tube bending

I am building the tailfeathers for a 14. I wondered how to bend the outer 3/8 tubes. I was told to bend them around a soft tire. That worked but I eventually found that using hardware store spring bending tubes and a conduit bender gave me better control. I put a larger spring over the 3/8 spring so the total size would be a better fit for the groove in the conduit bender. I then mounted the handle of the conduit bender in the vise at eye level so I could pull down on the spring covered tube while watching the progress. I could then slide the 3/8 tube through the springs to continue the arc. Having the bender elevated allows both ends to hang down so you can keep them in the same plane. I went slow and was pleased with the results.

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Unless you want to spend a lot of time building a form, you got a good method there. The form building is a PiTA as it takes a lot of time and tubing to get the spring back correct. If you are just building 1 or 2 sets, stay with your method.

I built a Pitts years ago. What I did was fill the 3/8 tubing with DRY clean sand and plug the ends with a wood dowel. Then found a tree about the right size and started. Had to change tree sizes as the radius changed but it worked fine for all the tail feathers...

Back in the mid 80's one of the ultralight designers was known to make cryptic references to his "7:50 x 16" airfoil, seems his pickup used that size tire and one thing lead to another![/b]