More of my random designs

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Sockmonkey, Jul 12, 2019.

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  1. Jul 16, 2019 #41

    Sockmonkey

    Sockmonkey

    Sockmonkey

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    Funny thing is, sketchup is actually ideal for creating faceted shapes like that.
    Structurally, a fauxcetmobile could also be made of lots of short bits held together with a latticework of cables inside. All struts would be in pure compression with the cables handling all the tension. When the cables are loosened, and the fuselage allowed to collapse, a full sized plane could fit in a closet.
    [​IMG]
     
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  2. Jul 16, 2019 #42

    pictsidhe

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    The aspect ratio is too low. You'd have to scale it up to get enough span for induced drag not to be an issue, the wing area is then huge. One could be made to fly, but not very well within 103.
     
  3. Jul 16, 2019 #43

    Sockmonkey

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    That's meant to be a head on view of the largest cross-section of a tensegrity fauxetmobile.
     
  4. Jul 16, 2019 #44

    jedi

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    I will try to answer any Sea Era questions.

    Limited damage in stall/spin from 20+ feet was due to good,non typical, seaplane hull design. Aircraft rigging of the Sea Era needs adjustment to correct right wing drop at stall.

    Aerodynamics of the above configuration were developed into a workable design configuration with the incorporation of variable incidence of the flapped Hershey bar forward wing and modifications to the delta aft wing to trigger vortex lift transition at a defined angle of attack to prevent unwanted pitchup at the vortex lift transition.
     
    Last edited: Jul 16, 2019
  5. Jul 16, 2019 #45

    Victor Bravo

    Victor Bravo

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    Actually, upon further thought, it seems like it may be possible to do a 7/8 size ultralight version of what he called a "Smoothmobile", using the riveted aluminum tube method for structure, using the very light/small tube hand-formed "ribs" like the Robert Baslee Nieuport wings do.

    I suspect that the Smoothmobile is a lot more efficient than the original slab version, but Mr. Wainfan would probably know a lot more about that than I would...

    The "wing section" is pretty thick, which means the structural truss could be pretty light. There are lighter engines now than what was used on the original FMX, so perhaps there is weight savings to be found there.

    But I have no clue about whether it could meet the stall speed requirements of part 103, no matter how light it is. A single landing gear, like the Verhees, could save some weight possibly too.

    BW, did you ever look into a slightly smaller ultralight-ish version of this?
     
  6. Jul 16, 2019 #46

    FritzW

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    Cool idea but I'm not seeing the tensegrity part. (the compression members are touching)
     
  7. Jul 16, 2019 #47

    Sockmonkey

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    I suppose it's not "pure" in that sense, but the solid members are all only experiencing compression forces, which is the main advantage of that kind of setup.

    One thing I should point out about my not-a-sea-era-seaplane is that being a species of tandem wing, the fore wing is what's keeping the nose up, so the aft delta doesn't need to sacrifice any lift by being reflexed. That means it's providing more lift for it's area than tailless deltas do.
     
  8. Jul 17, 2019 #48

    mm4440

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    Low AR wings can work really well If they are built light. With a lot of wing area that makes cloth covering most attractive. Milt Hatfield told me that the Arup S-4 had the best LG arrangement, the earlier ones were taildraggers. It had a nose wheel for low drag take off and a tail wheel for landing. The main gear was placed so it would sit happily in either position. I owned an S-2 replica. It was over weight but would be worth redoing a lighter version like the Little Bird. It would be great if Facetmobiles fly again.
     
  9. Jul 17, 2019 #49

    pictsidhe

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    Mr Induced Drag says no ****ing way to less span in a 103 Fauxetmobile. Full size at 103 weight may well stall at 103 speeds, but it will have the drag of a parachute. Some guesstimates suggest ~40hp would be needed to maintain level flight at 24kts and 500lb full size. You are keeping the 503? Don't forget to add a restrictor because 103 Fauxet will want to blow way past 55kts. 7/8 won't meet stall, will glide like a brick and will want to cruise at ~100kts.


    Interesting fact, the Concorde would sink even at full power without stalling if the nose was pulled high enough. It was hardly lacking in thrust...

