The New York herald., 1921-08-26
EXPERT POINTS OUT
WEAKNESS OF ship
Defects in Design and Con-
struction Caused Collapse,
Says T. r. MacMechen.
STRESS WAS UNEQUAL
Explosion Followed Crack
ing of Gas Bag, in Opin-
ion Of Engineer.
NOT A REAL ZEPPELIN
Principles Laid Down by Ger
man Builders Not Followed
in English Airship.
NOT A REAL ZEPPELIN


Vital structural defects in design
and construction caused the collapse
of the ZR-2, in the opinion of T. Ruth
erford MacMechen of MacMechen
Kamp, aeronautical engineers OF this
city.
Mr.. MacMechen has been a close
student of aeronautic problems 1or
more than a decade. In 1914-15 he
was president OF the American Aero
nautic Society. Before the world war
he passed three years in Germany
studying Zeppelin construction, and in
1914 designed and built in England
$50 foot rigid dirigible. which was
financed by the late E. Marshall Fox
for presentation to the British Ad-
miralty. Mr.. MacMechen's firm holds
the basic patents for what is known
as the spiralized method of construct
Ing dirigible frames, which was en-
bodied in the Marshall Fox airship.
To reporter for THE NEW York
HERALD Mr.. MacMechen said yester-
day:
an my opinion the horrible catastro-
phe resulting from the destruction OF the
ZR-2 was due to the fact that the
builders Of the craft failed to compre-
hend the fundamental principle which
lay at the base of the construction OF
the rigid dirigible, namely, the necessity
for securing evenness and uniformity OF
stress internally and externally through
out all parts of the structure.
1T is well known that the Germans.
who were the pioneers in the building OF
the rigid airship. gained their knowledge
on this subject through long years OF
experience in constructing craft of vari-
GUS sizes and OF different materials. The
information of the British builders was
gained principally through the wreckagc
OF Zeppelin airships lost over England.
As far as we know none of the experts
Of the allied Governments ever has been
able to determine the process by which
the Zeppelin metal was produced. and
therefore they were unable to use the
same material in the construction OF
such ships as they have built.
This establishes at once the funda-
mental difference between the Zeppelin
and British built airships.
Apparently the ZR-2 broke at some
point amidships during high speed test.
The explosions, from all the evidence at
hand. were subsequent to the parting
or breaking asunder Of the frame, and
were the very natural result OF the re-
lease of gas due to the ripping OF the
gas compartments and the parting Of
many pipes and connections.
Weakened by "Reenrorcement
Previous to the disaster reports had
reached this country that defects were
found In the frame, several girders hav-
ing snapped in the course Of some OF the
former trials. The fact that 1t was
found necessary to reinforce the ship
at certain points leads to the inevitable
conclusion that the original calculations
of stress were at fault. Furthermore,
reinforcement of the frame as II was
originally made by the engineers would
have the effect of actually weakening
the structure, because this would be
absolutely opposed to the theory that the
stress throughout the structure must be
evenly distributed.
There are two forces to be met by
the designers, one, the internal pressure
of the volume of gas. and the other the
external pressure of the air on the craft
set UP by its motion.
THE earliest Zeppelins were con-
structed with the same diameter
throughout their entire length, giving
uniform size of cylinder throughout
After the war broke out II was found
necessary to Increase the diameter of
the Zeppelin amidships n order to carry
greater loads to greater heights, and thus
both to escape gun fire and TO carry
aloft effective high explosives. 1t Is evil
dent that when the girth OF the airship
is increased amidships there is a greater
volume of gas at that point. which
places tremendous, uneven gas pressure
on this section of the frame. This would
give tendency to hump In the centre
IL there were any structural weakness
at that point. and any subsequent re-
enforcement at this point would only
tend to throw excess stress on that part
of the ship. which would destroy the
uniformity of stress fore and aft.
This defect would Immediately be-
come apparent whenever the ship was
driven forward at top speed or was
turned too sharply on Its end. II must
be understood that the stresses set up
by speed natui ally run along the length
OF the frame and in this case would ex-
pend excessive force amidships, where
they meet the stronger girders. instead
Of being carried to the stern, resulting
in equalized distribution OF the stress
throughout the ship.
German Principles Ignored.
"since the British began by imita ting
the German construction, II was error on
their part, In the construction OF ZR-2,
70 depart so drastically from the prlnci-
plies embodied in the Zeppelin, the sue
cess OF the Zeppelin construction having
been reached by step 10 step realization
embodied In the building OF successive
sizes OF airships. 1t was a great mistake
to undertake n novel construction on
such vast scale. It should have been
evolved by degrees.
"The R-s4 will be cited against this
proposition, but II must be remembered.
in the case of that ship, In the first
place. that while II did cross and re-
/ rrasa thn Atlantic II was not n demon