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I was re-reading an e-mail today from a builder I was gleaning some information from in regards to Nomex double tops. He mentioned that there were some builders using Nomex double tops with no internal bracing!
This got me to thinking that if you used this type of technique on the top married with a hollowback design with laminated sides ala McKnight guitars could you indeed build a guitar with "no bracing"?

Just a wandering thought...

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Guitar Building = Continuous Improvement Process

I would have my doubts on a steel string for sure, and even on a normal tension and high tension classical for that mater. On a still string 145-160 some odd lbs of torqe is a lot of moment to restrain with a top sandwich thin enough to still respond well. This may vary well be do able on a low tension classical, but you culd not get me to belive it till I see it.

I believe that RainSong uses unbraced tops. The top is a laminate based on a carbon fiber sheet. I do not know about the backs and sides.

I thought the Rainsong used a carbon fiber rod bracing system that was incorporated into the rim assembly much like a classical builder will do a back. Then the top plate of carbon fiber was adhered to this . It would be true that the top had no bracing before assembly to the guitar but the carbon fiber rods that are in part of rim assembly becomes it braces

But even If I am wrong here there is a world of difference in wood even double top w/ Nomex and Carbon fiber in a strength to thickness ratio

Why is that a good thing?

Bracing serves two functions: 1) Dealing with string stress, and 2) voicing the top (and back) tonally.

I was thinking that too but the other is seemed like a good place to start

This may come under the heading of "voicing" but my understanding is that the vibration travels more easily (less impedance) and more quickly with the grain than across the grain. So, the braces serve also to quickly spread the vibration across the top. I suspect that an unbraced steelstring top would favor bass over treble. If the top is all wood, and the strings end at the bridge, I would think an unbraced top would need to be quite thick, leading to more of a muted sound with a harsher, quicker attack.

This might be one of those things that you just won't be able to shake out of your head until you try it. If you do, please report your findings!

Dennis

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Dennis Leahy
Duluth, MN, USA
7th Sense Multimedia

http://www.freepatentsonline.com/7276868.html

This link to a patent may be of interest.

I believe the Ergo guitar by Charles Fox has no braces whatsoever. I've heard it on the website and think it sounds amazing. Check http://www.ergoguitar.com.

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Time is a great teacher, but unfortunately it kills all its pupils - Louis Hector Berlioz

Chansen / C hansen / C. Hansen / Christian Hansen - not a handle.

Christian

http://www.rainsong.com/deal/

And here is RainSong's site that claims they do not use braces. I don't know, but they may still have rims to attach everything together.

I just got back from a LINT(luthier's Interactive of North Texas) master's class with Charles Fox. His Ergo guitars don't have braces in the lower bout. They do have two transverse braces to help deal with stresses in the upper bout. He did mention that he is thinking about putting braces in, purely to voice the top.

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Matt Jacobs

"Don't tase me bro"

Did y'all not read the Brunkalla thread a week or so ago.....

I could see how you could possibly....possibly.....get by without bracing *IF* the top were domed quite a bit... lets say a 10 to 12 foot radius, ans then using the nomex double top in combination with some doubled sides and heavy kerfed lining to tie it all together. Tim has already proven that the double back works, so all we have to wonder about is the top.

Looking over the "bass bar" threads on violins on this forum and another forum, I have to wonder how this would work on a steel string with a pretty healthy domed top too.

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Reguards,

Ken H

I've built several without braces. Double/Hollow top, Double/hollow sides, and Double/Hollow back. I've used Nomex, Carbon fiber, and a polymer material developed for aerospace applications.

Using the right combination of materials is key to the overall voice and responsiveness. Structurally, I've had better results with some materials than others. It's definitely doable and can produce nice results.

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Don Sharp
Got Brazilian?
http://www.sharpguitars.com

I'm also in agreement. It's definitely doable. Double tops are just honeycomb panels and can be designed to take the load. They won't be the same thickness as a standard top however.
I don't know whether it's the right thing to do or not however.

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Jim Watts
http://jameswattsguitars.com

I read it several days ago. When I first saw this discussion I thought it was a continuation of the Brunkalla thread.

I designed one and built it over 5 years ago and it still is fine. sorry to link to that other forum
http://www.mimf.com/library/mckay_braceless_acousticguitar.htm

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Ken

Interesting that Charles Fox is considering putting braces in for voicing. I played a braceless Ergo (maybe it did have some upper bout bracing, I'm not sure) at Montreal last year, and it was very impressive. The most striking thing about it was the incredibly quick response. The sound just JUMPED out of that guitar. It was almost as if the guitar somehow anticipated what I was about to do and sung out a split second before I actually touched the strings. I played several other guitars there that were awesome in many respects, but no other had that particular effect in such a striking way. It was truly remarkable.

