Braces

I rough out the back braces out of 1/4" sitka brace stock with the bandsaw.  The curve is a 15' radius.  Then I perfect the curve by sanding the braces in a sanding bowl that has the same 15' radius.  Later, I will take a small, very sharp plane to make the bottom curvature of the braces exactly square to the sides.  I want the glue joint of the braces to be perfect, since the braces are so narrow and fine, and old guitars often suffer from detached braces.

The back will be bent to the braces when gluing.  In this way the back takes on a perfect 15' arc.  Similarly, the top is caused to adopt a 25' radius.  The curvature helps sound projection, but also makes a stronger box, since an arched back and top creates stronger shapes than flat panels.  In the bottom picture, you can see that the front braces have the nice curvature conforming to the sanding bowl, and the rear, unsanded brace is about a centimeter above the middle of the bowl.