Evening star. [volume] (Washington, D.C.) 1854-1972, 1905-10-28
FOR AERIAL FLIGHT
Experiments by the Catholic
University
MADE MUCH PROGRESS
THE WORK OF DIR. ALBERT g..
ZAHM.
Much Practical Work Done That Has
Helped Aeronautic In
vention.

The Catholic University for two years
past has been conducting series OF ex-
periments in aerostatics that have done
much toward solving some of the most per-
picking problems in connection with aerial
flight. The work has been done quietly
and few people outside a small circle OF
professional men know how much is due
to the work of DR. Albert f. Zahm of the
university for establishing the existence of
essential laws that have to be dealt with
in building a practical flying machine.
Dr. Zahm is not an aeronaut and he eX-
presses no ambition to build a flying ma
chine But he is intensely interested In
the problem and has done much practical
work for which inventors have to thank
him. He has kept in close touch with
Chaunte, Mindenhall, the Wright brothers.
Lord Raylegh, Prof. Langley and In
directly with Sir Hiram Maxim, All Oh
whom are interested in the same prooiem
and he has gained some valuable practical
results in his laboratory work
The aerostatic laboratory Is a plain
wooden shed eighty by twenty feet ana
was originally built and equipped by Mr..
Mindenhall. who had figured out what he
thought was a practical flying machine
but who wanted some practical Demon
STATIONS before putting money into actual
" building one. The laboratory's chief
and six feet square. The diameter of the
tunnel can be reduced at will in case
lighter wind velocities are required AT
the far end of the tunnel there Is hVe-
foot fan that draws the air through the
long passage. At the other end, where
the air enters, there is a door covered
with cheese cloth screen that "straightens
OUT the air currents that would other
wise be turbulent and billowy-
One of the first things that the ex-
periments in the tunnel did was to upset
a long-cherished belief among areonauts
that skin friction of the air on a body
passing through it was practically negli-
Bile quantity. AS matter of fact the
action of air was proved to be almost
identical with that of water, roughly
speaking, in direct proportion to the dem
sity of the two elements.
A Delicate Anemometer.
The tunnel was equipped first of all with
delicate thermometer, working much on
the same principle as a steam guage but
with long arm and sliding weights, by
which the wind pressure and velocity in
the tunnel could be measured to a nicely
from velocity of five feet a second up
to forty feet.
Then models of various shapes We're sus-
pended in the tunnel and connected by
wind-protected arm with a delicate weigh
ing machine above and outside the tunnel.
BY this machine the wind pressure was
accurately recorded. Commencing with d
wooden sphere of polished surface, the
models were varied into cigar-shaped cyl
Under, pointed at both ends. The cylinder
was made longer and sharper for each eX-
pertinent, but kept at the same diameter in
the thickest part.
Now the current theory was that the
sharper the cylinder the easier it would
cut through the air Nothing was thought
of the Skin friction which would be seri-
ously considered in modelling a vessel for
the water AS a matter of fact, it was
found that the sphere was reduced to a
sharp-pointed cylinder, the air resistance
rapidly diminished to a certain point. Then
il rose again as the length of the cylinder
increased. 1t found that about u to l
as the proportion between length and diam
eter was the shape of least resistance. Then
came another surprise. BY shortening the
forward section of the cylinder about one
half, and consequently making the end
blunter the air resistance was largely re-
duced. Now, by turning this cylinder
around and running it's sharp end forward
the air resistance. instead of being dimin-
ished. was almost doubled. Thus all pre-
conceived ideas about air resistance were
upset.
Shape Decided Upon.
The shape finally decided on as that of
least resistance very closely approximated
a fish, and except for lacking wings, was
more or less like bird with a comparative
ly broad, fiat breast and tapering body
and tail. II is also the shape adopted after
much experiment for the submarine tor
pedo, showing again that air and water
offer resistance in practically the same
way.
Another question presented to the expert
menters by designers of flying machines
was the form of least resistance for rods
and supports In their machines Sharp
edged rods that would cut through the air
4
pertinent that the shape of the rods fol-
lowed the same laws that of balloon
bodies, namely, that the skin friction of the
air had to be considered in proportioning
thickness and sharpness.
This is as far as the experiments have
gone at present. The work paused for a
while after the first Investigations were
completed. but Prof. Langley heard of it
and sent a check for $500 and asked that
the work be continued in the interests of
science.
Form of the Wings.
one of the next matters to be taken I'D
will be the best form of wings for areo-
planes. Many sorts of material and vari-
Gus forms of wings have been tried in Gid
ing machines. but definite data are lacking.
The tunnel will be utilized to measure the
lifting power of the various shaped wings
and the thrust necessary to drive the vari-
machines through the air Several
IOF1nS OF wings uSeQ IN various Rlldlng and
soaring machines are on hand, but the
active work of testing them has not yet
commenced.
One thing was established theoretically
by the experiments and that was that the
air resistance made a speed of forty-five or
fifty miles hour the economical limit
for flying machines. This may come as a
shock to laymen who have hazy ideas of
flying machines going at practically limit
less speeds, certainly not under hundred
or two hundred miles an hour.
The theoretically economical speed was
curiously confirmed by the Wright broth
ers. who wrote DIR. Zahm that they had
reached the same conclusions In their act
ual flights. OF course by crowding on
power the speed can be raised slowly at
a great expense Of fuel and power.
On ocean lines each quarter of knot
added above a speed of twenty knots an
hour costs much fuel as the first ten
knots cost altogether. Thus the airship
may probably obtain a speed of sixty-five
or seventy miles an hour. But the 100 mile
airship is not yet in sight.
Flying Has Been Done.
It may be news to most Westinghouse,
whose chief ideas of airships are confined
to Santos Dumont's Siderable balloons and
the one failure OF Prof. Langley's aero
drome down the Eofomac IN know that a