This inexpensive cello came in with a double soundpost crack that had been glued previously but left uneven. Rather than removing the top, the repair focused on re-leveling and stabilizing the cracks from the outside, then reinforcing the area internally using a molded structure and careful clamping. The goal was to secure the cracks cleanly and restore structural support with minimal intervention.. - Clean the Cracks: Lightly clean the soundpost cracks to remove old glue and debris.
- Create Outside Mold: Make a mold that matches the outside curvature of the top.
- Install Back Support Plate: Attach a rear clamping plate to support the instrument during repair.
- Glue the Cracks: Work fresh glue into the cracks and carefully clean off any excess.
- Protect the Mold: Use cellophane to prevent the mold from sticking to the top.
- Secure the Mold: Tape the mold in place so it won’t shift during clamping.
- Remove the Soundpost: Knock the soundpost down before applying pressure.
- Initial Clamping: Apply the large clamp first with moderate pressure—just enough to bring things into position.
- Perimeter Clamping: Add perimeter clamps to draw the top evenly against the mold.
- Dry and Clean: The next day, remove the clamps and clean up the repaired area.
- Prepare Internal Patch: Make a vulcanized fiber structure that can be installed internally without removing the top.
- Reinstall the Mold: Tape the outside mold back onto the top to maintain alignment.
- Hydrate the Fiber: Lightly hydrate the vulcanized fiber so it becomes flexible during installation.
- Prepare Support Discs: Create two white support discs, stacked and tiered, with string ties for later removal.
- Attach Support Discs: Use a small drop of CA glue to attach the white discs to the fiber.
- Mark Orientation: Draw reference lines on the fiber so the patch aligns correctly when clamped.
- Apply Glue to Patch: Apply glue to the fiber; lightly skin it with a heat gun so it doesn’t run.
- Add Final Glue: Apply a small additional dollop of glue before installation.
- Install Patch and Clamp: Slip the patch into place and tighten the center clamp.
- Adjust Clamping: Add one or two perimeter clamps, then remove the initial center clamp.
- Reinstall Soundpost: Set the soundpost centered on the white discs. (See note below.)
- Final Perimeter Clamping: Install the remaining perimeter clamps to secure the repair.
- Clean Excess Glue: Remove any glue drips while still workable.
- Remove Clamps and Mold: The next day, remove all clamps and the outside mold.
- Address Bridge Height: Shim the C-side bridge foot to compensate for a low bridge; final height left unchanged per customer request.
Note: Ugh Moment:
At this stage I ran into an unexpected problem. My soundpost jack was too wide to fit through the f-hole in the usual way, so the larger hole became the only option. With the clamps already in place, I couldn’t get the soundpost setter to bite deeply enough into the post to flip and seat it onto the white discs on the internal patch. After about ten failed attempts, it was clear the original plan wasn’t going to work. The intent had been to use the large clamp to push on the outside mold, with the soundpost jack acting as a temporary post; transferring pressure through the back, which was shimmed to bear against the rear clamping plate. That setup would have kept the top from flexing inward and ensured firm pressure at the center of the disc. But sometimes, with glue setting and gravity winning, you have to adjust the plan on the fly. IMG 20251219 134706 210 | IMG 20251219 134717 486 | IMG 20251220 121606 412 | IMG 20251220 122848 698 | IMG 20251220 122908 436 | IMG 20251220 124725 069 | IMG 20251220 124734 596 | | |
|
