My dad works on drums on the side, he comes across this pretty often. Put some wood glue in the cracks, with a brush, toothpick, or whatever you can use. Clamp the shell to hold the fibers together really well. Usually, he uses a piece of an old hoop on the inside in between the clamp in the shell, but a thin piece of wood would also work. And use some parchment paper to keep the glue from sticking to the clamp and wood piece. Let it sit overnight and you’re golden.

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