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| Author: | coach [ Tue Feb 17, 2015 11:47 am ] |
| Post subject: | bending side issues |
Hello all, Hope everyone is having fun and learning. I'm building my 8th guitar, and seem to frequently have an issue that maybe some of you have, and can share some wisdom about. I bend my sides using a press, heat blanket, spring metal slats, with the sides wet, and wrapped in paper and foil. I use a thermostat, sold by lmi, and usually heat to about 220, then they bend like butter. After bending one, and it cooling down to my shop temp, I take it out, and clamp it in my mold, then bend the other side. However, almost always, I get some kind of buckling, on one side or the other, usually around the lower bout, but not always. It's never a lot, thank goodness, but enough that it takes lots of work, sometimes with filling, to level my sides perfectly. Any advice will be appreciated. Thanks, Coach |
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| Author: | meddlingfool [ Tue Feb 17, 2015 11:55 am ] |
| Post subject: | Re: bending side issues |
Some woods just will, especially things with interlocking grain like Sapele. But most will do it somewhat. Try to be sparing with the water... |
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| Author: | Pwoolson [ Tue Feb 17, 2015 12:03 pm ] |
| Post subject: | Re: bending side issues |
220 seems like a very low temp to me. Maybe something like EIR where it bends if you look at it funny, but not anything tricky. I set my temp to 300, let it cook there for 5 minutes and then start my bend. Once bent, I cycle the temp 3 times (cool, bring up to 300, cool, bring up to 300, etc) let it cool one last time and then into the mold. Shy of any real tricky woods (The Tree mahogany), I haven't had any issues for a long, long time. (I just jinxed myself didn't I) |
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| Author: | DannyV [ Tue Feb 17, 2015 12:07 pm ] |
| Post subject: | Re: bending side issues |
In 20 some odd guitars I have never really had issues like that and I always use more heat than you. I start bending at around 260 f or higher. FWIW |
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| Author: | kencierp [ Tue Feb 17, 2015 12:18 pm ] |
| Post subject: | Re: bending side issues |
We use a separate fixture for the waist curve about 300 degrees water spritz. Upper and lower bouts water spritz about 220 degrees. No foil, no paper (except parchment to prevent staining of light wood) heat source always applied to the inside of the curve -- the compression side. |
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| Author: | coach [ Tue Feb 17, 2015 12:33 pm ] |
| Post subject: | Re: bending side issues |
Thanks all. I will try a higher temperature, and cycling through. I think I will also try a little less water without paper, and heating on the inside next. Good ideas, all worthy of a try. I think I'm also going to try and leave each side overnight, clamped to the bending form; maybe with some cauls along the way to hold the sides while they completely dry and settle. Thanks again. Coach |
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| Author: | MikeyV [ Tue Feb 17, 2015 2:03 pm ] |
| Post subject: | Re: bending side issues |
Yeah, I bend up near 300, and I usually do it dry. I experienced cupping and valleying while bending sides that aren't very quartered, when using water. So now I skip it. It seems the heat drives it off right away anyhow. |
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| Author: | Heath Blair [ Tue Feb 17, 2015 7:46 pm ] |
| Post subject: | Re: bending side issues |
Can you expound on what you mean by, "buckling" (aross the grain, with the grain, etc.)? What kind of bending form do you use (i.e. solid or open with cross members)? You mentioned that you "wrap" the side in foil and paper; do you actually wrap it with foil so that steam cannot escape or is it just a sandwhich open on all sides? If the side is wet and steam can't escape, I can see how you might end up with some buckling. |
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| Author: | WaddyThomson [ Tue Feb 17, 2015 8:37 pm ] |
| Post subject: | Re: bending side issues |
Need to use paper strips and foil strips the width of the blanket and slats. This lets the steam gas off and lets the wood dry out. It should be totally dry when it comes out off the form. Re-heating is a good way it insure that. |
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| Author: | Terence Kennedy [ Tue Feb 17, 2015 11:33 pm ] |
| Post subject: | Re: bending side issues |
Higher temps for me too. Two blankets, moist paper, start the waist (50% down) around 270 with lots of steam rolling off. Lower and upper bouts (around 300 now) and clamp the bouts and complete the waist around 320. Cook at 300-320 for 10-12 min, cool and cook again. If I have other stuff to do I leave it in the bender overnight, if not, remove when fully cool and into the mold. |
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| Author: | Rod True [ Wed Feb 18, 2015 12:03 am ] |
| Post subject: | Re: bending side issues |
It does depend on the wood you're bending, most of the common side wood are as noted from the guys above, but sometimes you have to be careful.... Sent from my iPhone using Tapatalk |
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| Author: | coach [ Wed Feb 18, 2015 8:11 am ] |
| Post subject: | Re: bending side issues |
Heath Blair wrote: Can you expound on what you mean by, "buckling" (aross the grain, with the grain, etc.)? What kind of bending form do you use (i.e. solid or open with cross members)? You mentioned that you "wrap" the side in foil and paper; do you actually wrap it with foil so that steam cannot escape or is it just a sandwhich open on all sides? If the side is wet and steam can't escape, I can see how you might end up with some buckling. Thank you regarding the idea to leave the sides open to vent the steam. I do use a solid form. After reading all these posts, I'm convinced I'm using too much water, not letting it dry out before I pull it out of the bender, and not using enough heat. Appreciate the comments. Coach |
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