jemtheflute wrote:Terry would be your man!
Thanks for the endorsement, Jem. Roughly translates as "Terry would be the only one around here stupid enough to try to explain this!" I'll have a go, possibly against my better judgement!
pflipp wrote:
I've been working on my flute some more lately. (Actually, I'm already playing on it, but I'll leave the final presentation to a point somewhere in the future.)
Well done!
One thing that I haven't quite figured out by myself is this:
- The original R&R drawings indicate that the bottom C octaves are tuned by only the slightest bore flare. I believe it's going from >10mm back up to <11mm (total difference maybe ~0.5mm) over a length of ~15mm.
- I 'cut off' my own flute so that its bottom note is D, but the first and second octave were off by half a note, easily, with the octaves, IIRC(!), being wide.
- So I added a flare to the bottom. But this time <1mm wasn't enough. I estimate it goes from <13mm to >14mm (total difference easily 2mm) over a length of ~40mm, and it's still not quite in tune. (The tuning improvements aren't very dramatical.)
I can't quite figure out why this would be (D foot requiring much more flare than C foot). Any takers? Do I see things wrong?
No, you are seeing what you should see. It might help to come at it from the direction of historical development, rather than trying to trace your way back against the tide.
The conical flute is assumed to have been developed in 17th France. The previous flute was a straight cylinder, similar to simple waterpipe flutes today, and suffered the same problem, the second octave went dismally flat as you ascended the tube. Our mysterious developer (possibly Hotteterre or someone nearby) found that this problem could be solved by tapering the tube into the shape we are familiar with. Problem was however, if you taper it enough to get all the notes more or less in tune with their octaves, the low D, which is the only one that was OK in the cylinder flute, went from being about right to far too flat. If you like, it was overcompensated.
There is an easy-to-understand reason for this. All the other notes vent through little holes through the side and those little holes look longer at the octave than they do at the fundamental note, making the second octaves tend flat. But the low D (remembering they had a short D foot at that time) is perfectly terminated - the vent is the end of the bore.
Fortunately, a solution was found - simply flare the foot so that the final note wasn't tapered so much. As you'll see on early flutes, French 5-key flutes, GLPs and my Short D feet, the flare is quite dramatic.
Sometime later, in the mid to late 19th century, someone had the bright idea of extending the low notes to C, to match the oboe, I think. Quantz and others ruminated against it, saying it messed up the rest of the notes, and I'd expect he was probably right. Once you extend past the D, the D, like the notes above has to vent out the side, so it goes from requiring a flare to requiring that the bore tapers even further down. Ditto C#. When we get down to the new bass note, C, it stands the risk of being overcompensated like the D was, but the main tube is now longer, and thinner, and the degree by which its open termination is too open is less. So a very small flare is typical, although I've sometimes found flutes that simply went cylindrical for the last bit, or even tapered right to the end. I think if you look at those flute-javelins that go right down to Bb, you'll find they have no flare at all.
Hopefully that will help de-mystify the issue! Sorry I wasn't around earlier to chip in, I've been a bit preoccupied doing cruel and unnatural things to Mr Potter's flute.
Terry
).