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55962RE: Understanding NAFlutomat Design tool

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  • rdbat1
    Dec 2, 2013
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      Yes, I keep having to remind myself that there is value in the journey and that you can't rush or skip steps in experience. I don't know why, but I am quite drawn to flutes with direction holes in them. They catch my eye every time. So I want to make flutes with direction holes as a result. I also love woodcraft in general and unique grains and burls.

      I realize that only being 3 flutes into my learning that I am adding new dimensions that just make it all more difficult. It would have been easier to become proficient making flutes without direction holes first. I think it felt like I had jumped in the deep end without knowing how to swim this weekend. I was rattled by my mistake on the first finger holes and I really wanted to avoid making a similar mistake. I realize it would have been smart to record the placement of the first finger holes so I could know where they were in relation to the second set.

      Thanks for all the feedback.


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

      The only point I'll add it to try to remind yourself *why* you are doing things.  Becoming mesmerized by the numbers can be a confusing and frustrating experience.   

      Consider the question of whether to measure from the direction holes or the open end of the flute's foot?  Why are the direction holes there?  What is their purpose?  Answer: It is to create an acoustical end of the flute, which is shorter than the physical end of the flute. 

      (Speaking in terms of acoustics, and not spirituality.  This post will only speak to things we can measure with a ruler;  and facilitating a connection with Spirit, is not one of these things.  I am also not speaking to "artsy" reasons.  Sometimes you want to keep the flute physical longer because you like the grain, for example, but you want the flute to play in a higher key.  So there are a variety of reasons one may wish to employ direction holes.) 

      So with the understanding in mind that the direction holes are there to create a flute which is "shorter" than its physical length, the answer of which end to use becomes easier to answer.  If you are measuring for a carrying case, use the full physical length.  If you are measuring for acoustics (such as which ending point to use for planning playing hole placement), then use the acoustical end of the flute, not the physical end.

      Which sounds great.  And it is.  But there is a little more to it.  At first you may wish to ignore this, and just take really good notes through your building process (which one should do in any event). 

      Depending upon the efficiency of the direction holes ability to pass air, the exact acoustical end will vary a small amount this way or that.  The smaller the flute the more impact such variations have upon your fine tuning efforts;  an 1/8-inch variation in a 20-inch bore is a much smaller percentage than in an 8-inch bore.   Assuming your bore is round-abouts a foot in length, I'd not be too worried about this, just keep notes so you know later what you did (did you calculate from the northern edge of the single direction hole, or did you measure from the center of it?  Etc.).  

      Anyway, it is my opinion that trying to think about what is going on inside the flute, how changes effect the passing of air, and where the nodes may be, and where the acoustical ends of the flutes really are (which is not precisely the physical ends for any flute), etc, all help a person craft better flutes over time.  And keep good notes so you know what you have done in the past.  This is not as much help on flute #3 or #4, as it will be on flute #30 or #40, but you gotta start sometime, and the sooner the better. 

      (When is the best time to plant an oak tree?  25-years ago.  When is the second best time to plant an oak tree?  Today.) 

      Enough rambling.  Need more coffee. 

      Best of luck and enjoy the journey!  :)

      Erik Weaver

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


      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.


      ---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.


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


      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.


      ---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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