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Old 07-11-2017, 04:53 AM
hat hat is offline
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Default Back bracing - stuck at ladder braces?

I'm curious as to why the back bracing is still being done in a ladder type style? Are there any builders that diverge from this for steel string guitars? My thought is that we've seen the difference that X bracing makes to the top, so why not apply some of the same principles to the back? I know a lot of builders see the back as a semi-rigid part of the guitar, but I like a very live, responsive back. I also wonder if using something of a modified X brace for the back might not help keep the neck angle and body geometry where it should be instead of tending to curl up. Your thoughts?
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Old 07-11-2017, 05:07 AM
Cincy2 Cincy2 is offline
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My Traugott Model R has a vertical brace on the back to counteract the bending force the strings exert on the neck and body. The picture shows it although not clearly.

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Old 07-11-2017, 06:27 AM
John Arnold John Arnold is offline
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X-bracing on the top is uniquely suited to resisting the torque on the bridge from string tension. There is no such force on the back, so X-bracing is not an an advantage from a structural standpoint. Flying braces are much more effective in reducing body distortion.
A more lively back can be achieved by reducing the height of the ladder braces....something Martin has done since its beginning in 1833. Other US makers followed suit in the early-1900's.
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Old 07-11-2017, 09:28 AM
Truckjohn Truckjohn is offline
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There are all sorts of various treatments of back braces... Every possible configuration you can think of....

My understanding is...

If you do plan to tune a live back to achieve some result - its easier to tune with one of the modified X brace configurations than it is with the ladder.... That said - many makers use the ladder and tune the backs just fine.... I have tuned live ladder braced backs and it works out fine...

If your intention is a non-live back - then it probably doesn't really matter all that much...

Pick your poison...
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Old 07-11-2017, 09:45 AM
Alan Carruth Alan Carruth is offline
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Over the forty years I've been building I've tried quite a sample of different back brace schemes: several configurations of X bracing, longitudinal braces once or twice, and variations on ladder bracing. I use Chladni testing to 'tune' the top and back, and one of my objects has been to find something that yields the results I want consistently and predictably, without having to go back in later and re-work things.

The scheme I'm using now is as successful as any I've tried. I'm getting to where I can tune the top and back off the guitar and end up with them pretty close to where I want them when the box is together. It's not 100% predictable, but it's a lot better than most of the ones I've tried. It also makes a pretty good sounding guitar.

What I'm using these days is pretty much the Martin ladder brace system: two fairly tall and narrow braces in the upper bout and waist, and two that are low and wide in the lower bout. I could go on and on (in my usual way) about why this works pretty well given the variation in back wood properties and the 'job' the back has to do as I understand it, but I'll spare the waste of bandwidth. Sometimes the old ways are the best.
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Old 07-11-2017, 09:48 AM
redir redir is offline
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I have been experimenting with live backs in keeping the ladder bracing but feathering the ends to zero, paper thin under the linings, to decouple the back from the sides. It definitely makes the back very active but I can't make any claim that I have any control over it. But yeah there are guitar makers doing all kinds of things with back bracing including X-Bracing.
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Old 07-11-2017, 10:08 AM
dekutree64 dekutree64 is offline
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I've been through this line of thinking as well, but ended up back on ladder bracing like everyone else... there's just not enough reason to change.

Wood is much stiffer along the grain than across. Lengthwise braces don't do much to prevent the wood inbetween from feeling squishy and easy to split. Squishiness is primarily determined by distance along the grain to the nearest brace.

X or asterisk bracing leaves large squishy spots between braces unless the back is pretty thick. May work with low density backs like mahogany or softwoods, but rosewood would be too heavy and therefore non-live, making the bracing irrelevant.

Lattice bracing works, but is more than twice the effort (at least double the number of sticks, have to notch them, and can't carve them with a finger plane).

Basically every other pattern I've come up with just ends up being 3 ladder braces with a bunch of pointless extra stuff added. 2 ladders leaves the lengthwise distance-to-nearest-brace too far, and for many guitars 3 ladders is all you need in the first place.

Soundboard X bracing is primarily designed to support the high stress at the bridge, and transmit stress around the soundhole. Since the back doesn't have anything pulling in the center of it or any giant holes cut in it, that level of complexity really isn't necessary. But it would work fine.
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