After a few failed attempts at making hat stiffeners for the main spar, I decided to try making a press die for them in much the same way I made my flanging dies. Here's what I came up with. I used the same timbertech composite material as I used for the flanging dies, and was able to fabricate the whole set using a table saw and some 5-minute epoxy from ACE hardware. I rounded all of the corners to the proper radius, and epoxied the male 45-degree press flange to the top die. To use them, I put a piece of .025 between the dies and put them under pressure with the shop press until the bend is formed, then trim the flanges to the proper size. Out comes perfectly shaped and repeatable hat stiffeners lookin' like the factory made 'em.
