Page 21 - Combined_73_OCR

2) With the spoiler installed, more air is forced over the

nose surface. The upper surface of the 18" extension

is more favorable from a drag standpoint than the 9"

extens ion.

The results in Figure 7 explain the selection of the 18" extension for

the Daytona Aerodynamic Package.

The effectiveness of front undernose spoilers is very sensitive to

front end shape. This point is illustrated in Figure 8 where the spoile

[D ffectiveness as a function of yaw angl c n presented for the 1969 race

car and the Charger Daytona. Spoiler effectiveness is defined as the

force coefficient with the poiler minus the force coefficient data with-

out the (n poiler. The incremental axial force coefficient data indicates

the spoiler on the Daytona nose is 4.5 times as effective in reducing

axial force as the 1969 spoiler at zero yaw angle. Similar results are

seen on lift. These data indicate the spoiler-nose combination is a

highly interactive aerodynamic system and must be approached and handled

as such.

The effect of spoiler position on the aerodynamics of the 18" ex­

tension was also studied and these results are presented in Figure 9.

Spoiler fore and aft location has a much greater effect on front axl rr
lift than on axial force. Since the underbody portion of the vehicle

in front of the spoiler is highly pressurized relative to the area

behind the poiler, the more forward spoiler results in the lowest
front axle lift. Rear axle lift also varies with spoiler size and

location but to a lesser degree. The three positions investigated are

shown; 8", 13” and 18”. Notice as the poiler is moved aft the poiler

chord becomes less if the 6.5" ground clearance is maintained. For the

-20-