Project Sign Progress Report, 1948

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10
282' THE AEROPLANE
and _pseudo-circular and pseudo-square wings thus exhibit
~ignificam d.fferences... 1 his also applies to the ground eff.:ct,
1.e., tbe tand.ng
• It ~"It ti0 11f 210 zc!, "
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AAo· •ASP(C f U flO ( •' 1J
Fig. 1
17.-These resulu from Zlmmermann's wind-tunnel
tests on disc; wings (1932) clearly show the character!stits
of low aspect ratio aerofoils.
• MARCH 5, 1948
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"<Cl ARK I AEAO FOtl SECTION "'0
(i-v-CA ZIMME~MANN, ..~l P No ()1) :;
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ASPEC T AATIO ., .,
18.-Furthcr results from Zimmermann's tesu shown here
also indicate the advantages to be gained from disc wings.
seem to. contradict the experience referred to above and it
w~s aunbuted. to. a ground effect arising from the rak~ of the
wing-tips. It 1s indeed rea:.onable to e)(pcct that the presence
of t_he ground would affect the formation of the marginal
vort1c~s to an ex\ent which may markedly influence the
beh~v1our of disc wings during take-off and landing. Hoffmann
proJected a ousher and a twin-engined version but these types
did not materialize. •
A further development was the Arup monoplane of
R: J. Hoffmann and C._L: Snyder at South Bend, Indiana. The
w!ng _shape ~as v~ry s1m1lar. I~ resembled a semi-circle flying
w11h 11s straight side a_s the_leading edge; to this wing, ailerons
were added as special ups. 1 he aspect ratio practically
corres~onded to. that of the previous Hoffmann types. Again,
aerofoils wtth little centre-of-pressure travel were used.
1 he latest type ~ad it~ _tailplane and elevator separately
locate~ over the wing tr:11lmg edge (similar to the .. Elytro·
plane o f De Rouge!). It seems that the longitudinal control
at certain incidences was not satisfactory. 1 he ailerons which
formed part of the wing shape and reduced the aspecl ratio
to a value ~f I:15 had a triangular shape and were greatly
s_kewed (taking_ into account the obliqui: flow over the wing
tips). The engine was a 70 b.h.p. Le Blond radial; a tricycle
undercarriage was fitted.
With the oilot alone, a gliding speed of 23.S m.p.h. was
r~o_rded (lhe wing loading was about 3.3 lb./sq. ft.) and a
gliding angle of 21 degrees was mea~ured, with a sinking speed
of 12.3 ft. ocr si:cond. wh.ch ~an be accommopated by a sturdy
undercarriage witho ut nattening out of the glide. 1 he maxi·
mum speed was 86 m.p.h .. and the take-off was stated to require
S secs. in zero wind.
Several more Arup types seem to have been constructed
an_d _flown during 1935. 1 h~ flying qualities were pr.iised
ghding angle~ or I : 2.6 bemg quoted- and the published
performance figures sounded extremely good. Yet, for reasons
never disclosed, the production stage was not reached and the
development ceased abruplly. It is worth noting that Charles
Zimmermann himself has taken no part in this development,
b1;11 he was an interested spectator at demonstration flights
wnh an Arup monoplane at Langley Field.
An Italian "Tortelllno "
At the time .of the Arup development (1934). F. Piana
Canova. an Italian, began to embark on a development for a
tajlless aeroplane with a low aspect ratio. In May, 1935, he
secured patents for a rhomboidal wing, one diagonal of which
coincided with the direction of flight. 1 he ailerons were to
be located at the lateral apices. elevator and rudder at the
rear apex. while the airscrew was in front of the leading apex.
Another patent related to bi-convex aerofoils with ducts and
control valve~ for the pilot, enabling the latter to neutralize
the negative oressure on the forward ventral surface when at
negative incidences. The latter patent was, apparently, never
submitted to flight experiments.NND 927545
(To ~ confin~d.)