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Old 05-31-2020, 10:34 PM   #3 (permalink)
JulianEdgar
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Quote:
Originally Posted by California98Civic View Post
Because people will ask for it, I went and found the cited airtab study (I think this is the one):

[Anon,] "LOCKHEED GEORGIA LOWSPEED WIND TUNNEL HONDA CIVIC HATCHBACK AIRTAB(R) MODIFICATION RESULTS" Airtab | Aerodynamic Fuel Savers | Test Results

"Executive Summary:
This report shows conclusively that the Airtab® product reduced aerodynamic drag
forces at the base area (the rear facing surface) of the test vehicle. The test showed a 4%
reduction in horse power required to maintain a steady speed of 55 mph. Only the sides
of the vehicle were fitted to assure the most aerodynamically symmetrical run data. By
adding Airtabs™ to the rear roof line as well, a conservative performance benefit
extrapolation of these findings would be in the 50% range resulting in a further HP
required reduction to approximately 6%. The test also shows that the vehicle drag
coefficient (CD) is reduced at every yaw angle from zero to thirty degrees angle from the
airflow and that this CD reduction increases at greater yaw angles."
The above test was done on a 1982 model Honda Civic with a Cd of 0.45. I very much doubt the relevance of that testing to any more modern car shape.

Ford tested Airtabs and found increased drag.

I tested AirTabs over a 150km daily round trip and found increased drag.

In my book I cite a paper using VG (not Airtabs) at the upper rear of a hatch-shaped car and they increased drag and lift.

I love using AirTabs to promote flow attachment but I don't think they work in reducing wake drag.

To the OP: good find on the flexible small VG, and I think the basic idea of VG behaviour changing with crosswinds is sound.
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