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| What's up with the wide upper transverse braces? http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=22254 |
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| Author: | Jeremy Douglas [ Mon May 04, 2009 10:03 pm ] |
| Post subject: | What's up with the wide upper transverse braces? |
I understand people want to beef up this brace to help keep the fingerboard extension out of the soundhole. I've seen massive 1/2" wide braces used but why not just make them taller and save some mass? Martin had some really narrow UTB's on their pre-war guitars, their dreads just used a 5/16" wide UTB; maybe that's not enough support but is there a reason people like to widen these braces as opposed to just making them taller? |
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| Author: | Darryl Young [ Mon May 04, 2009 10:39 pm ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
Can't say I know the reason but a wider brace would resist rotation more. |
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| Author: | Andy Birko [ Tue May 05, 2009 8:27 am ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
Jeremy Douglas wrote: why not just make them taller and save some mass? Maybe saving mass isn't the name of the game for the UTB. On the various forums over the last 6 months of so there have been a couple discussions regarding neck weight and finger board extension rigidity including one guy who thought notes played on his FB extension died very quickly compared to others - his FBE was not glued down. A little extra mass there might help tone. |
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| Author: | SteveSmith [ Tue May 05, 2009 8:47 am ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
Seems to me the wider UTB would help tie the top grain together to prevent splitting alongside the fretboard. |
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| Author: | Barry Daniels [ Tue May 05, 2009 10:00 am ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
I make them 5/16" wide. Seems plenty stiff to me. |
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| Author: | Sondre [ Tue May 05, 2009 10:13 am ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
I agree with Darryl. The strings pull in the same direction as the width dimension of the brace (parallel to the top grain), so a wide brace will be most effective in preventing rotation. With a wider UTB the glue surface is also greater, so the glue joint is less likely to fail. |
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| Author: | JJ Donohue [ Tue May 05, 2009 10:18 am ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
Some actually use 2 UTB's. Anybody know the rationale behind that? |
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| Author: | Flori F. [ Tue May 05, 2009 11:07 am ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
I'm guessing people who use two big utb braces see two big braces as better than one. As I understand it, there are two extremes on this issue and most of us fall in between those poles. With the extremes, it's basically Turner vs. Taylor, though I doubt they've ever viewed it that way. Rick Turner (and others like H. Klepper, I believe) use graphite buttresses rather than an UTB. I believe they do so because they feel the upper bout contributes to the instrument's sound in an important way. Bob Taylor's guitars basically eliminate the upper bout completely because Taylor puts an enormous graft under the fretboard extension. Or at least they used to. I don't know whether the Taylor method is any worse or better (tonally) than the traditional Martin method. Then again, I don't know whether a buttressed heel sounds better than an UTB'd heel either. As for the A frame alternative, having owned a Gibson A frame braced guitar that imploded, I would never, ever use A frame bracing on one of my own. Flori |
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| Author: | bluescreek [ Tue May 05, 2009 11:09 am ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
The TRB is handling a double load. The first is the shear force of the neck as it is trying to rotate , the other is the compressive load of the top and string tension. One point is that the old prewar Martin brace didn't have a hole. I think they beefed it up for that reason. I use a 3/8 brace 1/2 inch high. Taylor uses a double trb. I also make the popsicle brace smaller than the martin |
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| Author: | Alan Carruth [ Tue May 05, 2009 12:31 pm ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
One reason to make that brace wider is to increase the gluing area between the brace and the top. If the top splits on either side of the fingerboard (a common enough problem) almost the only thing keeping the neck from shifting inward is the shear strength of the glue line between the UTB and the piece of the top under the FB. This is the same shear load that the bridge is taking, but the FB is about 2-1/2" wide, where the bridge spans more like 7" across the top. And remember that the bridge is more like 1-3/8" wide along the line of pull, too. A bit more area, and particularly a bit more length along the line of pull, can help a lot. That, of course, is the function of the 'popsicle stick' brace. This, BTW, is one of the stronger arguments in favor of hot hide glue. Any glue that will creep under a shear load (and that seems to be most of the 'modern' glues) will eventually fail in this circumstance, no matter how much glue area you have or how well the joint is made. Granted, it might not be possible to get enough glue surface for HHG either, but at least it won't fail slowly through creep; it will either break or it won't. The Turner buttress is a 'floating' version of the A-braces that I use. The idea is to put wood, or graphite, in compression, rather than relying on the shear strength of glue. |
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| Author: | Michael Dale Payne [ Tue May 05, 2009 12:43 pm ] |
| Post subject: | Re: What's up with the wide upper transverse braces? |
What all said |
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