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Old 03-26-2010, 05:26 PM   #17 (permalink)
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Originally Posted by Frank Lee View Post
What possible aid could the wing provide if the flow is attached down to the bumper without it?
Here is the link for the AutoSpeed article where I believe the above drawing was lifted:

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And Julian Edgar's explanation for the terrible drag and lift coefficients for the New Beetle:

"So the problem must be at the back? And it is. But it's a different problem to that which we've seen before. Here the flow remains attached right down to the line of the guard/boot opening. And this results in a very small wake for the (it's larger than you'd think) size of the car. But it also means that the airflow wraps in one long curve from the base of the windscreen right around over the top of the car to nearly the rear bumper. Aeroplane wing, did you say? And not only will this shape have major lift (without an undercar ground-effects tunnel, anyway; and I looked under and didn't see that), but much of the force will be upwards and rearwards - creating that monster drag".

And farther down in the article, the VW factory wing designed fix, a spoiler to combat lift at high speeds.

Aerohead has suggested that the "birdbath spoiler" and the double wing on the Mercury Merkur also reduce lift and drag. But I'm no expert. I only know what I read on the internet and it can be rife with unsubstantiated opinions.
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Originally Posted by freebeard View Post
The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
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