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Official Freewing MiG-29 Fulcrum Twin 80mm Thread

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  • Originally posted by xviper View Post
    That's about 20mm further than the marks. I have my batteries as far as they will go without removing any foam and not touching the blue box. It just balances at 10mm further. Did you move the BB or add weight to the tail to achieve your balance?
    I've read it somewhere but can't remember the reason why now. What is the rationale for the small bit of reflex in the flaps?
    Reflex reduces the pitching moment of the wing so the tail doesn't need to generate so much downforce. This will reduce the loads both on the servos and on the tail structure.

    Comment


    • Originally posted by GliderGuy View Post
      Hi Gary,
      What altitude and temperatures are you indicating these airspeeds? I would like to roughly calculate the approximate true airspeeds. Some have reported GPS-measured speeds in the range of 125 mph when level and full throttle.
      -GG
      Hi GG,

      I haven't done an ICE-T problem since pilot training in the 70's. I always got TAS by flipping the switch on my HUD from C to T and just read the number! Good luck.

      I was flying near Bowman, SC yesterday. Temp was 70 F, Wind calm, Pressure was 30.10, and field elevation is 100' MSL.

      I was getting verbal telemetry call outs from my Jeti DS-24 generated out of a Digitech SB-IAS sensor. My friend Dave who wrote the LUA program for the speed call outs has bench tested several RC telemetry sensors with lab instruments and says this one is very accurate. It is the one used for the Digitech CTU auto throttle function. I'm sure I'm just getting raw IAS and is not calibrated but its probably close at the speeds I was flying.

      I make it a point not to fly my foamy turbine conversions too fast. I used to get 100mph with my F-22 on 8S so that's where I set my overspeed warning for the turbine conversions. I haven't tapped that much with the Mig-29. 60-80mph feels like the sweet spot at mid range thrust settings for most or my flying. I easily fly for 7-8 min with the fuel available and the Mig is a very comfortable jet to fly. It's a lot of fun.

      Gary

      Comment


      • Originally posted by kallend View Post

        Reflex reduces the pitching moment of the wing so the tail doesn't need to generate so much downforce. This will reduce the loads both on the servos and on the tail structure.
        Thanks for explaining and helping me understand that. It does make a noticeable difference on the stab trim settings. Thanks

        Comment


        • Thanks viper1....

          At those conditions, not a big delta. Using the TAS calculator at



          and assuming IAS is approx CAS...

          IAS to TAS in mph

          40 = 44
          60 = 65
          80 = 87
          100 = 109

          I agree....fun EDF to fly!

          -GG

          Comment


          • Originally posted by kallend View Post

            Reflex reduces the pitching moment of the wing so the tail doesn't need to generate so much downforce. This will reduce the loads both on the servos and on the tail structure.
            So, can it be said that in the case of this plane, it's like the opposite effect as when flaps down causes "ballooning"? You have to apply down elevator to compensate. When reflex is used here, some up compensation is dialed in.

            Comment


            • Originally posted by xviper View Post
              So, can it be said that in the case of this plane, it's like the opposite effect as when flaps down causes "ballooning"? You have to apply down elevator to compensate. When reflex is used here, some up compensation is dialed in.
              Essentially true. A wing producing lift normally has a nose down pitching moment (the wing wants to rotate nose down). In order to prevent this the horizontal tail must produce a tail down force that just compensates for the wings nose down moment. Adding reflex to the wing trailing edge reduces the nose down pitching moment of the wing, and thus less tail down force is required by the horizontal tail.

              Comment


              • Originally posted by xviper View Post
                So, can it be said that in the case of this plane, it's like the opposite effect as when flaps down causes "ballooning"? You have to apply down elevator to compensate. When reflex is used here, some up compensation is dialed in.
                As far as "ballooning" when flaps are lowered that's a different thing. Lowering flaps can increase the wing nose down pitching moment which you would think would require more tail down force (up elevator to compensate). But, often, as you note you need down elevator to compensate for flap deployment. This can be due to a couple of reasons....increased camber of the wing causes the wing to lift more; and, the flaps induce a downward flow over the horizontal tail causing the tail to produce more down force,

                Comment


                • Originally posted by radfordc View Post

                  As far as "ballooning" when flaps are lowered that's a different thing. Lowering flaps can increase the wing nose down pitching moment which you would think would require more tail down force (up elevator to compensate). But, often, as you note you need down elevator to compensate for flap deployment. This can be due to a couple of reasons....increased camber of the wing causes the wing to lift more; and, the flaps induce a downward flow over the horizontal tail causing the tail to produce more down force,
                  Completely dependent on geometry. Most narrow aspect jets in my experience nose down with flaps deployed, while most straight wing, especially high wing, aircraft tend to nose up. And plenty exceptions to be found in both groups.
                  Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                  Comment


                  • 160mm CG

                    Originally posted by viper1gj View Post
                    I moved the CG back to 160mm and have 3mm reflex on flaps and ailerons. With the CG back to 160mm it flies even better now.
                    Thanks for this interesting pointer. I am asking because with my current setup (slightly heavier fans, very light batteries, lots of stuff like the BB and many long wires eliminated), I really don't get 150mm. I can do something like 157mm. So if a position of 160mm works, that would be good news indeed.

                    And big congrats to that great conversion you made, very impressive!

