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Does anyone have any idea what this pattern means. The guitar will be a 12-fret 000, .110 thick, 250 grams. I tried adding some weight to the lower part of the x-braces near the bridge plate, with not very much effect. 227 is the frequency.

That appears to be the monopole mode and I'm not sure you want to drop that frequency much lower.

Take this with a grain of salt but the stiffness on the perimeter caused by the 2 tone bars and the lower X brace arm ending so close together and so near the edge/perimeter may be what is opening up the ring in the upper, treble side of the lower bout.

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Formerly known as Adaboy.......

Looks like the ring+ for that bracing pattern. Pretty tough to close due to the non symmetrical bracing. I agree with Darryl, I wouldn't want it much lower, but if the top is significantly oversized, you may have more room. If it is, I would suggest trimming it down as close as you feel comfortable and see what frequency you get.

Chuck

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Good point from Chuck. If you have the top oversize by 1/2" all around the frequency will change quite a bit when trimmed to final size (shape of patterns will change as well).

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Formerly known as Adaboy.......

Thanks for the input. The top is trimmed to the exact size, just left a little tab on the bottom for positioning.

That's the 'ring+', and with that bracing it's about as good as it gets. Glue it before something changes.

Is there a tutorial on this anywhere. Ive been very intrigued by how its done and what it all means but all I can seem to find is bits of info here and bits there and trying to piece it all together just isnt working.

If Alan Carruth won't toot his own horn about his great DVD on the subject, then I will. It's very good and well worth the expense, IMO. He's also written about it extensively on the web for years ,here and elsewhere.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

+1 . It´s good for a couple of laughs too (at least i laughed). Alan seems to be the most generous, amenable teacher.

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member of the guild of professional dilettantes

This is a pretty old pic, but I thought I'd put it up anyway. I rarely do Chladni patterns on free plates, but I've done a few when I happen to have the Chladni gear out for something else and happen to have a top in the right build state.


All the falcate ones I've looked at (not many!) came out with very similar shapes for what I assume is the ring +. I don't "tune" to this, it's just how it is. So those of you who aim for a closed ring +, maybe try falcate bracing on your next build as it seems to happen automatically.

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Good designs tend to work well without any need to coax them. Fan braced classical tops tend to have nice patterns if you get anywhere close to the 'right' top wood, thickness and bracing. I've only done a couple of scalloped steel string tops, but they came right in too. Asymmetric bracing does tend to give asymmetric patterns, of course, but they sound good with a 'characteristic' timbre that has been called 'traditional'. Whatever. The real utility of any of these methods is for those cases where things _don't_ just fall into place, and also, of course, as a means of optimizing things. Again, of a fan braced guitar I'll often see very nice patterns in the rough, but both through the frequencies of them and also just from experience, will also know that I could lose a bit of material in the bracing, which could help lighten the top a bit, and make it flex better, both of which can improve the sound. AS we all know, the difference between 'acceptable' a 'very good' can be tiny, and I'll take any advantage I can find.