Hi folks. I’m building Low C #2 in pvc, internal 21mm (53/64"), external 25mm (63/64"). Going to use the noisy end from #1 so just making the barrel this time. Now opening out the end as far as material allows - helps with the bell note I understand.
Has anyone got some distances from the end I should drill the holes. I’d start small and then adjust. #1 sounds lovely - it’s just a bit off key all over.
Waiting with bated,
David
From sound hole % to end of tube.
1st = 43%
2nd = 50%
3rd = 58%
4th = 68%
5th = 73%
6th = 83%
measured from sound hole the end of flute/whistle = 100%
I use the middle of the sound hole i.e. 1/2 way between windway and blade edge to the centre point of the tone hole.
None of my home made flutes and whistles are suitable for sale, but all are in tune, in every key and diameter.
Using %'s makes it easy to calculate because if you use millimetres you can’t be far out. Use a small drill to start e.g. 1/8" or 3mm. If its spot on in tune, and you want a bigger hole, widen it down towards the end. If it’s flat, then widen towards the blade. I use a cheap set of Die Sinkers Riffler Files and/or old chainsaw files.
HTH … but somebody else will no doubt come up with something better 
Here you go.
http://www.cwo.com/~ph_kosel/flutomat.html
Credit where credit is due. Serpent posted this long ago and I saved the link.
For the “embochure diameter” number, I believe you find the area of your voicing window and determine what diameter of circle will have the same area. (Someone please correct me if I’m mistaken.)
Best wishes,
Jerry
Jerry is Correct about the emboucure diameter, but I must point out that the whistle’s voicing hole diameter must be “averaged”. By “averaged” I mean that the inner square diameter (L + W)/2 must be averaged with the outer square diameter (L + W)/2 for a Final Averaged Diameter.
This final value can then be inserted into the “embouchure” box in Peter’s Flutomat. If the square whistle hole(rhombus)is not averaged, the whistle’s pitch will be very sharp. A final averaged diameter of 1/2 the bore diameter is a good start, but you can change this to suit your taste(small/quiet, large/loud etc.)
You can have a look(for comparison)at some “moldey-oldey” measurements of mine for a C flute with a 0.812 bore diameter made from a Bamboo “Tiki-Torch”. Your whistle’s tonehole spacings and sizes will be very close to those I calculated for this flute.(scroll down to the Jan. 12 post in the link below)
Cracking response folks, thanks.
All the best,
David
Thomas,
Could you elaborate as to what you mean by inner and outer voicing hole areas?
Looking at a whistle, it appears to me, you might be referring to the area where the voicing window is smallest, right at the edge of the soundblade (labium) as the inner voicing hole, whereas …
it looks like you might be referring to the area at the outside diameter of the tube where the soundblade ramp intersects the outside of the whistle as the outer voicing hole.
Is this correct?
Thanks!
Jerry
P.S. That’s a terrific discussion you linked to. If anyone’s trying without success to get it to come up, you have to register on the MIMF bulletin board and then you can get the page.
Jerry I think they think you’re talking about a low C flute and not a whistle… Or are you talkiig about a flute?? But I guessed whistle because this is a whistle board and you didn’t say flute…
Hi, Cy.
I’m talking about a whistle. If David’s talking about a flute, then the embochure diameter will be simple to determine and use in the Flutomat calculator. If he’s talking about a whistle, he’ll need to calculate the area of the voicing hole as discussed above.
Best wishes,
Jerry
I was asking about whistles, but its all fascinating stuff anyway. Will take a bit of study of what you’ve provided.
btw I’ve belled out the end of the barrel to near the outside diam, to improve the lowest note ( so the thoery goes ). I’m assuming this means a slightly greater length of barrel twixt lowest hole and open end. Anyone got any feelings about this?
David
My small experience with this has been to add about an inch and then trim until you get the bell note in tune. Then comes some experimentation with placement of the bottom hole, after which Peter Kosel’s calculator will be right on.
NOTE: There are a LOT of variables to consider even when using the Flute-O-Mat calculator, and it’s best to not expect to “get it right” in only a couple of tries. Especially tricky with low whistles, is balancing the diameter of the holes against fingering width, being small enough to cap with a finger pad, being large enough for decent volume, and having a hole-to-hole ratio in the upper 3, to allow for proper OXXOOO crossfingering. If you can get that in less than a couple 10’ (3M) sticks of your 1" PVC, hey, consider it a minor miracle! 
Belling the lower end of the whistle is also going to affect the performance in the second and third octaves. My experience has been that they will go slightly flat unless you compensate with placement variations that tend to put the bell note a few cents sharp. Caveat reader: That’s just me playing with - not building a serious whistle. The grain of salt should be modified by your own experience.
Good luck, and keep us posted!
serpent
Jerry: Yes, you have the correct comprehension.
I was speaking of the inner and outer measurements as bottom and top(respectively)of the square voicing hole as a “truncated cone equivilent”(truncated pyramid?). It is this equiv. truncated cone that must be averaged for false bore extension calculations.
Serpent has made a very good point about flaring the bore end hole. This will sharpen the bell note but be more evident in the upper registers. Because of the flattening phase shift that gets exponentially larger with the upper registers, this flaring will help a little to exponentially compensate/correct this flattening effect. (The angle is critical to inter-register matching, just as it is with a conical Recorder bore.) It will still sharpen the lowest register, but this will be less evident and easily corrected by a lower breath pressure in the 1st register. There is always a “give-n-take” with tweaks.
Historical note: The French Flageolet uses this type of bore with a slightly decreasing conical bore married to a slightly expanding bell flare. A good diagram of this is displayed in “Ancient European Musical Instruments” By Nicholas Bessaraboff (See your Library Reference area for this volume)