Official Luthiers Forum!

Bit of an odd question, perhaps, but it's been bugging me of late, as I stare into various instruments and note the fairly wide variation in basic brace heights.

I use: 1/4"x1/4" for finger braces, 5/16"x3/4" on X-braces (at the peak, without cap, 1/4"x1/2" for tone bars, 1/2" x 5/8" on the upper face. Pretty much following Cumpiano. Mostly, I'm wondering if my X-brace ain't a touch on the tall side; most guitars I've peered into seem to have it anywhere between 1/2"and 5/8" at the intersection. I'm planning on thinning the X to 1/4" for the parlour I'm building, but there's still the height issue. I realize it's dependent on the top in question and the overall bracing scheme, but still, a starting point, out of interest, would be good.

My back braces are 1/4" x 3/4" and 1/4" x 3/4" as starting positions for the upper transverses and the X, respectively (1/4"x3/8" 'fingers' between the arms of the lower X, shamelessly stolen from Howard Klepper).

What about you guys?

EDIT: I should add that part of this wittering is fuelled by my desire to try some CF laminated X-braces in some of the next guitars.Mattia Valente38786.7208912037

I hope someone answers this soon Mattia, I've been keeping an eye on this thread all day hoping someone had an answer. And you thought it was a quick one!

It's a good question, I've been wondering the same thing since I got the Sloane bridge clamp and found that it had trouble clearing the (Cumpiano 5/8") X brace, bridge and stewmac bridge clamp thingy at the same time, made me wonder if others are not using such a tall X brace. I'm also building a parlor at the moment and am not sure how high to go.

Heh. Yeah, that's pretty much the issue when you don't have all that much experience with the stuff, or access to that many old intruments to measure yourself...

Mattia,
I recently measured an old Gibson J-45 that had 1/4" braces throughout, even the X. And it was only 5/8" tall. Some folks feel that 3/4" is a little tall for the X. Others put a small spruce "bridge" across the X to reinforce it, and make the height of the total unit 3/4". I've always used 3/4" plus a thin bridge. Martin uses 1/4" bracing on some of their more custom models. There's different ways and schools of thought. One thing I would do is email guys like Bill Cumpiano and ask what he's doing now. He's not doing things the same as in his book anymore.

People are all over the place with back braces too.

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

   There are so many sizes out there. I have Martin braces in stock and will measure them out. Post to follow.
   

[QUOTE=PaulB] I hope someone answers this soon Mattia, I've been keeping an eye on this thread all day hoping someone had an answer. And you thought it was a quick one!

It's a good question, I've been wondering the same thing since I got the Sloane bridge clamp and found that it had trouble clearing the (Cumpiano 5/8") X brace, bridge and stewmac bridge clamp thingy at the same time, made me wonder if others are not using such a tall X brace. I'm also building a parlor at the moment and am not sure how high to go.[/QUOTE]


Same here, Paul. Got ready to glue the bridge (dry fit) and the goofy bridge clamp thingy wouldn't clear my braces. I just used three cam clamps and it worked great. The special clamp might be neato but it sure isn't necessary.

Ron

_________________
OLD MAN formerly (and formally) known as:

Ron Wisdom

Somewhere in the middle of Arkansas......

   The bracing from Martins is as follow
top 1/4 by 9/16 at the deepest point with a 28 ft radius
the 5/16 by 9/16 at the deepest point 28 ft rad
back is 3 sizes
1/4 by 9/16 Upper and waist
5/16 by 5/8   3rd
5/16 by 9/16   lower
traverse is 3/8 by 5/8
    

As you all know, the majority of a brace's strength is in its height. The lower limit for width is probably driven by the amount of glue surface necessary; 0.25" seems like something of a reasonable lower limit there.

I set my width at 0.30" but vary the height somewhat based on the strength of the bracing itself. I also cove the sides of the braces to maintain the height but to reduce the width along the beam.

The X-brace on every old Gibson I have measured was 0.25" thick, most still showing the marks from the table saw blade.