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PostPosted: Fri Jul 19, 2019 10:39 pm 
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Sometimes I have odd thoughts. Like why our instruments have such deep toneholes. Even boehm flutes and clarinets and saxes and such have the same basic trait. The sax, for example, has deeper toneholes while the walls are relatively thin. And does a tin whistle suffer for not having the same chimney setup?

If we theoretically change the wall thickness of a flute to be 1 micron thin, what would the results be? Obviously the intonation and finger spacing would be affected. What about bore perturbances? Would the overall intonation be more difficult to dial in? Assuming that there were no bore recesses or protuberances and the inner tube were perfectly smooth for every note, would a very bland sound be produced?


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PostPosted: Sat Jul 20, 2019 2:00 am 
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Reducing the tube wall thickness would bring the possibility of damaging it closer/sooner. :D

I've read that increasing the wall thickness creates a more mellow tone, but I'm not really sure, myself - but maybe it would make it ring out more, if you reduced the thickness.

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PostPosted: Sat Jul 20, 2019 7:14 am 
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Your fingers would protrude more into the bore of the instrument. This may explain why I find it easier (on whistles at least) to get clean cuts and taps on thicker-walled whistles than on thin-walled metal whistles. The finger protrusion requires a slight adjustment in tuning, as well.

A thin wall would eliminate the opportunity to under-cut toneholes to adjust the tuning.

None of this, of course, applies to keyed, metal Boehm flutes, so there must be other reasons.


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PostPosted: Sat Jul 20, 2019 9:44 am 
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the Clinton Flute for India was a simple system flute with a metal body, and the tone holes are raised significantly above the body to make a chimney similar in size to a wooden flute. i wonder why they did that: was it only for comfort or familiarity (to make it feel more like a wooden flute) or did they find removing the chimney affected the sound too much? from the picture, the keyed holes appear to have a similar chimney to the fingered holes, so the latter seems more likely.

Tunborough wrote:
Your fingers would protrude more into the bore of the instrument. [...] None of this, of course, applies to keyed, metal Boehm flutes, so there must be other reasons.


i'm not sure about that. on a Boehm system flute with plateau keys, the pad doesn't protrude at all into the bore, but with French keys, i think it must do - or if not actually into the bore, at least further into the chimney. it's well known that French keys require adjustments to the flute's scale, but the reason usually given for that is because the vented French keys allow more air to escape than plateau keys would. my Boehm flute is upstairs at the moment but i may go up later and have a look...


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PostPosted: Sat Jul 20, 2019 10:28 am 
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Been wondering abut this myself. I have an Ellis "essential flute" with significantly thinner walls and I find it much easier to "bend" notes, whistle style, on that flute. I wonder if it has anything to do with the thinner walls

Does anyone make a conical bore metal irish flute? Would be interesting to try.


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PostPosted: Sat Jul 20, 2019 10:44 am 
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well, i checked my Boehm system flute, which has French keys, and i discovered 1) it's actually quite hard to see the key from the inside of the barrel! and 2) the distance between the bore and my fingertip looked much larger (i.e., the chimney was longer) than the distance between the bore and the pad on a plateau key, and certainly much longer than it is on a simple system flute. does this affect the tone of the flute? some people claim French keyed Boehm flutes have a better tone than plateau keys, but i've always been a bit dubious about how true that is.


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PostPosted: Sat Jul 20, 2019 6:29 pm 
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When I first started making flutes, I made a thin walled Pratten, the thinner chimney on the tone holes will make it sharp, so you have to adjust the tone hole diameter.
viewtopic.php?f=2&t=35821&p=461261&hilit=thin+Pratten#p461261
To bad the photo is no longer on the thread

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PostPosted: Sun Jul 21, 2019 2:59 am 
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Jon C. wrote:
When I first started making flutes, I made a thin walled Pratten, the thinner chimney on the tone holes will make it sharp, so you have to adjust the tone hole diameter.
viewtopic.php?f=2&t=35821&p=461261&hilit=thin+Pratten#p461261
To bad the photo is no longer on the thread



Well so aside from it going sharp what else can you tell us?


