Triangulating the legs of the X-braces

[Chuck Dvorak]

Hi everyone,

I've been (slowly) working on an OM kit I got from John Hall, and I'm at a crossroads with the brace shaping. I triangulated the finger braces, and I also triangulated and tapered the tone bars. I still plan to feather those down to nothing where they will meet the rim. However, I was also considering triangulating and tapering the bottom legs of the x-brace starting at about 1" from where the braces intersect to where the braces will inlet the rims. Does this make sense?

Basically my goal is a good fingerstyle guitar--responsive and resonant. I have been working on the notion that triangulated braces maintain stiffness but reduce mass, which should make the top more responsive. I've also been trying to get a sense of tap tone while I do the brace shaping. I have some success pinching around for nodes while I tap on the top at the approximate location of the bridge. I've had the best tapping success when balancing the guitar top on my thumb at the soundhole while tapping the top.

Thanks for any advice.

Chuck

[tippie53]

here is a link to a bracing library that may be of interest.
http://theunofficialmartinguitarforum.y ... 2HIr3l2G9s
I think you may want to do a little scalloping. the crossection can be tweaked a bit but scalloping may be your better option.

[Chuck Dvorak]

Thanks for the advice and link. I have seen the forum thread from the UMGF before about Martin bracing, and it is an extensive resource. Most of the info is on layout, it seems, but there are a number of bracing profile photos, and there are variations across all body sizes and types.

If I scallop the lower legs of the x-braces I'll potentially allow the guitar to produce a bit more bass and possibly sound a bit louder, correct? At least this is what I've gathered based on reading I've done. Would this be a good idea on an OM-sized guitar, seeing as I'm trying to design a balanced instrument?

Chuck

[tippie53]

the key is how you scallop. Too much and you loosen the top too much. There is a key to this so if you start with taking 1/3rd you will have a better balance and not all bass

[Chuck Dvorak]

Sounds like a good plan. I'll try scalloping down about 1/3 from the current height (leaving 2/3) as a reference point. Thanks again for the advice.

[hummingbird]

John, would you mind posting a couple of pictures of your finished braced tops so we can get an idea of how the braces should generally look size wise etc.

[tippie53]

I think we can do that I have one I am finishing up

[Darryl Young]

Chuck, feel free to ignore anything I'm say here.......but if you want a responsive fingerpicking guitar, you may want to trim the braces further. How thick is your top? Here are some things to consider......but you might ignore most all of this if you have a fairly thin top.

On the finger braces, maybe leave them full height only at a point in the very middle and taper them down to nothing BEFORE they meet up with the lining.......and taper them down close to nothing where they meet the X brace......then finish off by triangulating.

On the tone bars, consider tapering them down to nothing well before they meet the lining. I personally don't want a lot of stiffness near the perimeter in the lower bout (I don't even tuck the lower X brace arms into the lining but of course I do the upper X brace arms). If you aren't going to scallop the tone bars, from the point after the scoop where it connects to the X brace, you might taper them in roughly a straight line down to nothing (well short of the lining). Then triangulate. On the John Mayes video, he scoops the tone bars out a little further from the X brace if it is a fingerstyle guitar. In general, the lower tone bar can be scooped more, and taken down more than the upper tone bar. (again, my opinion).

I would either scallop or taper the lower arms of the X brace and I would consider tapering the upper arms some as well (don't scallop the upper X brace arms). Then, either way, you can triangulate.

[hummingbird]

How thick is your top? Here are some things to consider......but you might ignore most all of this if you have a fairly thin top.

darryl. So do you usually keep the top thicker and use lighter bracing? is that what works for you? And what do you consider thin/thick?

[Darryl Young]

No, but if a top is on the thin side you might be more conservative in how you trim your braces. I measure the stiffness of the spruce to decide how thick I want to make it.