Saturday, July 30, 2011

The Soundboard

When the spruce arrived from Stewart MacDonald I started working on the top or soundboard. After the success of the back you would think that I would use the same technique to glue up the top that I used to glue up the back, but not me. Both of the books that I now was using for reference and most of the on-line videos that I had watched suggested using a different method of glue up. This method used no clamps, just a simple compression technique. So, I tried this method. It was simpler and required no special long bar clamps. I jointed the edges in the same manner as the back using the power jointer. Since I didn't need any long bar clamps I took the pieces home to glue them up over the weekend. I worked on building a simple glue up jig in my shop by using a 3/4" piece of MDF as a flat base. I drew a center line on the base and placed a 1/4" lattice strip on the center line to elevate the two halves of the spruce in the middle. After aligning the two halves of spruce so the edges to be glued were touching and elevated by 1/4", I screwed additional pieces of lattice to the base touching the outside left and right edges of the spruce. Now I could apply glue to the joint, pull out the center lattice strip and press the two halves down flat creating a nice compression fit.
Glue up jig with lattice strip in center.
Plastic sheet to keep the glue from sticking to the hold down bar.
C clamps securing the hold down bar.
Additional spring clamps to keep the top flat.
This method seemed to work great. . . but my finished joint was less than perfect. To check the joint I held the finished joint in front of a bright light to check the tightness of the seam. Uh oh, heck, darn (those were my exact words) I could see a slight gap at one end, so, I had to cut it apart and try again. I think the problem was that I waited almost two days after I jointed the edges before I glued them together. Combine the time and the fact that I changed locations with a change in humidity I think the two halves expanded and contracted slightly differently causing a bad joint. After splitting the joint apart on the table saw, rejointing on the jointer and regluing using the same compression method, I got a good joint. Weh! I used the same method to transfer the template and cut out the basic shape on the band saw that used for the back.
Back and soundboard cut out slightly over sized.

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