Sunday, January 31, 2010

Reed log

G4 and G5 got tips cut, G6 and G7 wired and numbered, G8 and G9 got shaped, beveled and formed. I tried to shape a little wider than my shaper tip with G8 and G9, with the idea of getting a bigger tube which wouldn't present as much problems with shrinking. I tried to add about 1 mm by nudging the cane after cutting one side. This was maybe too much, it looks ginormous, and the forming mandrel went in almost to the tip before I could get a round tube at the butt. I suspect they will play really flat, but I guess I'll have to wait and see.

Just to think a little harder: 1mm in width = 2 mm in circumference, = 0.6 mm in diameter. At a slope of 0.07, that's 9.1 mm in length, which is about two bocal sizes, ie the difference between a #2 and a #0. But it'll fit more onto the bocal, so shouldn't that bring up the pitch, rather than lowering it? This is actually a bit tricky. The bassoon's bore is a truncated cone, capped by a reed which makes up for the missing volume. The tube of a reed is more or less a continuation of the bassoon bore, so just increasing the tube size would change nothing, if the tube continued a smooth taper down to zero: you'd end up with more tube on the bocal, but the length from bocal to the point would not change. However the tube flattens into the throat and widens into the blades at a fixed position from the tip and butt. So changes which bring the throat and blade of the reed closer to the bocal, such as widening the tube, will shorten the overall length of the bore. Merely widening the whole shape, like I did, will affect the blade and throat as well as the tube, so maybe won't be a win overall, but I think the idea is okay.

Later: painted G4 and G5 with nail polish after they'd dried, 2nd wire to the butt, on the end and about 1 cm up the inside of the tube, wiping with the mandrel. I did this because I was pretty happy with the result of adding nail polish to G3: no loose wires, a dimensionally stable tube, and maybe better tuning. G4 and G5 had shrunk a bit -- as finished blanks, I think they went on the mandrel a few mm (3-4) beyond the mark, and now, after one soak-dry cycle, they go exactly to the mark. Hopefully, with the nail polish added, they'll become stable there.

Again: tube size is stable (yay), but I feel like they leak around the bocal more than others. Maybe the hardness of the nail polish prevents a tight seal.

02/06: Being struck by the difference in size between what I'm currently turning out and my models, M1 and M2, made by a local pro, I decided to try an architecture experiment. M1 is much shorter, ~23.5 mm, as compared eg to G3 at 26.5mm. I clipped G5 down to 25mm, and set about trying to shave it down to a short soft reed. So far it's still pretty resistant, requiring lots of air and lip pressure. But there's still lots of wood, and a prominent spine, so I guess I can keep going.

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