, are grouped on a platform
at the center Of the carriage. This plat
form can be raised or lowered 10 suit The
various models.
The dynamometer consists Of a very
clever adaptation OF the spring balance un
der electrical control. The model is at