Quote:
Originally Posted by MetroMPG
I've been assuming that the ideal teardrop as shown applies in both plan and profile views. Could be wrong. Phil?
The EV1 had a lot of plan taper (the rear wheel track is 9" narrower than the front according to this site), and a pronounced conical shape from the rear window aft that doesn't really show up in most photos. |
Somewhere,there is a photo of the EV-1,taken from above in GM's windtunnel.From this picture you can see that the frontal area is achieved about halfway down the door,then the body begins the progressive plan taper,growing "steeper" the further back on the body,approaching Mair's boattail geometry at the rear,with very aggressive reduction in area.This is where GM is getting Cd0.188.------------------ I really believe that the roofline geometry is a compromise for rear windshield outward vision.If the backlite is very steep,vision suffers from refraction and also internal reflections.-----------------This is also why windshields may never be steeper than what we see in contempory cars.------------ Here again,GM gets around this with complete wrap-around convex windshield,theoretically the "perfect" windshield.-------------------------- We notice that the roofline is also "dirty" with GM's Ultralite and PNGV.--------------------- Both have separated flow over the back of the car,but decent rear vision.