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INTER COMPANY CORRESPONDENCE

.biy I FILE DATE
| CODE 25 September 1968
TO - NAME DEPT. DIVISION PLANT/OFF1CE
Distribution
FROM - NAME DEPT. DIVISION PLANT/OFFICE
J. E. Vaughn 4831 Space 7804

Wind Tunnel Tests of 3/8-Scale Automobiles - A Performance Report Covering the
SUBJECT:
Period 9 - 21 September 1968

Scheduled testing of the Plymouth 3/8-scale model at Wichita State University
was completed on September 9th. Preliminary results indicate that the Plymouth Road
Runner is slightly less race competitive than the Dodge Charger. However, with minor
modifications in the backlight region, the car’s performance can be improved to approach
that of the Charger.

The Charger was reinstalled in the tunnel on September 10th for the purpose
of obtaining additional data inputs. Strak.es were added to the rear quarter panels
beneath the car in an attempt to shift the center of pressure location for sidewind or
sideslip conditions. The configurations investigated did not significantly change the
stability characteristics of the car.

Drafting studies (one car closely trailing another) were conducted on 10 - 12
September. Forces were recorded on the leading car while the trailing car was posi­
tioned at predetermined locations behind and beside the car. Data were also taken
while the cars were in yawed conditions. Results indicate that with the trailing car
in close pr oximity to the forward car (i.e., 1/8 car length), the aerodynamic drag
coefficient of the forward car is significantly reduced. Also, the aerodynamic
load in on the real' wheels of the forward car is virtually eliminated. These effects
have practically vanished on the forward car when the trailing car is more than one
car length away. No data were recorded, in the Wichita tests, on the trailing car
aerodynamics due to tunnel unadaptability. However, these data will be taken during
the testing scheduled in mid-October at Lockheed-Georgia’s Low Speed Wind Tunnel.

The Dodge Coronet was installed in the tunnel and force data recorded during
various parametric investigations. Its performance parallels the Plymouth Road
Runner’s. In addition, the angle of yaw indicator was mounted on the Coronet roof.
It revealed some cross flow across the roof during yawing conditions. With the car
at 12° of yaw, the indicator showed flow to be at 15°.

The testing scheduled at Wichita University was completed on 12 September
1968. All models, data and paraphernalia were crated and shipped to Central
Engineering on 13 September 1968.

£4-5:0-7279 REV. 1-63