Page 2 - Combined_23_OCR

I

1.71 sq ft and a 2.31 geometric aspect 045
ratio. FORCE
• A 58-in. span, 7.5-in. chord hori­ C O EFFIC IEN T 0 35
zontal stabilizer mounted 23.5 in.
above the rear deck between the A X IA L
vertical stabilizers. An inverted Clark 025
Y airfoil, the stabilizer has a 3-sq ft 04
aerodynamic surface and a 7.75 03
geometric aspect ratio. CO EFFICIENT 02
Additionally, the backlight slope O.I
is changed from approximately 45
deg to 22 deg from the horizontal L IF T O
and the side window to backlight O -
junction is faired. Although different -0.2
from the standard Charger, this is 04
a carryover from the 1969 race car. 0 3

Pack qe success COEFFICIENT 02
ra
The effects of these aerodynamic 0 I
modifications are substantial. Accord- FORCE O
m to to wind tunnel data (Fig. 2), -0.1
SIDE
-axial force is reduced 16% at zero -02
yaw angle. This reduction represents -9 -6 -3 O rO < £ > 12 15
about a 5-mph increase in lap speed YAW ANGLE, deg
at the Daytona Super Speedway. To
FIG. 2 Effect of the aerodynamic package is to reduce oxiol force 16% ot zero yaw ongle.
achieve a 1-mph faster lap through
engine modifications would require CHARGER DAYTONA I o WITH SPOILER
1 © WITHOUT SPOILER-
(18-in. EXTENDED NOSE)
an additional 17 hp and improved
CHARGER DAYTONA f O WITH SPOILER
.handling. (9-in. EXTENDED NOSE) I ❖ WITHOUT SPOILER
Bu t not only axial force is reduced. f D WITH SPOILER
The low- cc to nose and spoiler cut 1969 RACE CHARGER I b WITHOUT SPOILER
front axle lift 66% while rear
lift js practically unchanged. The net
effect is that the total lift coefficient
for the Daytona is zero or slightly COEFFICIENT
negative while the total lift on the
1969 race car is positive. So, the
aerodynamic forces tend to hold the FORCE
Daytona .on LT* Q road as speed Hi’
creases. Cor nering performance also A L
x
improves as the more negative nor­ <
mal forces at the wheels increase the
tires’ ability to accept side forces. D
The Daytona also enjoys improved 04
directional stability, the rear axle COEFFICIENT 03
side force being increased 2 to 3 0.2
times while the front axle side force 0 I ? -
is lowered. The unstable yaw Hl to LIF T o <
moment around the car’s center of -O.i
gravity is decreased, when compared
with the 1969 race car, diminishing 02
oversteering tendencies at race COEFFICIENT O.I REAR AXLE
speeds. o
L IF T -O.i
Component interaction -02
The major causes of the relatively -9 -6 -3 O rO o o? 12 15 18
YAW ANGLE, deg
high axial force acting on the 1969
race car are the blunt front end FIG. 3 The effectiveness of the undernose spoiler is very sensitive to front end

Volume 78, Number 5
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