Well, making ductwork took a lot longer than expected. Last night I got the passenger side oil cooler duct done. The rest should go a little faster now that I got the hang of it, and the driver side oil cooler will be easy because it's just the inverse of the passenger side.
I also tried to keep the number of pieces to a minimum. The sides and bottom are all one piece, then a top piece with flaps on the side comes down on top and gets riveted to it. I did it this way so that when looking at it from the outside of the car, you only see one piece with nice smooth bends instead of multiple pieces riveted together (you can't see the top piece with the rivets from outside of the car).
First, I mocked it up with cardboard. Then I laid the cardboard out on a sheet of 6061-T6 aluminum, 0.040" thick (it's white because it has a PVC backing) and traced it out:
Cut it out:
Mark lines to show where to bend the sides up:
Bend the sides on a break:
Test fit (make sure you test with the bumper on as well):
Trace out a top:
Cut the top piece out (one inch longer on each side so you have ears to bend down to rivet to the side pieces:
Clamp it where you want it, and then drill 3 holes on each side (through both pieces at the same time) for the rivets. I used 1/8" aluminum rivets. This is also just mocked up, I'm going to send the pieces to powdercoat (black), then rivet them together:
Next up: driver side, and then radiator/intercooler ducts:
