Official Luthiers Forum!

1st time builder here! I am trying to figure how the bracing interfaces with the sides. The plans I have don't show a section drawing at any of those points. It does show the bracing tapering down significantly. Does the bracing go all the way to the side/lining or do they stop just short?
TIA

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Steve Leonard
SEleonard

The first instruction I had l was for classical guitars. The heavy cross braces are tapered so that they can go all the way through the sides, but they will be trimmed off during the binding channeling and hidden by the bindings. The fan braces were tapered and did not enter the lining.

I wasn't trained in Classical guitars, but I always run my x-braces through the sides. At that point they are near 1/16" of an inch and serve mostly as a register for gluing the top/back on.

I insert the upper transverse brace and the upper legs of the X-brace into the linings tapered down to a height of 1/8", or a bit less. All of the other brace ends below get tapered down to a feather edge before reaching the linings. The justification is that the upper braces tend to be pulled off the top by string pressure, whereas the lower braces are pulled in tighter to the top.

great info guys.
I found a u tube video that shows what yall are talking about. Thank you very much!

SEleonard

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Steve Leonard
SEleonard

The rule of thumb is that any brace that can't be cut down to zero height for a significant distance back from the edge should be notched into the liners. This holds especially for the brace ends between the bridge and the upper end of the box, where the torque load is pushing the top down. Most glues have low peel resistance, and you don't want to give them any slack to start coming up at the ends.

Great guitars have been built by both notching and tucking into the linings or tapering to zero. It kind of depends on what you are going for. These days myself I mostly taper to zero wanting to have the perimeter of the guitar looser. What I do is taper the brace ends to a paper thin feather and glue the lining right on top of that. That prevents any pealing away in case of impact.

I've seen it said before that if you do notch into the linings then it's a good idea to not have the brace end touching the sides but have a bit of wiggle room there for expansion.

I tuck in the ends of all back braces. Like many here, I cut the ends to a specific thickness (a thickness which guarantees that the binding will cover it up) and cut notches out of the sides of a depth that matches the brace thickness at that spot.

For the top braces, I tuck in the ends of the X brace, but only on the neck end of the X. For all other braces, and the tail ends of the X brace, I taper down to nothing shortly before the kerfed lining in that area. I also chamfer the tail block where it glues to the top and the back, so as to not disrupt the line of where the top/back are glued to the kerfed linings.

A gap at the end of the brace is a good idea. Backs tend to shrink over time and get narrower, but cross braces don't get much shorter. If the brace butts up against the side or the liner it can push a bump out over time. You see this a lot on older instruments.

I tuck all the structural braces like Martin I do not go through the sides , plastic bindings don't like air spaces.
the more you do the the better you get.

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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've been pondering this tucked brace thing and have done it per discussions here and my plan. It doesn't make a hole lot of sense to me though. If the brace releases from poor gluing or high humidity situation, wouldn't it be easier to fix if it was completely free? I have never had to repair one so I'm not speaking from any kind of experience.

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Hutch

Get the heck off the couch and go build a guitar!!!!

It would be a bit more difficult to fix a brace that pealed away that was feathered to zero I would think. But marginally. If it's tucked into the lining and loose then you just work a pallet knife under it to push glue in. In either case it's a PIA but I don't think it matters much.

The idea is to support the end of the brace with he liner or a bracket so that it won't pop loose. It's important the inlet be no deeper than the height of the brace end, so that there's no 'wiggle room' for it to break loose under downward pressure.

