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Hi all,

First time poster here as well as first time guitar builder. I'm building an OM from an LMI kit with the Antes plan (AR Spruce, Indian Rosewood). I also have Cumpiano's book. I'm terrified of over-bracing this guitar as I've read novice builders often do that. It'd just be an enormous disappointment to spend so much time, energy, and money only to produce a dud. I'm coming up to bracing the soundboard and I've noticed a difference in the bracing patterns described by Antes and Cumpiano. I'm hoping for some feedback.

In his book, Cumpiano uses 2 soundhole braces and a very sturdy upper face brace. Granted, it's a dread, not an OM. Looking at the Antes plan, it seems there's no upper face brace, but there is a third soundhole brace tail side of the soundhole. This seems to drive the joint of the x-braces further toward the bridge and move the lower face braces close together (maybe, to my novice eyes, closer together than they need to be).

With all this in mind, I have several questions. First, does anyone know if I'm just not seeing the upper face brace on the Antes plan? Second, does anyone have an opinion on these two bracing patterns & which of them might be more suitable to an OM?

Third, I'm absolutely in love with the Collings OM sound (it's the reason I've dispensed with sanity and started doing this). From what I've seen poking around inside a Collings, they appear to put the x brace joint close to the soundhole and use just two soundhole braces. Does anyone have any suggestions on how to approach that sound?

Finally, if I were to improvise -- dispensing with the 3rd soundhole brace and moving the x brace joint toward the soundhole, would I need an upper face brace in order to keep the guitar from falling apart? If so, does anyone have a suggestion for dimensions? Cumpiano's is .5 by .5, which seems huge for an OM. Or if all this sounds idiotic, please help!

Thanks.

- Florian

If by 'upper face brace' you're talking about the big brace between the sound hole and the heel, then it's definitely OK to have it massive and overly stiff. This brace pretty much defines where the soundboard ends. When people talk about an 'overbuilt' guitar, they are generally talking about excess stiffness and/or mass on the soundboard where the top needs to vibrate freely. This brace defines that boundary, so if it is overbuilt it shouldn't make a difference to the tone. Conversely if it is underbuilt it might have very bad consequences.

As for shifting the X brace forward, either way should work OK. If you do shift the X brace, the most important thing in my opinion is to make sure the X still overlaps the bridge. If not, there will be big trouble both structurally and tone-wise.

Lex, thanks for your quick reply. In Cumpiano's book, the steel string has an "upper transverse graft" (.25 x 1.0) adjacent to the heel. Then, between the graft and the soundhole, there's a big "upper face brace." (.5x.5) Does that description fit with what you're saying?

One of Stew-Mac's weekly email tips concerned "forward shifted" x braces. When Martin moved the X brace to reduce warranty work they also changed the angle. If you private message me I'll dig upthe info and email it to you.


Steve

Florian, I don't have any advice for you on this, but I can offer you a big WELCOME to the OLF. It is a great place to get good answers to your questions. Those who know will make sure you do before you can do it wrong, if you just ask. Great, sharing bunch of people here.

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Waddy

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Sound Clips of most of my guitars

Florian,
I think your taking the wrong approach here. I sure that very few here, or anywhere else for that matter, have built the "perfect guitar" for their first instrument, or second or third. The whole process is about learning. You keep the good stuff and lose the bad.

My advice is, because you are building a kit based on a set plan, follow the plan and use Compiano's book as a guide. I'm sure that you will end up with a decent sounding instrument by following the plan that came with your kit.

Good Luck!

Cal

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Remember, there are no stupid questions, only stupid answers!

The question to ask your self is what force is this brace resisting. If you were a student and I a teacher I would not give the answer, rather I would tell you to research the problem. Find out what force the upper face brace (upper transverse brace) resists. I say this because too often here we forget that giving the answer does not always bring with it knowledge. So I am going to leave that to you to investigate. But will say IMO yes you need one. The third brace you add for the sound hole support does not resist the forces the the upper face brace (upper transverse brace) is designd to resist.

