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Flutes tend to overblow

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  • bobaldea
    I m just getting started building flutes, but I suspect I m consistently doing something wrong. I ve made two flutes with a 3/4 bore and 5/8 backspace. The
    Message 1 of 16 , Jun 1, 2004
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      I'm just getting started building flutes, but I suspect I'm
      consistently doing something wrong. I've made two flutes with a 3/4"
      bore and 5/8" backspace. The first is a G and the second will be an A
      or Bb.

      On my first flute I attempted to copy exactly what Dusty recommended
      regarding flue and TSH shape and size. When the flute had a tendency
      to overblow, I fashioned six or eight birds of different shapes to
      test their effect. A bird with ears and a roof that overhangs the
      TSH was required to hold the fundamental note and still allow an
      octave shift with the top hole half covered.

      On my second flute, I tried a flue that tapers in depth so that the
      roof and floor would meet at the cutting edge. This flute required
      the same type of bird with ears and overhang. A little at a time, I
      increased the depth of the flue, decreasing the taper and then filed
      the upper surface of the cutting edge to move it closer to the floor
      of the flue, testing at each minor change. Now the window is about
      1/4" and I still haven't resolved the problem.

      I would welcome any suggestions that would give me more flexibility
      in the shape of my birds.

      Bob
    • rjrobisonga
      Hello, What is the length of the sound chamber for the flutes. I too have had issues with overblow on the highest note or hole 1 from the tsh. The only way I
      Message 2 of 16 , Jun 1, 2004
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        Hello,

        What is the length of the sound chamber for the flutes. I too have
        had issues with overblow on the highest note or hole 1 from the
        tsh. The only way I could resolve it was the length. Hole
        placement would prevent the problem to begin with.

        Be well.

        --- In nativeflutewoodworking@yahoogroups.com, "bobaldea"
        <rca58@e...> wrote:
        > I'm just getting started building flutes, but I suspect I'm
        > consistently doing something wrong. I've made two flutes with a
        3/4"
        > bore and 5/8" backspace. The first is a G and the second will be
        an A
        > or Bb.
        >
        > On my first flute I attempted to copy exactly what Dusty
        recommended
        > regarding flue and TSH shape and size. When the flute had a
        tendency
        > to overblow, I fashioned six or eight birds of different shapes to
        > test their effect. A bird with ears and a roof that overhangs the
        > TSH was required to hold the fundamental note and still allow an
        > octave shift with the top hole half covered.
        >
        > On my second flute, I tried a flue that tapers in depth so that
        the
        > roof and floor would meet at the cutting edge. This flute
        required
        > the same type of bird with ears and overhang. A little at a time,
        I
        > increased the depth of the flue, decreasing the taper and then
        filed
        > the upper surface of the cutting edge to move it closer to the
        floor
        > of the flue, testing at each minor change. Now the window is
        about
        > 1/4" and I still haven't resolved the problem.
        >
        > I would welcome any suggestions that would give me more
        flexibility
        > in the shape of my birds.
        >
        > Bob
      • bobaldea
        The flutes are about 1:18 or 1:17 ratio of bore to length. Each one is a hair short for its key, so that s why the ears were needed. I suspect that I m getting
        Message 3 of 16 , Jun 1, 2004
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          The flutes are about 1:18 or 1:17 ratio of bore to length. Each one
          is a hair short for its key, so that's why the ears were needed.

          I suspect that I'm getting the cutting edge too high but my attempts
          to correct that don't seem to be helping, so I'm wondering what else
          I may have overlooked.

          Bob
        • BIKERJOE
          ... one ... attempts ... else ... Hau Bob Nice echo, should a brought my flute Cl;-{P} flue floor should be flat and level and approx 100th of a inch lower
          Message 4 of 16 , Jun 1, 2004
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            --- In nativeflutewoodworking@yahoogroups.com, "bobaldea"
            <rca58@e...> wrote:
            > The flutes are about 1:18 or 1:17 ratio of bore to length. Each
            one
            > is a hair short for its key, so that's why the ears were needed.
            >
            > I suspect that I'm getting the cutting edge too high but my
            attempts
            > to correct that don't seem to be helping, so I'm wondering what
            else
            > I may have overlooked.
            >
            > Bob

            Hau Bob

            Nice echo, should a brought my flute Cl;-{P} flue floor should be
            flat and level and approx 100th of a inch lower than tha cutting
            edge.

