ideas for kammback on my '93 Lumina

[Regenerit]

I'm pondering the idea of making a kammback for my '93 Chevy Lumina. It would extend from the rear window down to the tip of my trunk. I would use lexan and aluminum bars to attach the lexan to for support. Below is a quick sketch of what it would be shaped like on my car.
Also, please note, on the second picture, my spoiler is attached, it is no longer attached which means I have some holes I could use in the future for attaching the kammback if necessary. I'm not very familiar with how any of you have made kammbacks for your cars so I would like to hear how you made them and what materials you used. At the moment, I'm thinking of using Lexan and aluminum bars with screws to attach the lexan to the bars.

[Frank Lee]

You are aware that if the angle is too steep it will be largely ineffective.

[Regenerit]

So not suggested then?

[Frank Lee]

No, definitely suggested, but with proper angles.

[Sven7]

Frank, you're being difficult. You know the angles and yet don't share them. Why?

The angle on the rear should be anywhere from 15-20 degrees from horizontal, or if you're doing a curved Kammback should follow the "streamlining template", below. Knowing the car is 5,037 mm long you can scale the drawing up for a perfect fit.



Make a cardboard prototype and tuft test it (search the forum for how-to) to see if it's working. Second thought, tuft test the stock car beforehand just to get a feel for what the air is doing!

People usually use some sort of metal structure (Basjoos used aluminum flat iron on the AeroCivic) with coroplast over it. You should be able to get free coroplast at your local political campaign office.

If you can find a spare trunk with that luggage rack on it, you'd probably be a few steps ahead in securing the kammback. A couple small holes are nice but a rack would be great!

[Frank Lee]

I wasn't being difficult; he could go look at kamm threads and learn a hella lot more than he would by me just giving out an angle.

[Regenerit]

How much less inefficient could you ballpark my suggested kammback figure to be compared to the one you suggested with a very low slope?

[CigaR007]

Here is some food for thought : http://ecomodder.com/forum/showthrea...ack-19904.html

[Frank Lee]

Basically I think if it's too steep it could end up being a wee bit better than nothing (I hear stuffing the wake does some good) but it wouldn't be half as good as a proper kamm.

[Regenerit]

So according to the link, cigar007 provided, the guy got about a 6% fuel economy increase. If I did the same, would I get close to the same increase?