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55960RE: Understanding NAFlutomat Design tool

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  • rdbat1
    Dec 1, 2013
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      Wow...there is so much to know and understand. I am slowly adding a few bits of dust to my pile of understanding with each flute I make. I  wound up using a combination of what you said about making sure the top hole is about 1/3 the distance from the tsh to the foot to make sure I don't get nodal interference(not that I know what that is yet...but I do know what nodal points are on a drum) and then used the NAFlutomat tool to plot where to put finger holes that would be about 0.25-0.3" in diameter. I plan to give this flute to a friend who has much smaller fingers than I do. She can't play the G flute I made because the finger holes are so big. I realize now I could have moved them further north and had smaller finger holes. Learning.


      I am quite surprised by the difference in playability between the different flutes I have made. This A4 I tuned today just about plays itself. The fetish can be just about anywhere near the TSH and I get a note. My F4 has much less tolerance for where the fetish is. It's like each one has it's own personality.
      Thanks so much for your help tonight Mike. I was pretty stressed after messing up the finger holes on this A and didn't want to route it out again. I will post some pictures soon.
      Randy


      ---In nativeflutewoodworking@yahoogroups.com, <moosewinds_mike@...> wrote:

      Randy,


      First, the bore diameter has only a small effect on the frequency of the fundamental note.  The length numbers I came up with are the acoustic lengths of the notes--not the bore length.  The acoustic length is the bore length plus the acoustic end corrections at the foot and the sound hole (we usually call them k1 and k2, respectively).  K1 is at the foot, and it acoustically extends the flute about 1/3 the bore diameter.  K2 is tricky, and depends on the size of the sound hole relative to the bore's cross-sectional area, and the configuration of the bird whether it has a chimney or not.  The best way to find k2 is to measure the bore from foot to TSH, add k1, and then subtract that from the acoustic length of the fundamental note that is actually played with all holes closed.


      Mike



      ---In nativeflutewoodworking@yahoogroups.com, <rdbat1@...> wrote:

      This makes a lot of sense and I am beginning to see how you calculate these things now. But I know that bore size matters in the fundamental note, but I don't see that in your calculations here. How does bore diameter relate to bore length here?


      You are right that the fundamental was a G# before the direction hole was added. Also, why are my measurements for mine so different than what you calculated? My bore is 13.25" long and my direction hole is 1 13/16" from the foot. It is pretty well right on an A right now. I have used what you said about where my direction hole is at for A to get my thirds. They are pretty close to what was suggested using the NAFlutomat tool. I think I will start drilling for my second try.


      Randy



      ---In nativeflutewoodworking@yahoogroups.com, <moosewinds_mike@...> wrote:

      Randy,


      Here is my recommendation:


      Measure from the foot end.  There is too much variability in the TSH/bird design to use the TSH as a reference point.  The folks who measure from the sound hole are either the transverse flute community (who have a relatively "standard" embouchure from which to work) or maybe those who have a standard sound hole design for which their formula works.


      Don't worry about the total bore length--which means don't worry about the 3/4" backset (space between the plug & the TSH).  That comes into play when you worry about keeping notes in tune in the second octave, or if you used it in your bore length measurement and ended up putting the top hole too close to the TSH (which creates "nodal interference"--keeping the top hole about 1/3 the distance from TSH to the foot should take care of that).


      Now, for where your "foot" lies.  There are a couple ways of visualizing what is going on.  For instance, if you close the direction hole an play, you will get something like a G# that is flat by about 20 cents or so.  You can figure out the acoustic length of that note from the MIDI note numbers.  A is number 69 and G# is number 68, etc., and 20 cents is 0.20 (there are 100 cents between G# and A), so


      G# - 20 cents = 68 - 0.2 = 67.8 = MIDI


      The next thing you do is find the frequency of that note


      f(G#-20) = 6.875*2^((3+67.8)/12) = 410.5 Hz


      The next thing you do is find the acoustic length of that note


      L(G#-20) = 13552/(2*410.5) = 16.51 inches


      where 13552 in/sec is the speed of sound in air at 72 degrees F.  Likewise, the A (440 Hz) is 15.40 inches.  The difference is 1.11 inches, or about 1+1/8 inches.  So in your case, you can measure north 1+1/8 inches from the physical end of your flute, and that is where the end would be if you had a fundamental A with a bore without a direction hole.  Using that mark as the foot end, you can use the hole calculator of your choice to lay out the holes.


      Mike




      ---In nativeflutewoodworking@yahoogroups.com, <rdbat1@...> wrote:

      I have at least three ways of measuring finger hole distances. One is in an instruction booklet by Raymond Wells, another is the rule of thirds, and also the NAFlutomat design tool. All come up with finger holes in slightly different places. Thing is the NAF site measures from the south end of the flute, while the rule of thirds divides the distance of the bore, and the Ray Wells book measures from the north end of the air split. After my latest disaster placing finger holes I want to make sure I do it right. To add to the mix I have a direction hole too. It started as two direction holes, but now that I have put on a new finger board I only need one direction hole to get the A I want.
      So my question is about where to measure from to place finger holes.
      My fundamental note is A4. 3/4" bore, 3/16 thick walls at the finger hole area. Entire bore length is 13 3/4" but the TSH is only 13" from the south end of the flute. The direction hole is 3/8 across and the center of it is 1 13/16"  from the south end. So the north end of the direction hole is 2" from the end.
      So if I want to use rule of thirds do I measure from the direction hole or the end of the flute? Do I include that extra 3/4" in my measurement of bore when I measure for the NAFlutomat or do I measure from the TSH? It seemed like I had to make things a bit shorter to make the right note using NAF on this flute and now I wonder if it is because I should have been measuring the full length of the bore instead of from the TSH.
      So where should I be measuring for the bore length? TSH to direction hole? TSH to end of flute? Full length of bore?
      I am so confused at the moment. I sure get why I want to take notes as I go. It will make future flutes so much easier!.
      Any help would be so appreciated here.
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