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Re: Goat airfoil coords for comparation with CD, Floater etc.

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  • Jirka
    Hi Phil and Robin, sure, I know that main problem is parasite dragfrom pilot, wires, struts and so - am thinking to build composite D-tube with folding ribs
    Message 1 of 18 , Jun 30, 2010
      Hi Phil and Robin,

      sure, I know that main problem is parasite dragfrom pilot, wires, struts and so - am thinking to build composite D-tube with folding ribs (like on rigids) with simple wing strut and simple shield like on Monarch (smaller) - shield should be removable.

      Regards,
      Jiri

      - In Airchairgroup@yahoogroups.com, "Phils" <philsconcepts@...> wrote:
      >
      > A light weight lexan sheet cut into a butterfly type shape and laced togather at the top to provide a clear canopy that surounds the nose cone and pilot "might" work.
      > But man, would it get ever hot in side it. Winter wouldn't be so bad though.
      > Not worried I have engine to over come drag . An "anti drag motor ...? LOL
      >
      >
      > --- In Airchairgroup@yahoogroups.com, Robin Hilliard <robin@> wrote:
      > >
      > > On 01/07/2010, at 1:48 AM, Jirka wrote:
      > >
      > > > when am looking for any other airfoil than Clark Y, what have to have higher performance, I mean only slightly higher performance to reach L/D of rigid wings - around 20.
      > >
      > > Hi Jirka,
      > >
      > > You should consider that in a design like the AirChair, parasite drag from the exposed pilot, wires etc greatly outweighs induced drag, so an airfoil with improved L/D will make very little difference to the L/D of the overall aircraft. The AirChair (like para gliders) minimises drag by flying at low speeds and gets its usefulness from a low sink rate, which is chiefly a function of low wing loading and not L/D.
      > >
      > > If you want a better L/D you will need to look at the whole aircraft, not just the airfoil.
      > >
      > > Regards,
      > > Robin
    • stearman81n
      If a builder wants to use an under-cambered airfoil, first the rib truss should be designed to hold it s shape, with as light structure as possible. With a
      Message 2 of 18 , Jul 1, 2010
        If a builder wants to use an under-cambered airfoil, first the rib truss should be designed to hold it's shape, with as light structure as possible. With a proper rib jig, any style rib can be mass produced with accuracy.

        The fabric bonding to the lower surface does not have to be a problem. Start with a narrow line of adhesive on the lower rib caps and dope the fabric to each rib cell, keeping the fabric smooth as you go. Once dry, the cells can be lightly shrunk, but not heat calibrated. Top fabric can be applied and lightly shrunk as well at this stage.

        From here, standard rib stitching can be applied through the wing, or merely a loop stitch to bond the lower caps. When stitched, the fabric can be brought up to calibrated tension and the camber will hold it's shape. ...then tape and finish the covering process per normal

        Personally, even on a flat-bottom foil, I would go ahead and rib-stitch just for the added assurance... even though at airchair speeds, there is little likelihood of the fabric 'ballooning' under negative pressure. Unless its a really crappy cover job.

        As far as rib-stitching goes, once you figure it out, you are responsible for perpetuating the rumor that its hard to do.

        Build happy, fly safe....
        rex
      • stearman81n
        I neglected to mention the installation of reinforcing tapes applied over the ribs before stitching. Small (1 ) tabs of reinforcing tape can be used at each
        Message 3 of 18 , Jul 1, 2010
          I neglected to mention the installation of reinforcing tapes applied over the ribs before stitching. Small (1") tabs of reinforcing tape can be used at each stitch in lieu of a large strip... might save a few ounces.

          rex

          --- In Airchairgroup@yahoogroups.com, "stearman81n" <rexnstudio@...> wrote:
          >
          > If a builder wants to use an under-cambered airfoil, first the rib truss should be designed to hold it's shape, with as light structure as possible. With a proper rib jig, any style rib can be mass produced with accuracy.
          >
          > The fabric bonding to the lower surface does not have to be a problem. Start with a narrow line of adhesive on the lower rib caps and dope the fabric to each rib cell, keeping the fabric smooth as you go. Once dry, the cells can be lightly shrunk, but not heat calibrated. Top fabric can be applied and lightly shrunk as well at this stage.
          >
          > From here, standard rib stitching can be applied through the wing, or merely a loop stitch to bond the lower caps. When stitched, the fabric can be brought up to calibrated tension and the camber will hold it's shape. ...then tape and finish the covering process per normal
          >
          > Personally, even on a flat-bottom foil, I would go ahead and rib-stitch just for the added assurance... even though at airchair speeds, there is little likelihood of the fabric 'ballooning' under negative pressure. Unless its a really crappy cover job.
          >
          > As far as rib-stitching goes, once you figure it out, you are responsible for perpetuating the rumor that its hard to do.
          >
          > Build happy, fly safe....
          > rex
          >
        • Paul Dewhurst
          NZ Bantam ultralight uses a simple sock slid on over ribs and not attached to them in any way at all, no batten pockets or battens either. Just spanwise
          Message 4 of 18 , Jul 2, 2010
            NZ Bantam ultralight uses a simple sock slid on over ribs and not attached to them in any way at all, no batten pockets or battens either. Just spanwise tension with ratchet straps holds them taught and in place. I flew one for an airworthiness renewal last week. Up to the Vne of 80 knots it was perfectly fine, just a very very slight billow away from the ribs on the undersurface. Handling very nice.
             
