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Old 07-26-2012, 04:50 PM   #16 (permalink)
gone-ot walking...
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Originally Posted by drmiller100 View Post
what you wrote makes no sense to me.

I don't compare fish to birds. I don't compare tractor trailers to hatchbacks.

Comparing Cd is worthless between the two.

Cda is what matters, because if you combine speed, Cda, and weight, you can KNOW the drag of the car.

Cd is a way to sort of calculate Cda, but it is kind of worthless by itself.
...hmmm, let me try to explain Cd's "usefulness" like this:

1) Someone has a given vehicle, so it's A (frontal area) is set.

2) But, that someone wants to reduce the vehicles' aero drag at highway speeds but doesn't know *which* mods to do first.

3) So, that someone looks at the various "tweeks" available and their percentage-affect upon "total" Cd in general (ie: effectiveness).

4) Now they can select & use the tweek(s) that produce the most change in Cd, within cost effectiveness, in order of estimated "total" drag reduction (CdA).

Two "older" ROAD & TRACK magazine articles on this very subject worth reading are:

• Dennis Simanaitis, "Seeking Light at the End of the Tunnel: My Cx is lower than yours; or is it?" ROAD & TRACK, Aug-1982, pp. 32-35.

• Del Coats, "Aero Estimation, Self-Taught," ROAD & TRACK, Aug-1982, pp. 41, 42 and 44.

Last edited by gone-ot; 07-26-2012 at 05:10 PM..
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