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Old 11-03-2008, 12:22 PM   #3 (permalink)
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vectra a - '95 Opel Vectra GLS
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Technically you have an average % of vertical distance covered on a selection
that's right,sorry if i misuse certain terms here and's just one dimention, but than again, most dams i've seen where a little less wide than the wheels... i assume that's becouse they stay withing the overall bumper shape, and because the way the air separates of the edges wauses the dams to virually enlarge themselves a bit.

i had half expected a more inconsistent picture so i'm quite pleased with this.... the relation to the tire radius got me thinking...

in the past i tried to calculate the forward speed a the tire surface in the quadrant where it's exposed to the airflow...

since the bottom of the tire touches the ground, at that point there's no forward component to the motion (the only time that happens is when you slam the breaks so hard you start slideing)

So below about 56 % of this quadrant the surface of the wheel is actually moveing slower forward that the rest of the car. A dam in front of it would always have more drag as even a better Cd would be overruled by a slower speed and therefore less subject to aero drag.

i'm sure there's other forces at work here, but i think extending a dam beyond lets say 58% is a no-go...
aer·o·dy·nam·ics: the science of passing gass

*i can coast for miles and miles and miles*
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