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Old 06-07-2013, 11:53 AM   #110 (permalink)
COcyclist
Aero Wannabe
 
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Join Date: Dec 2007
Location: NW Colo
Posts: 738

TDi - '04 VW Golf
TEAM VW AUDI Group
90 day: 52.55 mpg (US)
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Quote:
Originally Posted by christofoo View Post
All of us have underestimated the potential for aerodynamic misbehavior in this design, although I think it will be fairly easy to repair by adding a baffle and controlling detachment lines.
I hope so. Even a small gap seems to have an effect.
Quote:
Originally Posted by christofoo View Post
That's right, I've got air moving up the rear glass. If I'm not mistaken, the low pressure at the base of the windshield and trunk is actually pulling air up from the underside of the car. It's unexpected, but something I knew was coming, since at 65 MPH last week I saw rain water fly up from behind the trunk and land in the middle of the rear glass. (And thought 'd&^#, what a spectacular goof'.)
I take it you did not notice the rain droplet phenomenon without the cargo carrier in place?

From the one photo you posted the tufts seem to be going in the right direction on the cargo carrier. Perhaps you end up with extra cargo space that doesn't hurt your mpg and some important lessons for the rest of us. It is easy to speculate but harder to do it right. Thank you for jumping in and trying something in real world conditions.
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Quote:
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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