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I have seen some guitars that use small sitka braces at a few points to prevent side splitting. My question to anyone who knows is if these make it easier for the sound to travel through the sides and interact with the back making for a more vibrational structure than just having nothing there. Sloan used cloth tape reinforcement, though I think the tape would damper more than aid the transfer of vibration from plate to plate. Any thoughts?

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They are not usually regarded as necessarily preventing the sides from splitting nor transferring energy from
the top to the back. But if a side did develop a split, they would contain it and keep it from growing.

Brian: Other woods are used also.Mahogany is a favored,also used is the same wood as the sides. If used a bit on the thick side they can help remove ripples on thinner sides.
Tom

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Martin used a brown ribbon tape . I use that myself now. Also Martin used them on deep bodies only. It is arguable if the do help. The ribbon is less mass.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I used to use them but don't anymore. I doubt you can find any credible data to suggest that they either help or hurt the tone. The idea is that they can help stop a split in the side. The argument against them is that they may actually help cause a split and that they may make it harder to repair a split.

I've seen cracks go right over the top of the side braces and keep going. Not saying they don't help to some degree, but I doubt they will prevent much. I stopped using them myself, although they are easy to make and install.

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John Mayes
http://www.mayesluthier.com

There was a thread debating this a while back... I think most people came to the conclusion that where the side brace meets the lining becomes a stress riser, and likely to split there if anywhere, and is a pain to repair because you can't splint it due to the lining being in the way. The cloth tape stops splits from spreading just the same, but without the stress riser effect, and thus is better.

I haven't heard much about beliefs on strength/stability of sides benefiting from having braces, or effects on tone. My personal feeling is that they might help long term stability a little bit, but for the most part the forces involved aren't pulling in a direction that they matter much. Tone, I can imagine that it would make a small bit of difference. Hard to say whether good or bad though. Do vibrating sides make a pleasing, if small, contribution to the overall mix? Or are you better off trying to keep them as motionless as possible so as to focus all energy into the plates? They do have a tap tone, but it's rather high pitched, like the upper bout of the top, and thus probably irrelevant. Although it does amuse me that we (or rather, the guitar buying community) so religiously cling to having matched side and back wood if the side species is purely a thing of appearance. Wouldn't it be far more logical to save those Brazilian sides and make 3 and 4 piece backs?

Anyway, getting back to side braces, I have a fun idea to try next time. Since I build with tentellones, and notching linings by chisel doesn't sound like my idea of a good time, I'm going to try using combo tentellone/side brace/back brace feet, and then glue short kerfed lining strips between them for the rest of the back linings. Basically what I did last time, except for having them extend all the way to the soundboard to act as tentellones in addition to the other roles, which also eliminates the stress riser at the gap between the side brace and the soundboard lining. And for the upper transverse braces (top and back), it makes a nice square where the side braces connect them, which seems like it could help with stability (assuming you line up your braces, unlike the photo). I think I've seen that done on some classical guitars before.

I've never done the side braces like your picture, where they are like feet for the back braces, but I have always wanted to. I don't know why, but I thought I would try it. I didn't think about the fact that the side braces might poke through the top after a while, that IS a big concern. I don't want to try and solve problems by creating new ones. Ah, well...guess it's sticking to braceless sides for a while longer.

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Hmm, that is a good point... maybe I should do the full-height brace/feet/tentellone things with cross-grained wood so they match the contraction of the sides better? But then the braces might split along with the side rather than catching splits... That tape's lookin' better and better.

Perhaps I'll try the full-height side braces on my retop test guitar, and then give it some extreme drying and see if the sides ever contract enough for the braces to pop the rim joints. Probably give me some practice repairing splits in the top/back too

Doubling the number of the braces may help as well, so there's not such a wide span between each of them for stress to focus at the tip.

This is exactly how I do it.



I never had problems with the side braces poping the top or back off.

Also, I'd like to add that I believe that, regardless of their original purpose, side braces will undoubtedly reinforce the sides. Take any piece of wood and add some brace accross the grain and it will be stiffer for sure. Plane and simple physics. My demo guitars received some hits that I'm convinced would have cracked the sides if it weren't for the side braces.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Thanks for that, Alain! I shall go ahead with the plan then, with double number (one for each back brace foot, and then another round half way between each of those).

And that is a good point about impact resistance. Even if they don't support much against string pull forces (which I'm not sure about anyway), that's not guaranteed to be the only force ever imparted to the instrument