guitar thicknesses

[Bruce Sexauer]

I think I said (should have) that I use slightly wider braces on both small and large EUROSPRUCE topped guitars. This would be as compared to Adirondack (American red spruce) topped guitars. Also, I don't mean a lot wider, short of 5/16, usually. I do mill my braces uniquely for every guitar, and do not keep a stash of precut stock.

Either of the two guitars you mentioned, Louie, and they are both 000, would be a fine candidate to represent my thinking. As it happens, they were made over ten years apart.

[LouieAtienza]

Originally Posted by Bruce Sexauer

I think I said (should have) that I use slightly wider braces on both small and large EUROSPRUCE topped guitars. This would be as compared to Adirondack (American red spruce) topped guitars. Also, I don't mean a lot wider, short of 5/16, usually. I do mill my braces uniquely for every guitar, and do not keep a stash of precut stock.

Either of the two guitars you mentioned, Louie, and they are both 000, would be a fine candidate to represent my thinking. As it happens, they were made over ten years apart.

Thanks for the info Bruce! Having heard them a year apart it was hard for me to make any comparisons, though the one at Dream Guitars definitely had more of a "vintage" sound for lack of better word (and whoever owned it, really played the heck out of it!). I did hear Paul play your pearwood on Sunday at the show, and it was a loud one! But he definitely has a stronger "attack" than I do.

I think my understanding is somewhat trending towards your direction, but hopefully soon I'll have some material to play with, and my new "shop" setup, miniature as it is, is coming along.

[Tom West]

Originally Posted by Bruce Sexauer

I am pleased to see some thought provoked.

I do view the top plate as a membrane which must have adequate integrity to span the distance between the braces, but does not need to do much more than that. With the addition of the braces it becomes a complete structure forming the face of the guitar, but without the braces it is nothing, thus needing no specific resonance on its own. Making it heavy enough to resonate as an unbraced whole is a waste of structure then, more efficiently handled by the braces themselves. There IS an opposing school of thought, which I attribute to Overholtzer, perhaps erroneously.

If you get a chance, play virtually any one of my guitars and see what you think.

William Cumpiano in his book "Guitarmaking Tradition and Technology" calls this " dispensing or quenching the fundamental".
Tom

[Alan Carruth]

Bruce Sexauer wrote:
"In my view, if an unbraced plate has enough integrity to produce a fundamental tap tone, it is too thick."

...So here's my problem. Technically, the 'fundamental' tone is simply the lowest pitched resonance of the system. EVERY system has a lowest resonance. Do you mean an AUDIBLE fundamental? How good are your ears?

I agree with printer2 here: IMO the top and the bracing should share the load. Other folks have different opinions, and make nice guitars, so this is not something that comes down from the mountain side engraved on stone. The important thing is that you develop a system that makes the sound you want to make, and come up with a way to find the thickness you need for the piece of wood you're using that works in your system.

BTW, .135 for some low density Engelmann is not really to thin at all, or for WRC for that matter. I've even run into REd spruce that pretty close to that light, and needed to be close the that thickness as a consequence. It's not about the species, it's about the piece of wood: there's plenty of overlap between species.

[Bruce Sexauer]

Originally Posted by Alan Carruth

Bruce Sexauer wrote:
"In my view, if an unbraced plate has enough integrity to produce a fundamental tap tone, it is too thick."

...So here's my problem. Technically, the 'fundamental' tone is simply the lowest pitched resonance of the system. EVERY system has a lowest resonance. Do you mean an AUDIBLE fundamental? How good are your ears?

It pretty much goes without saying that the top and the braces share the load. How could it be otherwise? It is then a matter of distribution, and there are a variety of opinions about that. I am talking about my own system, and by no means do I mean to say I have a corner on the market, only that mine works and is seeming reliably repeatable across species and sizes.

