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Old 06-04-2011, 03:37 PM   #138 (permalink)
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Originally Posted by cfg83 View Post
brucepick -

(this is subject to correction by aerohead)

When I was first learning to use the template I made a mistake. Here is a correct overlay onto a 1999 Saturn SL2 :

The "0 degrees" is at the center of roof camber.

When I tried to apply the template to my 1999 Saturn SW2, I moved the template to line up to the end of my wagon, which was my mistake :

Question: Why is the stock Cd so different between models?

Answer(?): Even though the car designs are nearly identical, my mini-wagon violates the overlay template. When I keep the template over the center of camber (aka the same as the SL2), you can see the rear roofline break out of the template :

Saturn Stock Cds for reference :

Hucho would say that the wagon is 'overshooting' the 'Template' and with the hyper-curvature it's losing pressure regain necessary for lower drag.I'm guessing that the tumblehome for the coupe,sedan,and wagon is the same,but the wagon may not have plan curvature of the greenhouse like the other two styles.
Today's Cadillac CTS Wagon has its roof pulled down to the 'Template' but suffers from its slanted chop,where Honda and Mazda etc. do the textbook Breer/Fachsenfeld/Kamm/Korff breadloaf chop.
At this 'length' Vesta II and Boxfish are already down to Cd 0.19 although their plan taper begins in the front doors like Impact/EV-1
In a perfect world,all cars would be provided with at least 3-view images.Flow is 3-D,we need to know what the car is shaped like in 3-D
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