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Thread: stall device

  1. #1
    Tim's Avatar
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    stall device

    For some reason I just thought about this. On the way home from Hew Holstien this year I stopped for gas I think in Illinois somewhere. There was a guy there with an old Supercub getting gas. He used the plane for banner towing and I was just looking it over. Underneath the trailing edge of the wing was a piece of angle aluminum running the length of the wing. I think it was about 1/4 inch angle. The guy said it lowered his stall speed. I've never seen anything like it before. Anyone ever seen this or know anything about it.
    Tim

  2. #2
    Nathan K. Hammond's Avatar
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    Sometimes called a Gurney Flap; they had REALLY good results with them on race cars. I've heard they can do wonders for an airplane.

    http://www.allamericanracers.com/gurney_flap.html

    nkh

  3. #3

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    Gurney flaps can give about a 10 to 15 percent boost in lift without much of a drag penalty. Typically, they are about 0.75 to 1.5 percent of the chord. For a Cub, I'd expect them to protrude about 5/8 to 3/4 of an inch (1/4 inch sounds skimpy).
    JimC

  4. #4
    KelvinG's Avatar
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    Would anyone have a few pictures showing a typical installation? Would light gauge 3/4" aluminum angle work?

    Thanks
    KelvinG
    "Only a virtuous people are capable of freedom. As nations become corrupt and vicious, they have more need of masters."

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  5. #5

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    Stall Device

    When Cessna certified the stretched Caravan (208B Grand Caravan) they added a gurney strip on the trailing edge of the flap to keep the stall speed down with the new higher gross weight. It is a fairly simple attachment.

  6. #6
    Tim's Avatar
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    I would love to try it, but can't figure how to attach them without screwing up the trailing edge in case I want to take them off.

    Tim

  7. #7
    behindpropellers's Avatar
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    Call 3M I'm sure they have some double stick tape that will work. The only problem...is when you want to take it off. I can show you some velcroe like stuff that will work if you want.

    Tim

  8. #8
    Mikey's Avatar
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    Is the famed 'bird strike deflector' on the trailing edge of the original Citation rudder a double Gurney?

  9. #9
    Tim's Avatar
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    If this was on a supercub, there must be an STC somewhere, Anyone know who has it. That might shed some more light on things.

    Tim

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    >Is the famed 'bird strike deflector' on the trailing edge of the original Citation rudder a double Gurney?<

    No. Gurney's by definition go only on one side ot the trailing edge. As an aside, Gurney's were originally called Wickerbills till Dan Gurney made 'em famous on race cars about 20 or 30 years ago. They've been known for most of a century now.

    I don't think there are any STC's for their installation on a Cub yet. The easiest way to install them is with rivnuts. Cut small individual circular holes in the fabric along the trailing edge that just fit the 'head' of the installed rivnut so that it minimises the protrusion and then mount the Wickerbills on that. The rivnuts aren't noticable when the Wickerbills are removed (particularly if painted to match the fabric), and Wickerbills can be removed and reinstalled in three or four minutes.

    JimC

  11. #11

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    I don't want them falling off. Would sheet metal screws work? Or is there a way to just use a length of Gorilla tape from the top to bottom while trapping a rectangular section to the bottom trailing edge?

    Don't need them looking too obvious either---

    So did anyone find an STC?

  12. #12

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    I would recommend against sheet metal screws. Rivnuts would work.
    JimC

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