Single Tube Fuselage idea

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by FritzW, Aug 11, 2016.

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  1. Aug 25, 2016 #181

    Victor Bravo

    Victor Bravo

    Victor Bravo

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    Yes indeed Sockmonkey... yes indeed :)
     
  2. Aug 25, 2016 #182

    Sockmonkey

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    Are you shooting for opel or pelican? Either way a monowheel with little outriggers on the rudders should be enough.
     
  3. Aug 25, 2016 #183

    Victor Bravo

    Victor Bravo

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    I was shooting for neither, although the Pelican is closest. The original discussion and challenge was an ultralight with a single tube fuselage. So the very high performance of the Facet Opal is not appropriate.

    The Pelican's performance was closer, however my initial idea was actually the Marske Monarch wing on a bent tube fuselage/seat. I had drawn a sketch of a Marske wing with a reclined seat as a higher performance answer to the GOAT and BUG type "airchair".

    Because the engine is quite a bit easier to install at the very rear, even a light weight engine would create a situation where you no longer require the forward sweep of the Marske layout to balance the aircraft. Being able to use a straight spar brings the Fauvel/Debreyer planform into play.

    Yes, the monowheel with tip outriggers, and/or little skid/wheels on the bottom of the rudders would be the appropriate lightest landing gear.
     
  4. Aug 25, 2016 #184

    Sockmonkey

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    I mean in terms of wing type for stability purposes, rather than speed.
    Sticking the prop in the rear also places it rather high for being so close to the wing, which means it has to fight that pitching movement in addition to being self-stabilizing. Won't that be kind of draggy, or am I missing something?
     
  5. Aug 25, 2016 #185

    Victor Bravo

    Victor Bravo

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    The airfoil would be far far closer to the 14-17% thick Pelican and Fauvel sections than the Facet Opal. This would be a slow speed ultralight type aircraft, and it may just be able to meet Part 103 if that were desirable. Any modern low drag airfoil might be wasted in this application, 35-55 mph cruise speeds, pilot out in the open, etc.

    The entire Pelican experiment by Debreyer was based on the idea that flight on low power and low speed does not reward drag reduction nearly as much as it rewards low "sink rate", low wing loading, and high lift.

    As far as the pitching moment type of stuff, the wing will not have a nose down pitching moment; that is why we use a reflexed airfoil. The nose-down pitch problem comes when you have the engine thrust line way above the aircraft's center of gravity. In this case, angling the thrust line downward is a quick and dirty way to avoid that issue. I have been informed by larger brain cells than mine own that even 6 or 8 degrees of thrust line angle will not appreciably reduce the aircraft performance, while delaying or preventing the "bunt" problems that happen with high thrust lines on gyrocopters and flying wings.

    On this morning's train ride, I figured out an even better way to do the engine mounting and thrust line adjustment, that will simplify this even further.
     
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  6. Aug 25, 2016 #186

    Sockmonkey

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    Okay, I was just concerned that the amount of reflex needed to counter the angled thrust line would be too draggy.
     
  7. Aug 25, 2016 #187

    Victor Bravo

    Victor Bravo

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    Oh heavens no, the thrust line would just be adjusted properly, so the wing didn't have to compensate for that as well as every other compromise on a flying wing..
     
  8. Aug 25, 2016 #188

    Sockmonkey

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    Ah, all is well then. We may go in peace. Will the tapered sections of the wings be removable?
     
  9. Aug 26, 2016 #189

    erkki67

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    I like the layout, but I've concerns about the position of the the main spar center section. On the Pelican, the pilot was or is sitting in front of the main spar carry trough and a bit lower too, with a low center of gravity.
    As this critter is drawn, the main spar would go trough the pilot.
    I would see two solutions, a second main spar running behind the pilot to take the bending load, and second to lower the center section wing and having the outer panels bent up by a few degrees to compensate for the raised center of gravity.
     
  10. Aug 26, 2016 #190

    Aerowerx

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    Too much weight up front.

    You will have to move either the engine or the pilot farther back. Remember a "plank" like this has enough trouble keeping itself stable without having to fight the combined engine/pilot out front. That is why most tailless aircraft are pushers.
     
  11. Aug 26, 2016 #191

    Sockmonkey

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    So noted. I guess I was influence by some of the flying wing deltas I've seen which always seemed a bit nose-heavy to me.
     
  12. Aug 26, 2016 #192

    Victor Bravo

    Victor Bravo

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    Sockmonkey, take the exact same rendering, leave the pilot in the exact same place fore-aft, but lower him 9 or 10 inches, move the engine back to the trailing edge,and put my serpentine 6" aluminum tube in place of the "fuselage" and fairing behind the pilot.... and you will be really close to what I had conjured up.

    Then take the engine and reduce the size down to the 30 pound 23HP Simonini Mini-4 engine ( http://www.simonini-flying.com/index.php?lang=en )

    Haven't decided on whether the outer panels come off, or a two piece wing.
     
    Last edited: Aug 26, 2016
  13. Aug 26, 2016 #193

    Victor Bravo

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    No, the spar in my original sketch is behind the pilot. The seat is bolted directly to the front of the spar with a small angle bracket to compensate for the seat recline angle.
     
  14. Aug 26, 2016 #194

    Victor Bravo

    Victor Bravo

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    Here is the idea for an improved engine mounting, allowing the thrust like to be adjusted more easily.

    FROG improved engine mounting.jpg
     
  15. Aug 26, 2016 #195

    Aerowerx

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    Tailless Aircraft require a higher static margin than typically seen in conventional aircraft, so they may seem nose heavy. There have been crashes because the builders ignore this. This can be hard to do with a plank, but if you sweep the wing you have another degree of freedom to play with. You can get a 0.0 pitching moment and a good static margin.
     
  16. Aug 26, 2016 #196

    Jay Kempf

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    That's just too cute not to build.
     
  17. Aug 26, 2016 #197

    bmcj

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    I see lots of flying planks being proposed, which begs the question: How did we go from a thread titled "Single Tube Fuselage Idea" to a bunch of designs that have no fuselage? :)
     
  18. Aug 27, 2016 #198

    Sockmonkey

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    It's the internet. Anyhow, say you use a fairly thin-walled large diameter tube. Would filling it with that expandable spray-foam be enough to prevent buckling?
     
  19. Aug 27, 2016 #199

    Victor Bravo

    Victor Bravo

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    In my opinion, and speaking only for me, we possibly got there because the concept of a single tube usually induces a shift in thinking toward the minimalist side of the tracks. That may be more my fault than anyone else's so pin the tail on me if you like!

    FWIW, it wouldn't bother me one little bit if this thread got split into "single tube minimalist", and "single tube conventional layout".

    IMHO it would be pretty difficult and counterintuitive if the concept was "single tube but more complex".
     
  20. Aug 27, 2016 #200

    Sockmonkey

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    Actually having you explain it like that helped me get it straight in my head how the down-thrust and levering counter each other. Does this arrangement cause an overall downforce on the plane as a whole as well needing more lift to overcome?
     

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