Roban - World Class Scale Helicopters

Official Freewing JAS 39 Gripen 80mm EDF Jet

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  • Airguardian
    Post Stall Svengali

    • Aug 2020
    • 1664
    • Catalonia
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    #1921
    Could also install the VT unit already and trim that instead. Plus it makes the jet much more interesting in post-stall! :)

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    • Airguardian
      Post Stall Svengali

      • Aug 2020
      • 1664
      • Catalonia
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      #1922
      There goes my first Gripen video showing hands on Tx, giving an idea of how I go about performing some maneuvers, have fun!



      The video also clearly shows gyro operation on the canards, making it clear the canards often point down even when I pitch up, which is exactly how I want them to operate.
      Except when they run out of authority and I pitch full-up, then the canards do indeed pitch full-up as they would normally.

      Hope that makes it easier to understand for some.

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      • RudyD54
        Member

        • Aug 2020
        • 104
        • Miami, FL
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        #1923
        I finally got my Gripen out again this past weekend after installing thrust vectoring. I had been having a ton of issues with wing rock on my gripen since I got it and it seemed no matter what I did with the roll gain setting on the gyro, I couldn’t get it to calm down in anything above a 5-10 mph wind so I wasn’t really enjoying it or taking it out to the field much. Another pilot out at the field who was flying some larger turbines told me “It’s not your aileron gain, it’s your rudder. What you’re seeing is a Dutch roll. Up the gains for your rudder and you should see it stop.” Well guess what, I got the gain on my Spektrum receiver for the rudder up to 100 and it eliminated the rock almost entirely with no wagging at high speed even though it got really gusty later in the afternoon.

        Some of you may already know this but I figured for anyone like myself who just couldn’t figure it out, it’d be good to post up.

        I had a ton of fun wringing it out afterwards until my gear door got caught on some tall grass and ripped it halfway off on takeoff. Now THAT made for an interesting flight. I program SAFE on all my Spektrum receivers as a safety net just in case something goes wrong and I was really glad to have it at that point. All the drag from the gear door acting like an airbrake was pulling the plane into a yaw/roll and SAFE gave me enough time to figure out what was going on without having to worry about it taking a dirt nap.

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        • Airguardian
          Post Stall Svengali

          • Aug 2020
          • 1664
          • Catalonia
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          #1924
          It makes sense, to combat dutch roll (wing rocking) through yaw and not just roll, as both motions are dynamically coupled on aircraft, although using very high gains on rudder can have other unintended, undesired side effects (flight feeling too stiff or unnatural, high speed oscillations, etc).

          But if you already did it and it's working for you, then that's great!
          I may experiment a bit further with my yaw gain, knowing this worked for you ;)

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          • xviper
            Hobby Squawk Regular

            • Jan 2014
            • 8749
            • Calgary, Canada
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            #1925
            Originally posted by RudyD54
            I finally got my Gripen out again this past weekend after installing thrust vectoring. I had been having a ton of issues with wing rock on my gripen since I got it and it seemed no matter what I did with the roll gain setting on the gyro, I couldn’t get it to calm down in anything above a 5-10 mph wind so I wasn’t really enjoying it or taking it out to the field much. Another pilot out at the field who was flying some larger turbines told me “It’s not your aileron gain, it’s your rudder. What you’re seeing is a Dutch roll. Up the gains for your rudder and you should see it stop.” Well guess what, I got the gain on my Spektrum receiver for the rudder up to 100 and it eliminated the rock almost entirely with no wagging at high speed even though it got really gusty later in the afternoon.

            Some of you may already know this but I figured for anyone like myself who just couldn’t figure it out, it’d be good to post up.