Yes, the .5x.5 brace is the one I'm talking about.

you are not referring to the upper transverse graft but the upper transverse brace. They are different. The upper transverse graft is low and wide and resists splitting of the sound board at the edges of the fretboard extension. The upper transverse brace is closer to the sound hole and is fat but has some height to it. It resist and spreads the downward force of the fretboard extension preventing the soundboard from wanting to belly in. the string tension pulls the peghead end of the neck up. That forces the fretboard extension (the part of the fretboard on the soundboard) into the sound board. This is the ½” x ½” upper face brace not the upper face graft. Many of us use two of these braces and many make them even taller than ½”. The force inward of the fretboard extension is one of the larger forces the sound board needs to resist and is one of the most common failure points. Most of the other forces on the soundboard are in either pulling outward or more correctly rotational towards the neck. This force is inward and causes a change of direction in the loading on the soundboard and puts added stress right in front of the sound hole. ½” x ½” is sufficient for an OM but I make mine ½”wide by ¾” tall.

There I gave you some of your research data after all

Everyone thanks for the replies. Waddy, I started posting here in part because of the feedback I saw you getting from other posters. Thanks for the welcome!

As for my questions then, it sounds like there must be an upper face brace (.5x.5) on the Antes plan. It's either not clearly marked or I'm not seeing it. Leaving it off would be structural suicide. (There is an upper graft. I misstated the dimensions. It's 1.0 wide by .125 high.) MichaelP, thanks for the insight.

So, does anyone have an opinion on what happens when one shifts the x-brace toward the soundhole and leaves off the 3rd soundhole brace?

Cal, thanks for your input. I'd build the Antes OM according to plan, except I've seen it criticized several times (on this board) as over-braced. I understand that this is a learning experience. God knows I've made plenty of mistakes so far. Still, I'd like to build a great sounding guitar.

I am not well versed with the Ante's plans so I can’t speak on that but I have heard the Antes plans are over braced in the lower bout. I t may be that the Ante’s plans have an A frame bracing to support the fretboard extension loading as apposed to an upper transverse brace. I am bit confused as I thought you were using the plans in the Tradition and Technology by Compiano.

It is hard to compare one bracing system to another and it is most often disastrous to mix two different bracing plans. This is especially true for an inexperienced builder.

To learn properly find a plan that you want to follow and follow it. As you gain experience and learn the function and engineering behind various bracing systems then the time to experiment and make persona preference changes will come.

As another post stated trying to build the perfect first guitar is not going to happen. Right now your best results will come from following a proven design. Not altering them.

The biggest mistake you can make on your first is to try to trick it out. Probably not want you wanted to hear but it is true.

Pm me if you like and I will give you a tracing of a bracing plan that will produce a great Om but only if you follow it

"So, does anyone have an opinion on what happens when one shifts the x-brace toward the soundhole and leaves off the 3rd soundhole brace?"

I don't know but pre-war Martins with 'forward shifted' braces traditionally had the 3rd soundhole brace.



'46 D-28

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Jeremy Douglas

In the OM style guitars that I make, I routinely dont put in the third brace you have pictured. In dreads I do use it.

The ther two braces you are referring to are the "popsicle" brace that is closest to the neck block. There has been a lot of discussion on using this brace and it's effectiveness at reducing cracks in the top of the guitar along the fingerboard. I think the jury is still out on whether or not this brace is useful. Sometimes I use it if there is no cutaway but I omit this brace all together if it is a cutaway. The other brace is the one that most people leave large and bulky. It is called the "upper transverse" brace. I tend to have large ones, but prefer to have a taller, thinner brace there than the traditional fat short brace. The main thing it to give that part of the upper bout as much strength as you can while keeping the overall weight of the top as light as possible.

Martin uses an 8 degree x-brace angle in their OM guitars. In other words, the X-Braces are not 90 degree angles but are opened up a little bit. By spreading the legs of the brace (a little), you can increase the bass response of the guitar. closing the legs together will create more mid range and trebles.


As far as a fear of overbracing, this is the gray area that one can only figure out by building...and building again. The first few of my guitars were overbraced. I kept thinning the top and the braces until I finally went too far and the top developed waves when I strung it up. It sounded great but looked terrible. Now, I finally have figured out how to brace one so that it stays structurally sound while being as light as possible.

I'm sure that following the plans you have will produce a good sounding guitar. The things I am sharing are meant to help you "tweak" that extra little bit out of the top. I hope it is useful information!

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Reguards,

Ken H

I forgot we were talking about OM's but I will say my SCGC OM/PW with forward shifted braces has that soundhole brace and they build pretty light.

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Jeremy Douglas