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Old 10-05-2008, 12:00 PM   #3 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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Regarding speed: tuft testing doesn't require high speeds. It's just flow visualization. Speed matters more when trying to quantify some aero mod, where 100 km/h may reveal something you can't detect @ 60 km/h.

Also... my camera rig probably wouldn't permit very steady pics @ 100. Or stay attached to the car, for that matter!

Julian @ AutoSpeed seemed to like 70-80 km/h for his tuft testing experiments. I was aiming for 60 km/h.

-----

I captured the "skirts-on" video this AM, and again I was surprised by the results!

Just as I was surprised at what the tufts showed on the rear window/trunk of the Corolla after sticking AirTabs on the roof, sticking cardboard wheel skirts on the Firefly had a bigger apparent impact than I expected.

Here's a still captured from the "skirts-on" video (I'll post that later today):


What I saw was ALL tufts streaming back cleanly/quietly, with the exception of the one on the bottom row immediately aft of the skirt (the curve at the aft end of the skirt was too great = flow separation). Occasionally the tuft aft of that one would wiggle too, but not as much.

The biggest surprise to me were all the other tufts on the door. Not nearly as much wiggling as in the first vid. The noticeable effects of an open wheel well extend much further back than I would have guessed.

More pics & vid coming...
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