If you're concerned about the x joint splitting, just cap it.

An interesting experiment, and I honestly don’t know what the result might be. But I’d be prepared for some looseness just south of the soundhole.

So I’d stick a brace just below the soundhole, connecting the 2 parts of the x-brace.

I’d also expand the footprint of the bridge plate, to minimize the inclination to pull up.

That is the fundamental joint in the guitar. I’d be vary careful about weakening it without building in some compensation.

On the other hand, to quote Stephen King, “god hates a coward”.

Steve

I don't really see a problem with traditional joint.
With the open part of the notches, a cap on one brace and the soundboard glued to the other gives quite a bit of reinforcement to the crossing point.
Can't remember seeing a failure reported on the OLF, or anywhere else for that matter.
Heavens, how many guitars have been made with just a cloth patch glued over a very sloppy or butt joint?

It would eliminate stress risers at the cost of all joint integrity. A glue soaked cloth will not help much.

My layman's interpretation says that whatever strength derived from the butt-glued sides of the x in contact with each other is lost. Whether the rounded shape if the complementary cutouts reduces a stress riser well enough to overcomes that loss, a structures engineer could enlighten us. But capping the top of the 'x' sure mitigates a whole bunch of weakness all by itself. Tapered splice, nice long gluing area?

I am not disagreeing on a traditional joint , I am curious to see how an alternative idea will work . Thousands if not millions I am sure . I have repaired several that split at the joint . I wish i had a way to deflection test this ..... May have to try to come up with an idea . Thanks for the comment

From a structural engineering standpoint the issue is that you have cut a round notch halfway through the brace which reduces its strength significantly (about 75%). There is still a stress riser in the notch. In other words, if someone sits on the guitar the notch is where it will break.

The square notch in a traditional x-brace gets another brace tightly fitted and glued, completely filling the notch. As long as the joint remains sound there is little strength removed from the brace.

Jim, your design is a solution in search of a problem.

as a repair shop I have seen more failures from caps that cloth. Martin has been doing this since 1833 and there are few failures. Most of them can be traced to failure from outside stress.

John, I am surprised that you have seen several failures from Capped braces; it seemed pretty bullet-proof to me. Can you tell us more about the nature of these failures? If there is a hidden problem with that approach, I'd sure like to know. It may be that I am misreading your post and you mean that most of the failures (Including capped braces) can be traces back to outside stress. If not, how/where are you seeing the failures? Is the cap failing? The top notched brace? The bottom notched brace. . .

Of course, I'm not directing this only to John, let's hear from anyone who has seen a capped joint fail.

EDIT: Sorry Wud, I don't mean to hijack your thread/ it seamed pretty closely related. . .

When I think of the strength of an arch, I think of the load being placed at the apex of the arch.

Another approach to strengthening the X might be to add fillets of wood - as the corners of some boxes are reinforced. So far I have been happy enough capping the X and still consider this to be a bit of "icing on the cake".

"Patented Tone Enhancing X Brace Joint"! "Engineered to blah blah..... "I think you're on to something Wud!