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Old 05-04-2020, 05:17 PM   #39 (permalink)
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Originally Posted by j-c-c View Post
Yes PW =plywood, is that what is in your test?

"Norm" being more those that are by professionals for wind tested applications vs those like some of us shade tree aero wannebe's. And even with a wide diversity in designs, from experiences, they usually fall into a 6-8" strake separation, yours looked wider, and hence my comment, and I am still in the dark as to what the separation was in your test.

If that boundary layer is that deep at that location, I suspect it's not a prime candidate for smaller strakes to begin with.

"Minor" is rather subjective, and it would have been straight forward to determine, if a test had been made without strakes and PW only, to better support your stated conclusion.
The strakes I trialed are 410mm apart. I've seen production cars with strakes as far apart as the full diffuser width, all the way to being only about 75mm apart. In my book, page 95 and pages 183 - 185 have some good views of strakes in diffusers of production cars.

The plywood (both strakes and base) is 3mm thick. I didn't bother describing the assembly because it's shown in the third post in this thread -

When it was in position, it was taped around all edges. The sheet was sized to be the same as the rear diffuser, which in this part is flat (ie not curved). I would guess the boundary layer as being something like 10mm thick at this point, so I can't see small discontinuities making much difference to anything. At their maximum, the strakes are 90mm deep.
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