Investigations of the damping in roll of swept and tapered wings at supersonic speeds Page: 5 of 36
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NACA RM L53A13
sheet. -The remaining two (wings 10-A and 27-A), used'to study thickness
effects on CZp, were 1/8 inch thick and of the same material. The
edged of the entire group were--beveled at an angle of 50 in a direction
parallel to the wing root chord. All surfaces were ground and polished
to insure a smooth finish.
The wings were mounted on a small cylindrical sting by means of a
tang inserted in a groove in the sting, and were secured by lock screws
and pins. The gap at the wing-sting juncture was filled in withplaster.
Photographs, of the damping-in-roll test apparatus are presented in
figure 1. The sting on which the wings were mounted was connected to ... .
shaft rotated by an air-driven impeller. Strain gages were so located.
on the shaft as to be sensitive only to a rolling moment applied by a
wing. In operation this rolling moment was measured on a strain indi-
cator unit which was wired to the rolling-moment strain gages by means
of slip rings and brushes. With minor exceptions, this unit was the
same as the standard Baldwin Southwark SR-4 strain indicator unit. - -
The rolling velocity was measured witha Stroboconn frequency indi-
cator which was modified to indicate revolutions per minute by means of
a generator attached to the rear of the shaft.
TEST PROCEDURE ... .. _
The models were rolled by means of a Jet of compressed air directed
against the impeller blades. The desired values of rolling velocity
were obtained by varying the mass flow of the compressed air through a
manual gate valve. The corresponding rolling moments were .indicated _on
the strain-gage indicating unit.
The rolling-moment installation was calibrated statically before
and at intervals .during the testing to determine any possible changes
in the strain-gage constant.
During a test of a given wing, the amount of air:exhausting from
the impeller into the tunnel exceeded the amount of air leaving through
the bleed valve which vented the tunnel stagnation chamber to the atmos-
phere. The result was a temporary increase in the tunnel stagnation
pressure (and dynamic pressure and Reynolds number). This occurred most
noticeably for wings with large damping, since a greater mass flow of -
air through the impeller was required. In all cases the pressurepwas
allowed to settle out to a constant value before data were taken. ---
S n ..
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McDearmon, Russell W. & Heinke, Harry S., Jr. Investigations of the damping in roll of swept and tapered wings at supersonic speeds, report, March 3, 1953; (https://digital.library.unt.edu/ark:/67531/metadc59536/m1/5/: accessed May 24, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.