When tapping on a plate, there is a point where it stops resonating. I do not mean I cannot hear it, I mean it actually lacks enough integrity to sustain a meaningful vibration. My technical term for this is that it goes "Floofy" . Instead of going Bonnnnng, it goes phwup, not unlike a piece of thick paper. To argue that this is a resonance or has a pitch below what I can hear, while possibly technically true, obviates the truth of what I mean.

[rogthefrog]

Originally Posted by Bruce Sexauer

It pretty much goes without saying that the top and the braces share the load. How could it be otherwise? It is then a matter of distribution, and there are a variety of opinions about that. I am talking about my own system, and by no means do I mean to say I have a corner on the market, only that mine works and is seeming reliably repeatable across species and sizes.

When tapping on a plate, there is a point where it stops resonating. I do not mean I cannot hear it, I mean it actually lacks enough integrity to sustain a meaningful vibration. My technical term for this is that it goes "Floofy" . Instead of going Bonnnnng, it goes phwup, not unlike a piece of thick paper. To argue that this is a resonance or has a pitch below what I can hear, while possibly technically true, obviates the truth of what I mean.

So to sum up, I should thickness until bonnng turns to phwup, then brace, shape the braces, and hope bonnnnnnggggg returns, even better than it was?

[Bruce Sexauer]

Originally Posted by rogthefrog

So to sum up, I should thickness until bonnng turns to phwup, then brace, shape the braces, and hope bonnnnnnggggg returns, even better than it was?

No no no, you left out the phloof!!! Otherwise, that's pretty much it.

I put my braces on in stages and shape each before the next stage. This allows me to re-approach the phloof, and to correct should I go too far. In reestablishing integrity, I have learned to look for a certain character in the sound that is neither phloofy nor too lumber-like. I offer another extremely technical term; "the quality of the drum", which quality is what I am talking about.

I do offer a master class which includes a hands on demonstration of every aspect of what I am describing, and so far have had but one taker, Peter Rodman. His experience did transform his work IMO, and being a real person, you could even ask him should any of you consider the experience. The per-requisite is to have a complete understanding of the parts of a guitar and some level of concept for the function of the whole. Ideally you have made a few to a few dozen. It is actually a Master Class, and not for beginners.

[rogthefrog]

Originally Posted by Bruce Sexauer

No no no, you left out the phloof!!! Otherwise, that's pretty much it.

I put my braces on in stages and shape each before the next stage. This allows me to re-approach the phloof, and to correct should I go too far. In reestablishing integrity, I have learned to look for a certain character in the sound that is neither phloofy nor too lumber-like. I offer another extremely technical term; "the quality of the drum", which quality is what I am talking about.

I do offer a master class which includes a hands on demonstration of every aspect of what I am describing, and so far have had but one taker, Peter Rodman. His experience did transform his work IMO, and being a real person, you could even ask him should any of you consider the experience. The per-requisite is to have a complete understanding of the parts of a guitar and some level of concept for the function of the whole. Ideally you have made a few to a few dozen. It is actually a Master Class, and not for beginners.

Phloof, noted.

I'll probably take you up on the masteclass thing after I complete a few. Hopefully you won't catch on fire in your race car before then.

[Bruce Sexauer]

Originally Posted by rogthefrog

Phloof, noted.

I'll probably take you up on the masteclass thing after I complete a few. Hopefully you won't catch on fire in your race car before then.

I worry more about getting hit by a car while riding my bicycle. Total miles is about the same on either vehicle, but elapsed time is many times more on the bike! The real issue, barring disaster, is that I am getting older and. . . and . . . you know.

[LouieAtienza]

Originally Posted by Bruce Sexauer

I worry more about getting hit by a car while riding my bicycle. Total miles is about the same on either vehicle, but elapsed time is many times more on the bike! The real issue, barring disaster, is that I am getting older and. . . and . . . you know.

Yeah, but the bicycle is less likely to catch fire! Though, you may have found a way to enjoy racing, and torrefy your guitar tops, at the same time...

