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Thread: Inter-rib sag reduction

  1. #11

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    Quote Originally Posted by Sam Buchanan View Post

    The leading edge is attached to the spar and ribs with pulled rivets. I also added aluminum angle to the trailing edge of the sheeting to prevent the fabric from deforming the sheeting:
    Wow that looks great thank you, the angle aluminum reminds me of like.. a stiffened skin structure or something! Did you use rivets to attach the angle aluminum to the skin also?

    Quote Originally Posted by rwanttaja View Post
    Shouldn't need many rivets. I'll leave it to guys like Frank and Joe to give a more-knowledgeable assessment, but it sounds good to me.

    Standard practice on the Fly Baby is to install ~0.025" gutter flashing across the front of all the wing, horizontal stabilizer, and fin. For more of an antique look, Kurt Gruber left it off the vertical tail:

    Oh perfect that doesn't sound too difficult, thank you, and may I ask, is the aluminum sheeting hard to bend by hand? The wing we are trying to make has a different shape at every rib, we are actually trying to make a crude approximation of Albion Bower's Bell Shaped Distribution Wing, if we are able to.

    Oh, I have a picture of the wing shape we are aiming for, it isn't finished yet but should look something like this:


    Thanks for all the help, wow there are a lot of experienced folks here.. I will definitely have a lot more questions once we have started our build if you all wouldn't mind entertaining them!

    Thanks very much
    Last edited by timi; 11-27-2018 at 06:28 PM.

  2. #12
    Sam Buchanan's Avatar
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    Wow....that will be a very complex wing to build.......forget the photos I posted, you are going to be in much taller weeds.......
    Sam Buchanan
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  3. #13
    George Sychrovsky's Avatar
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    Yeah , Looks like we got suckered into believing he had the wing to cover.
    Last edited by George Sychrovsky; 11-28-2018 at 11:24 AM.
    Disclaimer ; opinions of others will vary depending on what they’re selling.

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  4. #14

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    Quote Originally Posted by Sam Buchanan View Post
    Wow....that will be a very complex wing to build.......forget the photos I posted, you are going to be in much taller weeds.......
    I'm definitely concerned that it will be beyond our ability to manufacture, each wing should have a total of 20 sections. I wasn't able to achieve a nice bell-shaped lifting distribution without some pretty wild variations in twist.. hopefully we will be able to come close and I'm not in too far over my head.
    Last edited by timi; 11-27-2018 at 10:10 PM.

  5. #15
    Dana's Avatar
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    What kind of aircraft are you trying to build? That sort of shape is more suited to composites than aluminum tube and fabric construction. And it will likely have some rather unfriendly stall characteristics.

  6. #16

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    Quote Originally Posted by Dana View Post
    What kind of aircraft are you trying to build? That sort of shape is more suited to composites than aluminum tube and fabric construction. And it will likely have some rather unfriendly stall characteristics.
    Just a small ultralight with a bell spanload wing. It's my understanding that a bell spanload wing is supposed to have a nice stall beginning around 20 percent of the span from the root, and even with those skinny old tips I think it shouldn't be tipstalling weirdly. I also hope to give the structure a pretty big safety factor.

    I definitely understand that composite material would be much better for this kind of structure, but I have help on the project from someone who has a lot of metal fabrication experience and tools, relative to me at least. I hope I'm not too off base.

  7. #17
    cwilliamrose's Avatar
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    If you use the angles to stiffen the aft edge of the leading edge skin as Sam shows in post #6 think about making the skins a little oversized so you have maybe 3/4" extra material along the aft edges. That extra material could then be bent 90° to create the angle without needing any fasteners or suffering the extra weight from additional parts. Once the angles are bent you would only need to provide relief for the ribs. Or you could cut the reliefs first and bend the angles one at a time instead of all at once which would eliminate the need for a large brake.

  8. #18
    Sam Buchanan's Avatar
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    Quote Originally Posted by cwilliamrose View Post
    If you use the angles to stiffen the aft edge of the leading edge skin as Sam shows in post #6 think about making the skins a little oversized so you have maybe 3/4" extra material along the aft edges. That extra material could then be bent 90° to create the angle without needing any fasteners or suffering the extra weight from additional parts. Once the angles are bent you would only need to provide relief for the ribs. Or you could cut the reliefs first and bend the angles one at a time instead of all at once which would eliminate the need for a large brake.
    You just explained why I used angles instead of modifying the leading edge.
    Sam Buchanan
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  9. #19
    cwilliamrose's Avatar
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    His wing has two sweep angles so maybe the individual parts won't be real long. If they are doing the bends in small sections is workable with some very simple tooling.

    But I do understand your choice.

  10. #20

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    If that's a cantilever wing it will need more or thicker stressed skin than a strut braced wing.
    A D-cell skin must be riveted to the spar to make a complete D tube.

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