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Old 06-02-2009, 12:30 AM   #11 (permalink)
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Originally Posted by MetroMPG View Post
I'll be the last person to argue that trying to test outside of using a dyno in a lab isn't fraught with potential problems. It's not easy - it takes a lot of time to try to control as much as possible.
No doubt. I have a lot of respect for the people who go out and do the coast down testing. And yet, it seems as though all the that shade tree aerodynamicists (sp??) congregate here have managed to produce god results.

With the wheel skirts, I would have expected a larger impact. It makes me think twice about piling effort into making mine. 1% if fairly small. I guess every little bit counts.


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Old 06-06-2009, 03:49 PM   #12 (permalink)
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the effect

Originally Posted by MetroMPG View Post
A note on my speed choice for this test: I tend to want to test around 85 km/h because that's a "normal" speed for me. But I should probably test at higher speeds for aero mods because differences, if any, would stand out more clearly from the normal variability of readings. Plus, I'd like people who drive faster to see the potential gains to be had from aero mods instead of dismissing the smaller differences detected at lower speeds.

Also, it's likely that the effect isn't consistent for different vehicles - some will benefit measurably, others may not. Which just makes me want to re-test the Flea's skirts to see if it happens to be one of those vehicles that benefits more than others, or if my original "data" was off.
John Gilkison was the first person I know to use the expression "signal-to-noise-ratio" when discussing an attempt to deduce results from testing small features of streamlining.--------Darin, I'm willing to bet a box of donuts and some gourmet coffee that you've cut drag measurably.These are the hardest things to verify.And the energy you expend attempting to quantify the results is very much appreciated when viewing your scatter-plots.I think windtunnels and their highly sensitive force measurement equipment were created for "finessing" shapes and evaluating these subtle changes to body architecture.Most of my projects are the "pick-and shovel" stuff Alex Tremulis used to speak of,and much easier to verify.My hat's off to your continued efforts to nail down these micro-environments of drag reduction.Much obliged,Phil.

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