Current status of project - added roof extension panel. Also tapered the sides inward towards the rear. Did this by cutting away the lower edge, so the side panels can rest on rear qtr panel as they taper inward towards the trunk lid edges. I also added several aluminum bar stock stiffeners to the main lower center panel.
Have been driving with this setup for two weeks with pretty good FE numbers in fall weather.
If I'm very fortunate I'll be able to do some coastdown testing this weekend.
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Original posted message starts here:
With the rear of a notchback coupe contributing seriously to car's the aero drag, I've developed a plan to try to remedy it on my Civic.
This design is based on earlier discussions in this thread:
http://ecomodder.com/forum/showthrea...les-17796.html
The concept is to plant a long, flat spoiler with the rear edge at a point meeting the template curve. While not as effective as a proper shortened boat tail that would extend to the same point, the side panels will help sequester the air in the "chamber" above the panel, more or less "faking" the template as far as the air flow is concerned. And, you can see out the rear mirror and, with a few cuts and hinges, can still open the trunk lid.
Basically, it is a flat spoiler panel, who's rear edge meets the template curve, above the bumper's rearmost point. Panel's forward edge meets the rear glass. Two side panels extend the C-pillars rearward to a point even with the bumper's rearmost point, and support the flat spoiler panel.
The spoiler's forward edge is aimed at the rear view mirror, so the spoiler should appear as a thin edge from the mirror's viewpoint, and not block the driver's view out the back.
I also came up with a design for a bracket to attach the side panels to the edges of the rear glass. I expect to need additional attachment points but this has the benefit of being cleanly removable later if needed. Attaches to glass with silicone glue or double stick foam tape.
Photo above:
Tan = spoiler panel, aimed at rear view mirror.
White lines = template curve + vertical.
Yellow = side panel.
Photo above:
Heavy tan = spoiler panel, aimed at rear view mirror.
Thin tan = fold/hinge in spoiler, to allow trunk opening.
Yellow = side panels.
Thin red = cut/hinge in side panels to allow trunk opening.
Photo above:
Mount bracket attaching side panel to rear glass.
To be silicone-glued to glass.