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Old 07-24-2010, 11:25 PM   #46 (permalink)
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OurInsight - '06 Honda Insight
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Originally Posted by 3-Wheeler View Post

I decided to go with an underside angle of 13 which is shown in the picture above. This angle was chosen as a compromise between good air flow and scraping driveway aprons.

This angle also keeps the license plate at the same height as the stock Insight. Making the underside angle shallower would get the plate even closer to the ground, and I think the license plate and lights are getting pretty low already, thus the 13 angle.

Yep, the practical does seem to intrude If tuft testing shows too much separation, then you can simply add foam and fiberglas as a fix. The added weight will be small. You would even have the option of fabricating several rather simple "add on" bottom pieces of differing angles. Basjoos had rather steep bottom angles also, and has highly satisfactory reported results. Of course, he has gone well beyond boat tails, so it is a bit difficult to sort out the various improvement contributions.

On the question of underside angle, I have wondered if better results would be obtained by keeping the angle small and doing something a bit more fancy with the bottom rear edge. Several things come to mind. First, the bottom rear could be shortened and rolled up to create a bit more ground clearance. Another option would be to try some sort of captured vortex effect like I think is going on with the stock under bumper shroud. Or, maybe just build the rear transom at an angle of about 30 degrees, with a recessed license plate plane. Just thinking out loud. Hucho showed three "unconventional [termination] methods" in section 4.7.3, but he was not particularly positive about any of the three. I'm not seeing much encouragement on any of the more fancy meaures.

Last edited by jime57; 07-24-2010 at 11:32 PM..
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