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Re: [SCA-Archery] Fletching by the numbers

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  • William Arwemakere
    I recently learned that yes, an arrow will have some rotation imperted on it based on your release. I will be doing some hight speed video as soon as I get the
    Message 1 of 9 , Mar 4, 2010
      I recently learned that yes, an arrow will have some rotation imperted on it based on your release. I will be doing some hight speed video as soon as I get the new camera.
       
      At the velocities our arrows are generally doing (more importantly the angular, or rotational velocity) the gyroscopic stabilization is a minor factor. One important job that fletching does is to help dampen the vibrations (oscillations) in the shaft.
       
       
      In years past I have shot two and four-fletched arrows. Four fletch is nice because you get two effective sets of arrows; they will group differently depending on which way you shoot them (flipping them 180deg on the string). Two fletch were essential for shooting twin arrows in the speed ends of a RR. Many people have tried two arrows at once for the first shot, but I was shooting "twins" on every shot.
       
      William

      On Thu, Mar 4, 2010 at 12:28 PM, G P <gonfannon@...> wrote:
       

      I had always believed that rotation was due to the angles of the
      feathers, too, but I seem to recall coming across something recently
      (I wish I could remember what!) that said that the arrow will rotate
      all on its own, even without feathers; feathers are only there to
      stabilize wobble (like the tail-end of a weather vane--catch the wind
      in order to always be at the back). Is this true?

      Geirr



      On Thu, Mar 4, 2010 at 3:23 PM, Carolus <eulenhorst@...> wrote:
      > This is almost correct.  Drag is controlled by the number, size, shape,
      > and composition of the fletching and is a very complex formula.
      > Rotation is controlled by the angle of the fletching to the shaft.  the
      > amount of rotation will be the same regardless of the number of fletches
      > provided.  The confusion arises because the spin stabilization of the
      > arrow is determined by revolutions per time and, with increased drag,
      > thee time to target is increased thus giving more turns to target with
      > the slower arrow.  Increasing the rate of spin also increases drag.  It
      > would be possible for me to change the aerodynamics of the fletching to
      > reduce inherent drag while increasing spin (and spin induced drag) thus
      > maintaining speed while increasing spin stabilization if necessary.  The
      > biggest problem with this fletching would be contact with either the bow
      > or the rest (shelf, hand, etc).  This will be of minimal effect on a
      > longbow with the fletching parallel to the ground as archer's paradox
      > will serve to greatly mitigate it.  Similar fletching was used on
      > crossbows using stiff parchment.
      > Carolus
      >
      > Dan Scheid wrote:
      >> I have seen 2,3,4 fletch the point of the fletch is to stabilize the
      >> arrow. the more fletch incress rotation at the cost of drag. so 2 flech
      >> will rotate less but should fly longer.
      >> Damales
      >>
      >> G P wrote:
      >>
      >>> All of my experiences to date with arrows have three feathers. But I
      >>> was watching a video recently about making primitive bows and arrows
      >>> with simple tools and techniques, and the arrow produced in the video
      >>> used a slit-arrow technique to insert a single piece of thin birchbark
      >>> to stick out on two sides where feathers would be, then re-bind the
      >>> wood behind it.
      >>>
      >>> What effects would having two feathers instead of three have?
      >>>
      >>> Geirr
      >>>
      >>>
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    • Carolus
      Yes, an arrow without fletching will develop a clockwise rotation on its own due to torque. Once fletching is added, however, this force is overcome by the
      Message 2 of 9 , Mar 4, 2010
        Yes, an arrow without fletching will develop a clockwise rotation on its
        own due to torque. Once fletching is added, however, this force is
        overcome by the rotational or stabilizing effects from the fletching.
        When tuning a bow a bare shaft should be used. Search the web for "bare
        shaft tuning" for instructions. Using wooden shafts this can be really
        tough and do not expect to get results as perfect as described. Prepare
        your arrows as normal with balance and spine properly configured. Then
        build another arrow identical with the exception that there is no
        fletching. Use this arrow to tune the bow.
        Carolus

        G P wrote:
        > I had always believed that rotation was due to the angles of the
        > feathers, too, but I seem to recall coming across something recently
        > (I wish I could remember what!) that said that the arrow will rotate
        > all on its own, even without feathers; feathers are only there to
        > stabilize wobble (like the tail-end of a weather vane--catch the wind
        > in order to always be at the back). Is this true?
        >
        > Geirr
        >
        >
      • Edward deWitt
        Carolus, You said the bare shaft will rotate clockwise.  Is this just from a right hand bow or will a left hand one do the same?  If they both rotate the
        Message 3 of 9 , Mar 4, 2010
          Carolus, You said the bare shaft will rotate clockwise.  Is this just from a right hand bow or will a left hand one do the same?  If they both rotate the same way, could this be like toilets spinning the same way above the equator and opposite , below?

