by BMac » Fri May 21, 2010 6:06 pm
Being a fix-it-myselfer, I wouldn't immediately go to the expense of shipping and repair by others. You don't have a matched set anyway. Old Gon-Bops that are round can be found and bought. If you haven't already gone to great expense, why start now?
If there is tension in the head, maybe the head has distorted the shell. You may be able to simply remove the head and wait for the wood to recover a round shape. I think this is unlikely, but you tell us ... is the head very tight? Has it been left tight for years? If you are patient with the situation, you could attempt to measure diametric differences so as to be able to detect any return to a more round shape over time, with the shell being stored without a head. I wouldn't expect any differences for months. But you never know til you try.
I am not that patient. I would more likely remove all tension, rotate the current head ninety degrees (or to the orientation of poorest fit with the shell), and apply modest tension. Because the head and shell will no longer match in shape, the smallest diameter part of the head will bear greatest forces on the largest diameter part of the shell. So restoring forces will be applied. I'd leave it that way a few weeks, and check on it. You can judge by eye, or as I said, measure diametric differences over time. Modest tension is below playing tension. Go past finger tight, but reach only a very low tone.
A head and a shell go out of round together. When you rotate a non-round head atop a non-round shell, the head drifts up and down as relatively worse and better fits are found, and full seating is reached only when the head is returned to its original orientation and perfectly matches the shell. Such rotation is a sensitive way of detecting any out of round character. If you rotate the head to an unmatching orientation as I suggested, then of course both the head and the shell may change shape over time, and the picture will get more complicated. But you can always find a poorest fit orientation, and you can apply modest tension there. Ideally, though the picture gets more complicated over time, the shape of the shell gets iteratively closer to round with each step. When the shell becomes more visibly round, throw out the stressed old head and get a new skin. Rotate the new skin once every few months, again finding the high unmatching spot, to help prevent future distortion. I returned a quinto with a 3/16 inch diametric difference to apparently perfect round with this strategy. My drum was only out of round for a few months though, and the drum was only a year old. A much older drum, set in its eggy ways, may not respond as well to my treatment. But I would try.
No one has asked about the sound. If it sounds good, must you fix it at all?
In any event, I wouldn't pay to ship or fix that drum unless I had some emotional attachment developed already. If I was compelled to have a round old Gon-Bop, I'd fix that one myself, or I'd buy another one.
Let us know how it turns out, no matter what you do, please. This stuff makes for good reading for conga lovers.
Cheers,
BMac