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  1. #1

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    Sailplane - Spoiler or Flaps?? Or Both??

    I have ordered a Big Bird XL with 110" wing span that I will be building this week. This is my first sailplane and will be adding electric motor and possibly, flaps. It's an RES and I would like some opinions about flaps vs spoiler and if it's a good idea to have both. I've flown RC planes for 4 years and Flaps to me are like brakes on a vehicle. So anyone that's want to throw in your opinion will help sure help out a great deal! Thanks...

  2. #2

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    RE: Sailplane - Spoiler or Flaps?? Or Both??

    Flaps are not brakes, but aerodynamic devices that make the wing more efficient and provide extra lift when it is needed, usually at takeoff. What you need to slow a plane down are spoilers. I have been thinking along the same lines for building my next glider, a 200% normal scale Guppy. I would like to install one or two servos in the wing so that when the throttle stick is at the middle the flaps/spoilers are neutral, when I push the throttle forward the Flaps/spoilers come up to act as spoilers and when I pull the stick back the flaps/spoilers will come down as flaps.
    ...

  3. #3

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    RE: Sailplane - Spoiler or Flaps?? Or Both??

    jz,
    Flaps are more useful than spoilers. You can use them to adjust camber and increase lift or use them to brake the aircraft for landing. Just don't add both. It's kind of redundant (to me anyway) Good luck.

    papermache
    Slope Gliding - A Northwest Indiana tradition since 1896

  4. #4

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    RE: Sailplane - Spoiler or Flaps?? Or Both??

    Spoilers:
    If your planning on competing in the RES class, you can only run spoilers and your decision is made for you. Spoilers are used in sailplanes because they can be used to bring you down right now. You can come in a little high on landing and activate the spoilers and lose some altitude in a predictable manner. Spoilers are also very useful for getting you out of situations where you get caught in a boomer that is quickly carrying your glider out of sight (though you could just put your glider into a spin to lose altitude). Spoilers are simple to hinge and do not require re-engineering the trailing edge of that beautiful wing. They get the job done and are usually preferred on rudder/elevator ships for controlling decent. I say spoilers.


    Flaps:
    Flaps would serve you better if your ship was equipped with ailerons as you could set it up for "crow" on landing (flaps down, both ailerons up) to steepen your descent and limit your landing speed. Flaps can also be used to adjust the airfoil camber when you are soaring to achieve maximum performance (something that cannot be done with spoilers).

  5. #5
    skubacb's Avatar
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    RE: Sailplane - Spoiler or Flaps?? Or Both??

    "Flaps are not brakes, but aerodynamic devices that make the wing more efficient and provide extra lift when it is needed, usually at takeoff."
    True as far as it goes but not the whole thing. Flaps add lift up to about 17%. Any more than that and they add more drag than lift. Flew F-4s in the Air Force and you would never use full flaps for take-off. Too much drag. Also, when you hear all that noise prior to landing in an airliner it is because they are using the flaps to slow the aircraft down.

    BTW flap use at landing is used more often than for take-off with any number of planes.

    Some people set the sailplane flaps to come down to 90 degrees. This adds a considerable amount of drag and allows for spot landings.
    Cheers,
    Craig


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