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  • PLTemple
    commented on 's reply
    In flight testing my Patrol I had similar results. I did a series of stalls and found it indicated 50mph clean, and around 48mph with any amount of flaps. I was quite surprised at the little difference when extending flaps. So I had another very experienced pilot do the full series of stalls and he found exactly the same thing. The system is a Dynon HDX with the fancy pitot tube with the second hole for AOA. My Patrol is 1200lbs empty and has the O-360.

  • Gerhard Rieger
    replied
    Here are the photos
    You do not have permission to view this gallery.
    This gallery has 3 photos.

    Leave a comment:


  • zkelley2
    commented on 's reply
    I'm not 100%, but I want to say these wingtips are somewhat of a collaboration between Mike and CC.

  • zkelley2
    commented on 's reply
    Randy is using a split mold.

  • Gerhard Rieger
    replied
    This is what I build from my research

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  • Wyo Johnson
    replied
    I asked one of the aero guys I work with about it and he sent me this link: https://aviation.stackexchange.com/q...-wingtips-work

    Its a high level primer but it does a good job of explaining the basics. Basically you are getting more wing area lift with a lesser drag as compared to the standard "hersey bar" wing or with a standard rounded wingtip. The second pic in the article is actually out of the NASA paper that Hoerner documented his testing and findings.

    Was around a Super Cub as a kid that had Hoerners on it...flew into some soup at the edge of an airfield (i was a PAX) and the one thing I noticed is the vortices off the wingtips. They were a small radius and started right at the trailing edge, outboard tip.

    Andy
    1423B Scratch

    Leave a comment:


  • Sir Newton
    commented on 's reply
    Very very... Awesome man

  • Sir Newton
    commented on 's reply
    You have the coolest last name.

  • Bcone1381
    replied
    I hope its ok to share this screen shot from a Q4 2004 The Bearhawk Patrol Newsletter. A 1/8" plywood grid is fabricated over the airfoil block, then filled with foam. The article shows a typical cross sectional shape of round. Change it for the Hoerner to a triangle shape. An afternoon with a table saw, band saw and 12" disc sander would get a lot done on the mold I would think.

    When you cover it with FG cloth, If the cloth is oriented 45 degrees it will follow the shape fo the mold easier.

    Screen Shot 2022-04-15 at 8.00.11 AM.png
    Screen Shot 2022-04-15 at 8.00.22 AM.png

    Leave a comment:


  • Utah-Jay
    replied
    Geez, you guys like messing with stuff, I just want to fly. I will be using Bob’s carbon fiber wing tips.

    Big wings, big engine…. It is gonna land anywhere I want to fish.

    Leave a comment:


  • Pbruce
    replied
    Mike Silvernagel had about four sets of Horner tips made. Some were for sale a couple of years back. I don’t know if he kept any for himself to install on his Patrol, which flew first with factory fibreglass tips. If he has tried the Hoerner tips, would be interesting to hear from him. I imagine a person would have to do quite a bit of testing and use a sharp pencil to fairly document any differences, but I’d love to hear about it.

    I also have factory carbon tips. I would need to see pretty compelling accounts to undertake new tips.

    It could be a fun project though, if one was in the right state of mind to undertake it. I would probably build male molds out of extruded polystyrene like genuine Dow Styrofoam. I would vacuum bag the carbon and then glass onto the molds, and then scoop out the foam after curing. Any stuck bits could be dissolved with acetone. An internal support grid of ribs would be inserted as well, in order to keep the weight of the skins reasonable. I would insure that there was ample thickness of material around the outer perimeter so that a sharp edge could be formed in the finish sanding process. Whew. Lots of work. Lots of mess.

    Or maybe build the whole thing out of previously laid up carbon sheets? The leading edges would have to be formed by hand out of hard foam and then glassed, but the rest would theoretically be all flat or simple curves. I’ll probably just fly what I have though, and spend my attention on honing my technique.

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  • svyolo
    replied
    I have Bob's carbon tips, which are stupid light, but fit about the same as the fiberglass ones. That is how it will fly. I might try Wittman Tailwind tips down the road. I like the concept. I think with a big low aspect ratio wing, better tips will make a difference.

    Leave a comment:


  • Battson
    replied
    I tend to agree with Pbruce, I suspect compromises were made to allow mass-manufacturing, to the detriment of achieving a theoretically perfect Hoerner shape. This is a common compromise in aviation, perhaps one of the most common.

    Wingtip design is a whole profession / science all of it's own. I am not professing to be an expert. I have only completed a few years of university study into aerodynamics, there are surely more qualified people here. I researched the theoretical benefits of Hoerner wingtips (for obvious reasons) before I invested around a hundred hours and $$$$ into making a bespoke pair. I think this link has a fair summary.

    The objectives are increased lift and to a lesser extent, lower induced drag. These are achieved by projecting the vortex out beyond the end of the wing. This increases the effective wingspan, increasing lift, and increases the 'effective' aspect ratio which may reduce induced drag depending on many other variables. Per the pictures in the link above, one can assume a sharp-ended tip is most effective at projecting the wingtip vortex beyond the end of the wing. A rounded tip encourages attached flow to 'roll over' from the lower to upper surface of the wingtip, which brings the vortex closer to the wing, reducing effective wingspan and reducing the effective aspect ratio slightly.

    At least, that's my understanding.

    Leave a comment:


  • Battson
    commented on 's reply
    They actually look a fairly good shape from that angle....
    As you say, without wind tunnel testing or similar, it's hard to know what is really happening.

  • Pbruce
    replied
    Interesting subject. From the image, one can readily see that there is a fairly large radius at the tip, and a “bump”(unused nav light mount maybe?)
    ?) I’m wondering if that radius was a compromise made in the interest of an easier layup and de-molding perhaps? Perhaps the way to get the sharp edge of a Horner tip is to split the mold and so that both the top and bottom plies exit the mold at the tip. Didn’t the late model C-210 have a Horner-type tip with sharp edges? I’m always interested in measurable differences with various mods, any effect on safety margins and handling, and whether they provide cumulative improvements.

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