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  • 3 Axis Wing Area

    I've been playing around with a few ideas for a 3 axis SSDR and wondered what can be 'legally' included under wing area. Would it be possible for example to incorporate a lifting surface between the main U/C wheels? in order to reduce the main wing area and clean it up aerodynamically? If the leading edge had automatically retracting leading edge slats could you include the extra area of the extended slats in the wing area calculation? Even though the wing area would decrease in cruise? Even more crazy, what about telescopic wings? Would the extended wing for the slow flight envelope count for the wing area calculation? I'm sure you can see where I am heading with this.

    John

  • #2
    3 Axis Wing Area

    Paul D would be the man to advise, but certainly one can include the "area masked by the fuselage" and so, by adding, for example, a, "airfoil shaped protrusion" along each side, placed at a suitable angle of attack, provided you could show it contributed to lift, then the area between these "protrusions" could be counted as wing area, (quite how far along the fuselage one could go before it became considered as part of the tail feathers and hence not counted as wing area, I would not wish to guess).
    Similarly, so could any streamlined struts with the same proviso and hence in principle so could your "plank of wood between the wheels"

    I would suggest that the use of such things as retractable leading edge slats, or telescopic wings would not be counted.

    In any event the SSDR exemption is specific in that in addition to wing area, it specifies:

    c) has a maximum wing loading without its pilot and fuel of 10 kg per square metre

    With such complexity you would probably exceed the weight allowance and with such things retracted you would surely exceed the wing loading requirement and maybe even the max stall speed?. (SSDR machines still must comply with all other definitions of a Microlight)

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    • #3
      3 Axis Wing Area

      My back-of-the-envelope calculations on those sorts of things usually ended up with a 'this mechanism costs more in weight/drag that it is worth'. Which is not to say that there is not a better answer out there! (I'm thinking something like a Woopy wing on a Flylight trike might be a sweet spot.)

      On the legalities, Paul Dewhurst is probably the best-informed.

      Mike

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      • #4
        3 Axis Wing Area

        Hi John

        Kevs quote that it's 'maximum wing loading' gives the answer on extendable devices - as the 'maximum' wing loading would be with them retracted.

        As for lifting surfaces other than the main wing, CAA set precedent allowing Thruster to use the area of aerofoil lift struts to count against the 25kg/m loaded wing loading which was then in force. so we should be safe on that. Also I believe that the rear undercarriage of the quasar was shaped wing like for similar reason, so again there may be precedent in that.

        At the end of the day it would seem to me that any surface that has a positive angle of attack at the stall, and could realistically be said to be positioned / shaped to provide lift, should be justifiable. but for instance, flying a large horizontal flag could not..

        Would make sense maybe to have such a surface set at an angle of attack around zero at main wing cruising angle of attack, so you only get lift and the accompanying induced drag below cruise, on the approach to the stall.

        Best way to get a high wingloading/ low wetted area, is to come up with a novel design / construction that can be made as light as possible without compromising strength. A 60Kg machine would only need 6M of wing, and then with a 90kg pilot and 30kg of fuel would have a 30kg/m wing loading - and might need some high lft devices to keep within the stall speed!

        Another option is to do like the Ego and go canard - then the fore plane area can be counted as wing and main wing correspondingly smaller.

        Paul

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        • #5
          3 Axis Wing Area

          Thank you all for your input. It was the Dornier Do7 that got me thinking about this initially. I just love that twin engine pontoon/undercarriage. Variable geometry is definitely out then! So I'm left with a lift profile fuselage incorporating lift generating U/C and a small Pegastol wing. Monocoque lightweight construction. I just love this aerodynamic stuff when the weather is too crap to fly. SSDR has given me the will to live again!

          John

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          • #6
            3 Axis Wing Area

            Makes drag links worth having on the gear legs, as if you run into legal wingload limits you can fill in between, didn't Paul observe that Nigel Beale did this? (I've got 11.5mē so only option is weight reduction to stay under 115 kilos; still hard to believe G-MGIC is just under this.)

