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I used to use larger rosewood, or mahogany side braces. Looking back I think the ones I used for a while are horribly ugly and inelegant. Now I use rather thin pyramid shaped spruce or mahogany braces.

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John Mayes
http://www.mayesluthier.com

Yes, I had that concern at first but then thought about all the people that run their back braces through the lining, rout the binding channel, and then cap the brace ends with binding. Never heard of a problem there and that's on a 15" - 16" span. And by that logic, butting them tight to the linings would be problematic too, adding to the stress riser there or even causing a split. But it can't hurt anything to do what you suggest.

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http://www.chassonguitars.com

I may be wrong here, but in general wood does expand longitudinally when it swells correct?

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Lance@LuthiersForum.com

Yes, but at a small fraction of the amount that it does radially (in width for quartersawn) or tangentially (in width for flat sawn) or anything in between.

Why do you ask?

I think what Laurent was getting at was a concern that, if the sides shrink due to low humidty, the side braces would stay about the same length and, if left flush originally, would protrude from the sides potentially causing the top or back to pop loose or split in that spot. Personally, I think the glue won't creep that much and the differential will be taken up in other ways, as happens with other cross grain braces.

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http://www.chassonguitars.com

Regarding side tapes.
I tried the soaking in diluted titebond then applying to the side and it did not work well for me.
I ended up using straight titebond applied to the rim sparingly, pressed on the tape and let it dry for an hour, then applied diluted titebond by brush to saturate the tape.
This way the tape stuck to the rim not to my fingers as I pressed it in place, and it bonded quickly.
Jeff

Kent, Lance is correct. This is what I meant, wood expands the most longitudinally.
Regarding the top/back braces getting tucked under the linings I always trim them a tad short of the rim as well to avoid that problem and give them room to expand if need be, just like the side braces. A small detail, but just to be on the safe side, so to speak…

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/

Wood expands more longitudinally with an increase in humidity than it does radially or tangentially? That is quite incorrect. According to Hoadly, in northern red oak (used as a "typical species") a board going from 28% equilibrium moisture content to 0% emc would shrink 0.1% longitudinally, 4% radially, and 8.6% tangentially. Same would hold in reverse.

Did you mean something else?

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http://www.chassonguitars.com

I once repaired a Taylor that had been in a very dry climate for several years. The binding around the back had bulged and separated from the body in eight places, each one right at the end of a back brace.

Mark

Mark, that's good to know. I've never seen that of heard of it. Was that the first or the worst of the problems? My point being that all conventionally built guitars are going to have some serious problems if "stored in a very dry climate for years". If we built guitars to safely weather humidity extremes, we would never glue one piece of wood across the grain of another. In fact, ours is the only woodworking profession I can think of where that is accepted practice to begin with. Most woodworking 101 textbooks say don't do it at all.

Not trying to start an argument. Laurent's and your point about leaving space is a good one but I'm just not convinced that it would ever be a problem on side braces. Back braces are generally 3 to 4 times as long as side braces and therefore much more likely to show problems in that way. An aweful lot of guitars have been built like that Taylor and as far as I can tell, that scenario is rare. And there is still the point of butting side braces into the linings (another common practice) creating other problems.

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http://www.chassonguitars.com

Conventional wisdom says that wood will shrink across the grain as it dries much more so than with the grain. But for the brace ends to start poking the binding, it seems you'd have to have a fair amount of movement at the glue joint where the brace is glued to the plate, no? I've seen cracks in tops and backs you could stick 2 stacked quarters through, but none of these instruments had the braces pushing the binding out. Minor point, but I'd suspect that in the case of the Taylor that Mark mentioned, that perhaps heat might have played a role too?

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now known around here as Pat Foster
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http://www.patfosterguitars.com

Wood moves very little with the grain, most movement occurs across the grain, This is one of the reasons why a guitar is constructed the way it is, a radius allows for that cross grain movement with expansion and contraction.

If you need evidence of this, pull up the skirting boards in a room with tongue and groove floor boards. You will find that the gap between the end-grain of the boards and the wall is minimal yet the gap along the cross-grain sides is considerable. This is done to prevent the boards from cramping against the wall as they expand and either pushing the wall off it's plate, or compressing the boards off the joist as they bow in the centre.


Cheers

Kim

Kent, apologies for my hasty and incorrect reply. You (and others) are absolutely right and obviously wood shrinks faster across the grain than along the grain. Otherwise we wouldn't see top (or back) cracks on instruments subjected to extreme dryness. The top wants to shrink, but has nowhere to go because it is locked in by the bracing and the rim.
I knew that…
Mark's Taylor example may be uncommon, but not so rare. As the plates (or sides) shrink across the grain, the braces pretty much stay where they are. I wouldn't want to repair a guitar where the side braces have so slightly pushed on the top or back, though…

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Laurent Brondel
West Paris, Maine - USA
http://www.laurentbrondel.com/