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I'm staying away from a discussion about brace shaving, Hesh mentioned that a cloth patch at the 'x' intersection is intended to be slightly flexible (my inference). I've always thought that the he patch is intended to be a factory quick-and-dirty reinforcement of the 'x'intersection. I can't see how an interlocking joint can be a little bit flexible without being a little bit degraded.

Am I missing something?

Thanks!

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Peter Havriluk

No you are not missing anything. The cloth patch is intended to be both a reinforcement but still capable of some flex. It's an intentional.... sloppy joint if you will.

Cloth was and is used for side tapes to arrest a traveling crack and works quite well I would add having personally repaired many side cracks that did indeed usually stop at the first tape they encountered.

So I'll add that I don't think the use of cloth was intended to be quick and dirty. For the materials that they had to work with, that we still have to work with the cloth patches and tapes do their job very well are not known as a source of any issues down the road.

If you think of it the X intersection has the very most bracing in the smallest space on the entire guitar top. Since a top needs to move and pump it was too stiff so a sloppy, intentionally sloppy patched joint simply loosened things up and did so for some of the most iconic tone machines ever produced.

I make that joint tight and glue it. Are you saying I shouldn't glue the joint to allow for flex?

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Hutch

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

No you may be using a wood cap on top of the joint? If so you are approaching the joint differently than people who prefer the cloth patch.

What I am saying is that the cloth patch produces a looser joint with more possibility of flex and many builders prefer this approach. Some of the most valuable, vintage instruments ever produced used cloth patches at the intersection.

For those who see the value of lowering the X intersection to 1/2" or less you will understand the benefit of reducing the stiffness of the top a bit in this area. That's what the cloth patch does as well.

Hutch it's simply a different approach to the joint and one that I like.

Si far, I haven't put anything across the joint. I always meant to put cloth across it but haven't yet.

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Hutch

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

Interesting. A notched X brace produces a major stress riser, sort of a "weak link"
May I ask how many have you build like that, and do you still have them all?.

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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.

I'm chuckling a bit here because it crosses my mind that many here on the OLF come to lutherie from woodworking. You have learned to make very strong, neat, precise joints (hopefully) and here we have an example of an intentionally weaker joint and it's in play because unlike that live edge coffee table that needs to be solid as a rock... a guitar top needs to move.

If you think about it the two largest except for the UTB (upper transverse brace) braces on the inside of the box, there is a large brace on the outside of the box too, the bridge... the two largest braces inside the box get doubled at the X intersection. So say a 1/2" high brace meets a 1/2" high brace and you have as much brace wood in that intersecting location as if you had used a 1" high brace.

Guitar building is A different mindset for sure where as Colin rightly pointed out even some best practices such as avoiding stress risers are ignored to try to keep the top able to move and pump. I would call it a learning experience but for some it may be more of an unlearning experience where we intentionally build in a manner that permits and perhaps even encourages movement.

I have only completed 1 so far. I have the second body made. This one got closed before I I installed the side clothes as well. I hate myself. At least the binding came out perfect, yay.

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Hutch

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

Something I picked up from Somogyi was to carve down the x-brace at the intersection allowing for more movement. The x-brace notch is asymmetrical allowing one to cut the height at the intersection down with out compromising strength. My standard x-brace starts at 1/4”x 5/8”. The x-brace @ the intersection gets cut down to around 1/2”, maybe a bit more, followed then by a thin cap.

It may be a bit tough to see in the pic,

M

I have owned three Collings guitars and none of them had anything on the x brace intersection. I assume none of them do. Does anyone know?

Coming at this from a different viewpoint. If the x-brace joint moves and flexes more than a tiny bit then the glue joint has failed. At that point, a glue soaked fabric swatch would come into play providing a bit of resistance to further movement. However if the joint has not moved significantly and the glue joints are still intact then the fabric has done nothing. A wood cap provides a splint that seriously strengthens the joint. One of these days I should do some destructive testing to prove my theory. I have seen one Martin with a broken X-brace that the fabric patch did not prevent.

I'll put forward a possible spanner in the works.
Surely the stiffness of the X bracing system is the least at the point of the X itself (ignoring tapering/ scalloping)
Just above and below that point there are 2 sections of bracing.
At the junction of the X bracing there is only one, so the stiffness at that point is reduced by half. (ignoring a small cap on the bracing or any contribution from a cloth cap)
I understand some Gibsons butt one of the X braces halves and use a cloth "cap" to "hold" it together.

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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.

I always thought Gibson used the cloth to cover up the fact that even the butt joint was sloppy.

Sorry…. Carry on.


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You're not necessarily wrong

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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.

Probably adding a monkey wrench to the spanner. Having spent a lifetime building and fixing all manner of things, I'm a wood capper of the X and sometimes more, just makes structural sense to me. When I build for someone I tend to be a little more conservative but that's <1:4. The rest are all experiments in the guitar world. It's part of the fun for me. I tend to be heavy at the X all the way around. But so far so good and I've been lucky in tone and volume. If anything I've learned is more important than there is a ton of "flexibility" in guitar design I'm not sure what it is. Note: Most of my gits have fingerboard extensions detached from the top and no UTB adding to my strong X rationale.

Couple of examples -

First for a customer, he loves it.



