Side bending advice

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Stray Feathers
Posts: 677
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Side bending advice

Post by Stray Feathers »

I have bent two bubinga sides for an OM copy, but they look more like dreadnought sides. I used a home-built Fox bender with slats, blanket, controller and thermometer from John Hall at Blues Creek. I followed John's video instructions carefully; sandwich of slat, parchment paper, wood, parchment paper, blanket, slat. I used ammonia Windex lightly on the paper. Took the temp to about 225 to start bending, lower bout was about 240 when I bent it, upper bout a little higher, then waist a little higher, max temp about 290. There is no scorching on the sides. At the same time side by side with each side I bent a bundle of two bubinga binding strips with laminated purfling, and two separate purfling strips. They took the same shape as the sides. A couple of differences from the only other set of sides I have bent this way (walnut): I used an additional galvanized steel slat under the sandwich to see if it helped eliminate some rippling in my walnut sides (there is no rippling in the bubinga), and I tried a method used by luthier Josh House. He uses a Blues Creek bender, but when the side has cooled, he reheats it and then lets it cool again; he claims it reduces springback. The sides are pretty much face grain, sanded to about .082. So I can try putting these in the bender again, or try finishing them on a pipe bender, or? More heat? More moisture? Suggestions welcome and thanks - Bruce W.
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tippie53
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Re: Side bending advice

Post by tippie53 »

they would work as is take the sides and place them so they are standing up. Put the mold on it and see if then flex into the mold
feel free to call me

next time sides are .075 thick take the heat to 325F then hold at 275 F for 15 min let cool before pulling from the machine
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
Stray Feathers
Posts: 677
Joined: Sun Sep 08, 2013 11:39 pm
Location: Ladysmith, BC

Re: Side bending advice

Post by Stray Feathers »

Thanks for the quick reply John. I thought I remembered a reference to higher temps but maybe I was using a different video version of your guidelines this time. I am inclined to carefully get the sides back in the bender with moisture, paper etc. and go to 325 as you say. By the way, the sides are at .082 as I wanted a little leeway for level sanding if I had ripples or cupping, both of which I have experienced. I am looking for reasonable price to get a rolling pin sander shipped to Canada.
Bob Gleason
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Re: Side bending advice

Post by Bob Gleason »

You probably don't need to use the paper again. It's very hard to get it on a side that is already bent anyway. I would drench the side and put it back in the bender. 320 is what I set my max temp at and run it for about 12-15 minutes, depending. If the side is not dry when I open the bender, i turn it on again until it is dry.

I see mention of people using rolling pin sanders, but I am not a big fan of them. Since I do this for a living, I own almost every hair brained lutherie tool that can be invented. Stew Mac and LMI would go broke without me to buy their stuff.There will be a very confusing garage sale at my shop when I'm gone! I have hard rubber and inflatable rolling pin sanders. I do occasionally get them out, but find very little use for them. Good luck with your building.-Bob
Diane Kauffmds
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Re: Side bending advice

Post by Diane Kauffmds »

I use the Blues Creek bender. It takes longer, but I like to bend, cool them completely in the bender (sometimes leaving the side in the bender overnight). I take it out, immediately put it into 1 side of the mold, and I use as many clamps as it takes to keep the side 100% against the mold, while I do side 2. I do the same thing with side 2. After clamping them, I draw a line along the top and bottom, along the mold, where they meet. I cut them to length along these lines.

The result is that, when both sides are placed in the mold, they're so tight along the neck and tail seam, that the pressure of them pushing against each other, keeps them tight to the mold. I just use the spreader on the waist, and they stay tight.
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Diane Kauffmann
Country Roads Guitars
countryroadsguitars@gmail.com
Stray Feathers
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Location: Ladysmith, BC

Re: Side bending advice

Post by Stray Feathers »

I did follow John's suggestion and re-bent the sides, up to 325 or so (should have done that in the first place), and left each one to dry in the bender, did not use House's method of reheating and recooling this time. They came out better, though I still had to spring them into the mould. The sides previously felt like they were just too stiff to force into the mould. I have both sides clamped in the mould, plus the binding bundles and purflings, and am in a position to leave them for a few weeks so will see how it goes. Bob, I appreciate your thoughts on rolling pin sanders. One model seems to have mixed reviews, the other more expensive (rigid) model is currently out of stock and being replaced with a new model. I'm just looking for ways to go easier on my joints with tendinitis and arthritis and maybe a few other -itises too. I have heard of modifying bending forms to compensate for springback but have not seen any specifics. Then I found an old book by Irving Sloane I was given many years ago which illustrates the principle, but without dimensions, so I am going to try modifying my present OM form and see if it works better. Diane, thanks for illustrating your method. I am doing pretty much the same, but still fighting springback, so it helps to know I can be a little more persistent with clamping. Bruce W.
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