Side bending problems

[seangil]

Hi Folks,

I'm bending sides for my first couple builds on a fox bender. So far, I have been using mahogany, limba, and maple. I've been experimenting a bit with different approaches to sandwiching. I am consistently having a problem that the waist comes out fine, but the ends spring away from the form by 2-3 inches. I've mostly been heating to temperatures around 300 degrees and maintaining for 7 minutes or so.

Is there any generic rule of thumb that might help me out? For example, failing to hold the form on the end is usually about the duration of the heat or the temperature or whatever?

Thanks,

Seangil

[Bruce Sexauer]

I make my bending forms’ curvatures about 15% more exaggerated than the side is to be.

[redir]

Yup, bend further than necessary and it's always nice to have a hot pipe to touch up on.

[Fathand]

I also heat to around 300F, around 7 minutes seems about right. I then seem to have better luck if after cooling for 15 minutes or so, I bring it back up to temp for another 5 min. then let it cool overnight before releasing the side. I seem to get less springback this way.
I spray my sides with water and wrap in tinfoil, bend on a solid plywood or chipboard form with a heat blanket, my gloved hands and clamps and cauls. I do not use sheet metal sandwiching.

I do however get annoying water stains that need to be sanded off.

[mirwa]

Sometimes the easiest solution with springback is after taking them out of the fox press, use a pipe and hand bend to finish them off