Arch the ribsUnlike the soudboard, my guitar backs are curved in two directions. Each model has a unique head-to-tail curve, but they all share the same parabolic side-to-side curve.
After the glue dries on the kerfing, I plane it to to the approximate curve and nearly flush with the ribs. Final shaping is done with the same curved workboard that I use when gluing in the back braces. I clip a large piece of sandpaper to this workboard and slide it back and forth over the ribs. When finished, the ribs have a two-dimensional curved edge that will mate perfectly with the back.