            BikerJoe

            http://NativeFluteClub.Com
          • dogfox66@yahoo.com
            ... That will work, Bob, but there are many others that also will. They just aren t as easy to quantify. I m impressed with your analytical approach to the
            Message 5 of 16 , Jun 1, 2004
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              --- In nativeflutewoodworking@yahoogroups.com, "BIKERJOE"
              <bikerjoe_a1@y...> wrote:
              > --- In nativeflutewoodworking@yahoogroups.com, "bobaldea"
              > <rca58@e...> wrote:
              > > The flutes are about 1:18 or 1:17 ratio of bore to length. Each
              > one
              > > is a hair short for its key, so that's why the ears were needed.
              > >
              > > I suspect that I'm getting the cutting edge too high but my
              > attempts
              > > to correct that don't seem to be helping, so I'm wondering what
              > else
              > > I may have overlooked.
              > >
              > > Bob
              >
              > Hau Bob
              >
              > Nice echo, should a brought my flute Cl;-{P} flue floor should be
              > flat and level and approx 100th of a inch lower than tha cutting
              > edge.

              That will work, Bob, but there are many others that also will. They
              just aren't as easy to quantify.

              I'm impressed with your analytical approach to the problem. You'll
              learn a lot that way.

              Hang in there.

              Don
            • bobaldea
              ... Don t know how my reply got tripled, but I deleted the spare copies. I m not sure I can eyeball a 100th of an inch but I ll try harder. I ve got four more
              Message 6 of 16 , Jun 1, 2004
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                >
                > Hau Bob
                >
                > Nice echo, should a brought my flute Cl;-{P} flue floor should be
                > flat and level and approx 100th of a inch lower than tha cutting
                > edge.
                >
                > BikerJoe
                >
                > http://NativeFluteClub.Com

                Don't know how my reply got tripled, but I deleted the spare copies.

                I'm not sure I can eyeball a 100th of an inch but I'll try harder.
                I've got four more blanks routed and waiting for glue-up.
              • bobaldea
                ... Don t know how my reply got tripled, but I deleted the spare copies. I m not sure I can eyeball a 100th of an inch but I ll try harder. I ve got four more
                Message 7 of 16 , Jun 1, 2004
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                  >
                  > Hau Bob
                  >
                  > Nice echo, should a brought my flute Cl;-{P} flue floor should be
                  > flat and level and approx 100th of a inch lower than tha cutting
                  > edge.
                  >
                  > BikerJoe
                  >
                  > http://NativeFluteClub.Com

                  Don't know how my reply got tripled, but I deleted the spare copies.

                  I'm not sure I can eyeball a 100th of an inch but I'll try harder.
                  I've got four more blanks routed and waiting for glue-up.
                • Brian Revheim
                  ... Hi - you don t have to eyeball it. I bought a pair of digital calipers from Harbor Freight for less than $20.00. I open the calipers to my desired depth,
                  Message 8 of 16 , Jun 1, 2004
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                    --- In nativeflutewoodworking@yahoogroups.com, "bobaldea"
                    <rca58@e...> wrote:
                    > >
                    > > > >
                    > > http://NativeFluteClub.Com
                    >
                    >.
                    >
                    > I'm not sure I can eyeball a 100th of an inch but I'll try harder.
                    >

                    Hi - you don't have to eyeball it. I bought a pair of digital
                    calipers from Harbor Freight for less than $20.00. I open the
                    calipers to my desired depth, and use the extended "tang" (?) on the
                    end to set my flue depth. Hope that made sense - good luck, Brian
                  • Edward Kort
                    Hi Bob, If all your notes play fine except the fundamental, which overblows, your bore diameter may be too small, as noted by others. However, I make flutes
                    Message 9 of 16 , Jun 1, 2004
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                      Hi Bob,

                      If all your notes play fine except the fundamental, which overblows,
                      your bore diameter may be too small, as noted by others. However, I
                      make flutes with smaller bores than most (I like the second octave
                      notes). I control the fundamental overblow by the amount of bevel on
                      the flue edge that forms the back of the TSH.

