Bending wood with a Fox-style machine

[Gary Nutt]

Donald Fortune's forum thread about bending wood piqued my interest, even though I have been using a Fox-style bending machine. The first problem I am having is that I do not seem to be able to get the wood to bend quite enough, so there is quite a bit of forcing and clamping when assembling the sides, and putting them into a mold -- maybe this is just par for the course. The other problem I have is on a few sets I have had the sides crack on the upper bout shoulders or on the waist -- is this typically from impatience (bending too rapidly), not enough water, too much water, not enough heat? Recently I bought a blanket, but have not yet used it; I see that people often use the lights AND the blanket. Is this likely to help me with side bending?

Thanks very much,
Gary

[Bob Webster]

"The first problem I am having is that I do not seem to be able to get the wood to bend quite enough, so there is quite a bit of forcing and clamping when assembling the sides, and putting them into a mold -- maybe this is just par for the course."

All side sets will show some degree of spring back when bent in a Fox bender using a form that is an exact copy of the half-guitar outline. The degree varies with the type of wood and between wood sets of the same species. some folks make a bendng form that has exaggerated curves to counter this but it's still a crap shoot. If I were you, I'd resign myself to the fact that touching up the shape of the sides on a bending iron. You DO NOT want to be using hard pressure afterwards to get the sides to conform to the mold.

"The other problem I have is on a few sets I have had the sides crack on the upper bout shoulders or on the waist."

You're moving too fast and/or not getting the wood up to bending temperature. Using both the lights and the blanket are definitely the way to go with the Fox bender. The lights tend to cast alot more heat on the waist and much less on the extremes of the bouts. My routine is as follows:

1. Moisten the wood on both sides with just a moist paper towel, but don't saturate them. Once they're in the bender, I take ~ 20 minutes to bend the waist in several stages using the lights only. Take you're time and make sure it's HOT before you start turning the crank.

2. Turn on the blanket and give it about 2minutes to warm the wood. It heats pretty fast. Place a bout block on its springs but don't move it yet. With a gloved hand on the outer metal sheet, press relatively gently on the sandwich. When it's adequately heated, you will feel it resist and then finally yield. DON'T force it to move too fast. Do each bout that way in a progressive fashion and finally place the bout blocks at the ends of the form. As you gradually bend each bout, you are making sure that the side has good contact with the blanket and gets heated sufficiently. The controller for the blanket should be set at a medium setting, not max. You can expect to hear some sputtering and bubbling from rosewoods. Total time with the blanket is 15 minutes.

3. Blanket off and lights back on for another 20 minutes to anchor the waist. I then let the setup cool until a bare hand is EXTREMELY comfortable in touching the metal next to the waist block.

Hope this helps.

Bob

P.S. From bottom to top, the arrangement of my bending sandwich is metal slat>wood>blanket>metal slate. Also, it helps to wrap the moistened side in parchment if you want to keep rosewood pitches off of the blanket and metal slat.

[Gary Nutt]

Bob,
I combined your wisdom with Ron Frazier's advice and just bent some sides (this is the first attempt since I posted the original note). I am happy to report that with this advice, the sides bent very nicely. Patience, and adding a blanket, seemed to have done the trick.
Thanks very much,
Gary

[Ron Frazier]

I would have to read my agenda and it is in the shop as it is written on the side of my homemade fox bender.

the steps are to heat the bender with all blankets and no wood to I think 140 degrees as the first step.
next add the side material into the hot bender after soaking the sides in water and tighten the waste down some and I insert the cooking thermometer between the blanket and the wood and heat to 140 degrees and then tighten the waste about 1/2 way and slowly ease the ends down and clamp. I let the heat tell you how much to bend. When the side is hot enough it will bend fairly easy. then heat to 140 again then tighten the waist to all the way make sure the heat between the blanket and the wood is 140 then turn the heat off and let cool below 100!! If you take it out at too hot it will want to straighten out some. I have been trying to do the over bend but have not mastered it yet. I also bend my wood binding the same way only I use masking tape to bend a lot of binding at one time. A few fices of tape across all the pieces will make them stay in shape to bend. If I need more bend I will use my heated pipe to finish.

Ron

[Gary Nutt]

Ron,
I combined your wisdom with Bob Webster's advice and just bent some sides (this is the first attempt since I posted the original note). I am happy to report that with this advice, the sides bent very nicely. Patience, and adding a blanket, seemed to have done the trick.
Thanks very much,
Gary