Double Bass Rib Crack Repair | Molded Rib Restoration and Cleating

This bass came in with seams popping open and a couple of bad rib cracks in the lower bout. The rib cracks were brought back into shape and glued from the outside using a mold. Once everything was aligned and glued, there was a small opening in the rib, which allowed a cleat to be fished in from the outside to help reinforce the repair.

With the rib stabilized, the instrument could then be brought back into alignment with the top and back, and the remaining open seams were glued.

There was some time pressure on this job since the owner had a gig in San Francisco. The clamps were removed the next morning and the bass felt solid with no buzzing. With a couple of hours left before pickup, the edges of the top were sized with hide glue to help protect them.

When the bass was picked up and tested, however, a noticeable buzz had developed. After taking another close look, a small crack near the f-hole along the edge was found to have opened up, likely from the tension created as the sizing dried. The separation at the purfling was glued and clamped, and once set, the bass was solid and playing cleanly again.

Bass Rib Crack Repair Steps

• Assess the damage and make a plan: Evaluate the cracked rib and determine the best approach before starting the repair.
• Stabilize the upper bout seams: Glue the seams on the upper bout to help stabilize the bass before working on the rib.
• Protect the rib from heat: Use chipboard to shield the rib and surrounding areas during the repair process.
• Fit the external molds: Bend and position the molds around the outside of the rib to match its original shape.
• Force the rib back into shape: Using clamps, wood wedges, and bar clamps, bring the cracked rib back into alignment with the mold.
• Secure the main crack: Reinforce the worst part of the crack by installing a cleat at the center.
• Install a cleat through the gap: Since there was a small opening in the crack, fish a cleat through that gap and glue it in place to help secure the joint from the inside.
• Address additional rib cracks: Work on the remaining rib cracks using the same mold and clamping technique.
• Check overall stability: At this point the bass should feel much more solid and stable.
• Size the top edges: With time remaining, apply hide glue sizing to the edges of the top.
• Diagnose a new rattle: When the bass was picked up, a bad rattle developed, likely related to the recent sizing work.
• Identify the separation: Inspect the instrument and find that the entire edge of the C-bout had separated at the purfling.
• Glue and clamp the C-bout: Reglue the separation and apply significant clamping pressure to pull everything back together.
• Final check: After the repair, the bass is solid and stable once again.

IMG 20230601 122816 427	IMG 20230601 122830 353	IMG 20230602 173414 717
IMG 20230604 170234 526	IMG 20230604 173437 522	IMG 20230604 173539 881
IMG 20230604 185558 191	IMG 20230604 185606 164	IMG 20230606 083546 951
IMG 20230606 083834 126	IMG 20230606 091914 653	IMG 20230608 102654 725
IMG 20230609 131109 787	IMG 20230609 131205 114	IMG 20230609 131239 271
IMG 20230609 180843 459	IMG 20230609 181540 795

After three years, the bass is still going strong. The rib repairs and cleats have held up well, and the instrument remains solid with no recurring issues.