With
the sleeve in place and the bore restored to a consisent and
concentric shape (see previous post) I moved to the outside of the
instrument. The two enormous cracks running down either side of the
upper joint could still leak or even continue to grow, especially
with a plastic liner that expands at a different rate than wood with
temperature and humidity changes. While I usually choose to pin
cracks because of the relative ease of installation and minimal
cosmetic damage, that wasn't a feasible option in this case.
Drilling holes for the pins would have required going through wood,
then plastic, then wood again, and since different speeds are
necessary for drilling plastic and wood there was a good chance of
either overheating/burning the wood or melting the plastic. So
installing bands, while more cosmetically disruptive, made a lot more
sense. If you saw the previous post about this instrument, you saw that it came in with metal bands installed, which is an older method of doing this repair. However since the development and proliferation of graphite ribbon, sometimes also referred to as carbon-fiber, that's become the preffered material for banding. It's easier to work with and slightly more flexible than nickel, so there's less chance of it causing the bore to constrict as the wood expands and contracts over time (as had happened with this instrument).
Ideally I would have cut the channels for the bands deeper than in this example, so
that they could be installed below the surface and covered with
mixture of super glue and grenadilla dust, a technique I first heard
about from a technician in the UK named Chris Peryagh. But since a
lot of wood had already been removed from the inside of this
instrument, I tried to minimize the depth of the channels and
therefore keep as much wood as possible between the band and the
sleeve.
Before
cutting the bands, though, the top three tone holes had to be
re-drilled since they were covered up by the sleeve. Cutting a new
tone hole would ideally be done on a mill to ensure an absolutely straight
and level cut with an even pad seat. In this case since the top half of each
tone hole was still intact I was able to use that as a guide for
drilling out the sleeve on a drill press.
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| Re-drilling the C trill tone hole. Do you like my expertly constructed clamping jig? |
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Wax is applied to the outside of the joint to prevent epoxy from sticking to the surface. That's the goop you can see in the top couple tone holes.
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Next the channels were cut on the lathe to .040” deep. Epoxy will adhere in the channels since the waxed area was cut out.
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Strips of graphite are pulled from a ribbon, approximately the same diameter as the channels. They're coated in a generous amount of plain old 2-ton epoxy. The strips are laid into the channels and pulled snug but not tight, to avoid constricting the wood. Although, that's less of a concern on this instrument since the plastic liner is less likely than wood to buckle.
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| After the epoxy is dry the excess is trimmed on the lathe, but not all the way to the surface. The outside of an instrument is rarely concentric with the bore (eccentric), and that's even more true of this instrument than most, so final cleanup will be done by hand. |
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| The rest of the excess is filed off, then sanded until the bands are flush with the body of the instrument and the surface is smooth. |
Finally
the joint can be oiled. This is only done after the bands have been
installed so that the oil won't interfere with the adhesion of the
epoxy. After a week in the immersion oil bath, this joint is ready
for key fitting and padding.
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| The joint was immersed in oil for a week, then allowed to dry for about 3 more weeks so it had a chance to fully absorb as much oil as it needed. This is how it looked at the end of that process. |
After all of that was done, I ventured back in to Philadelphia to visit Mark Jacoby again, who has a set of factory reamers designed especially for cutting the necessary tapers in a clarinet. Actually, before taking on this project I didn't know that the upper joint of a clarinet is tapered at all - another thing I learned from this process. On this instrument, as with many others, there's a slight reverse taper in the top of the upper joint that transistions into a short straight section, then back out to a taper. Since the bore of the insert was cut straight on the lathe, reaming restored that original taper. No pictures of that process, sorry.
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| After installing all new pads and corks and making a lot of fine adjustments, this instrument has a new lease on life. |
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One last before-and-after, how the instrument looked when it came in, and just before packing it up in the case.
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