                      Without at least rounding this edge a bit, most flutes will overblow.
                      I put from 1/32" to 1/16" bevel (slowly walk your way into it). I put
                      a slightly less aggressive bevel on the corresponding edge of the
                      bird.

                      This may work differently for other flue/TSH geometries. Mine has the
                      top of the TSH flat and even with the top of the flue (with flue in
                      flute, not bird).

                      Give it a gentle try. Could cure your problems. I also get
                      substantially greater volume with this simple process.

                      Edward


                      --- In nativeflutewoodworking@yahoogroups.com, "bobaldea"
                      <rca58@e...> wrote:
                      > I'm just getting started building flutes, but I suspect I'm
                      > consistently doing something wrong. I've made two flutes with a
                      3/4"
                      > bore and 5/8" backspace. The first is a G and the second will be an
                      A
                      > or Bb.
                      >
                      > On my first flute I attempted to copy exactly what Dusty
                      recommended
                      > regarding flue and TSH shape and size. When the flute had a
                      tendency
                      > to overblow, I fashioned six or eight birds of different shapes to
                      > test their effect. A bird with ears and a roof that overhangs the
                      > TSH was required to hold the fundamental note and still allow an
                      > octave shift with the top hole half covered.
                      >
                      > On my second flute, I tried a flue that tapers in depth so that the
                      > roof and floor would meet at the cutting edge. This flute required
                      > the same type of bird with ears and overhang. A little at a time, I
                      > increased the depth of the flue, decreasing the taper and then
                      filed
                      > the upper surface of the cutting edge to move it closer to the
                      floor
                      > of the flue, testing at each minor change. Now the window is about
                      > 1/4" and I still haven't resolved the problem.
                      >
                      > I would welcome any suggestions that would give me more flexibility
                      > in the shape of my birds.
                      >
                      > Bob
                    • rjrobisonga
                      Ed, What if it is the first hole from tsh that overblows? Is this the bore to len ratio causing the problem? I am curious to know. I ve recently had alot of
                      Message 10 of 16 , Jun 1, 2004
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                        Ed,

                        What if it is the first hole from tsh that overblows? Is this the
                        bore to len ratio causing the problem? I am curious to know. I've
                        recently had alot of this issue. When I shorten the len and re tune
                        to new fundamental, I can correct the problem.

                        Be well.


