The Worcester spy. [volume] (Worcester, Mass.) 1898-1904, 1898-11-04
THE NEW MODELS
Thirty-foot Warships Which
VIII GO in a Tank.
Washington Post)


Within a few weeks the navy depart
ment will be able to test the speed and
other properties of warships by their
models The construction Of the much
talked-about tank at the navy yard is
completed after about two years of
work, and only some of the machinery
is wanting to put the plant in perfect
condition. The dynamOmeter for in
stance a contriYance for pulling the
wax models of warships through the
water, was to have been delivered some
time ago, but on account of the war the
company building it has been delayed.
The bureau of construction and repair
Of which Chief Constructor Hichborn is
the head, win undertake the expert
ments in the model tank with great
deal of interest. These experiments will
not be confined entirely to the models
of battleships and other war craft the
government proposes to build but to
some of the battleships that are al
ready in commission. The experiments
in the tank are not expected to be eX
act prototypes of the actual behavior
of the ships on the ocean 1t is, there
fore, proposed to experiment with some
of the models of present American bat
tleships that the proportions may be
figured out and proper allowances
made in calculations as to what new
battleships can be expected to do.
MODEL TANK.
The model tank has long been urged
by Constructor Hichborn. He had adj
vocated its construction for several
years when, about two years ago, Rep
resentative Hilborn of California a
member of the committee on naval af-
fairs, took the matter before the house.
After quite struggle an appropriation
for constructing the model tank was
authorized as part Of the naval APP
preparation bill.
The new tank at the navy yard. from
which so much is expected, is 800 feet
long, 40 feet wide and II feet deep, 1t
will be filled with clean, fresh water
The building just completed covers the
entire tank and excludes all air
draughts. The water will be as free
from currents as possible. Along the
side of the tank is railway on which
a carriage, propelled by it's own electro
cal motor, travels at any desired speed.
This carriage. or the model if so de-
sired, will bear the delicate mechanism
that is to record the power in pounds
needed to pull or draw the model
through the water, mark distance trav-
eled and the time consumed and regis
ter the presence of disturbing draughts
or currents, no matter how slight.
Checks and counter checks eliminate
the possibility of error of any kind.
The models, which are to float be-
meath and be attached to the movable
carriage will vary in size from ten to
thirty feet, being made as large as pos
sible that their performances may be
on a corresponding scale, and less like
ly to disguise small errors multiplied
correspondingly in the greater vessel.
These small-sized ships are to be made
of paraffin wax, because that substance
does not change its weight by absorb
ing water, Is easily cut and readily
modified to suit alterations suggested
BY experiment, and the wax can be
melted again and used for other trials.
About a framework of wood, covered
with canvas, is cast the paraffin, some
what in excess of the proposed dimen-
sions. When cold. the rough model is
placed in a machine especially designed
for the work. and a series of lengthwise
steps or water lines is cut from stem to
stern, beginning just above the keel and
repeated at regular intervals upward.
simultaneously the two sides are cut
alike, and the wax between these steps
subsequently removed and smoothed
up by hand.
After it has been trimmed to the de-
termined water line, or draft, the
model viii then be attached to the car
riage and lowed at several suitable
speeds. The resiStances are measured
| by means Of the extension of a spring
on the principle of ordinary hand
scales, and the amount of that extern
sion recorded in pounds on revolving
| cylinder On the same cylinder, timed
to turn in accord with the speed of the
carriage, are registered time and dis
lance diagrams, by which a correct
measurement of the speed may be OBJ
tanned. From these results curves are
plotted and the possible performances
between the actual experiments regis
tered without further trials.
The total resistance of the model es-
tablished, the propellers will then be
tried separately, and the one that gives
the best equivalent in push and efii-
cheney for a like force in power applied
will be accepted. Then the propeller
will be tried in connection with the
model to note the mutual action of
screw and hull and to see how far
backward the suction of the working
screw is exceeded by the forward push
of the wake, as the eddy at the stern
is called This following current Of
water the consequence of the hull, and
not the screws, and against deter
minable speed pushes against the
backward thrust Of the propellers,
saves the screws that amount of work
and represents the conversion of
faulty motion of the water to so much
helpful energy.