Slot in wing for pusher prop???

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Aerowerx, Jul 16, 2019.

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  1. Jul 16, 2019 #1

    Aerowerx

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    There are a number of RC tailless planes with a slot in the wing for the pusher prop.

    Other than the likelihood of increased noise from the prop blast hitting the trailing edge of the wing, what would the consequences be of doing this on a full size wing?
     
  2. Jul 16, 2019 #2

    bmcj

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    Any gap in a wing can cause a loss of lift and increase in drag due to flow from the higher pressure lower side to the lower pressure upper side.
     
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  3. Jul 16, 2019 #3

    Steve C

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    Really loud and not very good for prop efficiency. Potentially damaging to the prop as well since it could cause resonance issues.
     
  4. Jul 16, 2019 #4

    pictsidhe

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    Look at how mechanical sirens are made...
     
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  5. Jul 16, 2019 #5

    Aerowerx

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    My reason for asking this is that it would allow the engine to be placed in a more suitable location with respect to the CG. If the engine was placed at the trailing edge of the wing, then you will need a lot of weight towards the front to get the desired CG location.

    Or change the sweep to move the neutral point farther back. But there is a limit to this, as the pilot has to sit in front somewhere, which moves the CG again.

    The ideal situation would be to have the pilot (and passenger, fuel, and luggage) at the empty CG location.

    I read somewhere (Bengelis??) about the minimum spacing between the trailing edge and the pusher prop. Would the same rule apply to the slot dimensions?
     
  6. Jul 16, 2019 #6

    TFF

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    RC planes with the prop in a slot are really loud. Two or three times louder. There use to be a couple of kits out there. Probably gone now. I think Laddie Mikalasco (sp) designed some. Pretty prolific.
     
  7. Jul 16, 2019 #7

    slevair

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  8. Jul 16, 2019 #8

    pictsidhe

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    I think you're doomed to a long propshaft. That fixes the cg problems nicely, but brings new issues to solve. Have you chosen an engine?
     
  9. Jul 16, 2019 #9

    bmcj

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  10. Jul 16, 2019 #10

    plncraze

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    There was a German motor glider with prop running between the vertical and the rudder. The caption for the picture said vibration issues. I can't remember if it was Strojnik or Carmichael (spelling!).
     
  11. Jul 16, 2019 #11

    BBerson

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    Just move the wing lower.
     
  12. Jul 16, 2019 #12

    Aerowerx

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    No.

    This is just a theoretical question.
     
  13. Jul 16, 2019 #13

    Aerowerx

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    Uh, wouldn't that be the same as moving the engine higher? And there are practical limits to moving the wing lower, like running into the ground maybe?o_O

    Then you run into problems with the line of thrust being too high above the CG, and the resulting pitching moment change with thrust.
     
  14. Jul 16, 2019 #14

    Aerowerx

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  15. Jul 16, 2019 #15

    BBerson

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    Not quite the same. There are practical reasons for not putting the engine and prop inside the wing also. Actually, a slightly high thrust line is ideal with no pitch change. Somewhat higher might get a minor pitch change. All low wing airplanes have a high but ideal thrust line because the increased speed with increased power would normally require a trim down change if the thrust line was low like a high wing.
    A low wing doesn't hit the ground with a bit of dihedral.
    The Custer channel wing curves the wing under the props.
     
    Last edited: Jul 16, 2019
  16. Jul 16, 2019 #16

    Aerowerx

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    I was trying to be funny with that comment, BBerson

    The original statement implied keeping the engine fixed and lowering the wing.

    By the way, what happened to all the good ole' emojis we had on the old forum software?
     
  17. Jul 17, 2019 #17

    pictsidhe

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    If the mountain will not come to Mohammed, then Mohammed shall go to the mountain:

    [​IMG]
     
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  18. Jul 17, 2019 #18

    BBerson

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    I knew a guy in Alaska that built a twin boom, single engine, Custer channel wing.
     
  19. Jul 17, 2019 #19

    slevair

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    Just google Archon plane in Greece.
     
  20. Jul 17, 2019 #20

    Aerowerx

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    Ducted fan, not prop-in-slot tailless.
     

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