            I had a ton of fun wringing it out afterwards until my gear door got caught on some tall grass and ripped it halfway off on takeoff. Now THAT made for an interesting flight. I program SAFE on all my Spektrum receivers as a safety net just in case something goes wrong and I was really glad to have it at that point. All the drag from the gear door acting like an airbrake was pulling the plane into a yaw/roll and SAFE gave me enough time to figure out what was going on without having to worry about it taking a dirt nap.
            Interesting that you had such a difficult time with the wing rock. Three of us have the Gripen at the field. Mine has the VT as does another and one has the stock Gripen, no VT but he has a HobbyEagle gyro in it with all the control surfaces hooked up to it. For some strange reason, after I installed the VT, there was no wing rock even without a gyro, where it has come before. I've always had the upgraded FMS Pro fan in it. The other one with the VT (no gyro) has a bit of wing rock and the stock one with the gyro has no wing rock.
            Mine and the one with the gyro has the canards only on ELE, while the other has elevons on the canards.

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            • Evan D
              I'll fly anything

              • Jan 2016
              • 5385
              • Charlotte
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              #1926
              I was trying to up mine until I remembered I don't fly with gyros.

              I really don't see much rocking unless it's really windy and I very seldom even notice it. BTW I have have two Gripens flying, one with and one w/o TV.

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              • Airguardian
                Post Stall Svengali

                • Aug 2020
                • 1664
                • Catalonia
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                #1927
                Originally posted by xviper
                Interesting that you had such a difficult time with the wing rock.
                This has already been debated ad nauseam, thought the conclusions were already widely understood.
                The Gripen doesn't like TURBULENT air, so it's not a matter of wind vs no-wind, but rather a case of whether the field you operate at is prone to generate rotors and turbulence or has clean laminar flow.

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                • RudyD54
                  Member

                  • Aug 2020
                  • 104
                  • Miami, FL
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                  #1928
                  Originally posted by Evan D
                  I was trying to up mine until I remembered I don't fly with gyros.

                  I really don't see much rocking unless it's really windy and I very seldom even notice it. BTW I have have two Gripens flying, one with and one w/o TV.


                  I'm just glad it's now as fun to fly as everyone said it was. I was beginning to think I got a .

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                  • Evan D
                    I'll fly anything

                    • Jan 2016
                    • 5385
                    • Charlotte
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                    #1929
                    You want "ad nauseam"? They are discussing alpha lock AGAIN on some other thread.


                    But I think you know that!

                    And yes by wind we mean turbulence caused by wind... Straight line wind without turbulence is almost invisible to the aircraft.




                    Originally posted by Airguardian

                    This has already been debated ad nauseam, thought the conclusions were already widely understood.
                    The Gripen doesn't like TURBULENT air, so it's not a matter of wind vs no-wind, but rather a case of whether the field you operate at is prone to generate rotors and turbulence or has clean laminar flow.

                    Comment

                    • RudyD54
                      Member

                      • Aug 2020
                      • 104
                      • Miami, FL
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                      #1930
                      Originally posted by Airguardian

                      This has already been debated ad nauseam, thought the conclusions were already widely understood.
                      The Gripen doesn't like TURBULENT air, so it's not a matter of wind vs no-wind, but rather a case of whether the field you operate at is prone to generate rotors and turbulence or has clean laminar flow.
                      Agree completely. Anytime the wind was steady, which is rare at our field, it was steady. Gusty days, which happen more often than not, were a nightmare to fly it in.

                      Comment

                      • T-CAT
                        Senior Member

                        • Jan 2016
                        • 2137
                        • On planet earth....right
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                        #1931
                        Unfortunately, I haven’t had the chance to fly this jet on anything but gusty winds, LOL. It flew better than I thought it would, although it definitely exhibited wing rock as expected. I’m looking forward to flying it again on a day with better conditions though just to see and feel the difference.

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                        • HockeyMac!
                          Member

                          • Nov 2019
                          • 34
                          • Send PM

                          #1932
                          Originally posted by Airguardian
                          Awesome stuff T-CAT! :)

                          Flew my Gripen today, the first flight was short of savage.

