I've just bent my first set of sides using a home made bending machine following the John Mayes dvd's. Everything has gone well with the bending except that the sides have sprung in all sorts of directions and won't fit the outside mould. I've made the bending machne mould about 3/16" inside the shape of my outside mould.

Does it need to be shaped to compensate for the springback, and if so on which parts of the mould?

Thanks for all the suggestions for my last problem (humidity) I think I've got that sorted.

A little springback is to be expected. You can minimize it by letting the sides cool in the bender and heating a second time. Be sure to allow them to cool before removing and clamp into your outside mold immediately. Also, the hotter you can go (without scorching, of course), the less springback.

Compensating the bending form works too. I've done it by trial and error. Not too hard to figure out.

Another option is to touch up by hand after the side comes out of the bender.

Good luck.

Mark,

I just finished my first with a luthier who has been in this forever and we bent it same way, set up the initial bends on a heating iron close to the mold, and then over to the fox bender for final shaping.

Since this was my first and it is the only way I know how to bend, am I weird too?

I was hoping to turn out to be a cool luthier guy. (Though weird would be OK if I could end up with something half as good as yours, I'ld even settle for an 1/8 as good)

I spray my sides with SuperSoft II the day before, then let them dry out flat overnight. The next day,I spritz the wood with plain water and then I line up the waist in the bender with the blanket on top of the wood and a slat under the wood and over the blanket. I tighten down the waist just enough to keep it from moving on me, then turn on the heat. I heat at medium high until I can feel the heat on the underside of the wood, then clamp down the waist......s....l....o......w.....l....y. When that is all the way down, I bend the lower bout and then bend the upper bout. I leave it on medium high heat for 15 minutes, then let it cool for about 2 hours. Then I reheat it again for 15 minutes and then let it cool to room temperature (over 2 hours).

So far I have had really good luck with no breakage and very little if any ripples or springback.

Thanks for the advice.

I used John Mayes sandwich method- blanket,slat, wood, slat and blanket. I left the first side in the bender for about 2 hrs, then put it straight into the outside mold. The 2nd side stayed in the bender  overnight, then got put into the mold. I left them there for two days, but when I took them out they sprang out about an inch at each end and the middle bout had also moved.

My sides were rosewood at 80/1000 , and I took them to about 320 degrees then down to 290 cycling four times.

Charles.

[QUOTE=Bruce Dickey]I bend my waist bend over a pipe, then toss it on the bender for the easy parts....

Springback, not much, I compensate my forms at head 3/8" and tail 1/2".

I yank 'em and clamp in the mold and let 'em cool.

It all works, heck I saw a guy bending over the tailpipe of his truck the other day!      That was right before he keeled over from CO poisoning.... (not recommended) [/QUOTE]

Bruce,

Thank you for your concern. You'll be pleased to know that I'm back on my feet. Doc says I should be bending sides again soon. (Me thinks he likes repeat customers!)

J.R.