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| Gluing on back that may have a twist? http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=44268 |
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| Author: | lengthtimeswidth [ Thu Oct 02, 2014 11:41 am ] |
| Post subject: | Gluing on back that may have a twist? |
I've been working on a parlor style guitar and I just got the chance to box up the body. The top went on no problem with go-sticks. As I began to attempt the back I noticed that it didn't fit quite like it used to. It appears to have developed a twist while sitting braced in the shop for a few months. Since its such a small guitar the back only has two braces, one at the shoulder and one at the bout. I didn't want to limit movement too much and over-brace this little guy. I'm wondering if anyone has any suggestions as to how to fix this problem? Do I force the back to glue in an unnatural position (for it, seeing as it wants to twist a little) or do I put a couple more braces to help it bend to the shape I want? I should mention I'm a new builder and It's taken me awhile to set up my shop so this guitar has been in the works for a good portion of a year. |
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| Author: | LanceK [ Thu Oct 02, 2014 11:47 am ] |
| Post subject: | Re: Gluing on back that may have a twist? |
Im not sure I follow 100%, but I can tell you that my backs always need a little coaxing in to place to get the glue joint to touch all the way around. |
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| Author: | lengthtimeswidth [ Thu Oct 02, 2014 11:53 am ] |
| Post subject: | Re: Gluing on back that may have a twist? |
I just realized its not really a twist. The ends of the back have turned slightly opposing my desired radius. Like how plants turn and bend towards the sunlight. |
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| Author: | lengthtimeswidth [ Thu Oct 02, 2014 11:54 am ] |
| Post subject: | Re: Gluing on back that may have a twist? |
Thanks for the reassurance, I think I'm going to glue up and try to force it back into its original position. |
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| Author: | Rodger Knox [ Thu Oct 02, 2014 11:56 am ] |
| Post subject: | Re: Gluing on back that may have a twist? |
There's also the possibility that gluing the top to the rims introduced some distortion, and the back hasn't moved. If the gaps are less than 1/8", I think you'll be fine. I suspect there are those here that have everything fit perfectly, but I usually have to coax things a bit also. |
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| Author: | Linus [ Thu Oct 02, 2014 12:04 pm ] |
| Post subject: | Re: Gluing on back that may have a twist? |
Has the humidity changed in the space where the back has been residing since it was first braced? |
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| Author: | meddlingfool [ Thu Oct 02, 2014 12:11 pm ] |
| Post subject: | Re: Gluing on back that may have a twist? |
It can happen. It will stay in shape once it's glued to the sides. The one thing I would check is if the braces are at the radius that they are supposed to be along their length. |
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| Author: | lengthtimeswidth [ Thu Oct 02, 2014 1:13 pm ] |
| Post subject: | Re: Gluing on back that may have a twist? |
The radius is correct and it fits close to 1/8 of an inch at the shoulders and through the waist. Then as it gets towards the bout and past that brace it turns up slightly and I'm left with a pretty serious gap--measuring 1/2 inch. |
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| Author: | meddlingfool [ Thu Oct 02, 2014 1:34 pm ] |
| Post subject: | Re: Gluing on back that may have a twist? |
Glue one go forth IMO. Don't forget that the sides are on a downslope from the waist compared to the shoulders, so the sides are sloping away from the back past the waist... |
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| Author: | DennisK [ Thu Oct 02, 2014 2:37 pm ] |
| Post subject: | Re: Gluing on back that may have a twist? |
How did you create the radius on the rim? Sanding in a dish, flat sanding board as in the Cumpiano book, radius sanding stick, hand plane? Sounds like the "peak" at the waist might be too high, if I'm understanding the description properly. But as others have said, it should involve a little flexing and forcing to get a formerly flat plate to conform to a spherical radius. |
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| Author: | lengthtimeswidth [ Thu Oct 02, 2014 6:30 pm ] |
| Post subject: | Re: Gluing on back that may have a twist? |
So it appears to be too big a gap to force. I know this now because I tried and the bout brace started to pry off at the edges. So it's been a few hours but I steamed the brace off and shaved it down to fit the back a little better. Now I'm waiting for the brace to set and I'll try again tomorrow. Thanks for the help y'all. |
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| Author: | meddlingfool [ Thu Oct 02, 2014 7:46 pm ] |
| Post subject: | Re: Gluing on back that may have a twist? |
Time for some pics. |
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