            On a flex, closer in the wing area, the less effort in roll, so a Raven or Blade style wing with slender tips would float my boat.

            You can amuse yourself by inventing an aerofoil shaped engine cowl; a Shorts 330 had a wing profile to the entire fuselage, this often draws comment about aerofoil fuses on airliner and anorak forums.

            Happy new year

            Kev

            Attached files
            G-KEVA
            BMAA 5696

            "If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: it's all balls."

            R.J. Mitchell :- Designer of the Supermarine Spitfire

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            • #7
              3 Axis Wing Area

              The Sorrells hooked onto this "lifting fuselage" idea some 30 years ago with the original "Guppy"

              It being claimed that the Hiperbipe fuselage (the aerobatic big brother of my Hiperlight) generated a fair proportion of lift..

              Attached files

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              • #8
                3 Axis Wing Area

                Burnelli designed a number of lifting fuselage aircraft. See: http://www.burnelli.com/wp/pics
                My brother worked on Shorts 360's for a couple of years and the construction and presumably the shape is a natural progression from Shorts Flying Boat designs which also happen to be an aerofoil shape. The new Ison looks like a lifting fuselage too.

                If you Google lifting bodies there's some interesting stuff on NASA's designs including a You Tube video.

                I'm looking at the feasibility of ply monocoque construction for my project. I built a Mirror dinghy many years ago using stitch and glue and it was an amazingly strong structure and the hull was fully aerodynamic of course!

                Had a good look at your redrive last week Kev. Beautiful bit of engineering. I can understand your misgivings about Solo's offering, it was never going to last.

                John

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                • #9
                  3 Axis Wing Area

                  Not generally realised, maybe, is that Airships of the Hydrogen and Helium type, had a portion of their lift, when loaded, generated by their shape. Although they would 'float when empty, most would not rise without aerodynamic lift. Modern stuff uses swiveling engines when starting off, changing to form lift as they speed up a bit, provided by up elevator.
                  A 3 axis Aircraft doesn't have to be a true Cannard for all the surface to count as area. It counts in a tandem wing layout too, although the rear wing does have less lift than the front due to lower incidence. Used to be a popular layout in France - don't know how they spin though. Ever spun one Paul?

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                  • #10
                    3 Axis Wing Area

                    When you look at the Luciole and similar high wing load aircraft, makes you think that a cosmetic trailing edge, freely pivoting to reduce the effects of sudden gusts, might be a dodge?

                    Recently a winglet maker had a small panel at the tip that could lift and unload under gust conditions, this prevented the increased efficiency of the winglet over stressing the wing further inwards.

                    So a relaxed panel or two that can rise under turbulence would give the same effect? What would happen if you spring-loaded the lift struts?

                    Another approach is the Freewing, which has a floating pivot for the entire lifting surface.

                    I reckon a flexwing glider could easily be made in two halves, then bolted to a fuelage; this would unstress itself nicely, as it does on a flexwing, under high G

                    Cheers

                    Kev
                    G-KEVA
                    BMAA 5696

                    "If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: it's all balls."

                    R.J. Mitchell :- Designer of the Supermarine Spitfire

                    Comment


                    • #11
                      3 Axis Wing Area

                      And also consider the Controlwing (e.g., http://speleotrove.com/wings/controlwing_plans.html). Worth revisiting, I suspect .. the ancient NACA reports were more positive than one might have expected.

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                      • #12
                        3 Axis Wing Area

                        At Popham circa 2009 I saw a Chaser with two little bits of plastic stuck on the side of the nosecone and laughed at what I assumed was the designer's little joke...that it added some lift surface to make it an SSDR.

                        But apprently it was entirely serious!!!
                        X-air pilot
                        Previously owned flexwings, incl. Quantum 15-582 and Flylight Dragonfly.

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