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vortex generators

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  • Robert
    Hi all .we have just moved our dragonfly to the airport for testing and at the moment just running up the aeropower engine and all is good . Today our vortex
    Message 1 of 5 , Nov 1, 2012
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      Hi all .we have just moved our dragonfly to the airport for testing and at the moment just running up the aeropower engine and all is good . Today our vortex generators arrived so we would love to hear from anyone in dragonfly land that has these installed and if there was a major difference in performance .We intend to test fly without these installed and see if we really need to use them .we have the mark 11 canard and would mainly be looking to decrease the stall speed .not sure if we need to put them on the wing as well .looking forward to your comments cheers Rob from oz
    • Miguel Chabolla
      Robert, The two areas of interest to me with regard to VGs are pitch trim and contaminated canard performance. I purchased N189SM, a MK II, with VGs already
      Message 2 of 5 , Nov 1, 2012
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        Robert,

        The two areas of interest to me with regard to VGs are pitch trim and contaminated canard performance.
        I purchased N189SM, a MK II, with VGs already installed at about 1/3 chord on the canard and flew it in that configuration for six years. VGs were then removed to refinish the top surface of the canard and I flew it without them for several months.
        Without VGs, it was difficult to adequately trim the pitch when the CG was toward the limits. With aft CG I would trim full forward and still had to hold constant forward pressure on the stick. Also, encounters with the lightest rain would brought about a considerable loss of canard lift and down pitch that was controllable, but it did get my attention. And, dont even think of taking off with a wet wing, you will likely enter PIO as soon as you become airborne and are likely to impact the ground. At least that was my experience.

        I installed new VGs with their leading edge at 1/2 canard chord, each pair spaced at 4".  Trim is working fine and a contaminated canard surface only brings a very slight down pitch, almost unnoticeable.


        I hope this helps you decide how to configure your DF. If you have any questions for me I will be happy to tell you what I know.

        Miguel




        >________________________________
        > From: Robert <resmart@...>
        >To: Dragonflylist@yahoogroups.com
        >Sent: Thursday, November 1, 2012 4:27 AM
        >Subject: [Dragonflylist] vortex generators
        >
        >Hi all .we have just moved our dragonfly to the airport for testing and at the moment just running up the aeropower engine and all is good . Today our vortex generators arrived  so we would love to hear from anyone in dragonfly land that has these installed  and if there was a major difference in performance .We intend to test fly without these installed and see if we really need to use them .we have the mark 11 canard and would mainly be looking to decrease the stall speed .not sure if we need to put them on the wing as well .looking forward to your comments  cheers Rob from oz 
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        >Yahoo! Groups Links
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      • Charlie Johnson
        Rob, There are two main wing configurations for vg s. Most applications are for STOL on bush planes, with the vg s applied within 30% of the leading edge. This
        Message 3 of 5 , Nov 1, 2012
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          Rob,

          There are two main wing configurations for vg's. Most applications are for STOL on bush planes, with the vg's applied within 30% of the leading edge. This decreases the stall speed on a conventional airfoil.

          The GU airfoil is a laminar flow airfoil it has to produce lift beyond 30% of chord. The vg's are not used to decrease stall speed but are used to prevent loss of lift due to the laminar flow breaking down with contamination. They will not make a difference except in the rain or contaminated with bugs. That is the only time you really need them. Of course when you need them you cannot put them on then so putting them on before you need them is the wise thing to do. The rear wing does not need them it is a conventional airfoil and does not have laminar flow breakdown issues.

          Regards,

          Charlie Johnson
          Flying Phase I testing Dragonfly/Corvair Mk-II



          Sent from my iPad

          On Nov 1, 2012, at 5:27 AM, "Robert" <resmart@...> wrote:

          > Hi all .we have just moved our dragonfly to the airport for testing and at the moment just running up the aeropower engine and all is good . Today our vortex generators arrived so we would love to hear from anyone in dragonfly land that has these installed and if there was a major difference in performance .We intend to test fly without these installed and see if we really need to use them .we have the mark 11 canard and would mainly be looking to decrease the stall speed .not sure if we need to put them on the wing as well .looking forward to your comments cheers Rob from oz
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          > Yahoo! Groups Links
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        • dkeats
          I flew for a few years before I installed the CCI vortex generators. I almost had to learn to fly all over again. Before, the wing would always fly a long
          Message 4 of 5 , Nov 1, 2012
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            I flew for a few years before I installed the CCI vortex generators. I
            almost had to learn to fly all over again. Before, the wing would always
            fly a long time before the canard and now the canard will fly just after the
            wing lifts if you let it. In rain, there is only a slight back pressure to
            maintain level flight. Without the VGs, in rain, the airplane would need a
            lot of back elevator and would not fly slower than 110 mph. I would highly
            recommend using the VGs from the start. There is also somewhere that
            Nathon Rambo explains the placement of the VGs. That is what I followed. I
            made a template out of stiff paper with slots cut to the proper angle,
            that would allow me to clear silicon about twenty at a time in place. Took
            a couple hrs and a few bucks , but no regrets.--------- Canada Chris



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          • G & S Wood
            Hi Rob, The purpose of turbulators on the Dragonfly is to get over a problem with the section used on the canard whereby it loses lift when it gets rain or
            Message 5 of 5 , Nov 1, 2012
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              Hi Rob,



              The purpose of turbulators on the Dragonfly is to get over a problem with
              the section used on the canard whereby it loses lift when it gets rain or
              bugs on it. This objective is quite different to putting turbulators on a
              Cub or similar, where it is to reduce stalling speed.



              So convinced was I by the evidence from other people about the positive
              effects of putting turbulators on the Dragonfly canard that I have never
              flown without them. My aircraft does not show any significant difference in
              handling with light rain or with bugs, so I'm pleased to have them. On my
              Dragonfly I followed the recommended procedure of putting them at half the
              chord, 4" spacing, 15 degrees to the airflow.



              BTW, your Dragonfly should fly quite OK without turbulators when it's clean,
              which I'm sure it will be when it's being test flown round the field. The
              need comes when you fly away from home into unpredictable conditions.



              In my opinion you should NOT put turbulators on the wing. There is no
              background on this and you would be an instant volunteer test pilot.



              If you Google GU- 25 and Eppler 1212 you'll find lots of useful discussion,
              some of it pretty knowledgeable.



              All the best,



              Geoff (also) in Oz



              _____

              From: Dragonflylist@yahoogroups.com [mailto:Dragonflylist@yahoogroups.com]
              On Behalf Of Robert
              Sent: Thursday, November 01, 2012 9:57 PM
              To: Dragonflylist@yahoogroups.com
              Subject: [Dragonflylist] vortex generators





              Hi all .we have just moved our dragonfly to the airport for testing and at
              the moment just running up the aeropower engine and all is good . Today our
              vortex generators arrived so we would love to hear from anyone in dragonfly
              land that has these installed and if there was a major difference in
              performance .We intend to test fly without these installed and see if we
              really need to use them .we have the mark 11 canard and would mainly be
              looking to decrease the stall speed .not sure if we need to put them on the
              wing as well .looking forward to your comments cheers Rob from oz





              [Non-text portions of this message have been removed]
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