The Yale expositor., 1918-07-11

InlS property is secured partly by
weaving and partly by doping" At
ter the fabric has been stretched on
aircraft wings. 1t is doped up with
preparations somewhat like cOllodiOn,
which you have probably used for
treating cuts. Then, for battle work,
airplane wings must hold their taut-
ness to the highest degree even though
punctured by bullets or other missiles.
and this Is where tear resistance
comes in-despite the pressure of air
upon the fabric it must be of such
mechanical structure that a hole will
not spread by tearing while in flight.
Making Use of Cotton.
The bureau of standards men set
out to develop a satisfactory cotton
airplane cloth. Cotton is more diff
cult to weave than linen, especially In
the very fine counts needed for air
craft and not so widely made in this
country as abroad. They changed the
structure of the yarn, mercerized it,
developed finer weaves, and by close
teamwork between textile manufac-
turers, checking results by accurate
tests and original specifications, have
developed a cotton alrplane cloth
which is declared to be better than
linen-and when the bureau of stand
ards men say "better" they mean 1t
in terms of measured factors of
strength, tear resistance, and the dop-
ing quality which gives tautness. In
cidentally, this American cotton air
plane fabric, while being better, is not
restricted by scarcity of raw material,
and is considerably cheaper. Results
have been secured chiefly by the con-
structiOn Of the yarn and by tension In
weaving.
Under a microscope a piece of this
cloth shows no special novelty In weav-
ing-it Is perfectly plain cotton cloth.
but about as fine in count and mesh
as has ever been woven In this cOun-
try. Dozens of samples of airplane
cloth submitted by patriotic manufac-
turers anxious to help solve this prob
lem show more Ingenious developments
In weaving, but are not found as suit
able when submitted to the final meas
urement tests for tear resistance, taut-
ness, etc.
With the problem of aircraft woods
most encouraging progress has also
been made in finding possible substi-
tutes for spruce in airplane frames.
and mahogany. utilized for propellers.
People often ask why wood is used SO
largely In the making of an airplane.
This Is easily mans most advanced
..,I,a s.Ne Va
turns his back upon his own highly
developed modern metals, with which
he builds practically every other mod
ern mechanism, and sets out for the
forest with an ak on his shoulder. The
answer Is that, contrary to popular
opinion, wood is much stronger than
any metal for the particular require
ments of the airplane-strength with
lightness, and elasticity with the stiff
ness needed for the framework.
True, mahogany has been found bet
ter than metal for airplane propellers,
because ii stands rough usage, and at
the tremendous speeds required, which
would often burst a metal flywheel, is
not subject to the distortions involved
weight-torsion Of the propeller blades
In flight of course would affect speed
and perhaps mean disaster. Mahog-
any is the best wood, because 1t Is least
affected by moisture.
May Use other Woods.
Spruce for American airplanes has
to be found In lengths up to 40 feet
and is rigidly inspected for straight
grain and sound growth. 1t has high
strength for its weight, takes heavy
impacts and shocks, and its residence
Is such that 1t bends without break.
ing or distortion as no metal will do.
Careful investigations and tests point
to the use of at least one other wood
for airplane frames, and perhaps two.
Fir promises to be a good substitute.
having higher specific strength than
spruce, but somewhat heavier and not
the equivalent in sustaining shocks.
Cypress also seems to be promising at
this stage of the experiments, and
probably walnut or oak may be found
satisfactory substitutes for mahogany
in airplane propellers.
~ luteL luc VI CuTOuOiue-
ters in navigating our new mercantile
fleet. Uncle Sam is working with the
American watch industry to provide
something just as good-a new substi-
tute in the shape of the ships watch.
This is a somewhat larger watch
than one would want to carry In his
pocket, mounted on cushions in ma
hogany chronometer box to withstand
the vibrations, shocks, and swaying
aboard even torpedo boat, which
gives probably the hardest service con-
ditions for ship timepieces. The speci-
fications for these ships watches were
drawn up by the bureau of standards.
They are now being made In quantities,
and under the rigid tests of the bu-
reau Of standards have shown high
accuracy, so that with three aboard
each Ship giving a check upon each
other, they should be as satisfactory
as chronometers. Incidentally, they