TEACH ME! Challenge Budget Rear Spoiler

Hello all! Im in the process of building a 2018 Challenge Car and I wanted to get some ideas/help on a challenge budget priced rear spoiler. 

Here is the link to my build if you are interested: G20 BTCC Build

I know that there are many options out there but i want functional. This car will have a life after the challenge as a low buck track day and autoX car. I don't really car about competing in autoX so I don't care about SCCA autoX rules. 

I have seen past challenge folks do all types of stuff from plexi glass, to wood to PVC to metal you name it. What would you do? What have you done? What would you try? Let me know what you all think. 

Here is how the car sits now:

The car will be finished with this BTCC Livery:

Thanks in advance yall! 

I'm pretty sure this is as cheap as you can build a functional spoiler.  3/8" plexy and a single piece of Home Depot aluminum.  And it works!  At the lower speeds of autocross you need big and steep for your spoiler to be effective.  Less so on a road course although this is stout enough for 100+ mph

In reply to KyAllroad (Jeremy) :

Oh yeah that is one of the ideas that I have been exploring. How did you determine the curvature of the spoiler? Also, Could you send me some picture (if you have them, dont go out of your way) of the mounting hardware you made? 

your miata looks really sweet. i bet that thing rips. 

Subbed for miata spoiler porn.

If you are not worried about any particular rules package, then set your spoiler back off of the rear deck between two solid endplate fences, with a floor that extends to the decklid. This will give you the most leverage and support for your spoiler. If you design/build it with some adjustability included, you should be able to tune the balance for higher speed track days (lay the spoiler back).

Also, while you are prepping the car and repairing the front fenders, try to incorporate some sort of dive planes ahead of the wheels. They were not the norm with the BTCC cars at the time, but they will help with downforce.

All the items above are likely to be draggy, but that should not be an issue with the challenge auto-x (maybe for the drag portion). You may want to make plans for the parts to be adjustable/removeable for track days.

In reply to B13Birk :

Thanks, it's been sold now but it was a fairly good approximation of a CSP car.  I used a piece of cardboard to get the shape of the spoiler.  If you zoom in on the pic you can see how the brackets are triangulated.  Class rules are no more than 10" high, but that's plenty.  Angle of attack is around 60 degrees.  Here is another pic, mine is the third car over.  The other two are "real" CSP cars.

It was enough downforce that on heat cycled R7s i data logged 1.45g on concrete.  Someday I want to be able to afford fresh Hoosiers and see how they feel.

Say it with Me- coroplast. Ita gotta be coroplast season somewhere. 

I've done one similar to KyAllroad's, although I used ABS plastic.  If you can use hinges at the bottom, adjustment becomes pretty easy.

As far as coroplast is concerned, there's lots of it still around here- what is the challenge policy on theft?  

Mine on the datsun is a 2x4 that i fit to the hatch, then screwed coroplast to that in my shape and covered with fiberglass 

In reply to KyAllroad (Jeremy) :

Oh man yes! This angle is perfect thanks!

In reply to Patrick :

I love this idea. Good stuff.