                          The rest, we filmed some air to air scenes and had to batteries die on me. The first one I managed to land but the second one ended up as an off-field. No great damage but will have to replace the pitch nozzle arm, and the front gear tore off... so I will take the chance to install it in reverse to help CG go a bit more aft. :)
                          Keep us posted on the surgery for the nose gear! I think it's a great way to fix CG and add more scale looks.

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                          • Airguardian
                            Post Stall Svengali

                            • Aug 2020
                            • 1664
                            • Catalonia
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                            #1933
                            Will do!

                            Originally posted by T-CAT
                            I’m looking forward to flying it again on a day with better conditions though just to see and feel the difference.
                            It's pretty massive you'll see.
                            This jet flies amazing on calm days!

                            Originally posted by Evan D
                            You want "ad nauseam"? They are discussing alpha lock AGAIN on some other thread.

                            But I think you know that!
                            I know, right?

                            Comment

                            • xviper
                              Hobby Squawk Regular

                              • Jan 2014
                              • 8749
                              • Calgary, Canada
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                              #1934
                              Originally posted by RudyD54



                              I'm just glad it's now as fun to fly as everyone said it was. I was beginning to think I got a .
                              I think each person has a different view of any given plane. My friend was just about to put his Gripen up for sale because he hated the wing rock and the overly reactive flight controls. Then he put a cheap gyro in it and suddenly, it has become one of his favorite jets. It's like night and day for him. For me, it's neither here nor there. It's a nice plane. I'm not overly fond of it yet it's enough fun to keep it hanging around.

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                              • Gary S.
                                Member

                                • Apr 2020
                                • 52
                                • Fort Worth, TX
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                                #1935
                                Some fun Gripen Rippin vid
                                 

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                                • kallend
                                  -----

                                  • Nov 2016
                                  • 1859
                                  • Send PM

                                  #1936
                                  Originally posted by Airguardian

                                  This has already been debated ad nauseam, thought the conclusions were already widely understood.
                                  The Gripen doesn't like TURBULENT air, so it's not a matter of wind vs no-wind, but rather a case of whether the field you operate at is prone to generate rotors and turbulence or has clean laminar flow.
                                  Additional datum:

                                  My Gripen would rock its wings in even a gentle breeze - our field is surrounded by trees that cause some turbulence.

                                  AS3X partially cured it.

                                  HobbyEagle A3 Pro cured it completely (normal mode). Now it's rock solid.

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                                  • Airguardian
                                    Post Stall Svengali

                                    • Aug 2020
                                    • 1664
                                    • Catalonia
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                                    #1937
                                    Originally posted by kallend
                                    Additional datum:

                                    My Gripen would rock its wings in even a gentle breeze - our field is surrounded by trees that cause some turbulence.
                                    The exact same is true for mine, and got an A3 Pro to replace the S8R, but haven't installed it yet!

                                    Comment

                                    • Airguardian
                                      Post Stall Svengali

                                      • Aug 2020
                                      • 1664
                                      • Catalonia
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                                      #1938
                                      Originally posted by Gary S.
                                      Some fun Gripen Rippin vid
                                      Great flight!
                                      Is that the 90mm EDF conversion?

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                                      • falkon
                                        Member

                                        • Jul 2019
                                        • 2
                                        • Valasske Mezirici, Czech Republic
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                                        #1939
                                        Originally posted by kallend

                                        Additional datum:

                                        My Gripen would rock its wings in even a gentle breeze - our field is surrounded by trees that cause some turbulence.

                                        AS3X partially cured it.

                                        HobbyEagle A3 Pro cured it completely (normal mode). Now it's rock solid.
                                        Hi guys, do you have any recommendations or photos for the location of the gyro?

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                                        • radfordc

                                          • Jul 2017
                                          • 375
                                          • Lansing, KS
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                                          #1940
                                          Here works for me Click image for larger version

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