[LouieAtienza]

Originally Posted by Bruce Sexauer

It pretty much goes without saying that the top and the braces share the load. How could it be otherwise? It is then a matter of distribution, and there are a variety of opinions about that. I am talking about my own system, and by no means do I mean to say I have a corner on the market, only that mine works and is seeming reliably repeatable across species and sizes.

When tapping on a plate, there is a point where it stops resonating. I do not mean I cannot hear it, I mean it actually lacks enough integrity to sustain a meaningful vibration. My technical term for this is that it goes "Floofy" . Instead of going Bonnnnng, it goes phwup, not unlike a piece of thick paper. To argue that this is a resonance or has a pitch below what I can hear, while possibly technically true, obviates the truth of what I mean.

I thought that might have been obvious too, because it has no choice but to contribute in carrying the loads. I suppose the search is as to how much does the top wood contribute to the overall strength, and how much does the bracing? It would be obvious that the bracing without the top would "displace" very significantly under load, since it would not have the benefit of being attached to the soundboard. Yet the soundboard, unbraced but at final thickness, would warp significantly as it's torqued by the bridge.

The thinnest I've made a top was actually for a dread, about .063" pretty much all the way through, but it was Douglas fir, and it seemed so darn stiff no matter how thin I made it. I do thin my tops a little after box assembly but before routing for binding... but I didn't doo too much with this particular top.

[Bruce Sexauer]

When courting structural limits, it has been shown that biasing the structural duties toward the top increases the weight of the system. If the only goal were structure, using lumber would be the way to go, but we also want response and volume, not to mention tone and balance. Light weight and flexibility bring the first two, integrity and consistancy (even application of integrity) bring the second two, IMO. My goal, then, is to move as much of the structure as possible to the bracing while maintaining enough membrane to guarantee integrity. Distributing the braces to minimize the necessary membrane thickness is a big deal, for me. I'm do not use templates for my bracing, but instead draw them on the top uniquely. This allows, or forces, an ongoing metamorphosis of my concept.

[Alan Carruth]

Bruce wrote:
"My technical term for this is that it goes "Floofy" . Instead of going Bonnnnng, it goes phwup, not unlike a piece of thick paper."

What you're describing is an 'over damped' system. The mass of air that the top has to move as it vibrates is so high relative to the mass of the top that it sucks all the energy out. You get this with balsa. People say that balsa has high damping, but when I measured a 2 x 2 of balsa the damping in the wood was no higher than that of the usual spruce. It's just that a thin sheet is so over damped by the air. Another good example is a loudspeaker cone. Anyway, you can still drive a system like that, and it will have resonances, they just get hard to hear. Thanks for finally clarifying that one for me.

Bruce again:
"When courting structural limits, it has been shown that biasing the structural duties toward the top increases the weight of the system. "

Yup. A bare top has a lot of the same sorts of resonances that a braced one does, but if you made it thick enough to be structurally sound it would be 'way too heavy for the strings to drive. Bracing adds stiffness without too much mass. OTOH, I'm not a big fan of heavy bracing with a thin top, either. IMO I get a better sound b finding the right balance. Other folks have other opinions, and build things differently. It all works for somebody.

[rogthefrog]

Alan, Bruce, I don't know if you realize how valuable all this insight is It's a principled way to say "the top needs to be neither too thick, nor too thin, but precisely the right thickness."

I'm hoping to reach phloof, phwup and then ultimately bonnngg soon.

[LouieAtienza]

Originally Posted by rogthefrog

Alan, Bruce, I don't know if you realize how valuable all this insight is It's a principled way to say "the top needs to be neither too thick, nor too thin, but precisely the right thickness."

I'm hoping to reach phloof, phwup and then ultimately bonnngg soon.

Or more precisely, the right thicknesses at all the right points for the particular piece of wood you're using, with the bracing used.