CPVC. The C stands for clarinet, or chalumeau… (part 3)

The problem with large woodwinds in a straight form factor is to get the bore spacing — the distance between holes measured along the bore — large enough to produce notes the right distance apart, without making the stretch — the distance between holes “as the crow flies” — so large your fingers can’t reach them all at the same time.

Here’s a tenor, alto, and soprano recorder (and my old PVC clarinet):2015-03-26 09.02.57You can see the tenor, which is a little shorter than a soprano clarinet, needs one key to bring the bottom hole within reach.

Hence the Papalini bass clarinet, with its serpentine bore, that inspired my contra-alto chalumeau project. It turns out, though, that if you’re making an instrument mostly out of CPVC elbows, you have the opposite problem: getting the bore spacing short enough. Of course if you want two holes at a bore spacing of a couple centimeters that’s no problem, just use a straight section of tube and put them as close together as you want. But once you resort to elbows to bring larger spacings within reach, you start to run up against minimum spacings.

You can make a planar serpentine arrangement like this:2015-03-261The red dots show possible tone hole positions. Of course (for all but the thumb hole) they need to be more or less in a line on one side of the instrument. With this geometry the holes are about two elbows apart measured along the bore, around 100 mm with 3/4″ CTS CPVC. The stretch between holes is about 50 mm, which is too large to be comfortable though maybe isn’t unthinkable for a couple of holes. But the holes can’t go any closer together without moving them out of line. If you want a bore spacing of 70 mm, you’re hosed.

If you want something a little longer than 100 mm, you can extend a zigzag sideways with a couple short pieces of tubing. That’s fine for the zigzags that go away from the hand, but going toward the hand just makes an uncomfortable grip worse.

Another geometry is a right angle serpentine:2015-03-262The stretch here is again about 50 mm, and now you can extend the zigzags in either direction without running into the hand. That’s good, but now the holes are placed three elbows apart for a minimum bore spacing of about 150 mm.

Geometry number three is a helix:2015-03-26

Here the good news is the stretch is a lot smaller, more like 25 mm. Pretty playable. And the loops can be stretched, again without colliding with the hand. But the holes are now four elbows apart. That’s a minimum bore spacing of 200 mm. There’s the irony: to get shorter stretch, you have to have longer bore spacing!

There are three places where you can easily make the hole spacing smaller (but not too small). One is between the top (left thumb) hole and the next (left first finger) hole: put them on opposite sides of a 3/4″ CPVC helix and they’re at a 100 mm spacing. Another is between the last left hand finger and the first right hand finger, where you don’t have to worry about stretching from one to the other. That’t be the fourth and fifth holes if you follow the standard woodwind convention of not giving the left little finger a hole to cover (but give one to the right little finger, as in recorders and kinderklarinettes and ancient clarinets/chalumeaus.) The third is between the last finger hole and the foot of the instrument. If those hole pairs correspond to semitones, and the others to tones, then starting say on E (8 holes closed) you’d get (bottom to top)

semi – whole – whole – whole – semi – whole – whole – semi

e.g. F♯ – G – A – B – C♯ – D – E – F♯ – G

which happily corresponds to the notes of a D major or B minor scale. Unfortunately clarinetists are used to

(depends on which little finger lever) – whole – semi – whole – whole – whole – semi – whole

e.g. F – G – A – B♭ – C – D – E – F – G

but I may be stuck with an alien arrangement. I’ll live.

Pollak’s Mr Curly’s holes are spaced around 145 to 150 mm apart (and I’m surprised uniformly sized holes so uniformly spaced work out, but he says they do. One note is a quarter tone below G, the others, he says, are okay — not a diatonic scale, though; it goes E♭– F – G half flat – A♭ – B♭ – C – D – E – F.) It’s in contrabass clarinet range. For a helical instrument with minimum bore spacing of about 200 mm you’d have to make something more like an octocontra-alto clarinet:

have put a (soprano!) mouthpiece on a ten foot piece of tubing and played ridiculously low notes with it, and that’s fun, but I’d like to build something closer to contra-alto territory:

So I’m thinking a 3/4″ CPVC helix just isn’t going to work.

But how about the right angle serpentine? The problem there is the long stretch. How bad is that? Well, let’s experiment.

I marked four places my fingers could reach on a right angle serpentine, drilled holes with the drill I happened to have chucked already in the drill press, stuck on t1 and t2 and t3 in some order using a couple other fittings and added a reducer for a pretty much nonfunctional bell. Behold, the instrument I built in about ten minutes:

IMG_3647Considering the tuning of the available notes was purely random, it’s not that bad sounding. The second note from the bottom is stuffy, probably because it has only one tone hole plus the distant foot to vent through. The rest sound better. The bottom note is pretty close to C2 (around 65 Hz), just below the bottom end of my bass clarinet (which goes to E♭2 written, D♭2 concert — some bass clarinets go to B♭1 concert).

The stretch, well, it’s a stretch, but it can be done… as far as it goes here. A fifth hole 50 mm below the fourth would probably not be reachable. I could consider a hybrid serpentine/helix geometry: Serpentine at the top (for the left hand), where I want shorter bore spacings and don’t need to accommodate the little finger, and helical below (the right hand) where the longer spacing would be okay and I want four fingers to reach their holes. But I’d presumably wind up in contrabass, rather than contra-alto, range. Which isn’t the end of the world.

Or I could try 1/2″ CPVC. It has an OD of 0.625″ (16 mm), vs. 0.875″ (22 mm) for 3/4″ CPVC. Presumably that means the bore length of an elbow should be about 36 mm instead of 50 mm, making about 144 mm spacing in the helix geometry — almost identical to the spacing in Mr Curly. So a helical contrabass clarinet range instrument looks within reach. Furthermore the serpentine geometries would have a stretch of about 36 mm, a good deal easier than 50 mm, so a serpentine/helix hybrid might work just fine for a contra-alto range chalumeau. The bore diameter would be 0.485″ (12 mm), pretty narrow for that length but a good deal larger than Mr Curly’s 8 mm.

I went into SketchUp to draw up an idea of what this might look like. Just wild guessing on the relative lengths of things and so on, and I didn’t draw in tone holes because that’s hard. I went looking into the SketchUp 3D Library and stumbled across… can you believe it? … a carrot clarinet. With a link to Linsey Pollak’s page. Sheesh! So I included that in the drawing. It may not be to scale. Screen Shot 2015-03-27 at 12.46.54 AM

Anyway, here’s a tune.


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