Gibson used to take the braces down to nothing at the very end with a sander, so that they sloped upward from the end to be, maybe, 1/16" high at the inside edge of the liner. Rather than cut inlets they would simply clamp really well over the brace ends as they glued the plates on, trusting that the brace would crush the liner a bit and make the space that way, insuring good contact and saving time. The problem was that they used spruce for the liners and braces, ans sometimes the liner was harder than the brace, so it was the end of the brace that got crushed. They would peel up, particularly the upper transverse brace above the sound hole, which has a lot of down load on it. I had at least two Gibsons come in at different times for repair due to the neck shifting and the action getting high because the UTB was simply gone. When asked about it the owners said that there had been a stick rattling around inside, and they tossed it. For the repair you have to cut out a bit of the liner where the brace goes, put in a new one with properly tall ends, and glue in brackets on the side to support the brace.

Anywhere a brace intersects with the lining, I epoxy a 1.5" tall hardwood tentallone to the ribs. This allows me to leave all braces full height and hammer them into place with two-penny nails. I learned this technique from a time-traveling master luthier who had apprenticed under Archimedes, Da Vinci, Einstein, and Ted Nugent.

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George :-)

George, you are making me feel like I am on one of the Facebook amateur luthier groups! Lol

Pat

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Pat

Hey George,
Nice to know we studied under the same time traveling Master Luthier! Did you get the Master Luthier Certificate after finishing the three day course?
Oh! - where have you been getting the stainless two pennies, - I've run out?

Now that's bracing built to last!

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George :-)

I tuck the ends of all the back braces, the upper face brace, and the upper arms of the x-braces into the lining with the ends 1/8" tall. The brace ends don't go through the sides and I leave a small gap between the tips of the ends and the side.

For the lower x-brace arms, I initially tuck the ends into the ling with the ends 1/8" tall. Once they are fitted into the lining, I carve the x-brace ends down to no more than 1/32" tall. This produces something kind of intermediate between tucked and untucked brace ends. The brace ends are held down by the lining, but the x-brace ends are also quite thin which theoretically loosens up the top a bit in those locations.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Super clean work, as usual!

M

I've wondered why it wouldn't be a better idea to hold brace ends down by gluing tentalones over them rather than relying on a mortise
whose function is useless if cut even slight too deep.

Anybody?

You would have to choose either top or back for that unless you reach in through the sound hole. I used to do that with the top since I build off the top but the back has to be closed by cutting out pockets in the linings. My method for that is to use calipers. I try to get every brace end that will get tucked to the same size but what I do after carving them close is measure the end of each brace with the caliper and lock that measurement in place. Then I set the Dremel router bit to the depth of the caliper by pushing the bit to the base with the fixed caliper. Then rout out the slot and it's to the exact depth.

Some classical guitars are built that way. They use similar but larger side braces under the Transverse (harmonic) bars. The "load" on the bracing at the waist and upper bout is pressing down on the braces so using fairly substantial side supports under them makes sense.
The "load" in the lower bout is pulling up on the top so supporting the underside of the braces is less critical, except in cases of impact damage - and even then it may be the choice of having an untucked brace come loose or having the top sustain more damage because a tucked brace doesn't allow it to spread the force.
I tuck the brace ends in the upper bout and taper them to nothing in the lower.

I like to leave the upper ends of the UTB and X braces on my tops fairly tall, and the notches would cut away most of the liners at those points. Instead I just cut the liner out entirely, and pout in short sections of liner down on the side at the right height to support the brace ends. In repairs, such as replacing the missing UTB on those Gibbys, I epoxy in a side bracket that has end grain against the brace (which is standard practice in classicals) after the brace is in place. The important thing is to have something in good contact with the brace to keep it from pushing down and starting to peel loose from a load on the top.

Is that a guitar or a new roof?

The "Beam" that is supported by the side brackets doesn't add much weight, nor a whole lot of stiffness to the top, and the bearing point of the top on it is close to where the "X" of X bracing lands. The fan braces look fairly massive, but actually measure about 4mm X 6mm and will get tapered down in the lower bout. This fan braced guitar is built for steel strings so I felt a little heavier scantlings to start out with was in order. Keep in mind - there is a large tail port I can use to rework the braces if I find them to be too stiff.
But I can take a little "ribbing" - all in fun!