could a wooden soundboard be braceless?

[heavyg]

heres a interesting concept in bracing from Boulder Creek
http://www.bouldercreekguitars.com/sbs

[djh1765]

Originally Posted by mc1

this is just a "learn something about bracing" brainstorm thread from a player with little knowledge of the physics of luthiery.

could a guitar be built without braces by varying the thickness of the top? or are the braces partly there to prevent splitting? i suppose if one had a piece of wood as thick as the top plus the braces a person or machine could carve away everything except the top and the braces, which would be terribly inefficient, but i'm more thinking about more graceful curves to give the top the strength it needs. i also imagine a traditional top and braces allow for strength in some areas/directions and flexibility in others, but perhaps that could be accomodated via thicker and thinner regions of the top.

again, just a thought for discussion.

In 1981 the Daion Acoustic/Electric Caribou was manufactured with no braces front or back.
This was a very nice guitar.

Daion was a high-quality Japanese builder for a few short years in the late 70’s and 80s. This guitar has a solid cedar top, wine-red finish, arched flamed-maple back and sides, excellent cutaway and an endpin area that "cuts in" to the lower bout. It has a Rosewood fret board with fretboard dots. It has gold Schaller-style Daion tuners with the tuning fork logo and large buttons. The guitar has a big oval sound hole, top and back binding as well as headstock and neck binding, a sweet red wine finish, maple back strap and end strip.

I owned this guitar from 1981 until I sold it in 2012.

[pfox14]

Early Gibson archtops hardly had any bracing at all and they worked just fine.

[Ned Milburn]

Originally Posted by pfox14

Early Gibson archtops hardly had any bracing at all and they worked just fine.

An archtop is a totally different beast, and the 2 standard archtop bracing patterns have only 2 braces each. Reason for this is fixed bridge vs. tail piece.

@djh - So what did the Daion guitar do to mitigate its lack of braces?? Ply?? Super thick?? The builder had to do something, otherwise it would have imploded.

[Alan Carruth]

Actually, there's no reason you couldn't make an archtop with a fixed bridge: Orville Gibson did.

As someone who makes both arch tops and flat tops, it seems to me that arch tops do with arching what flat tops do with bracing. Both are methods for increasing the structural stiffness of the top without adding too much weight. Also, either one shapes the sound to some extent, and the details of how you do it (arch shape vs brace profiles, for example) matter.

If you pay attention to the Chladni patterns on the top and back of the guitar prior to assembly, you'll find that the bracing on the top of an arch top usually has the function of making up the stiffness lost in cutting the sound hole(s). In fact, that's one of the best ways to know if you got the brace profile right: if everything is pretty much back to what it was before you cut the hole, you're there.

Speaking of Chladni patterns; the patterns on a flat, unbraced top are often quite similar in shape to those on a braced one when the bracing is properly done. What's different is the frequencies of the patterns, which are much higher with the bracing. This signifies that the braced top has a higher ratio of stiffness to weight, and that's what the bracing is doing for you. You could simply leave the flat top thick enough to have the necessary stiffness, but for two things:
1) it would weigh more, and
2) it would lack the requisite strength in some places.

Weight matters because there is not much horsepower in a vibrating string. The only way to get decent power and treble response is to keep the weight down.

A thick unbraced flat top of spruce or whatever would be likely to split along the sides of the fingerboard, and allow the neck to fold up. That happens often enough on braced tops, and I'm sure it would be an even bigger problem without the braces. There are ways around this: some makers are using 'flying buttresses' of carbon fiber between the neck block and the sides at the waist to take up the neck stress, and this allows for much lighter upper bout bracing. So far I have not been too convinced by the results in terms of sound, but it's worth trying.

Even if you use a minimal arch, and keep everything else as much 'the same' as you can, an arch top instrument will sound different from a flat top one. It's not so much in the way the strings drive the top as it is in the mechanics of the top itself. Arching and braces to much the same job, but they do it a bit differently, and, in this case, details count.