Page 20 - Combined_73_OCR

while increasing the flow over the top and sides of the vehicle. When

the front end shape is very blunt, the increased flow over the unfavor­

able hood and fender leading edges results in an axial force increase

which may more than cancel the axial force reduction obtained by shield­

ing the rough underbody. If a streamlined front end is used, the axial

force increase at hood and fenders is minimal and total vehicle axial

force is reduced. This is an axial force reduction in addition to the

benefits of the streamlined front end. Reducing underbody air flow with

the spoiler results in a lower pressure under the car and accounts for

the lift reductions associated with spoilers. This lower pressure nJ r— 4 03 O

improved cooling air flow by increasing the pressure differential

across the radiator at any road speed. If cooling air flow is already

adequate, cooling inlets can be made more restrictive as has been done

on the Daytona.

The wind tunnel development of the Daytona low form drag front end

included a wide pectrum of nose configurations. The nose configurations
investigated fell into two broad categories; a nine inch extension

and an eighteen inch extension. Both basic shapes were developed with
respect to achieving minimum axial force. The results of this investi­

gation are presented in Figure 7. The data indicate the 9” extension
without a front undernose spoiler is superior to the 18" extension with­

out spoiler. However, the 18" extension with spoiler is significantly
better than the 9" extension with spoiler. The phenomenon is probably

caused by two effects:
1) The spoiler chord on the 9" extension is less than on the

18" extension for an equal distance from the nose.