The 'three inch rule' for scallop peaks - O'Brien

[Dave Bagwill]

BTW - the last two pictures on the first page of that link show a comparison of the 00-12 and the 00-14 bracing. Quite a bit of difference.

[Dave Bagwill]

This might be the wrong place for this, so feel free to move it, Ken.
From that bracing page at UMGF. Do you guys think that this is sound advice/information? :
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The position of the soundhole depends on a couple of things that I will go into later. Remember for now, it's not always in the same place on every guitar (plus the size varies), so measuring from it is not a very safe way. If you know all the variables it CAN be a quick and rough way to know more about the bracing. But what it's all about is the bracing's position relative to that thing that is pulling and twisting like mad, AKA the bridge. And north of the soundhole the upper transverse brace is fighting against the fretboard pushing in. There are more things going on, but let's keep it simple for now.

The bracing is the most stiff at the crossing point of the X. Moving this forward (away from the bridge) will loosen the top. Moving it backward will do the opposite. But that's not the whole story. Widening the angle of the X-legs (and arms) will also give the bridge less support. Loosening can be good for sound (not necessarily though), but it will make for a weaker structure. So it's a compromise.

So even if you have a very accurate way of measuring from bridge (or saddle) to cross (I'll tell you mine soon), there's still the angle of the X to take into account, too.

Much simpler is just to look where the X-legs cross the bridge. This is the real thing that matters, and this way you have the position and angle combined. To me "vintage position" or forward or whatever, is when the legs cross the SIDES of the bridge, usually just north of the bottom corners of the bridge. (It can be higher, especially on Martins from the gut era, and on some Gibsons they even miss the bridge altogether). "Modern position" has the legs crossing through the bottom of the bridge, south and between the bottom corners. (Like e.g. the Clapton, the D-35 and also the 00 on this page). Another characteristic of "vintage bracing" as I've seen it, is that the tonebars are relatively close together, more transverse (more towards horizontal if you will) and starting more south of the bridge, i.e. BELOW the lowest fingerbrace. Usually they angle off the X at about 63 or 64 degrees. Compare the custom M and OM's to the Clapton, D-35 and the HD-28 for instance, and you'll see what I mean. On the latter, the angling off is more like 72 degrees or so. The 00 is "odd" in that the tonebars are close together (vintage style), but angled and positioned in the modern way (not below the lowest finger brace).
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[ken cierp]

Spreading the X legs and or moving the X intersection closer to the sound hole allows the bridge to rotate more. I suppose that could equate to a "weaker" sound board assembly. I think most would agree that guitars built this way tend to be a bit louder -- the mythological "banjo killer." Do they sound better? Better than what? There is a large contingent of players that would much rather have an old J45 than an old Martin --- claim they are loader (despite the shorter scale) and sound way better. Look inside an old Gibson -- the bracing could not be more simple -- a bunch of 1/4" x 1/2" sticks. The quality is astonishingly crappy, plus profile and finish work varies greatly from sample to sample. But in the end they are just as prized as Martin's

OK, OK --- what I am getting at is that the informational tidbits in your post are an individual's "observations" or a collection of popular conventional wisdom talking points, as for establishing any sort of science -- I don't think so.

[Dave Bagwill]

Makes sense! I do enjoy reading tidbits and rules of thumb and conventional wisdom on guitar theory - it's fun and every so often I learn something.

[ken cierp]

I do enjoy reading tidbits and rules of thumb and conventional wisdom on guitar theory - it's fun and every so often I learn something.

Me too !!

[Herman]

Ya, great stuff for romantic guys.
Herman