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Do makers of true flat-tops tend to brace their soundboards differently than domed flat-tops? I realize each maker has a unique design, but are there any trends or guidelines that tend to work well with these? Also, would anyone have a picture of the bracing for a Ryan or other flat flat-top?
Thanks, David

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David Malicky

That's a great question. Bravo!

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I think there are some pix of an Olson floating about somewhere.
I also posted pix of my recent flat top build...

True flat tops sound wonderful, but also tend to belly/potato chip more than a domed top would.
On a completed guitar, A Domed top ends up looking "Flat" where a real Flat top can look dished in.

The domed area in front of the bridge adds far more stiffness and resistance to buckling than you think it would... so you have to make up for that with bracing and top thickness...

The bracing basically looks the same... You would have a very hard time distinguishing the two from a picture.
...... Except for a general impression that the bracing on one maybe looks a little heavier...

Good luck

John

If you are building in a "significantly" lower humidity than where the guitar will live, you can simply glue flat braces to a flat top.

If you are concerned about cupping caused by the introduction of moisture at gluing time, heating the top, especially the brace side, at bracing, will help.

You can also slightly arch the braces, and spring them down at the ends when bracing to the flat top, but that sounds suspiciously like building an arched top.

I would not think the structure of a flat-built top would need to be any heavier than an arched top. A possible shifting of the braces may be in order.

When I have built a flat-top. it has less belly at stringing up, and after, than the arch-top builds.
On the ones I have seen years later, there is more sinking before the bridge than the arch-tops, as you would expect. That is why altering your bracing pattern may be in order.

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https://www.facebook.com/profile.php?id=100008907949110

Beefing up the soundhole reinforcement braces (up to 5/16"x5/16") resolved that issue for me.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Thanks, all, for the replies! That UMGF thread is remarkable. Good tip on heating and the glue moisture. We currently use CA for our braces (this is for a class project... need to speed it up) but some students may want to use Titebond.

The depression around the soundhole is .040", measured off a straight edge lengthwise along the body (strung up 1 week ago). Is that about typical? X braces are 5/16 x 9/16, forward shifted (which I think would help the soundhole depression, though of course not the stress above the bridge), with a small 0.15" x 3" scallop near the bridge. I'm currently using 1/4 x 1/4 soundhole braces and could upsize if that's needed, but then I see many guitars have tiny soundhole braces so I'm concerned that would hamper the tone.

Thanks, David

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David Malicky

I build with braces flat on the upper legs of the X and starting a slight (50 ft.) radius at the X intersection, down through the entire lower leg of the X braces. This has my bridge trying to "rotate" into a slight uphill arch between it's leading edge and the soundhole. That, coupled with tall, thin braces gives more than enough strength in that area to avoid the "sinking feeling".
Photo shows the high, thin braces (1/4 x 9/16 at the X intersection), but you can't see the slight arch. But it's there.

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Hank Mauel

That is funny, Hank.
On the one I did the mixed flat / arch, I have my braces flat below the X and curving down at 30' above the X.
I like the way it came out, and the tone is different from all the arched X's I've done before.

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https://www.facebook.com/profile.php?id=100008907949110

That right there my very well be the perfect compromise between the two extremes.

Probably resulted in a "floppier" top in the lower areas...like the old Martin's with flat braces...and that gives a much more flexible, easily driven sound plate. Mine would have just the slightest pre-load on the lower top area and that gives a different tone palette.
Just goes to prove there are mutliple ways to skin the cat.

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Hank Mauel