Introduction
So, having read all this, and
having a flute that is thread wrapped, should you worry that
strangulation should happen to you? Unfortunately, although our
experience shows that flutes get strangled, and our experiment shows a
mechanism by which it can happen, we can't yet predict whether and when it's
going to happen to your flute.
But here's one circumstance that
would definitely ring alarm bells. If you find, from time to time,
you have to add thread, but you don't find you ever have to remove any,
I'd be worried. Unfortunately, it's probably a bit late to be
worried, as it probably means serial strangulation has already set in. But the sooner you stop making
things worse, the better.
I'd be more worried about the
softer and less stable boxwood than the stronger and more stable
blackwood. But having said that, it's only because I have no
experience of blackwood compressing, and that's because I have no
experience of threaded blackwood flutes. The blackwood test tenon
was moderately encouraging, showing considerably less distortion after
the same tribulations. But it wasn't a whitewash either.
Cocus, from our survey above, is obviously at risk,
as is ebony. The older the flute,
the more likely the risk. The thinner the tenon, the more likely
the risk. The deeper the thread pack, the more likely the risk.
I'd keep up the oiling, as
this should slow water intake. I'd be very thorough about mopping
out, as that at least terminates the water uptake period. I'd
definitely unwrap any flute with a tight binding, and look
for something softer I could apply more loosely. And while I had
the wrapping off, I'd look to see if the thread trough is uniform in
diameter or hourglass shape or in some other way distorted. Holding a rule against the tenon
shoulders and looking at the size of the gap along the trough is a
reasonably sensitive test. if in doubt, I'd measure and graph the bore for
the first 50mm (2") or so at each tenon, and look for signs of
compression.
If you don't feel motivated
to go that far, at least investigate the top few layers. If you
found more than two or three separate windings were involved on any one
tenon, I'd be worried that serial strangulation might be happening.
If that were the case, I'd definitely check out the tenon below using
the rule method.
What about blackwood?
The discussion so far has
centred on the timbers we find most commonly in old English flutes -
boxwood, ebony and cocus. We haven't looked at blackwood,
Dalbergia Melanoxylon.
I'd have to admit that,
personally, I'm not too concerned about blackwood. It wasn't used
in 19th century England much, or in the US as far as I can see, except
in modern times. Most of my own made flutes are blackwood, but
then, I use cork, so I have nothing to worry about. It has seemed to me
that other makers using blackwood and thread need to conduct their own
accelerated aging tests (with realistically-sized tenons) to see how it
stands up.
I'd expect blackwood to be
less affected that the three timbers we have been following. It
seems stronger to me, more stable, and more water resistant.
Still, Lord Rayleigh's words nag at my soul.... "What we cannot measure,
we do not know". Sigh. Alright, m'Lord, let's check it out....
I knocked up another tenon,
identical to the first, but in blackwood. I ran it though the same
hoops. The most dramatic changes to the boxwood tenon had been the
end bore and the middle bore, which ended up +0.5 and -0.75 respectively. The blackwood tenon followed the same pattern
- end larger, middle smaller -
but the results were +0.25 and -0.25mm, less than half that of the
boxwood. Encouraging, but....
Note, though, that it wasn't
zero. Blackwood, for all its merits, wasn't unaffected. Just
affected less than boxwood. What our experiment doesn't reveal is
whether that's because blackwood is stronger, or more water resistant,
more stable, or some combination of all three. If, for example, we
went on longer with our humidity cycling, would it catch up to the
boxwood, or is this as bad as it is likely to get? These are the
sorts of questions that anyone thinking of using thread wrapping needs
to research.
What did rather surprise me was the
degree of ovality that set in - about 0.5mm in an 18mm bore - even when
the humidity returned to normal. As if one axis remained strong,
and the other buckled under pressure. Interesting....
A single point check
I mentioned further up how to
measure a flute for bore compression. That's OK for the
well-equipped maker, restorer or repairer, but what about the owner
without access to T-gauges? Is there no check they can do?
Although to really understand
what's going on, you need to measure and graph the bore for at least the
first 50mm, our survey at the top suggests one pretty easy "single point
check". The typical 150mm (6") vernier callipers can reach about
16mm (5/8") down the bore if you use the internal anvils (the pointy
ones). Larger callipers have longer anvils, but often only the
first 16mm or so are chamfered to prevent interference, so they can only
read accurately to the same depth. Fortunately it's enough to take
us to the middle of the tenon, where the shrinkage is likely to be
mostly felt. If you haven't any callipers, you probably know
someone who has, even if it means a trip to your motor repair shop.
Be gentle in taking the measurement, you don't want to rough up the nice
bore on your flute with the sharp pointy ends!
So the question becomes what
would we expect to see at 16mm down the bore. That's obviously
going to depend on the flute type, but we could hazard a few guesses.
A small-bore flute, if we take the Geo Rudall, Willis fecit as an
example, should be around 17.75mm. A small bored Rudall style
flute more like 17.9mm. A larger bored Rudall or Nicholson's
Improved say 18.1mm, and a Prattens around 18.3mm. If you compare
your measurement with the flutes on the graph at the top, you should be
able to form a good idea of what condition it's in.
Checking the lower tenons on
either the LH or RH section is much easier. Measure just inside
the end of the tenon, and compare it with the measurement you get when
you insert the callipers to full depth. The end measurement should
be smaller. If the full depth measurement is similar or smaller,
then you have clear evidence of bore compression.
There's one case where that
might be misleading though. If the foot on your flute flares
dramatically (eg on a flute with a Short D foot), the back reaming might
have been taken past the foot and into the lower end of the RH section.
In which case you might legitimately see a very small reduction in
diameter when you insert the callipers fully. But if it's a large
reduction, it's bore compression.
Getting it corked
You might decide, on the
evidence so far, that it's time to get your pride and joy corked.
In theory, that's a straightforward operation. Any woodwind
repairer who handles clarinets (and that's probably all of them) is
accustomed to replacing cork. But there are some significant
differences between old wooden flutes and clarinets. Clarinets
were made with cork in mind, so the trough depth is ready-to-go.
Clarinets have smaller bores than the top end of flutes, but similar
outside diameters, so the wall thickness is much greater, lending much
greater strength. Old wooden flutes were usually designed with
thread in mind, so the trough depth could be anywhere. And if bore
compression has set in, it may well be deeper in the middle than at the
ends. Putting cork on tenons made for thread is likely to put too
much force on the thin socket walls, unless the tenon and/or socket
dimensions are adjusted to accept the cork safely. That's a job
for a wooden flute specialist, although once done, any woodwind repairer
should be able to replace worn or damaged cork in future. An
alternative process is to put on the cork, then sand it to fit the
socket nicely.
Now here's something sobering
to think about too. Imagine an old flute suffering both general
timber shrinkage and bore constriction (probably 90% of the old flutes
that haven't cracked already?). While the dimensions of the socket
might be enough to sustain cork under normal circumstances, the stress
from shrinkage over the barrel liner might already be close to whatever
the wood can stand, and any increase from any other source might be
unwelcome and unwise. I guess the answer there is humidification or
relieving the timber around the slide - take the stress off the barrel
wood before applying the cork to take the stress off
the tenon and bore.
It would be a shame to
compound your tenon compression issue with a split socket issue!
So, ask around and find someone specialising in wooden flutes and cork.
Or at least alert your woodwind repairer to the issues and ask them how
they intend to deal with it.
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