I have done a whole bunch of research, and I have found a whole bunch of info on making your own metal bending brake. One warning, you can get a small brake from Harbor Freight for remarkably little money, but as with anything from HB, caveat emptor... However, buying one would make you a mindless consumerist, and that's not what this website is about.... So on with the DIY goodness...

Here's a brake that was used to make the spars for a BD-4, he found the original plans over at the Van's Airforce website. He must be a Portlander, or have very good taste in beer.

This website has links to several interesting metal forming projects, including a tube bender. The bending brake is towards the bottom, and is a link to a reprint from one of the old DIY magazines from the 50's (and is stored on the website I linked to yesterday...)

If you are more interested in using brute force and a hydraulic jack, this brake is probably what you want.

Even though he uses the html marquee tag, the author of this website seems to have some good advice on building a brake as well, this one seems to also be of the 'hydraulic brute' type as well. Oh, and he also has a copy of the Corvair Shop Manual on his website, although the scanning job doesn't seem very good (the first few letters on every line are missing from the pages I looked at). Oh well, it's only about $20 to buy one from Clark's Corvairs. (click on the 'homemade tools' link...)