A German “shop bass” came to us where the top was badly sunken and cracked around the sound post area. After opening the bass it was clear the the top had been regraduated at some point and had been thinned too much in the area around the F holes. So after stabilizing cracks we started with a partial plaster cast of this area to help reshape the top. The work involves removing the bass bar, thinning the top where you want to make changes, “correcting” the mold to give you the shape you want, then pressing hot sand bags into the top as it sits in the mold.
After we pushed the top back to the original curvature we prepared a large bed for a “belly patch” and fit the reinforcing spruce patch into place. This new wood stabilizes the shape, reinforced numerous cracks in the area and allowed us to thicken up the top plate a bit where over thinning had weakened it. After this work was done we could move on to other repairs on this bass.
A complicated job – really more of a “restoration” than a repair. To all my customers patiently waiting on me to finish up big projects – please bear with me. These projects have a way of getting out of hand!