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Date:         Fri, 4 Nov 94 12:24:39 AST
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         smitht@jupiter.sun.csd.unb.ca (Tim Smith)
Subject:      Re: Kamm tail + mpg

>i'm not sure, but i think that kham was/is from pakistan or india. i'm >not sure maybe somebody else remembers beter than i do. > I think he was german, Kamm, and the Kammtail represents a balance between surface area drag, ie skin friction, and flow turbulence drag at the rear end of the vehicle. Essentially, a long gently tapered back end allows the air flowing over/under the car to merge together cleanly, without creating a turbulent suction zone, but the surface area of such a long back end increases skin drag countering the drag reduction gained. Kammtail is thus a workable compromise for overall drag reduction. Those whale tails are to create down force only, plus push some cooling air through to the P-motor and AC cooler. The air screaming over the top of an unadorned P-car is going faster than that passing under it, since it travels up and over the car. This generates nice lift at high speeds, like a good airplane wing should, hence the need for a whale tail, to push the back end into the pavement. Preventing air from getting under the car is also a great help in cutting this lift effect, hence the massive air dams seen on the front of P-cars. Whale tails are supposed to be used only with a front dam in place to avoid unwanted floating of the front end at high speeds. I have seen drag coefficients of 0.36 for fully fitted P-cars, not exactly low nowadays, but if you've got 400+ HP and the car corners like it's on rails, who cares. tim s.


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