                        --- In nativeflutewoodworking@yahoogroups.com, "Edward Kort"
                        <edkort@c...> wrote:
                        > Hi Bob,
                        >
                        > If all your notes play fine except the fundamental, which
                        overblows,
                        > your bore diameter may be too small, as noted by others. However,
                        I
                        > make flutes with smaller bores than most (I like the second octave
                        > notes). I control the fundamental overblow by the amount of bevel
                        on
                        > the flue edge that forms the back of the TSH.
                        >
                        > Without at least rounding this edge a bit, most flutes will
                        overblow.
                        > I put from 1/32" to 1/16" bevel (slowly walk your way into it). I
                        put
                        > a slightly less aggressive bevel on the corresponding edge of the
                        > bird.
                        >
                        > This may work differently for other flue/TSH geometries. Mine has
                        the
                        > top of the TSH flat and even with the top of the flue (with flue
                        in
                        > flute, not bird).
                        >
                        > Give it a gentle try. Could cure your problems. I also get
                        > substantially greater volume with this simple process.
                        >
                        > Edward
                        >
                        >
                        > --- In nativeflutewoodworking@yahoogroups.com, "bobaldea"
                        > <rca58@e...> wrote:
                        > > I'm just getting started building flutes, but I suspect I'm
                        > > consistently doing something wrong. I've made two flutes with a
                        > 3/4"
                        > > bore and 5/8" backspace. The first is a G and the second will be
                        an
                        > A
                        > > or Bb.
                        > >
                        > > On my first flute I attempted to copy exactly what Dusty
                        > recommended
                        > > regarding flue and TSH shape and size. When the flute had a
                        > tendency
                        > > to overblow, I fashioned six or eight birds of different shapes
                        to
                        > > test their effect. A bird with ears and a roof that overhangs
                        the
                        > > TSH was required to hold the fundamental note and still allow an
                        > > octave shift with the top hole half covered.
                        > >
                        > > On my second flute, I tried a flue that tapers in depth so that
                        the
                        > > roof and floor would meet at the cutting edge. This flute
                        required
                        > > the same type of bird with ears and overhang. A little at a
                        time, I
                        > > increased the depth of the flue, decreasing the taper and then
                        > filed
                        > > the upper surface of the cutting edge to move it closer to the
                        > floor
                        > > of the flue, testing at each minor change. Now the window is
                        about
                        > > 1/4" and I still haven't resolved the problem.
                        > >
                        > > I would welcome any suggestions that would give me more
                        flexibility
                        > > in the shape of my birds.
                        > >
                        > > Bob
                      • bobaldea
                        ... Thanks for all of the suggestions. I ll try increasing the lower chamfer, and reworking the flue geometry tonight. If different builders can get it to
                        Message 11 of 16 , Jun 1, 2004
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                          --- In nativeflutewoodworking@yahoogroups.com, "Edward Kort"
                          <edkort@c...> wrote:
                          > Hi Bob,
                          >
                          > If all your notes play fine except the fundamental, which
                          > overblows, your bore diameter may be too small, as noted by
                          > others. However, I make flutes with smaller bores than most
                          > (I like the second octave notes). I control the fundamental
                          > overblow by the amount of bevel on the flue edge that forms
                          > the back of the TSH.
                          >
                          > Without at least rounding this edge a bit, most flutes will
                          > overblow. I put from 1/32" to 1/16" bevel (slowly walk your way
                          > into it). I put a slightly less aggressive bevel on the
                          > corresponding edge of the bird.
                          >
                          > This may work differently for other flue/TSH geometries. Mine has
                          > the top of the TSH flat and even with the top of the flue (with
                          > flue in flute, not bird).
                          >
                          > Give it a gentle try. Could cure your problems. I also get
                          > substantially greater volume with this simple process.
                          >
                          > Edward

                          Thanks for all of the suggestions. I'll try increasing the lower
                          chamfer, and reworking the flue geometry tonight. If different
                          builders can get it to work properly with a cutting edge that ranges
                          from the top of the flue to .01 from the bottom, I can't be too far
                          off. (he says with ignorant bliss...)

                          I'm assuming that the TSH and flue should be perfected, before
                          trimming the bore to length or drilling any holes, and left alone
                          thereafter. Is that correct, or are they part of the balancing act
                          involved in tuning?
                        • dogfox66@yahoo.com
                          ... Correct. Some will wish VERY minor tweaks thereafter. D.
                          Message 12 of 16 , Jun 1, 2004
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                            --- In nativeflutewoodworking@yahoogroups.com, "bobaldea" <rca58@e...>
                            wrote:

                            > I'm assuming that the TSH and flue should be perfected, before
                            > trimming the bore to length or drilling any holes, and left alone
                            > thereafter. Is that correct, or are they part of the balancing act
                            > involved in tuning?

                            Correct. Some will wish VERY minor tweaks thereafter.

                            D.
                          • Edward Kort
                            I ve never had overblow problems with the top hole. But I want to interject a note of caution in ascribing all such problems, as Don points out, to aspect
                            Message 13 of 16 , Jun 1, 2004
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                              I've never had overblow problems with the top hole. But I want to
                              interject a note of caution in ascribing all such problems, as Don
                              points out, to aspect ratio.

                              Lew Price, whose books are filled with a wealth of information on
                              crafting flutes, discusses two aspect ratios. The first is the one
                              that everyone in this thread has used, length/bore, with an "optimum"
                              value of 18:1. A second is length/(bore*bore), with an optimum value
                              of 24:1.