Last edited by PB+J on Sun Jul 21, 2019 6:13 am, edited 1 time in total.

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PostPosted: Sun Jul 21, 2019 4:53 am 
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I think the body thickness of wooden flutes was probably set by physical issues such as having walls thick enough and strong enough to withstand robust use, to house socket/tenon joints, and to allow for keyseats to be let into the walls, rather than any consideration of acoustics. Once the thickness was set, the acoustics of the bore taper were then optimised, which would thus have locked in resistance to change. So that, for example, when Clinton did his all metal Flute for India, it was easier for him to artificially deepen the finger holes than start again on the acoustics. You can see such a finger hole here (as well as the intriguing uni-pivot design for hinging his keys):

Image

If you did make a very thin-walled metal version, you would need to reduce the diameter of the tone holes considerably to compensate for the lack of depth (which could be a good thing - it would make the flute easier to finger accurately). Flutes being rather complex acoustically, you'd quite likely run into some trouble and have to do some bore tweaks too. Tunborough, on a day when you have absolutely nothing better to do (!), it would be interesting to take any flute design you have reasonably well documented on your flute model and reduce the wall thickness at the fingerholes to say 0.8mm. I'd expect them to go sharp in every octave, and the ones at the top of the tube to go much sharper due to the cumulative effect of the better venting further down. Is reducing their diameters enough to restore the flute to good tuning or do you still end up with a progressive octave sharpening issue?

When we look at saxes, metal flutes, etc, another practical issue arises. Unless you want to use a curved pad (arggghhhh!), you need to deepen the holes on the player's side and the listener's side to be able to use a flat pad.

Good to keep in mind Nicholson's flattening of the top outside of the flute around the three fingerholes of each hand here. He did it to make covering his larger holes more reliable. The flattening does take us some small way towards more shallow holes. You can see it on this flute but only on the right hand section.

Image


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PostPosted: Sun Jul 21, 2019 11:35 am 
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That's very helpful, Terry.

What about undercutting? How does this physically help the tuning? Making the toneholes deeper from the increased volume of air?

IIRC, Geoffrey Ellis talked about tuning of Xiao flutes being very good with a cylindrical bore and no undercutting. Maybe wall thickness has something to do with this?


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PostPosted: Sun Jul 21, 2019 12:33 pm 
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awildman wrote:
That's very helpful, Terry.

What about undercutting? How does this physically help the tuning? Making the toneholes deeper from the increased volume of air?

IIRC, Geoffrey Ellis talked about tuning of Xiao flutes being very good with a cylindrical bore and no undercutting. Maybe wall thickness has something to do with this?


In the case of the xiao, I would not say there is no undercutting at all. Rather it is limited compared to some flutes. But something that most Chinese makers do is to use oval holes instead of round. The amount of undercutting that is necessary on these flutes is definitely reduced using oval holes (only took me about ten years to figure this out). On a D xiao, the F# note needs some undercutting (much like a conical bore flute) and I do blend the inside edge of each finger hole so there are no sharp angles.

I don't know how well oval holes would go down on something like a Pratten, however. Mind you, on the xiao the ovaling of the holes is not radical, but it doesn't take much. The theory on undercutting is that you undercut to the South (away from the embouchure hole) to emphasize the second octave pitch, and you undercut to the North for the first octave, generally speaking. So if you have a flat second octave, undercutting fools the flute into thinking that the finger hole is farther down the bore than it is. But if you make an oval hole, you are in essence making two holes right next to each other. One favors the first octave, and another favors the second octave. If you get them placed correctly, you get the best of both worlds.

When I first started making the xiao, I thought the Chinese makers used oval holes as some sort of trick to reduce the splitting of the bamboo. I assumed that if you make a narrower hole that didn't go as far in a perpendicular direction across the grain of the bamboo that perhaps it made it less susceptible to cracks. Having never worked with bamboo this theory had no practical experience behind it--it was just a theory. A wrong one, as it happens. They made the holes oval because they figured out about a thousand years ago that it improved intonation.

So the intonation on the cylindrical bore xiao is excellent as a result.

