This f-hole crack proved to be much more difficult than expected. This f-hole had become quite misshapen, to the point where the wood naturally wanted to spring back toward its distorted shape. That constant stress made it difficult for the crack to remain closed. After the crack was initially glued, it looked good, but within a few days it began to separate again. A second repair produced a better shape, yet the crack eventually opened once more. Although each repair showed some improvement, it became clear that simply gluing the crack was not enough. The area needed additional reinforcement from the inside. To strengthen the repair, I developed a method of installing a small fiber reinforcement through the f-hole. A flexible plastic carrier and folded tape were used to position the fiber, while two strings allowed it to be accurately guided and clamped from the outside. The reinforcement bonded successfully, but when the plastic carrier was removed, the tape unexpectedly remained attached to the fiber, apparently because a small amount of glue had squeezed between the tape and the reinforcement. Using a mirror and a small bent wire, I carefully worked the tape free from the fiber reinforcement. Fortunately, the reinforcement remained securely bonded in place. With the tape removed, I was hopeful that the added reinforcement would finally keep the f-hole crack from separating. Although the reinforcement was successful, the shape of the f-hole had become slightly distorted during the earlier repairs. I worked fresh hot hide glue into the crack and clamped it once again to improve the alignment. The following day, a final application of glue and a little additional clamping pressure brought the crack together more tightly, restoring a more natural shape to the f-hole.  IMG 20260810 102558 455 | IMG 20260813 150016 044 | IMG 20260813 152956 719 | IMG 20260813 154742 306 | IMG 20260814 130659 965 | IMG 20260815 134304 321 | IMG 20260815 135458 840 | IMG 20260815 135506 225 | |
Note: In hindsight, I think this repair would have been a little easier if I had first made a mold of the outside arching. Since the damaged area was so small, I could have made a hard positive mold, reshaped it to the exact contour I wanted, and then created a matching negative mold. Using the negative, I could have formed a clear plastic clamping caul that matched the finished shape of the top. The transparent mold would have made it much easier to verify that the crack was fully closed while clamping the fiber reinforcement in place.
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