          --- On Thu, 3/4/10, Carolus <eulenhorst@...> wrote:

          From: Carolus <eulenhorst@...>
          Subject: Re: [SCA-Archery] Fletching by the numbers
          To: SCA-Archery@yahoogroups.com
          Date: Thursday, March 4, 2010, 4:03 PM

           

          Yes, an arrow without fletching will develop a clockwise rotation on its
          own due to torque. Once fletching is added, however, this force is
          overcome by the rotational or stabilizing effects from the fletching.
          When tuning a bow a bare shaft should be used. Search the web for "bare
          shaft tuning" for instructions. Using wooden shafts this can be really
          tough and do not expect to get results as perfect as described. Prepare
          your arrows as normal with balance and spine properly configured. Then
          build another arrow identical with the exception that there is no
          fletching. Use this arrow to tune the bow.
          Carolus

          G P wrote:
          > I had always believed that rotation was due to the angles of the
          > feathers, too, but I seem to recall coming across something recently
          > (I wish I could remember what!) that said that the arrow will rotate
          > all on its own, even without feathers; feathers are only there to
          > stabilize wobble (like the tail-end of a weather vane--catch the wind
          > in order to always be at the back). Is this true?
          >
          > Geirr
          >
          >


        • Carolus
          it is a factor of torque and is not related to the handedness of the bow. To remember torque effects use the right hand rule. Curl the fingers of your right
          Message 4 of 9 , Mar 4, 2010
            it is a factor of torque and is not related to the handedness of the
            bow. To remember torque effects use the right hand rule. Curl the
            fingers of your right hand and extend your thumb. The thumb points the
            direction of travel and the fingers the rotation. This applies to the
            lateral forces generated by rotational torque as well. If you were to
            remove the lug nuts from a tire and move the car forward, the left side
            wheels will want to pull away from the car but the right side wheels
            will be held in place. Remember the rotational effect imparted to an
            object moving in a straight line is very slight and is easily overcome.
            It really doesn't give any stabilization to an arrow but it is
            detectable. One of the best places to see this effect is in the old
            films of the Apollo moon shot launches. The black and white paint was
            so the rotation of the Saturn V could be tracked. That rotation was not
            induced by intent but by rotational torque induced by the movement of
            the rocket itself.
            Carolus

            Edward deWitt wrote:
            >
            >
            > Carolus, You said the bare shaft will rotate clockwise. Is this just
            > from a right hand bow or will a left hand one do the same? If they
            > both rotate the same way, could this be like toilets spinning the same
            > way above the equator and opposite , below?
            >
            > --- On *Thu, 3/4/10, Carolus /<eulenhorst@...>/* wrote:
            >
            >
            > From: Carolus <eulenhorst@...>
            > Subject: Re: [SCA-Archery] Fletching by the numbers
            > To: SCA-Archery@yahoogroups.com
            > Date: Thursday, March 4, 2010, 4:03 PM
            >
            >
            >
            > Yes, an arrow without fletching will develop a clockwise rotation
            > on its
            > own due to torque. Once fletching is added, however, this force is
            > overcome by the rotational or stabilizing effects from the fletching.
            > When tuning a bow a bare shaft should be used. Search the web for
            > "bare
            > shaft tuning" for instructions. Using wooden shafts this can be
            > really
            > tough and do not expect to get results as perfect as described.
            > Prepare
            > your arrows as normal with balance and spine properly configured.
            > Then
            > build another arrow identical with the exception that there is no
            > fletching. Use this arrow to tune the bow.
            > Carolus
            >
            > G P wrote:
            > > I had always believed that rotation was due to the angles of the
            > > feathers, too, but I seem to recall coming across something recently
            > > (I wish I could remember what!) that said that the arrow will rotate
            > > all on its own, even without feathers; feathers are only there to
            > > stabilize wobble (like the tail-end of a weather vane--catch the
            > wind
            > > in order to always be at the back). Is this true?
            > >
            > > Geirr
            > >
            > >
            >
            >
            >
            >
            >
            > ------------------------------------------------------------------------
            >
            >
            > No virus found in this incoming message.
            > Checked by AVG - www.avg.com
            > Version: 9.0.733 / Virus Database: 271.1.1/2721 - Release Date: 03/03/10 11:34:00
            >
            >
          • Geirr pík
            (Small side note: That s not actually true. http://www.snopes.com/science/coriolis.asp) Geirr
            Message 5 of 9 , Mar 4, 2010
              (Small side note: That's not actually true.
              http://www.snopes.com/science/coriolis.asp)

              Geirr


              On Thu, Mar 4, 2010 at 7:31 PM, Edward deWitt <sagebowman@...> wrote:
              >
              > Carolus, You said the bare shaft will rotate clockwise.  Is this just from a right hand bow or will a left hand one do the same?  If they both rotate the same way, could this be like toilets spinning the same way above the equator and opposite , below?
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