Quote:
Originally Posted by drmiller100
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.
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...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 (
Cd·A).
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.