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Hi,

J45/dreadnought do you support the area circled in the picture.

Its on the j45 plans, but what purpose does it serve to put some thin plates there?

Tia

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Picture of area

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Called a popsicle brace commonly.
Serves (mainly?) to stop the soundboard splitting at the fretboard edges due to humidity changes.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

While not historically accurate, I think that area of any acoustic guitar with otherwise standard X bracing and a standard neck block would benefit from a trapezoidal patch. Just search here on the OLF for the word trapezoidal and the discussions should pop up.

In order to accommodate a truss rod that adjusts through the soundhole, I build my trapezoidal patches in three pieces: one on each side of the space needed for the adjustment, both pieces a little thicker than the space I need for the adjustment wrench, and a 1/8” cap over both to close it in.

Thanks, what are the benefits, does it structurally benefit the neck or is it just to protect an open area from potential cracks?


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I use it for crack control. I just use an offcut from the top...

the Popsicle is there to hold the top . the top will crack from the differential shrinkage rate between the spruce and fretboard. I have yet to see a guitar that I reset a neck that doesn't show signs of that crack.
Martins are the worst at this. Gibson's are pretty good but they also glue the extension differently. Martin glues the entire extension and Gibson often just places a good dollop of glue. The Popsice brace has a long history.
I do agree that a smaller trapezoidal brace would do the job more efficiently.

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I think the main problem the 'popsicle stick' brace was meant to address is cracks in the top along either side of the fingerboard. The ebony fingerboard shrinks for a long time, and will pull a crack in the top on either side where it runs along a grain line. This weakens the top in the area that is under the greatest stress. Without some sort of reinforcement the only thing keeping the neck from shifting inward is the glue line between the upper transverse brace and the top. Often it's not up to the job, especially if the guitar gets dropped or falls backward off a stand.

In theory the large glue surface of the popsicle stick brace should keep this from happening. In practice it's often not as effective as you'd like. Most of the 'modern' glues, such as Titebond, will 'cold creep' under a sustained shear load like that: I've seen guitars where the neck has shifted inward by 1/16" or more but the glue has not actually let go: it just flowed. White glue is notorious for that, and at least some manufacturers have used it. Hide glue doesn't creep, but it also has low shock resistance, so it will sometimes let go when the guitar is dropped.

The best solution is probably to use a brace of some sort to take the load in compression. Some folks use a 'flying buttress' between the neck block and the waist, sometimes of carbon fiber. Others have use a column between neck block and tail block. I've been using an 'A' brace setup for decades now. I'm pretty sure it's effective; I've had a few come back for visits that have been dropped or fallen in ways that should have caused the neck to shift in, without any sign of it. I use a couple of braces that are about 5/16" square in section, glued to the top, that would converge on the center line at the upper edge of the top, and run outside of the soundhole. They are inlet into the upper block for 1/2" or so to their full height, run through the notched UTB, and end at the upper arms of the X. I also use a doubler around the sound hole in the space between the UTB and the X, bounded on either side by the 'A' braces. The lower ends of the 'A' are taken down to the height of the doubler (usually about .100") and trimmed down to a low triangle that gets inlet into the X arms. In theory, if you fit it well, this should take up a lot of the compression load of the neck and distribute it around the hole, preventing the neck from ever shifting forward. We'll know for sure if it worked in 75 or a hundred years....

That does not address the issue of fingerboard shrinkage, though: you can still get cracks along the sides. For that, in part, I use an extended 'chin' on the neck block that runs most of the way down to the UTB. It's made 3" wide at the upper edge, and tapers down to 2-1/2" wide, about the width of the end of the fingerboard, at the lower end. This keeps the edge, which sticks out past the sides of the 'board, from running along a single grain line. It's still possible for the board to shrink and pull a surface crack in the top, but at least it should not weaken the area. To prevent that I usually only glue the fingerboard down to the top in the center.

Great info, thank you [SMILING FACE WITH SMILING EYES]

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The way John Arnold described the trapezoidal patch here on the OLF some time ago (where I got this info) is that you make the grain run the same direction as the top, and you make it fit snug between the neck block and the upper transverse brace. This helps counter the force of the neck pulling into the body once the strings are on. The sides of the patch are angled (same width as the neck block at that end, same width as the soundhole at that end) to both spread that force out a bit more, and avoid having the side of this patch run parallel to the grain lines of the top. This helps avoid cracks along grain lines. So, it winds up doing what the popsicle is supposed to do, and a bit more. I think it is a grand idea.

If you are going to use a trapezoidal patch You might consider running the grain slightly askew of the grain of the top similar to how the braces run. That might keep any grain lines from lining up, but not create the stress cross grain gluing creates.

I use 2 angled braces, the upper end butting the neck block, going under the A brace, (too late for you) angling beside the sound hole, butting the upper X legs. I have used this pattern for many years on all my guitars. I think it is the answer to upper bout deformation.
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As Clay S. says, it's always a good idea to cut patches so that the grain of the patch is not exactly aligned with the top. This goes a long way toward eliminating future cracks. If the grain of the patch is angled about 3-4 degrees across the grain of the top there will not be enough difference in the shrinkage rate to introduce harmful stress, but the patch will run across the grain enough to greatly reduce cracking issues. This is common practice in the violin repair field.

Interesting looking, David. I like it! Of course it's just another lap joint for me to mess up, but it looks effective.

Going back to the popsicle that goes all the way across, that is normally installed perpendicular to the top grain, correct?

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This is what I do, kind of A bracing in the top and in the back.
The braces stop at the Upper transverse brace. I leave them fairly thick maybe 3/16- 1/4 at the UTB.

One complaint I've heard about making "tall" braces around the soundhole is that it makes some electronic systems difficult to fit ( I still generally use them).
The X brace system keeps the braces somewhat oblique to the grain of the top, and the X provides maximum support right below the soundhole - the area I've seen "fold up" when an old parlor guitar is strung with steel. That is probably why some of the early gut strung Martin's can survive light gauge steel stringing.The popsicle brace was a later addition to the system, and some people remove them. I don't think they have much effect either way.
I sometimes wonder about all the additional effort put into stiffening the upper bout, ostensibly to reduce the need for future neck resets. I think some resets become necessary because of the "bellying" of the lower bout area of the soundboard and the overall deformation of the body.

Yup, had that problem retrofitting LR Braggs Anthems, and now I'm using JJB pickups with the small volume wheel in the soundhole I'm moving to flat soundhole bracing.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I use this pattern too but mortise the ends into the neck block.