This one will be strung up by the end of the month I hope. Capped and even side blocks in the X. I'll know then if I went too far.

I brace tops and carve and tap till the top comes alive, seems like there is a distinctive point where that happens.



When I was building more banjos I noticed as I increased tension on the head during setup, all of a sudden the whole banjo would come to life even feeling vibes running up the neck. Guitars have a wood "head" but I treat the top as a whole if that makes sense, similar to what I see in banjos.

Funny, 15 posts here and at least half that many different approaches.

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Brian R, Wood Mechanic
N8ZED

Beautiful work Michael that bracing even looks like it sounds great! Hope you don't mind if I point out how much of the material on your braces that does not contribute to stiffness you have removed. Looks like a very responsive top.

Naw G*bson could care less about covering up their sloppy work.... That's way the expression "good enough for a Gibson" endures in the Lutherie trade.

Good point Colin and also I wish I had a pic of the Gibson butted and patched joint, talk about sloppy.... That is a very good example of an X intersection specifically engineered to let the top pump in and out.

More beautiful work thanks Brian.

I voiced similar to you but I tried to isolate braces. For example, and this produced some great sounding guitars if I do say so myself I voiced the top with ONLY the X brace in place first. Holding it on a node I carved and removed material until that point that you describe as distinctive, good word! You can hear it open up and then you hear the diminishing returns after that point. The top becomes and here is my word more "musical" right before our ear and it starts to sound like a musical note.

This is with again only the X brace glued on the top.

Then I added a tone bar and repeated the process and I think I kept it symmetrical where I could so all finger braces were added during the same tapping process, etc.

There was more such as the intentional mismatch with the back frequencies and what I tuned my tops to but your comment about the "distinctive" change brought me back to a relaxing afternoon with my piano hammer tapping my top.

Anyway thanks for the memory

Here is a very good discussion on the patch and some of the participants are folks we all know.

Please pay attention to our friend John Arnold and what he has to say about what he does and what results tone wise. He is sure that the joint is plenty strong and again I submit that this is a joint that benefits from not being over built.

https://www.acousticguitarforum.com/forums/showthread.php?t=337769

Also although a bit off topic I wanted to throw out the severed head of bringing up the idea of what results when we over build. It will still sound like a guitar and in fact it will sound like most guitars because most guitars are over built...

But when we start to let the thing be free to vibrate and flex and move they come alive and can turn heads.

I once visited with Ervin Somogyi in his booth at a show and played both of the guitars he brought. They both sounded incredible and they both did something I have rarely heard a guitar do. You can play a bass note and right before your ears that bass not would gather strength and projection as if the guitar had a turbo charger only without as long a lag. The structure of the instrument was permitting vibration to happen and that is a beautiful thing.

It's also the goal...

I recall having this discussion early on in my time at Greenridge after observing that a 50% depth cut for the X-brace joint was not consistent across guitar marques or even across early, non-jigged construction within brands. As the boys opined, Occam's Razor should be applied to this 150-200 year after the fact analysis.

We must assume that:

A. That the craftsmen involved knew enough in the way of engineering to determine that the desired stiffness could be achieved with a bias-oriented glue-soaked fabric patch, but somehow failed to recognize their seemingly intentional creation of stress risers at the corners of the 'notch down' brace, bur somehow failed to apply then-contemporary craft knowledge that would achieve the same desired flexibility with a simple adjustment in notch and brace depth.

B. That fiber characteristics (material, weave, warp and weft physical properties, etc.) and glue (really, matrix) characteristics would not vary significantly (>10 percent) so as to introduce a large variation in what were both small shop and factory-made artifacts.

C. That the notch-up and notch down scheme for the X braces were consistently applied (unidirectional hinge) versus bidirectional hinge.

If I had more time, I could likely list a few more implicit assumptions, but much like scarification of bridges and fretboards done due to a fundamental lack of understanding as to how adhesives actually functioned, I suspect that these early practices resulted less from any degree of engineering knowledge and more from a desire for neatness and economy in what were largely craft environments driven by traditional practice.

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A constellation only takes shape when one maps the whole.
- Beth Brower

from an engineering point the X brace is not weakest at the X the X braces are actually more of a structure and the top , bridge and plate all work together.
Many confuse the Braces and think more like a joist structure when in reality it is about controlling movement and expansion. It is fascinating at how little you actually need in bracing. Without a patch or cover plate that will weaken the joint.
The cloth patch makes the joint CONTIGUOUS are a fancy was of saying acting as a unit or touching. If you make the joint too tight you won't get the glue into the joint structure and you want a little clearance for this. Hesh and I work on a lot of guitars and I am sure he has seen sloppy joinery ( Gibson ) and yet they sound great.
I am a cloth joint guy but again there is more than one way to skin a cat and this is just proving there is no one perfect way. When I voice a top I am in the school of keeping top and back voice to avoid harmonics. I enjoy all the posting it helps the new guys.. DISCOVERY it the path to learning

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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

Thanks so much for posting this! When everyone else scallops, this is the opposite!

Is this a technique you always use, or is it something you use occasionally with a particular goal in mind?

Yup, it’s pretty much the pattern I’ve used on the last 50 guitars. I’d love to try a Falcate pattern sometime…