[aerohead]

Originally Posted by pstrbrc

OK, this is something I'm working on for my Escort. And one of the limitations that I have is that TOWMBO will not tolerate any public display of eccentricity.
So, a belly pan is acceptable, but a boat tail is not. Wheel discs are borderline acceptable, rear wheel pants are clearly not. So, I might get away with vg's, but...
So, my back glass is ~30* from horizontal, and a line from the back of the roof line to deck height at 14* says I need a 8"+ shelf attached.
What does the collective mind know about the +/- of rear window dust deflectors? I know, those are usually only for "wagon" backs, but a deflector with an included arc of 25* would certainly be a place to start. Yes, this would cause lift at high speeds, but at econ speeds, what would be the down side? Would a smooth deflector blade cause more drag than 8 vg's across the back edge?

What I've read about them is that the act of directing air towards the wake is good,but air separates off the back side of the deflector for a net drag increase overall.--------- simple flat plates extending straight back,which capture vortices along a quasi-Kamm profile have been demonstated to help,although you have the "length" issue.