I liked everything about its sound, in fact. I didn't notice anything lacking. Of course, as with all the guitars there, I only played it for a few minutes, and, in spite of the "quiet rooms", there was a lot of noise, and the acoustics in there were far from ideal. In that setting, though, it was, to my ear, among the top 3 or 4 guitars of the many I played over the course of the show.

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Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

I did a search and found a brief explanation of Charles Fox's design here:
http://www.acousticguitar.com/article/d ... cleid=6655

He mentions he incorporates a floating fretboard in conjunction with his "braceless" top to make it all work.

As for the reason "why is this a good thing?" I was thinking weight, stability, aesthetics, and tone. (refer to Todd Rose's post on the ERGO's sound)

Again, these are just thoughts/questions that I am putting out there, not to rebuke traditional tried and true building processes, but to merely stimulate thinking in different directions. Who would have wanted to drill a hole in the side of there custom guitar 5-10 years ago but today "sound ports" are becoming very popular!

Ray

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Guitar Building = Continuous Improvement Process

Today I tried my link to MIMF above and got the front page, not the link. I don't know what the reason for that is, but if you want to see my bracing design you can log into mimf and search for it in the library. Sorry it doesn't work as it should.

My guitar has very quick attack also, with a sensitive response and lots of dynamic range.

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Ken

Let's think about this. We use braces because they add a lot of stiffness for the weight. Most of us use braces with a more or less plain rectangular cross section. Yeah, you round off the top, but still... You could think of that, or even a traingular brace, as a bunch of tall narrow rectangular braces of different heights side by side. At least, that's what my calculus teacher said.

A more efficient use of materials, giving greater stiffness for the mass, is an I-beam. The 'flanges' at the top and botton take most of the tension and compression forces, and the 'web' in the center only has to withstand the shearing forces, and keep the flanges the right distance apart. The main problems with using these on guitar tops are that they require extra effort to make, and you can't voice them much once they're glued in.

The lattice in the Smallman guitars amounts to a bunch of I-beams. The flanges are carbon fiber, and the webs are balsa. Because of the relatively low modulus of ruture of balsa the webs have to be as wide as the flanges to hold up, but the idea is the same. The top surface is just a membrane to move air; he uses wood, but you could use mylar, as Tim White did in the 'Crysalis' guitars.

Suppose you sliced the webs up into paper thin pieces, leaving them as tall as they were before. You could space them pretty closely. If you used wide flanges on the top and bottom, you could glue those together to produce the surfaces. What you've got then is a sandwich top. In a sense, the sandwich isn't 'braceless', it's ALL brace!

It's still an I-beam though, getting most of it's stiffness from the material in the flanges/surfaces. These can only be made so thin before they become too fragile to work right, so there's a limit to how much stiffness you can remove. That's why these things are hard to tune; they either work or they don't.

Of course, as John Calkin said: "Give them volume and they'll hear tone". You can shave 40% or so off the weight of the top by making a sandwich, and it can be just as stiff as any normal braced top if you do it right. That weight saving translates into a lot of attack and power, and evens up the sound simply because there are no weak notes.

Since most of the weight of a top is in the top surface, rather than the bracing, it makes a certain amount of sense to make a sandwich for the top part that is only just as stiff as a normal unbraced top, and then brace it to get the rest, and allow for voicing. A normal steel string top might weigh 150 grams before bracing, so saving even 30% of that would get you down to 110 grams or so. Add in 30 grams of bracing and you're still not back to where you would have been with a normal top without the bracing, except this top won't fold up within the first week. You've saved over 20% of the weight. Sweet!

Now you're talking, Al. Precisely my implied (though admittedly quite veiled) point.

Note, though, that the tonal characteristics classical makers are striving for are almost diametrically opposed to what most steel string makers are trying to get. So a super light top brings out what's weak in the nylon strings, whereas a certain amount of well placed weight and bracing help voice steel strings.

Tops are not just impedance converters; they're also tonal filters...

And by the way, Al Carruth helped me design my braceless top, he called it "continuous bracing".

Overall my top weighed more than a conventional top because the "hard points" were heavy. But the other parts are very light with variable stiffness. This guitar is so loud that it would put a dreadnaught to shame. Yet it still sounds well balanced. So maybe just plane light and stiff is not good for steel string guitar sound but rather some well placed weight in the mix.

One problem is that a top without braces, made from wood that expands and contracts will vary with seasons, raising and lowering the height, and thus the string height off the fingerboard. Similar to a cello, double bass.

This shows the hardpoints and the core material which is Airex, PVC, closed celled honeycomb foam. And the shaping of the core. The last thing I did was put the inner skin on and then plane the outer skin until I heard a good tap tone. Kinda like voicing an archtop. Try it you'll like it.

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Ken