Ukuleles are traditionally rather modest instruments, and they
have much lower string tension than guitars, so it's quite common to see a
low level of craftsmanship applied to their repair. In decades past, the value
of even the most venerable of the ukes was much lower than it is today, a situation
that also contributed to their apparent state of neglect.
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For example, this ukulele bridge looks pretty messed up - there's lots
of glue spread around under it from the last time it had been reglued to
the top, and it's clearly very loose again. |
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You can see the gap underneath, all around it. Chances are that the person
who reglued the bridge didn't clean up the mating surfaces and didn't use
sufficient clamping pressure to achieve a good glue joint. In fact, there's
so much glue left around the edges that I think it's safe to assume it
was not a "professional" job at all. |
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My first task was to remove the bridge, and that proved quite easy since
it had been so loose. I slipped my thin palette knife under and was able
to separate the glue joint without damaging either the top of the uke or
the underside of the bridge. |
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Here you can see the glue piled up in the joint. A
properly constructed and glued joint would have no visible glue. Wood glue
has very little cohesive strength, but terrific adhesion. For best results,
a wood joint should fit very tightly with no gaps, and should be clamped to
squeeze out almost all the glue. That way, the wood is basically in contact
and the joint can take advantage of the adhesive strength of the glue without
relying on it to fill gaps. |
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So, that was my next step - preparation of the gluing surfaces. I started
with the top of the instrument, carefully scraping the old glue off the
area where the bridge was to be glued. My scraper is a tool I made from
an old kitchen carving knife. I cut the blade to about 3/4" long,
and sharpened it straight across. With that tool, I had good control and
was able to exert quite a bit of force as I scraped the area level, right
up to the edges of the original finish. Notice how I'm holding the
scraper. I have my palm and forearm planted firmly on the instrument and
I'm pulling the scraper with my fingers only, using my thumb to keep the
handle virtical. That way there's no chance I'll slip and scar the
top with that sharp tool. |
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Cleaning up the bridge was a comparatively simple matter. I used some
80-grit sandpaper laid on a board, and simply rubbed the bridge bottom
across it. |
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After a few strokes, the bridge bottom looked fresh and
clean, ready to be glued. |
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Some years ago I modified this small deep throat clamp for regluing ukulele
bridges. It's a standard clamp that I drilled and tapped to receive a machine
screw. I can screw on a "caul," or clamping pad, so I don't have
to fumble with a separate piece as I assemble my glue joint. |
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To make certain that I get the bridge in exactly the right place, I made
a little "corral" with several layers of regular masking tape.
That way, I would be able to slather glue on the bridge, and slide it right
into place without having to rely on visual cues that might be obscured as
the glue squeezed out from under the bridge. |
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My glue of choice is "hide glue" made from animal skins. It's the traditional
wood and instrument makers glue, and even though there have been generations
of adhesive development, this stuff remains the best choice for regluing
bridges. It's strong as the devil, quite heat resistant (which is important
for instruments left in parked cars or played in the sun) and it becomes
very rigid as it sets. Some luthiers believe that it's better for tone,
too. Hide glue must be heated to just under 150 degrees Fahrenheit
for use, and must be fully clamped before the temperature drops below
about 100 or so. That meant I had to move quickly once I applied the glue! |
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So, with a block of hardwood to protect the top of the bridge from being
scarred by my clamp, the tape in position outside to align the bridge and
my block screwed to the bottom of the clamp, I was able to get everything
cinched down with time to spare. |
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Hide glue has legendary "fast grab," so once I applied the
clamping pressure there was no tendency for the bridge to slip out of position,
and I was able to remove the masking tape. Some of the glue had started
to "gel" and came right off with the tape. |
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I removed the rest of the residual glue by dissolving it in warm water
and washing it right off the face of the uke. |
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Set up with a new set of strings, this old timer was ready to play. |
