Who has made their own rear diffuser out of aluminum?

[anguilla1980]

Out of frustration that there appears to be ZERO companies who sell a pre-made lower rear air diffuser for a 1969 Camaro/Firebird, I've decided to embark on making my own out of aluminum. I have no metal fabrication experience and no welding experience.

I plan to use CAD for the templates (cardboard aided design) and tack everything together using a torch and Alumaloy rods. Then I'll take it to a local shop for proper TIG welding of all the seams.



It will be designed to attach fully to the bottom of the rear valence and to the bottoms of the rears of the fenders (think a giant rectangle). I plan on using dzus fasteners. I *think* there is just enough of a lip on the fenders and rear valence for drilling to make this happen so the flat sheet will be close flush with the actual body panels.

So, I have a few questions lol.


1) What gauge aluminum sheets and what grade aluminum should I buy for this?

2) What size Alumaloy rod should I use for the tacks?

3) What should the front look like in terms of where I end it? Like do I wrap the front up around the rear of the fuel tank and fasten the front sealed to the bottom of the trunk between the rear frames above the axle?

4) For the verticals, how many should there be? I'm obviously not an aerodynamicist so I need to depend on what others that found to work. Knowing how many will then tell me how far apart to evenly space them.

5) How far down into the air stream do the verticals need to protrude?

6) Should the verticals just be perfectly straight, or slightly contoured out towards each side just a tiny bit?


To clarify, the car will be participating in top speed events, however, I plan on staying in the sub-199mph class. I am more concerned with the stability of the vehicle from a safety standpoint than I anything else. I also plan to run the car on road courses which can be 145mph+ in some areas (think Big Willow).

Pictures are worth 1,000 words if anyone would care to share pictures of their functional rear diffusers (not just made for looks).

Thanks!!!! All comments/suggestions are welcome!

Alex