One of our students labeled the endblocks of his guitar incorrectly and subsequently glued his back guitar back to the top side of his instrument. After using heat to remove the glued down back, there were several failures of glue joints that had to be sanded and re-glued. The brace ends all had to be re-ahered and the center seam was split on the ends over the neck and tail blocks.
After some consultation it was determined that since the center reinforcing strip was still well adhered and that only the the seam between the two halves of the back had separated in areas the best course of action was to rout a backstrip into the guitar to create a solid seam and ensure a viable glue surface for fixing/ hiding the split center seam.
Jim Mcwilliam brought in a jig that he constructed to rout the channel and the repair was made with a 1/4″ router bit.
We added 2 layers of blue painters tape (.005 thickness) to the edges of the router base, by removing them after the first pass we were able to widen the rout by .020 by running the router agaist each side of the jig without moving the setup. This allowed us to acommodate the addition of maple purfling strips to the outside of the 1/4″ ebony binding that we used as a backstrip.
The red material in the photo is heavy grade paper used to shim up the ends of the radiused back (which is resting on its braces) therby ensuring that the surface is solid and well clamped down before routing the channel.