[gumby79]

Originally Posted by JulianEdgar

So I tried some rear Edgarwits to see if I could reduce wake size. These were additional to the front ones, and taller. GOE222 true aerofoil profile.



I did some throttle stop testing with the following results (km/h at 30 per cent throttle, low-moderate gusty headwind):

• No rear Edgarwits: 95
• 1 finger rear gap: 93
• 2 finger rear gap: 95
• 3 finder rear gap (ie about parallel): 96
• 4 finger rear gap (ie diverging): 96.5

That would make 4 finger vs std about 3 per cent improved in drag.

4 finger gap:



For people interested, but having other cars, don't forget Insight boat-tails a lot with its narrower rear track.

Interesting to see the better performance at the rear with the diverging duct - opposite to what occurred at the front.

I'll do some more testing on a still day, but to me this result is borderline. I'd need to see a big jump in drag reduction on a still day to go in this direction.

Would the rear wing experiment not be just a vertical "blowen diffuser "?

What was the wind direction for the Eroding Clay test? It will help with interpretation of the results.



My interpretation based on what I see, assuming wind from the left ( American driver side)
▪ The airfoil profile has too much curve on the convex side , evidenced by severe separation less than 1/3 Cord at the bottom and 1/4 cord at the top. This would be a good application for test of VG's in a specific use case, (maintenance of attached flow in extreme angle of attack as demonstrated). I have seen a proper demonstration you're witty Edgar's work as intended to a benefit, is there room for improvement, possibly/ possible not.

¿ I'm taking it this was the downwind side?
▪ The up wind /drivers side I expect to see almost,but not quite,a poler opposite. Eg cleaned off by attached flow out side and dirty/covered by sepperated flow on the convex wing surface.

▪ the up wind turning vane / wing is acting like a blown diffuser blowing the wrong direction ,at a yaw angle between 45-180° at typical road going speeds.
E.G. By ~45° yaw (angle of attack~ 90° negative) the wing is past full stall and by ~50°ish yaw it becomes a blowen diffuser.