But getting back to thin walls: I do make the walls on my Essential flutes thinner--probably about 3mm thick. Thicker than a bansuri, thinner than a Pratten. There is less "meat" for undercutting, but some tweaks to hole sizing and placement greatly reduce the need for undercutting, especially given the taper in the headjoint which already helps balance everything.

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PostPosted: Sun Jul 21, 2019 6:35 pm 
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Terry McGee wrote:
Tunborough, on a day when you have absolutely nothing better to do (!), it would be interesting to take any flute design you have reasonably well documented on your flute model and reduce the wall thickness at the fingerholes to say 0.8mm. I'd expect them to go sharp in every octave, and the ones at the top of the tube to go much sharper due to the cumulative effect of the better venting further down. Is reducing their diameters enough to restore the flute to good tuning or do you still end up with a progressive octave sharpening issue?
I started with an anonymous keyless flute that paddler has measured, with a tapered bore, a C foot, and wall thickness around 4.5 - 5.5 mm. To start from a level playing field, I tweaked the hole sizes to give balanced tuning across two octaves, leaving the hole positions unchanged; most of the holes were 6-8 mm, with B2 at 10.5 mm.

When I reduced the wall thickness to 0.8 mm, everything went sharp, as you predicted. Both C-nat came out a full semitone sharp, and the second octave was generally worse than the first. I could bring it back in tune by reducing the hole sizes to 4-5.5 mm. B2 was 7.4 mm, and B3 was the smallest at 4 mm, the smallest diameter I allowed WIDesigner to use. Tuning wasn't noticeably worse; it was a hair sharper in the second octave than the first. The two Es were 10-15 cents sharp.

A wall size of 0.35 mm (typical of a Generation brass whistle) pushed the limits of making the holes smaller. Even with T3 and B3 down to 4 mm, both Es were still 20-25 cents sharp. At this point, you'd have to start moving holes.


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PostPosted: Mon Jul 22, 2019 7:30 am 
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Good man, Tunborough. So, unless we make the walls really thin, we could probably get away with it just by making the holes smaller. A few tweaks to hole position would clinch the deal.

But, if you were going to go to that trouble, you might want more bang for your buck. It would probably make sense to fiddle the bore and finger hole placement a bit, put the hole diameters somewhere closer to where they are now and get some significant benefits in terms of power without losing too much in terms of fingerability. And WIDesigner would be the tool to direct your efforts. I look forward to seeing some of our young bucks making these innovations. (Young bucks, these days, I don't know....)

But all of this requires being able to make a conical metal tube body. I did briefly investigate doing this (some years ago) using the hydraulic force system that makes my tuning slides. it would produce a very accurate and repeatable body shape. I would hope we don't have to descend to the level employed on those period Clarke C-tin whistles with their crude and uncomfortable folded seams!


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PostPosted: Mon Jul 22, 2019 1:03 pm 
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Speaking from the consumer side, I could maybe be interested in a thin-wall metal version of a conical bore wooden "Irish" flute, if it actually offered some acoustic advantage over what I'm playing now.

Louder, "warmer," "brighter," whatever quality the end-user would consider an improvement. That would have to be the selling point, because the other aspect of ignoring environmental damage is already covered with Delrin and Ebonite models. Maybe more precise fingering if the holes are smaller?

The aesthetic possibilities might be interesting. Maybe contrasting materials like copper or brass for the body, with silver lip plate, end cap and rings (even though rings would just be cosmetic).


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PostPosted: Mon Jul 22, 2019 2:16 pm 
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Terry McGee wrote:
So, unless we make the walls really thin, we could probably get away with it just by making the holes smaller. A few tweaks to hole position would clinch the deal.
Conical bore wrote:
Speaking from the consumer side, I could maybe be interested in a thin-wall metal version of a conical bore wooden "Irish" flute, if it actually offered some acoustic advantage over what I'm playing now.
That's the thing ... we could do it, but is there any advantage to be gained. I don't see an advantage in the intonation, although maybe we could move the B3 hole closer to B2 and leave it a little larger. Does the resulting flute sound better? Play better? In whistles, the instruments I prefer have deeper holes. Other than my earlier comment on cuts and taps, though, I can't say if my preference is because of the deeper holes or something unrelated.


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