                              I have been using the second ratio for a while, with IMHO good
                              results. You must pay a little closer attention to overblowing
                              issues, but the fundamental tone has much richer harmonics.

                              If my experience is any judge, I depart considerably from the 18:1
                              ratio. Below is a table of length/bore ratios for flutes I have
                              crafted to a length/(bore*bore) ratio of 24:1. This is for the way I
                              craft the sound mechanism, and uses Clint Goss's key categorization.

                              Key
                              tenor A 17.5:1
                              tenor F# 19:1
                              tenor D 22:1
                              baritone G 27:1
                              baritone E 29:1

                              In the "normal" range for flutes, there is not too much difference
                              between the two ratios, but I don't think that there is any magic in
                              the 18:1 ratio.

                              Just my opinion, but I hope it frees you up from thinking about a
                              strict aspect ratio. Experiment and listen to the sound. Many things
                              can cause overblowing.

                              Edward


                              --- In nativeflutewoodworking@yahoogroups.com, "rjrobisonga"
                              <rjrobisonga@y...> wrote:
                              > Ed,
                              >
                              > What if it is the first hole from tsh that overblows? Is this the
                              > bore to len ratio causing the problem? I am curious to know. I've
                              > recently had alot of this issue. When I shorten the len and re
                              tune
                              > to new fundamental, I can correct the problem.
                              >
                              > Be well.
                            • rjrobisonga
                              Ed, Thanks for your response and insight. I have found that my flutes made with 3/4 bore, 9/32 by 5/16 tsh, and 15 sound chamber gives me a G for the
                              Message 14 of 16 , Jun 2, 2004
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                                Ed,

                                Thanks for your response and insight. I have found that my flutes
                                made with 3/4" bore, 9/32 by 5/16 tsh, and 15" sound chamber gives
                                me a G for the fundamental. I think that the hole placement is
                                critical for me. If I place the last hole (nearest tsh) too high, I
                                get an overblow because the hole is too big (because of the hole
                                placement). If I move it down (which is too late or I could plug
                                with wood or stone), the overblow is fixed. So, when I use your
                                program, I am not getting the fundamental. It is usually a half
                                step shaper. For example, I get G for F# setting.

                                Can you give me some guidance when using your program here? I want
                                to use it for an A that I am working on. I want to use 3/4 bore and
                                9/32 by 5/16. I use the woodlands style with the air channel in the
                                flute.

                                Thank you.
                                --- In nativeflutewoodworking@yahoogroups.com, "Edward Kort"
                                <edkort@c...> wrote:
                                > I've never had overblow problems with the top hole. But I want to
                                > interject a note of caution in ascribing all such problems, as Don
                                > points out, to aspect ratio.
                                >
                                > Lew Price, whose books are filled with a wealth of information on
                                > crafting flutes, discusses two aspect ratios. The first is the one
                                > that everyone in this thread has used, length/bore, with
                                an "optimum"
                                > value of 18:1. A second is length/(bore*bore), with an optimum
                                value
                                > of 24:1.
                                >
                                > I have been using the second ratio for a while, with IMHO good
                                > results. You must pay a little closer attention to overblowing
                                > issues, but the fundamental tone has much richer harmonics.
                                >
                                > If my experience is any judge, I depart considerably from the 18:1
                                > ratio. Below is a table of length/bore ratios for flutes I have
                                > crafted to a length/(bore*bore) ratio of 24:1. This is for the way
                                I
                                > craft the sound mechanism, and uses Clint Goss's key
                                categorization.
                                >
                                > Key
                                > tenor A 17.5:1
                                > tenor F# 19:1
                                > tenor D 22:1
                                > baritone G 27:1
                                > baritone E 29:1
                                >
                                > In the "normal" range for flutes, there is not too much difference
                                > between the two ratios, but I don't think that there is any magic
                                in
                                > the 18:1 ratio.
                                >
                                > Just my opinion, but I hope it frees you up from thinking about a
                                > strict aspect ratio. Experiment and listen to the sound. Many
                                things
                                > can cause overblowing.
                                >
                                > Edward
                                >
                                >
                                > --- In nativeflutewoodworking@yahoogroups.com, "rjrobisonga"
                                > <rjrobisonga@y...> wrote:
                                > > Ed,
                                > >
                                > > What if it is the first hole from tsh that overblows? Is this
                                the
                                > > bore to len ratio causing the problem? I am curious to know.
                                I've
                                > > recently had alot of this issue. When I shorten the len and re
                                > tune
                                > > to new fundamental, I can correct the problem.
                                > >
                                > > Be well.
                              • Edward Kort
                                Hi, ... Those numbers check out. By either of the aspect ratios I discussed in the previous message, a G is a bit long but will probably work OK. I make A
                                Message 15 of 16 , Jun 3, 2004
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                                  Hi,

