For materials, I used 1/8" X 1" aluminum flat bar. I ended up using about 30' feet total.
To fasten it all together, I used 3/16" X 1/2" aluminum rivets, because it is quick, easy, secure and helps to keep things simple and clean. Also, I already had a rivet gun and a supply of rivets.
The skin is going to be made from a 4'X8' sheet of coroplast. I have not attached the coroplast yet, and I am still debating the best way to make the compound curve required for the back corners. I want to do it all in one piece, but that may not work too well. To attach the skin, it will also be riveted. To attach it along the rear window, I am going to bend up 2 or 3 "L" shaped pieces of aluminum per side to attach to the aluminum frame, and give a good mounting location.
I have all sorts of progress pictures of building the frame, but I won't bore you with those unless you would like to see them to see the order I built it in.
Here is the kammback frame. The hinges are mounted to the frame here already.
What I learned from my smaller kammback, was that any white or brighter surfaces reflected off the back window and caught focus when looking in the rear view mirror. So when I put the skin on this one, the inside of it will also be painted a flat black. Here you can see that I painted any parts of the aluminum that will be visible, to help with getting a good view out of the back.
This part of the build went very quickly, probably because I have already built this about 5 or 10 times in my head by the time I touched any metal.
Other than the "L" brackets for attaching the coroplast by the window and actually attaching the coroplast, I'm pretty close to being done. I still need to put a pair of pins in the trunk at the back, which will work basically like hood pins to keep the kamm down, and centered and prevent it from "wiggling". Then all that is left is to mount the hinges to the car and do some testing.
I will be mostly doing tank-to-tank averages for testing. But I'm really excited to get some solid numbers, so I might do some A-B-A tests. The hinges will be mounted to the roof of the car with about a half a dozen rivets. So I might just bring out a drill, a handful of rivets and the rivet gun and do some coastdown testing.
But that is for later.
I need to send a huge thank you to everyone here who has helped me out with inspiration, theory, and direct input with my build. I really appreciate it! You guys rock!