Caution: This information is for dedicated tweakers (the reasons will become obvious as you read the following).
As you all know, the technique of filling under the windway of a Generation type whistle has been discussed here a lot. Some have been enthusiastic about the results, some have been less enthusiastic or even critical.
After considerable research, here’s what I’ve been able to determine about what the poster putty fill does:
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In many cases, it stabilizes the whistle and makes it easier to play, reducing the tendency to buzz, making the bottom notes less fragile, etc. These effects are desirable.
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It mutes the brightness of the whistle’s timbre. This result is undesirable.
I have experimented with removing and reinserting the poster putty fill in several whistles and concluded that the improvements in playability are too important to give up, so I mounted an expedition in search of a material that would have the exact properties to provide the benefits without the drawback.
Such a material would have to be:
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Opaque to the flow of air. In other words, it would need to have the same effect on the airflow in the whistlehead that the poster putty fill had, so as to reduce the random turbulence and stabilize the whistle. But it must also be …
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Accoustically transparent. In other words, even when the fill is in place, sound should resonate inside the whistlehead as if there’s nothing under the windway at all. This will allow the thin plastic shell to resonate freely, which contributes a certain characteristic brightness to Generation type whistles.
The material I selected for this purpose is lightweight spackling compound (Ace brand, to be exact, available in small containers at hardware stores).
I have installed it in a dozen or so whistles with excellent results and expect to use it now instead of poster putty. In addition to retaining the brightness of the timbre, it seems to work better than poster putty in other ways, as well. It seems to be more effective in stabilizing the whistle, and it seems to produce a sweeter sound overall.
So here’s how you do it:
Lightweight spackle isn’t something you can roll up in a ball, drop in and tamp down like poster putty. Imagine now, instead of working with a claylike material, you’re working with ricotta cheese. That’s what the stuff is like.
You’ll need to fashion a tool (a bit of flat metal, wood or plastic; a strip from a cut up credit card would work) that you can insert into the window of the whistlehead and use like a spackling knife.
Lightweight spackle doesn’t tamp down. It sticks to the end of anything you press against it. You have to work it into the cavity under the windway and then “trowel it off” with the aforementioned implement, like you would if you were spackling a hole in a wall.
So basically, the challenge is to put it where you want it and keep it off of the places you don’t want it. No matter how you try, it will tend to get into the windway and elsewhere, so you’ll need to carefully remove it where you don’t want it. You can push it out of the windway with the aforementioned implement, and you can carefully remove it from elsewhere inside the whistlehead with an exacto knife, etc.
After drying overnight, you may find the spackle has shrunk a bit, in which case, you’ll want to apply a little more to bring it up flush again with the end of the windway.
OK. So far, so good.
Now, if everything’s gone well, you’ve done the tweak and been pleased with the results. There’s one more step …
Lightweight spackle is an interior/exterior product, but for applications where it will be exposed to water, it must be sealed with an oil based product. You could use linseed oil, exterior spar varnish, exterior urethane varnish, etc.
After allowing it to dry thoroughly (this may take a day or two), you can seal the fill using cotton ear swabs, using one swab wetted with the varnish to apply the sealer and then using a dry one to swab off the excess. I would recommend using two coats. I’ve found that a little of the varnish gets on the plastic at the window end of the windway. This needs to be carefully scraped off after drying, or it makes the whistle sound breathier.
Anyway, that’s the news.
To follow up on some previous conversations …
This confirms what several people have stated, that the thin plastic shell under the windway does contribute to the voicing of the whistle. Thomas Hastay calls this part of the whistle a “paraboloid reflector.”
What I’ve been able to determine about the functions and effects of this part of the whistlehead is …
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The open airspace under the windway does contribute to unwanted turbulence in the airstream, which has undesirable effects on the whistle’s playability.
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The resonance of the thin plastic shell contributes to the brightness of the whistle’s timbre, which is desirable.
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The space under the windway, whether left open or filled, does not make a difference in the tuning of the whistle (I’ve studied this carefully).
I think you can see, if the unwanted turbulence can be eliminated without impairing the resonance of the thin plastic shell, that would be ideal.
Happy tweaking!
Best wishes,
Jerry
. I used cut down packaging from a pen to make a pouring chanel.
(no offense to you UK residents, I envy you). I believe the material itself (generically) goes under the monkier of “joint compound” but I could be completely off base on that one…