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Weak bell note in DIY PVC whistle

Posted: Sat Apr 04, 2020 5:53 pm
by Alaskamike
Today I made a B flat whistle, following the low tech whistle instructions. The bell note is in tune (or close enough for me) but I have difficulty playing it. Every other note is strong.
The window is about 7.5mm wide and 8.5 deep. I adjusted the window and this was the best result.
The windway is only 18mm long.

Here are a couple of pictures to show what I’ve done.

https://ibb.co/GM8fH9Z
https://ibb.co/Vw2vrq0

Any idea what I need to do to fix it, short of starting over?
Thanks.

Mike

Re: Weak bell note in DIY PVC whistle

Posted: Sun Apr 05, 2020 7:21 am
by Tunborough
What's the bore diameter? From the caliper scale, I'm guessing nominal 3/4" pipe. That's a bit wide for a Bb, and would normally favour the bell note over the higher notes. 8.5 mm may be on the long side for window length. I wonder if there isn't something subtle in the angle of the air stream. I would aim to have the floor of the windway (top of the fipple) absolutely parallel to the top of the inside of the bore, and a hair's-breadth lower, so there's a sliver of light visible when you point the mouthpiece to the light and look up the tube from the bottom.

The clear tubing is a neat effect, although it will show the condensation. (It may also make that sliver of light less obvious.)

Re: Weak bell note in DIY PVC whistle

Posted: Mon Apr 06, 2020 10:05 am
by Alaskamike
The tube is actually 1/2in ID. I wasn't looking for transparent, but this was the thinnest tube that I could find on Amazon! The fipple is a 1/2in polycarbonate rod that fits it well. I've cleaned up the blade, so it is about a 45 degree angle, with no major change in performance. I'm thinking that the windway is too short, preventing the air from hitting the blade smoothly. The cap on the mouthpiece is snug at the window but there is a slight (sheet of paper thick) gap for about 1/4in at the mouthpiece end.

Re: Weak bell note in DIY PVC whistle

Posted: Tue Apr 07, 2020 8:30 pm
by Tunborough
1/2" bore is narrow for a Bb, but I know from personal experience that it's possible to make a decent Bb whistle with that bore. It does put the bell note at a disadvantage: it's harder to avoid it breaking into the second octave. A longer window helps to compensate, but I still think 8.5 mm sounds too long. 6.5 mm would sound better to me. Is it possible the mouthpiece cap is angled with respect to the tube, so that the top of the windway slants downward? This would have two effects: the windway would narrow toward the window, making it harder to blow gently enough for the bell note, and the airstream would point more into the whistle than at the blade.

You could aim for a longer windway--no harm in that--but you'd need to make a new whistle to do that. I suggest you first take a closer look at the angle of the mouthpiece cap on the whistle you've got.

Another suggestion after looking at the pictures again ... It looks like the blade has a bit of a curve to it. If so, trim it so it is flat, not curved, and trim the corners of the window at the blade so they are square.

Re: Weak bell note in DIY PVC whistle

Posted: Wed Apr 08, 2020 2:29 am
by trill
Alaskamike,

I went through a spasm of whistle building a number of years ago. One lesson I learned from that episode was that the whistle's voice + playability are very sensitive to mouthpiece geometry. Tiny variations can yield huge differences.

With that in mind, I'd like to make comments on two subjects: 1) window proportions, and 2) windway exit beveling.

Window Proportions:

You mention that your window dimensions are 8.5mm long and 7.5mm wide, a ratio of ~1.1.

I just looked at all my (purchased) whistles. Most have ratios in the range of .4 to .8.

Windway Exit Beveling:

Most of the whistles have some sort of "bevel" on the floor of the windway exit. Some have a flat bevel (~45deg, ~1mm). Some have rounded bevels.

Have you tried beveling ? Could you post a pic showing the windway exit ?

Honestly, I think the clear tubing looks cool !

Also, one more thing I noticed: your window looks to be very wide relative to the inner diameter - half, if not more. Most of the windows on the whistles I have are narrower - visually, somewhere between a third and a half.

Best of luck !

trill