                    Cheers,
                    Henrik

                    Comment


                    • Originally posted by HK111 View Post
                      160mm CG
                      And big congrats to that great conversion you made, very impressive!
                      Cheers,
                      Henrik
                      Thanks Henrik, this conversion has been the best one yet. I think 157mm would be excellent. Let us know how it flies there.

                      I just hung all the rails and missiles on the wings today and rechecked the CG with the Xicoy CG machine. I found the CG shift was 2mm aft so now at 162mm. Based on my recent flights this weekend at 160mm I think it will be fine at 162mm. I will test next weekend and report back.

                      Gary

                      Comment


                      • I posted this on RCG also, but wanted to get opinions here also:

                        If I use ProModeler DS150CLHV servos for the stabs plugged directly into the Rx, retain all the other original servos, use a castle 20 amp Pro and run everything at 5v, what 2s LiPo should I use to fly at least 2 flights safely? I will most likely be using a Cortex gyro, which also uses some power. I've never used an external BEC before.

                        The BEC battery will need to power an after burner also.

                        I already have two of each of these:

                        Admiral 1300, 30c
                        Roaring Top 2200 25c

                        Comment


                        • Originally posted by RC Rich View Post
                          I posted this on RCG also, but wanted to get opinions here also:

                          If I use ProModeler DS150CLHV servos for the stabs plugged directly into the Rx, retain all the other original servos, use a castle 20 amp Pro and run everything at 5v, what 2s LiPo should I use to fly at least 2 flights safely? I will most likely be using a Cortex gyro, which also uses some power. I've never used an external BEC before.

                          The BEC battery will need to power an after burner also.

                          I already have two of each of these:

                          Admiral 1300, 30c
                          Roaring Top 2200 25c
                          Both of those are certainly more than big enough for a few flights. Obviously check between each though.

                          If buying new, I would look at 500-800 mah for this purpose. But as always, try.
                          Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                          Comment


                          • Re-maidened mine over the weekend after my re-paint. Moved the CG back to 165mm and I won't be looking back.

                            Video of the painting/airbrushing process for those who are interested:

                            Repaint of the Freewing Mig 29 "Fulcrum" twin 80mm EDF jet. This project called for a mixture of rattle cans and airbrush. As always, the airbrush colors a...




                            Attached Files

                            Comment


                            • Originally posted by krakenreleaser View Post
                              Re-maidened mine over the weekend after my re-paint. Moved the CG back to 165mm and I won't be looking back.

                              Video of the painting/airbrushing process for those who are interested:

                              Repaint of the Freewing Mig 29 "Fulcrum" twin 80mm EDF jet. This project called for a mixture of rattle cans and airbrush. As always, the airbrush colors a...



                              Congratz, that's a sick & really nice scheme
                              https://www.youtube.com/icarusthe2nd

                              Comment


                              • Maiden flight and 2 more flights done today. Had a strange problem though in the 3rd flight. Here's the vid from that 3rd flight.

                                https://www.youtube.com/icarusthe2nd

                                Comment


                                • Did you change rates between 2nd and 3rd flight?
                                  Gyro was in the same state in all the 3 flights?

                                  Originally posted by krakenreleaser View Post
                                  Re-maidened mine over the weekend after my re-paint. Moved the CG back to 165mm and I won't be looking back.
                                  Love that scheme!

                                  Comment


                                  • Originally posted by krakenreleaser View Post
                                    Re-maidened mine over the weekend after my re-paint. Moved the CG back to 165mm and I won't be looking back.

                                    Video of the painting/airbrushing process for those who are interested:

                                    Repaint of the Freewing Mig 29 "Fulcrum" twin 80mm EDF jet. This project called for a mixture of rattle cans and airbrush. As always, the airbrush colors a...



                                    Superb, you're a real artist!
                                    Hugh "Wildman" Wiedman
                                    Hangar: FL/FW: Mig 29 "Cobra", A-10 Arctic, F18 Canadian & Tiger Meet, F16 Wild Weasel, F4 Phantom & Blue Angel, 1600 Corsair & Spitfire, Olive B-24, Stinger 90, Red Avanti. Extreme Flight-FW-190 Red Tulip, Slick 60, 60" Extra 300 V2, 62" MXS Heavy Metal, MXS Green, & Demonstrator. FMS-1700mm P-51, Red Bull Corsair. E-Flite-70mm twin SU-30, Beast Bi-Plane 60", P2 Bi-Plane, P-51.

                                    Comment


                                    • Originally posted by Icarus the 2nd View Post
                                      Maiden flight and 2 more flights done today. Had a strange problem though in the 3rd flight. Here's the vid from that 3rd flight.
                                      That is odd. Do you have both signals on one channel, or two independent channels driving the two elevator halves? Regarding the large trim change...I'm assuming you put the same batteries in the same place as previous trim flights?

                                      Comment


                                      • The thrust line is such that keeping full throttle after a pitch-up at take-off is going to require some down elevator to counter the thrust line. Did you use the same take-off technique on the 3rd flight? In the video, it appears you may have been behind the pitch-up after take-off. If you want to keep full power right after take-off, use the technique of going into a bank after lift-off. This will minimize the amount of pitch-up you'll experience while staying at full power. It looks cool, too!

                                        -GG

                                        Comment


                                        • [QUOTE=Icarus the 2nd;n287439]Maiden flight and 2 more flights done today. Had a strange problem though in the 3rd flight. Here's the vid from that 3rd flight.

                                          Just a guess. Is it possible one of the servos skipped a gear tooth?

                                          Fly low, fly fast, turn left

                                          Comment

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