Page 3 - Combined_23_OCR

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NO SPOILER
8-in. POSITION-6.9-in. CHORD
13-in. POSITION-5.2-in. CHORD
18-in. POSITION-4.1-in. CHORD

65-in REFERENCE
GROUND CLEARANCE

I HORIZONTAL STABILIZER
-
ANGLE ~ 0 deg
COEFFICIENT 0.35 COEFFICIENT P O _L O ' cnO Q

FORCE 0.30 FORCE O oj <J! I I

AXIAL AXIAL O j u O t

0.5 ,0.3
COEFFICIENT 02 COEFFICIENT 0.1 o
0.4
0.2
0.3

LIF T 0.1 o LIFT -0.1 FRONT AXLE

-0.! 0.2 REAR AXLE
071
COEFFICIENT 02 o COEFFICIENT -0.1 o -O n o o o
0.1

o
LIFT o - LIFT -0.2 o
2
-0.3
-9 -6 -3 o cu O U3 12 15 18 -6 -3 o rO < n 12 15
YAW ANGLE, deg YAW ANGLE, deg
-n 4 Position of the undernose spoiler on the nose extension of- FIG. 5 Angular position of the horizontal stabilizer is chosen to
Teets front cxle lift. The Daytona race car uses the 13-in. location. give the desired oxle. lift coefficients ct expense of axial force.

Aerodynamic devices affect both axial force permits a wide range of axle lift
coefficients (Fig. 5). The trade-off is
and axle hit coefficients. Test set Cl C l (D C n O ibed.
an increase in axial force.
Comparison of the horizontal sta-
shape, large cooling openings, and in. nose extension with the spoiler bilizer and a 1 -in. hi sb, 4 - on cL Cj rear
a rough underbody. Fitting a front cuts axial force significantly more deck lip spoiler shows the-horizontal
spoiler, restricts airflow under the than a 9-in. nose extension-spoiler stabilizer is a more effective and
vehicle while increasing the flow over pair. Conversely, the 9-in. nose is efficient aerodynamic system. The
the top and sides. If a streamlined superior when spoiler is not fitted. ratio of lift to axial force is the usual
front end is added, axial force in­ While the position of the spoiler measure of aerodynamic efficiency.
crease at the hood and fenders is on the extension hardly affects the On this basis, rear deck lip spoiler
minimal and total vehicle axial force axial force (Fig. 4), it does change efficiency is 7 and that of the stabili­
decreases. front axle lift. The 13-in. location is zer is 19.
The effectiveness of the undernose used on the Daytona. Two-dimensional flow theory pre- *
spoiler is very sensitive to front end The 12-deg angular adjustment diets separated flow over the back­
shape (Fig. 3). For instance, the 18- built into the horizontal stabilizer light area of any car with less than

54 SAE Journal, Moy 1970