            Paul
             
             
            ----- Original Message -----
            Sent: Thursday, July 01, 2010 6:20 PM
            Subject: [Airchairgroup] Re: Goat airfoil coords for comparation with CD, Floater etc.

             

            I neglected to mention the installation of reinforcing tapes applied over the ribs before stitching. Small (1") tabs of reinforcing tape can be used at each stitch in lieu of a large strip... might save a few ounces.

            rex

            --- In Airchairgroup@yahoogroups.com, "stearman81n" <rexnstudio@...> wrote:
            >
            > If a builder wants to use an under-cambered airfoil, first the rib truss should be designed to hold it's shape, with as light structure as possible. With a proper rib jig, any style rib can be mass produced with accuracy.
            >
            > The fabric bonding to the lower surface does not have to be a problem. Start with a narrow line of adhesive on the lower rib caps and dope the fabric to each rib cell, keeping the fabric smooth as you go. Once dry, the cells can be lightly shrunk, but not heat calibrated. Top fabric can be applied and lightly shrunk as well at this stage.
            >
            > From here, standard rib stitching can be applied through the wing, or merely a loop stitch to bond the lower caps. When stitched, the fabric can be brought up to calibrated tension and the camber will hold it's shape. ...then tape and finish the covering process per normal
            >
            > Personally, even on a flat-bottom foil, I would go ahead and rib-stitch just for the added assurance... even though at airchair speeds, there is little likelihood of the fabric 'ballooning' under negative pressure. Unless its a really crappy cover job.
            >
            > As far as rib-stitching goes, once you figure it out, you are responsible for perpetuating the rumor that its hard to do.
            >
            > Build happy, fly safe....
            > rex
            >

          • charlie
            The Bantum wing profile came from a Jodel D11. This translates to the old reliable naca 230132. This of course was found on a glider in the 30 s regards Chas.
            Message 5 of 18 , Jul 5, 2010
              The Bantum wing profile came from a Jodel D11.
              This translates to the old reliable naca 230132.
              This of course was found on a glider in the 30's
              regards Chas.

              --- In Airchairgroup@yahoogroups.com, "Paul Dewhurst" <paul@...> wrote:
              >
              > NZ Bantam ultralight uses a simple sock slid on over ribs and not attached to them in any way at all, no batten pockets or battens either. Just spanwise tension with ratchet straps holds them taught and in place. I flew one for an airworthiness renewal last week. Up to the Vne of 80 knots it was perfectly fine, just a very very slight billow away from the ribs on the undersurface. Handling very nice.
              >
              > Paul
              >
              >
              > ----- Original Message -----
              > From: stearman81n
              > To: Airchairgroup@yahoogroups.com
              > Sent: Thursday, July 01, 2010 6:20 PM
              > Subject: [Airchairgroup] Re: Goat airfoil coords for comparation with CD, Floater etc.
              >
              >
              >
              > I neglected to mention the installation of reinforcing tapes applied over the ribs before stitching. Small (1") tabs of reinforcing tape can be used at each stitch in lieu of a large strip... might save a few ounces.
              >
              > rex
              >
              > --- In Airchairgroup@yahoogroups.com, "stearman81n" <rexnstudio@> wrote:
              > >
              > > If a builder wants to use an under-cambered airfoil, first the rib truss should be designed to hold it's shape, with as light structure as possible. With a proper rib jig, any style rib can be mass produced with accuracy.
              > >
              > > The fabric bonding to the lower surface does not have to be a problem. Start with a narrow line of adhesive on the lower rib caps and dope the fabric to each rib cell, keeping the fabric smooth as you go. Once dry, the cells can be lightly shrunk, but not heat calibrated. Top fabric can be applied and lightly shrunk as well at this stage.
              > >
              > > From here, standard rib stitching can be applied through the wing, or merely a loop stitch to bond the lower caps. When stitched, the fabric can be brought up to calibrated tension and the camber will hold it's shape. ...then tape and finish the covering process per normal
              > >
              > > Personally, even on a flat-bottom foil, I would go ahead and rib-stitch just for the added assurance... even though at airchair speeds, there is little likelihood of the fabric 'ballooning' under negative pressure. Unless its a really crappy cover job.
              > >
              > > As far as rib-stitching goes, once you figure it out, you are responsible for perpetuating the rumor that its hard to do.
              > >
              > > Build happy, fly safe....
              > > rex
              > >
              >
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