The sun. [volume] (New York [N.Y.]) 1833-1916, 1897-11-28
TANE' TRIALS OF MODELS.
no morn GOVERNMENT PREMIUMS
FOR SPEED IN SHIPS,

or the Heaviest ships May be Pr-deter
u,tBeu TO n Nicety-how the Plant Works
It has cost the Government over three mil
Hons Of dollars in speed premiums to verify
by performance the calculations Of the design
ing bureaus of the Navy Department, but here
after, by means OF the experimental model tanh
ct the navy yard, Washington, and upon an
original outlay of hardly more than a hundred
dollars, the possibilities OF the heaviest Of oul
future ships may be determined to a nicely. The
last regular session OF Congress completed a
total provision of 500, 900 for the construction
Of this experimental plant. and by induttriods
work the establishment has already been has
tened half way to completion. Easily with
In a year tho place will DO ready for practi
cal application.
For years such n plant has been recognized
BY tho principal European naval powers as q
necessity. and tho praisewortby performance OF
our ships reflects all tho more credit upon our de.
signers, handicapped by the absence of such
practical facilities. Much as mathematical
science has done in other directions, It still Is
unequal to the solutions of oil the difficult ques.
lions involved In the motion of o body In water,
and It is only by practical experiments that the
forces at work can no rightly measured and
divided among tho elements Of wavo motion,
surface friction, and mechanical propulsion.
Based upon the Investigations of tho late DIR.
William Froude of England. it Is known that
the performance of n model bears a mathcmati-
cal ratio TO tho performance Of q full.sized
ship. and by multiplying the known functions Of
the miniature by its ratio to the proposed craft
tho possibilities and peculiarities of the con.
templated vessel nre predetermined beyond
question. What this may mean when peculiar
forms of hull or exceptional speeds nre involved
is easily grasped even by the layman, and tho
discovery OF what must be expected Of O ship
built upon those lines may mean the success or
ruin of n vast enterprise. The application OF
the model tank applies as well to merchant craft
No to naval vessels, and 1t is the purpose of tho
Navy Department to place the establishment
at the disposal OF civilian and commercial I'M
dertakings.
The present tank may be said truly to be the
result Of the persistent efforts of Chief Con-
structor Hichborn. and. following out his direc-
ton, the plant will be Mt once upon n scale and
of a character considerably in advance of any
thing now cxtant abroad. The completed
structure will consist primarily Of a concrete
lined basin surrounded by q o~ne-story brick
building. which is surmounted by a steel.trussed
roof of an approved pattern. Tho building Ia
BOO feet long and 30 feet wide, with two small
extensions for the installation of the ventilating,
heating, pumping, tltcring. and power plants.
By this means the main body OF the structure
The main basin Is $40 feet long and AZ feet
wide, and will have a uniform depth OF Il feet.
A. ono end will be u narrow, shoul extension,
trial runs will be started. and at the other end,
one 81 feet long and : feet wide. into which
the models will be carried uDon the completion
Of the runs. The latter extension will have no
special features; but al the starting end there
will be a pit on each side and at tho rear for the
measuring the models as they float in the basin
preparatory TO the trials. There, too, will be O
standard weighing apparatus for adjusting and
standardizing the dynamonetcr which meas.
ures the resistance OF the models or the correla-
tive, the power required to tow them at their
,o, On the, The inner m lip; so to speak: Of the main
uTruS which u Pho eC cnTrias. vii tr rest ths tracks tks
runs. These tracks, Of which there are two on
each side Of the basin. extend from end to end
type, and are so fastened to the foundation as
TO make them as nearly rigid as possible. The
the carriage which spans the basin and tows
u; Nth i shs ii least sIas smo ssnss p JAZZ !; II I'll I.s i ESSEN s%s
delicate Instruments that register and record
accurately the various elements of the trials.
on the trolley system. There are four Of these
from i to IL knots, while ali four viii Be re-
CURED from that up to the maximum Of 20
rn1's on Il tho may TSrt &c Of Ss a @od sffs Is t the c q HS.HrSs
Contemplated craft
N'hb wv tulb 4 Il Dt
needful, IN utilizing, the whole length of the
deep main, basin, that the carriage with the
tended test by the time it energies from, the
extension at the starting. end. otherwise the
would be materially Reduced. To this end,
ample power will be provided to overcome the
inertia OF the heavy carriage, which. when once
In motion, Will be kept at IA uniform speed by
tho expenditure OF very little power-its own
weight contributing To, that end while absorb
inE whatever slight vibration may be present.
The dynam0meter for measuring the resist
ence of tho models, together with the apparatus
for recording the results and the necessary Ak
lures and electrical arrangements required,
are grouped O. a platform at the centre OF the
carriage. This platform can be raised or low
cred to suit the various models.
Tho dynsmometer consists OF a very clever
adaptation OF the spring. balance under electri-
rod to one end of a spring, while an electrical
motor moving a threaded shaft holds the other
end under control. The moment the carriage
starts an electrical contact, working nutomatl-
tension Of the spring and Keeps it up till the
the pull of tho model at the o.her end; another
electrical contact preserves this counterppise.
spring denotes the tension or resistance Of the
model; and an arm reaching up to a cylinder
sarrying, 2 ,f sheet OF paper traces with a pen a
cylinder, before which one OF the operators sits,
revolves at a fixed ratio to the advance OF tho
Other pens register any change Of trim, 1. e.,
settling by the bow OF IN. stern, at regular. pc.
TlOub,hnu INC hCtual Instance ana position or the
carriage at every interval of the run. These
latter elements are checked electrically from
the track and must be positive, and, by the COM.
bination with the time record, determine the
actual speed Of the carriage at any point In it's
run. The result is a diagram Of simultaneous
records. from which everything can be read and
checked with case. The springs used will nee.
essarily vary In strength with the speed and
character Of the model; and the standard
weighing apparatus will BIO used to standardize
each one before trials.
Every conceivable precaution will be taken
In lnSlra nhHnlnfA ArCnrany In the tnQtG and a
careful record of each experiment will be tabu-
lated and filed away for ready reference. In
tho matter OF details and the method Of apply
Ing the .dynamometrical mechanism, we have
departed entirely from all previous practices,
with the promise of records FREQ from that
jumpiness and vibration common to other
model tank registers.
In addition to these more simple experiments
arrangements will be provided for testing the
functions or qualities OF the models; the effects
of pr0pcllers of various sorts and at different
speeds, and their relations to the form OF tho
hull about the stern where the water runs In to
tho screws; and also TO tell what proportionate
part of the total resistance Of the model Is due
To friction of the underwater surface, what to
wave resistance, and what TO eddies.
All n ithaca AZ .nruk - - IA-