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    NASA Prandtl-D Flying wing

    Following the suggestion of our fellow member my77gmc I´ve designed for 3d printing the NASA Prandtl-D flying wing:



    And this is where the idea came from:

    http://www.amaflightschool.org/PRANDTL



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    Will make it glider only and post files on thingiverse.

    My model will be 2.4 meter span, probably printable on a Prusa i3, 250X210X200 the chord at root its only 230mm plus a little bit because the wing is swept back.

    #2
    Half wing printed, 225 grams!

    final AUW should be around 450+2 servos+receiver+1 small bec and one 2s 700mA battery+some lead? 600 grams perhaps.

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    • earthsciteach
      earthsciteach commented
      Editing a comment
      Does the wing incorporate the twist?

    • derfred
      derfred commented
      Editing a comment
      Yes, this is exactly as the one shared by nasa. In fact I used their shell and just did the inner structure and sized it to 2.2m span.

      I have this wing almost ready, the other day was to finish it and add the servo pockets to the wings but the wing is so thin that I had to use long links instead. Them a new work project came up and my time for this and other printable plane projects I have in hands run out. But I´ll finish it one of these days.And I´ll share it on thingiverse.

    #3
    Left half of the wing printed:
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      #4
      Click image for larger version

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ID:	649 First prototype printed, will do some free flight tests and find the cog.

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        #5
        May I suggest ailerons and servos are unnecessary.
        Two very small motors, controlled differentially, may provide enough thrust to engage proverse roll.
        Enough thrust to climb to 100 feet in 60 seconds.
        Battery sized for 4 minutes flight...to acquire flight experience.
        Doug

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        • earthsciteach
          earthsciteach commented
          Editing a comment
          That might be problematic. The Prandtl wing is designed for zero load at the wingtips so it probably wouldn't support them well structurally.

        #6
        humm... this wing design provides proverse yaw already, I have never flown it but I suspect that with more action on the elevons the wing will roll.

        Putting motors on the tips could be an interesting experience, have you seen it before on a flying wing?

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          #7




          or even very small fans.


          Doug

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            #8
            Right. I was imagining the motors at the tips like the cl-400

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            I think the kind of control you get with motors is not comparable to elevons, you could fly and control on a very quiet flight but just landing that way would be problematic.

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              #9
              The Air Hogs PowerHawk twin electric bi-plane has a non-functioning propeller on the nose.

              Two pusher propellers provide the thrust: half throttle for straight and level, full throttle for climb.

              Bank left by reducing power on one motor and increasing power on the other motor.

              I enjoy entering a stable bank of five feet radius, kinda / sorta as if flying on control lines around me.

              This is why I suggest ailerons and servos are unnecessary.

              Two very small motors, controlled differentially, may provide enough thrust to engage proverse roll.

              Why take the weight out of the wingtip?

              The moment of inertia of the servo plus wiring degrades the proverse roll induced by the forward leaning lift vector of the wingtip.

              Glider guiders know from experience to build the lightest outer wingtip panel possible, to be able to better read the air.

              So move the servo plus wiring inboard closer to the centerline of the wing,

              Then make a paradigm shift by taking the motor out of the servo, and using it to turn a propeller or fan for thrust.

              50 watts per pound will easily fly this efficient flying wing.

              With two 50 watt motors, controlled differentially, mounted on pylons above the wing, the 3d printed NASA Prandtl-D flying wing should fly well like the PowerHawk.

              Doug






              Image result for air hogs powerhawk



              Comment


                #10
                "I had a spare Warp4 motor and an APC 6x4 electric prop. Input power is 125W."
                Derate to 50W!

                Doug



                Build Log Minimoa Motor Pod TugBoat
                Registered User
                NSW, Australia

                Joined Jun 2003
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                  #11
                  You may have a point here. It would be an interesting experiment.

                  Many years ago I played with that air hogs plane you posted, back then it was the smallest receiver and actuator system we could get, we replaced the motors by actuators and it was fun.