                                  > I have found that my flutes
                                  > made with 3/4" bore, 9/32 by 5/16 tsh, and 15" sound chamber gives
                                  > me a G for the fundamental.

                                  Those numbers check out. By either of the aspect ratios I discussed
                                  in the previous message, a G is a bit long but will probably work OK.
                                  I make A flutes in 3/4" bore.

                                  > I think that the hole placement is critical for me. If I place
                                  > the last hole (nearest tsh) too high, I
                                  > get an overblow because the hole is too big (because of the hole
                                  > placement). If I move it down (which is too late or I could plug
                                  > with wood or stone), the overblow is fixed. So, when I use your
                                  > program, I am not getting the fundamental. It is usually a half
                                  > step shaper. For example, I get G for F# setting.

                                  I'm a bit confused here. For a given pitch, the higher (closer to the
                                  TSH) you move a hole, the smaller you need to make it.

                                  If the top hole (the f hole) is too close to the TSH, based on your
                                  TSH/bird geometry, you get nodal interference - you can't play the
                                  note. But it looks like you have plenty of headroom; shouldn't be a
                                  problem.

                                  I have made a few flutes where it looks like NAFlutomat puts the top
                                  hole (the f hole) a bit high - at most 1/8", but not a semitone.

                                  I have a couple of cautions:
                                  1. If you use a lathe to shape the outside of the flute, take O.D.
                                  (outer diameter) measurements at each finger hole. Use these values
                                  (and a presumably constant I.D.) to calculate the wall thickness.
                                  2. My experience, using careful measurements, is that the calculated
                                  hole diameters match actual within a couple of hundredths of an inch.
                                  Nonetheless, I still drill the holes substantially undersize and ream
                                  them in the tuning process.


                                  > Can you give me some guidance when using your program here? I want
                                  > to use it for an A that I am working on. I want to use 3/4 bore
                                  > and 9/32 by 5/16. I use the woodlands style with the air
                                  > channel in the flute.

                                  As I mentioned above, the A flute should work just fine. If you want
                                  to send me the NAFlutomat parameters, using the latest program
                                  version, my email is at the end of the program docs.

                                  Good luck,
                                  Edward
                                • Bob Aldea
                                  I implemented Ed Kort s suggestion because it was the easiest to do without inlaying a piece of wood and recutting the flue. As I expanded the chamfer on the
                                  Message 16 of 16 , Jun 3, 2004
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                                    I implemented Ed Kort's suggestion because it was the easiest to do
                                    without inlaying a piece of wood and recutting the flue. As I
                                    expanded the chamfer on the back of the TSH and filed it to a radius
                                    the fundamental became more stable with each step. I quit with a
                                    radius of about 1/32", or maybe a little more.

                                    Ears on the bird still help, but the big lesson was how much that
                                    edge could be rounded without the tone getting fuzzy. For now, I'll
                                    continue on to drilling and tuning so that I wind up with another
                                    flute.

                                    Later, I want to try pushing the limit by continuing to round the
                                    edge until the tone deteriorates. I Also need to experiment with the
                                    flue and TSH, but I want to set up a jig for routing the flue instead
                                    of chiseling it out by hand. Last night I made some mandrels so I can
                                    turn the outside on my lathe rather than route it but I may try the
                                    router/pseudo lathe jig also. I have four more blanks for
                                    experimenting before I start on the good wood.

                                    My thanks go to everyone for sharing your knowledge and enthusiasm.

                                    Bob
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