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Bearhawk STOL mods

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  • #61
    Started following this thread. Very interesting. I'd like to put slotted flaps on our BH but haven't figured out how to have a hinge by the cargo door.

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    • #62
      That sounds like a detail I would have discovered right after I installed slotted flaps.

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      • #63
        Regarding AoA flap bias, for simplicity sake, in GA, just set it to stall with flaps full, which will be a lower AoA than with flaps retracted. If you approach the calibrated critical angle of attack while clean, you'll then have a healthy buffer before an actual stall.
        The only thing with the fowlers is you'll have a very large difference in the critical angle of attack vs a plain or slotted. Where it's 2-4 degrees for the latter, the former looks like it could be 5-7 degrees according to the graph from the naval aviators book. 7 degrees is massive(considering an aircraft usually has a longitudinal flight envelope of 0ish to 15ish degrees AoA), and might result in stall warnings at rather high airspeeds. Might be worth contacting the manufacturer of your AoA system to see if flap bias is programmable.... if you have fowlers.
        Last edited by zkelley2; 09-21-2019, 04:44 PM.

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        • Battson
          Battson commented
          Editing a comment
          The Dynon system accounts for this possibility and has had a calibration process dealing with this, for about the last 10 years.

        • zkelley2
          zkelley2 commented
          Editing a comment
          How does it know flap position?

      • #64
        Originally posted by Battson View Post

        Someone is doing this at the moment.

        The design will allow Airframes AK to offer a standard bolt-on solution for Bearhawk aircraft wings, hopefully they do.

        The issue (big unknown) is the pitching moment. Bob has advised that the tail may not be large enough to overcome the increased nose-up pitching forces created by the double slotted flaps. The ultimate solution will be larger tail wings, if gap seals / VGs / greater control deflection don't solve it first.
        Can you share any more info regarding progress on this development?

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        • Battson
          Battson commented
          Editing a comment
          Checking...

      • #65
        Originally posted by Shopperly View Post

        Can you share any more info regarding progress on this development?
        The plane should be finished and delivered in a week from today. Then they'll be doing paint and probably flying within another week.

        98.5" of double slotted fowler flaps. I can hardly wait to hear the reports.

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        • #66
          Originally posted by Battson View Post

          The plane should be finished and delivered in a week from today. Then they'll be doing paint and probably flying within another week.

          98.5" of double slotted fowler flaps. I can hardly wait to hear the reports.
          Where is the airplane? In Alaska? Oregon?

          This is an A model or a B model?

          Does the pilot know how to fly slow well enough to properly evaluate?

          VERY interested in this!

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          • #67
            The Bearhawk being modified is an A model based in Utah. The owner is a retired airline pilot who is very good with the plane. He will give a report that we will learn from. Mark

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            • #68
              Is he installing a true Fowler that actually moves aft or the STOL Performance flap from Airframes Alaska?

              Mark or Jono, If you thinks it’s appropriate I’d appreciate the owners contact info. I’d sure love to go see this plane and get a ride when it’s done. He’s likely only an hour or two flight from me.
              Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.

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              • #69
                Whee, let the guy fly first and evaluate what he is having done to his BH. After that if he is willing - no problem. Mark

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                • #70
                  Originally posted by Mark Goldberg View Post
                  Whee, let the guy fly first and evaluate what he is having done to his BH. After that if he is willing - no problem. Mark
                  Is there an update on this very interesting project?

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                  • #71
                    Mark - do you know whether the builder is prepared to share any of his experiences yet with these Airframes flaps?

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                    • #72
                      I have seen the flaps installed and functioning.
                      They look great and function well with the Bearhawk drive modification, to convert the Bearhawk flap handle through to a cub throw.
                      He has indicated they just bolted straight on, and were easily installed. Of course there are some simple wing skin modifications around the flap pocket too.

                      One opportunity missed, the modifications to the wing pocket have not created the 'ideal' pocket for the first stage of the flaps. The first stage will probably be un-blown. Though this could be improved at a later stage.

                      The aircraft is not flight-ready yet. All builders will understand this, 90% finished and 90% still to be done.
                      It will be interesting to see how they perform.


                      IMG_2163.JPG

                      Yes that is a Bearhawk 4-place, and those flaps are 98.5" long.... They increase the wing area by several square feet when extended, not to mention the camber!!
                      Last edited by Battson; 11-21-2019, 08:46 PM.

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                      • AKKen07
                        AKKen07 commented
                        Editing a comment
                        Pardon my ignorance but can you please explain what you are saying about the first notch not being “blown” due to the pocket being imperfect? Do you mean that the slot won’t get extra airflow at that setting as the lower skin blocks it or something to that effect?

                    • #73
                      I assume (hope?) that we will learn what the "ideal" pocket for the flaps is? Maybe I'll just plan on building for these off the bat? Looking forward to flight test impressions.
                      https://www.youtube.com/user/fastfox23
                      Patrol plans #398

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                      • #74
                        Very interesting. Thanks for posting the pics and information.

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                        • #75
                          This is really interesting news - thanks for updating us!

                          Are these flaps a 3 or 4 hanger design?

                          Can you post some more pictures please?!

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                          • Battson
                            Battson commented
                            Editing a comment
                            Three hangers to match Bearhawk design.
                            They are not my photos to post, I will have to ask about more sharing.
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