                  Comment


                    #12
                    Anyone venture to guess the Reynolds Number this wing flies at, anyone?

                    Oct 30, 2015, 11:36 AM
                    Alien_Tech
                    “Hi Steve,
                    Wing Area =41 ft^2
                    Wing Span = 25 ft
                    GTOW = 31 lb
                    Wing loading = 0.75 lb/ft^2
                    Launch height was 135' Design cruise is .6 CL.
                    No airspeed instrumentation on board this one yet, my guess was about 18 mph.
                    CG is forward, safe for first flight, but you can see I'm carrying up elevator as is passes by.
                    We are going to do a couple flights next week to get some flow vis photos,
                    then it will be brought down and instrumentation installed.
                    Cheers
                    Red”

                    Jul 17, 2017, 12:02 PM
                    Alien_Tech
                    “The latest 25' span P-3c took to the air this morning for it's maiden flights.
                    This one is all carbon & weighs 32 lbs (12 lbs lead ).
                    It will now be integrated with with it's fiber optic, pressure sensing & air data probe payloads
                    and continue with data flights later this month.”

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                      #13
                      Is it this?

                      http://airfoiltools.com/calculator/r...&yt0=Calculate

                      The chord at root is 23,5cm, I´m not sure that on a swept wing like this the correct value to use is this.

                      Kinematic viscosity may not be correct, from what I´ve seen for air at 15ºC should be 1.81×105

                      Comment


                        #14
                        Originally Posted by derfred

                        Is it this?

                        http://airfoiltools.com/calculator/r...&yt0=Calculate

                        Yes!

                        The Reynolds number is a dimensionless value that measures the ratio of inertial forces to viscous forces
                        and describes the degree of laminar or turbulent flow.

                        The key is to reduce the moment of inertia of the wingtips.

                        You can't change the design of the printed wing, but you can move the servos = (motor / propeller), closer to the centerline of the wing.

                        "Once we had found the center of gravity, our mentors selected a specific location where they
                        then wanted us to place the center of gravity. We used small iron coupons that we inserted into
                        the aircraft's wings to ballast the aircraft. Our mentors asked for the center of gravity to be
                        located 13.24" aft of the nose along the x axis, as close to the centerline of the aircraft as possible
                        along the y axis, and they were not concerned with the center of gravity along the z axis."
                        Test and Analysis of the Mass Properties for the PRANDTL-D Aircraft 50-50-1-PB(1).pdf

                        "Mass Properties
                        The aircrafts’ mass properties are: roll inertia 5.425 slug-ft 2 ; pitch inertia 0.2717 slug-ft 2 (estimated);
                        yaw inertia 5.818 slug-ft 2 ; and x-z plane cross product of inertia 0.5054 slug-ft 2 . The inertias were measured
                        using a bifilar method, except for pitch inertia, which was estimated from the computer-aided design
                        geometry and the point mass locations of the onboard systems. The center of gravity was placed at 0.128
                        of the mean aerodynamic chord. The aircraft mass was 14.5 lb.
                        The lateral-directional mass properties proved to be critical to the experiment.
                        Maine and Iliff (ref. 7) show a very high sensitivity to x-z plane cross product of inertia in the estimation of Cnda
                        (yawing moment due to aileron deflection coefficient)."
                        On Wings of the Minimum Induced Drag: Spanload Implications for Aircraft and Birds NASA-TP—2016–219072 Bowers1.pdf

                        Oct 28, 2015, 03:51 PM
                        Alien_Tech
                        "So I guess we can officially claim it's an airplane now.
                        P-3 completed its maiden flight this morning from a bungee launch to about 200' altitude.
                        No instrumentation on board, just simple 2 channel elevon control.
                        31 lbs gross weight with 9lbs of lead to CG lol.
                        Flies super sloooooow, not kidding looked like about 15 kts."

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                          #15
                          This is a huge bird I had not seen this one yet. I suppose this is the one on the igs files, at least that one was about 8 meter span if I remember well. Is there a video of this wing flying? They made a manned one you know?

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