to tuck braces or not to tuck braces

[tippie53]

This is an often asked question and to he honest, a simple one to answer. I can tell you that tucking, in order to key into the kerfed lining is a good way to secure and align the top or back for gluing.

I like to do it in order to key the top. If you are thinking "is it needed structurally?", I say that as long as the braces are near ( within 1/8" ) you should be fine. The top is under a number of stresses. I would strongly suggest that the upper braces are more structural than the lower. I will not go through the sides but that is more my personal traditional leaning. I know a few builders who will fade the braces without notching.
There is great potential for discussion of whether to notch or not to notch, and I eagerly await comments.

[justrfb]

Hello All,
Although I am no expert (very far from it but trying to get there...) I followed John without knowing it and notched my kerfing to accept the faded braces, leaving the sides untouched, for "keying" purposes. I figured I would have to be pretty darn accurate to be able to notch the kerfing and the sides with no gaps or errors so I went with just the kerfing notched... Looking forward to hearing what others have to say. Thank you.

Sincerely,
Rich

[B. Howard]

As I build with no forms or molds I use the pockets for the main braces not just to index the top but to help get the rims to follow the correct outline. I also feel that tucking the lower ends while maybe not as structurally necessary will help prevent a large bulge from forming behind the bridge and help prevent bridge roll over the long term.

[Alan Carruth]

I've always used a simple rule to know when to inlet the brace ends: if the brace has any height at all at the end, inlet it. If it fades away to nothing you don't need to so long as it's low for a reasonable length. Here's the reasoning.

Most braces go at least partially across the grain. Wood is a lot stiffer along the grain than across. A brace with any height at the end is thus likely to be stiffer than the wood it's glued to. That, of course, is the point of bracing: to add stiffness without too much weight.

Visualize a top that's glued to the rim, with a brace that's not inletted. Some idiot (you would never do that...) knocks the top over the brace, say, with a microphone. The top, being flexible, will bend a bit, but the brace is stiffer and doesn't. This puts a lot of peeling stress on the glue line between the brace and the top, a,d glue is not usually very reliable when subjected to peeling stress, particularly if there's a shock involved. The brace peels loose.

This is, of course, exacerbated by the torque load of the bridge on the brace ends above the bridge. Those I always inlet, except for the ends of the finger braces, which are pretty low and can be shaved away to nothing. Some folks shave the lower ends of the X braces away, too, and in that case, if they're down nearly to the top for a long enough distance (an inch or more?) you could probably get away with not inletting them. Mine end up with some height, so I do.

Note that what counts here is the contact between the top of the brace and the bottom of the pocket. A space on the side of the brace is not a structural issue; just a cosmetic flaw.

One other thing: if the liners are 5/8" tall on the side, and you like to leave the ends of the upper transverse brace 1/2" high, that doesn't leave a lot of liner to support the brace end. In that case you might want ot use a side bracket, like the Classical makers do.

Back when I did more repairs I'd get in Gibsons with the UTB missing. At one point they seem to have used a drum sander to take the brace ends down to almost nothing, over a distance of maybe an inch or a bit more from the top to the bottom, and then, rather than inletting them, they just relied on clamping pressure to crush the liner where the braces were. The problem is that both the braces and the liners were spruce, and if the liner was harder wood, it was the end of the brace that got crushed. This effectively left the brace end trimmed up just short of the liner, and they'd peel off. At some point there would be this stick rattling around inside the guitar, and the guy would pull it out and toss it. Then the action would start to rise... Moral: cut the pocket.

[tippie53]

Personal thanks to Al Carruth for participating. You and your advice are always most welcome.

[Ben-Had]

Personal thanks to Al Carruth for posting. You and your advice are always most welcome.

Hey, I have a scraper with the same name:)

[tippie53]

Thats the guy