    Mr Wainfan, I would like to apologise for the all the butchering of the name of your Facetmobile. I think that any Facetmobile-like aircraft not designed by you would be a Fauxetmobile, and lots of other people here simply can't spell.
     
    Last edited: Jul 17, 2019
  10. Jul 17, 2019 #50

    LittleBird

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    Do you have any photos of the S-2 replica? Did you build it? If so, what did you use for plans/drawings? Thank you.
     
  11. Jul 17, 2019 #51

    jedi

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    The straight fore wing and delta aft wing creates a pitch instability issue that needs to be considered.

    The fore wing as a typical two Pi lift slope curve while the aft delta wing has a reduced swept wing lift slope curve. This issue does have possible solutions.
     
  12. Jul 18, 2019 #52

    Sockmonkey

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    So how do I address that issue, while factoring in how the downwash from the fore wing passes over it?
     
  13. Jul 18, 2019 #53

    mm4440

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    It was pre digital and I am not sure if I can find them. It was built from pictures in a Sport Aviation article by a character at the airport I learned to fly at, Sky Manor in NJ. Search ARUP in the Archive and Little Bird.
     
  14. Jul 22, 2019 #54

    jedi

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    First let me clarify one issue. The Sea Era has the delta wing lifting body center of pressure ahead of the straight Hersh bar wing. The CG of the aircraft is located three inches forward of the Straight wing leading edge. That is about negative 5% MAC, very much outside the CG range of normal aircraft. The aircraft is currently being rebuilt and will probably be flight tested with the CG farther aft. It has gained 13 pounds, most of which is in the tail booms. The aircraft has no pitch up tendency at stall (unlike the 737 Max and other aircraft with a broad fuselage area forward of the CG like the Cessna T 37 twin jet trainer).

    Your question is a good one and one that I am interested in discussing. I favor the aft delta wing configuration. Look at any bird and you will see the practicality and usefulness of that configuration. If there is a simple answer it eludes me at the moment. There are many solutions to any problem. One must pick and chose and then test the solutions to determine how well they work and see what additional issues are created.

    I think it is safe to say that the solution lies in the control system. Note that canard deltas and swept wing aircraft (long easy) have solved this issue as have the birds. Other aerodynamic solutions may be possible. Free flight models are a useful experimental tool. The first step is to identify the problem and then to determine if it is actually a problem that needs attention.

    My post #51 was merely intended to point out a potential problem. You are invited to start a new thread for further discussion.
     
    Last edited: Jul 22, 2019
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  15. Jul 22, 2019 #55

    Sockmonkey

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    Done and done.
    https://www.homebuiltairplanes.com/...a-tandems-and-the-people-who-love-them.31964/
     
  16. Jul 31, 2019 #56

    Sockmonkey

    Sockmonkey

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    forgot to add this guy.
    Pou type with a sparatt fore wing so the left and right halvess tilt independently of each other. That gives you pitch and roll control with one system. That means no moving parts aft of the pilot and no control runs. Just a pair of pushrods from the stick to the wings. Fewer moving parts, and fewer parts overall. Fixed fins on the aft wing for directional stability.
    [​IMG]
     
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  17. Jul 31, 2019 #57

    jedi

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    Post #56 above is close the the Spratt configuration. Spratt's aft wing was a large V tail. It also has the Pou heritage. It should be a good configuration. Substituting the aft delta for the straight aft wing may be a positive change.

    Those that have split the left and right halves of the Spratt control wing have reported a very strong roll response. You may want some sort of flexible or controllable interconnect.

    I like the aft delta pusher seaplane with the Pou/Spratt fore wing. Keep up the original thinking and follow through with results and comments. I like the small simple motorcycle of the air concept of post #56 also.

    Generally the gap between the fore wing halves of post #56 would be a strong negative but I think it may have an advantage with the aft delta configuration as the aft wing can ride the upwash from the fore wing center section gap and recover the losses with some pitch stability improvements to counter the aft delta pitch stability issue mentioned elsewhere.
     
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  18. Aug 1, 2019 #58

    Sockmonkey

    Sockmonkey

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    I think the instability was an issue because the delta in question wasn't really an aft delta, but an extension of the main wing root. The Rutan Vari Viggen had a true aft delta and flew fine.
    [​IMG]
     
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