OM Style Bracing Questions

[sgonwa]

I am building a Martin style OM guitar based on LMI plans. The plans are good, but still leave some unanswered questions for me.

1. The bottom two braces for the back plate are 3/4" wide by 1/4" in height. They run the width of the back plate. Should these flat-type braces be radiused in my 15' radius dish ? That would make them quite tapered or thin at the ends since the braces are only 1/4" high to start with.

2. On the top plate, should I radius the top two braces above the soundhole or leave one or both flat ? The brace above the soundhole is 1/2" square and the top most brace is a typical flat, thin brace. I am using a 28' radius dish for the top braces.

This is my first build. Because it's a smaller guitar and the braces are generally no higher than 1/4 to 1/2 inch, it just seems that because of the 15' radiusing, the braces will be quite a bit lower in height at the ends than at the center, even before I taper them with a chisel. I guess I'm just looking for confirmation that that is correct.

I ask this because when I look at photos of unscalloped bracing, to me the braces often seem to maintain the same height along the length of the brace until they are chisleled to a taper at the ends. Are some braces cut with a radius on the top to match the bottom or am I just experiencing an optical illusion ?!? Mostly I just want to ensure structural integrity with these smaller braces.

Thanks for any feedback.
Steve

[tippie53]

Are the plans drawn by Antes ? As for the back braces , you are correct , they are radiused. This lower brace profile was the way Martin did it up until the 80's. Top braces are radiused on the bottom and don't get radiused on the top. As for the upper braces the radius depends on your building style.
I like to do them straight and angle the upper area of the top for the neck angle. You need to get the fret board on plane so you can have the proper action.

[sgonwa]

Thanks much. Yes, they are the Antes plans.

Regarding angling the upper part of the top, I understand what you are referring to. I was planning on using the JSimpson self-adjusting neck jig to set the angle and cut the neck mortise and tenon. Would flattening the top in the manner you suggest affect the use of that jig in any way ? Would it be better to radius the top most braces and rely on the jig to set the proper angle instead ?