Facet Opel

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Topaz, Apr 13, 2006.

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  1. Oct 25, 2018 #341

    Hot Wings

    Hot Wings

    Hot Wings

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    Strictly for visualization purposes:
    ducks 2.jpg

    The one with the canard was used for examining how to package a hybrid and actually has the same CG location as the Briggs powered one. Though they don't look like it they both have the same thrust angle and offset. 30 inch props (x4) compared to one 54" prop. 8 foot wide center section. The long fuselage is just because I want my eye well forward - just a personal want.
     
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  2. Oct 25, 2018 #342

    EzyBuildWing

    EzyBuildWing

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    Why doesn't Scotty just put an electric-motor up front on the nose, with a foldable-prop?
    Batteries behind the seat.
    Very simple structurally.
    Alex Strojnik's laminar wing-construction for his S-2 super-smooth Sailplane as detailed in Sport Aviation March 1983 and January 1990 editions, looks very simple, elegant, inexpensive and easily accomplishable in any garage.
    Main Spar is simple: Just 2024-T3 angle-flanges bonded to a plywood shear-web.
    Plywood ribs are bonded to vertical aluminium-angles which are themselves bonded to the Spar's plywood shear-web.
    Wing-skins are fiberglass segments about 3' wide, "pre-molded" to the exact airfoil shape (over a vertical "form"), and then glued to the ribs.
    No bolts or rivets anywhere!
    And no complicated leading edge. Of course, nowadays, carbon-fiber skins could be used instead of f'glass.
     
  3. Oct 25, 2018 #343

    Victor Bravo

    Victor Bravo

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    Yeah... we need to have a little talk about gluing aluminum to wood, Mr. Strojnik :)

    The Strojnik aircraft layout, low-boom configuration, and using laminar shapes to achieve very good performance has been brought into the "present" very very well by the Janowski J-5 and J-6. I did not know Strojnik or Janowski, but I'm pretty sure Strojnik would be very proud to say the J-5 and J-6 are perfect examples of what he was trying to achieve.
     
  4. Oct 26, 2018 #344

    Sockmonkey

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    I did not know this. It's counter intuitive as I would have assumed the opposite.
    Why does it work that way?
     
  5. Oct 26, 2018 #345

    Hot Wings

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  6. Oct 26, 2018 #346

    Norman

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    Thanks, that saved me some typing. I might add though that jets also develop side forces at the intake lip. That's probably why you don't see jets with the intake on the nose anymore.
     
  7. Oct 26, 2018 #347

    BBerson

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    The pusher prop aft of the CG is stabilizing even when windmilling. I think of the windmilling aft prop as kind of like how a drag chute is stabilizing. Or the badminton birdie with aft drag fins and is extremely stable. https://en.m.wikipedia.org/wiki/Shuttlecock
     
  8. Oct 27, 2018 #348

    rotax618

    rotax618

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    I was fortunate enough to be at Evans Head airfield when Scott Winton was attempting his altitude records many years ago. The first thing the Facet Opel reminded me of was my control line combat flying wing models, which could loop in their own length. When Scott took off the aircraft appeared to oscillate in pitch until he gained control, Scott was a very accomplished pilot.
    I suggest if anyone is contemplating re-designing the Fact Opel that they engineer more longitudinal stability into it or possibly suffer the same consequences with over pitching at speed.
     
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  9. Oct 27, 2018 #349

    Sockmonkey

    Sockmonkey

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    Ohhh, I get it now. Thank you.
    I mistakenly thought the tractor prop would prevent the yaw in the first place rather than exacerbating any yaw that happened.
    This puts my view of pushers in a new light.
     
  10. Oct 27, 2018 #350

    lr27

    lr27

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    In his books, Strojnik makes gluing to aluminum sound pretty scary, but it's probably better to glue wood on it than another piece of aluminum. I'm not sure it's something I'd want to try. It would be nice if you could get aluminum with a thin layer of something already reliably glued to it. A quick stroll through the internet indicates a lot of work going on about bonding aluminum. So it's possible they've come up with something better since Strojnik. I wonder if a gazillion fasteners could do the job without too much of a weight penalty? Of course, there's always "black aluminum" (hides under desk). ;-)
     
  11. Oct 27, 2018 #351

    Vigilant1

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    That real estate on the nose is too important to be used for jet intakes--it is needed now for the radar.
     
    Last edited: Oct 27, 2018
  12. Oct 27, 2018 #352

    Sockmonkey

    Sockmonkey

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    In light of what I've just learned, an electric pusher plank with the motor on a slight fuselage extension could exploit that stabilizing effect pretty well and be easier to balance by sticking the heavy battery pack in the nose so the variable pilot weight can be closer to the COL/CG.
     
  13. Oct 28, 2018 #353

    EzyBuildWing

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    Alex Strojnik's wing-skins construction might be applicable to the Plank. Carbon-fiber could be substituted for fiber-glass :
    ...put a layer of epoxy on a mirror-smooth Plexiglass surface and cover it with a first-layer of fiber glass. Just before the first-layer matrix has cured, the second and third layer follow. Before the last 2 layers have cured, all 3 layers are lifted from the Plexiglass and draped over a small, upright precisely made positive airfoil "mold" and pressed against it. After fully curing, an accurate and light "skin" with a mirror-smooth outer-surface is lifted off the mold. ....the nose-ribs are installed(are glued) inside the skins BEFORE the skins go(are glued) onto the wing.
     
  14. Oct 28, 2018 #354

    rotax618

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    From what I understood, Strojnik layed the glass on mylar sheets and before they cured hung the sheets up by two opposite edges, producing the airfoil shape.
     
  15. Oct 28, 2018 #355

    lr27

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    The sheets, with weighted edges, were placed over a male form that was airfoil shaped.

    a10285617-242-StrojnikIllustration01.png
     
  16. Oct 28, 2018 #356

    rotax618

    rotax618

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    I stand corrected, the method I described was used, not by Strojnik, but I can’t remember where I read it.
     
  17. Oct 28, 2018 #357

    lr27

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    I meant the fiberglass sheets, partially cured, if that wasn't clear.
     
  18. Oct 29, 2018 #358

    Victor Bravo

    Victor Bravo

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    All that stretching and mylar and weights and clamps is antique ideas now... it has all been rendered obsolete.

    Today they would hot wire the wing shape out of foam, cover it in several layers of composite, lay mylar sheets onto the outside of the composite, then pack the assembly back into the foam "beds" that the cores were cut from, put the whole thing into a large vacuum bag, weight it down with a thousand pounds of sandbags, and pull vacuum on it until it is cured.

    And that's the simple "solid core" version instead of the "sandwich" version.
     
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  19. Oct 29, 2018 #359

    jedi

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    VB. Good start but you missed the part where one more wire cut will remove much of the solid core and save a bunch of weight. Then you could slice the removed core and bond the ribs back in with or without a cap strip.

    An alternative that works quite well is to lay up the foam and skin on a flat work table then bend as in post #355 for a light LE sheet of a ribbed D Tube spar. A really light weight construction would combine the two systems with a little more work.

    If anyone wants more details, contact me.
     

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