You must Sign-in or Register to post messages in the Hobby Squawk community
Registration is FREE and only takes a few moments

Register now

Announcement

Collapse
No announcement yet.

Freewing 80mm Mirage 2000

Collapse
X
Collapse
First Prev Next Last
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #41
    What size (or more preferably, weight) batteries are people using in this thing?

    As usual, I'm having serious issues getting the cg far enough aft. Fair enough, using 4400 batteries atm, at about 620 grams, which is slightly over the recommended 4000, but still, cg is FAR off even with as much as 40 grams of lead at the extreme aft of the model.

    With 40 grams in the butt, AND carving foam to get the fairly slim batteries even farther aft, I get as far as about 520mm measured from the aft end. Which, as usual, is still a fair bit nose heavy.


    Even if I was running 3500 batteries, I don't see how I could cg this thing successfully without counterweight in the aft of the model.
    Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

    Comment


    • #42
      My favorite is a Hobby Star 5200, 620-640g. This gives me a slightly more rearward balance than the book CG. I did remove a slight amount of foam on the sides so I could move the battery back slightly but have added no weight. I also use the Admiral Pro 4000 which is the same weight and dimensions and even 3700 Zippy compacts and the Hobby Star 3500.

      Post a pic of where your battery is (also want to see how you set up the compartment. And a picture of specifically where you are trying to balance it.

      Comment


      • #43
        Originally posted by Evan D View Post
        My favorite is a Hobby Star 5200, 620-640g. This gives me a slightly more rearward balance than the book CG. I did remove a slight amount of foam on the sides so I could move the battery back slightly but have added no weight. I also use the Admiral Pro 4000 which is the same weight and dimensions and even 3700 Zippy compacts and the Hobby Star 3500.

        Post a pic of where your battery is (also want to see how you set up the compartment. And a picture of specifically where you are trying to balance it.
        I'm going out flying later today, will try to remember to snap some shots.

        In short, my battery is as far back as it goes, unless I'm going to poke actual holes in the inside walls of the intakes. The strap in its stock location wraps over the battery at the very front end of it.

        Measured my CG fairly accurately yesterday, with that battery location + 40 grams stuck to the small pontoon behind the vertical stab, it balances at 520mm measured from the very aft of the model (the end of the exhaust).

        Which, unsurprisingly, is still a bit nose heavy.


        I do have my rx up front, but that thing weighs next to nothing.
        Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

        Comment


        • #44
          Somethings not right. With a 620g battery pushed as far back as I can It balances easy at 520 and I can balance and fly it at about 507mm. It flies really nice there too. But the odd thing is that on mine the front of the battery is at the rear of the square opening where you can see the front wheels retracted. Sounds like my battery is further forward than yours.

          Comment


          • #45
            Originally posted by Evan D View Post
            Somethings not right. With a 620g battery pushed as far back as I can It balances easy at 520 and I can balance and fly it at about 507mm. It flies really nice there too. But the odd thing is that on mine the front of the battery is at the rear of the square opening where you can see the front wheels retracted. Sounds like my battery is further forward than yours.
            Yes it is. Possibly my scales are off, so I might be flying a heavier battery than I thought? Just about the only remaining explanation at this point.


            Attached some pics. With this config, it balances pretty much exactly at 520 (and like you said, I want it further back)

            520 is just a smidge forward of the foam joint in front of the wheel bay
            Attached Files
            Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

            Comment


            • #46
              Your battery is about 10-15mm further back than I have mine. So either a heavier battery or it's the wires? I don't have any magical suggestions. Maybe put the receiver aft and plug in the battery and then insert it with the wires aft?

              Either way I wish you luck in getting it sorted.

              Comment


              • #47
                Originally posted by Evan D View Post
                Your battery is about 10-15mm further back than I have mine. So either a heavier battery or it's the wires? I don't have any magical suggestions. Maybe put the receiver aft and plug in the battery and then insert it with the wires aft?

                Either way I wish you luck in getting it sorted.
                Thanks.

                The rx weighs about 15 grams, and a few more for the servo leads I guess, and it is very far forward currently. Will try to relocate it, but it is difficult to see that making enough of a difference.

                Will double check the weight of my batteries.

                The only other difference is that I haven't glued on the pylons for the tanks. But let's be real... they weigh like 3 grams each and are just the tiniest smidge behind cg. So should make any real difference neither.
                Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                Comment


                • #48
                  I don't have the pylons either...

                  Comment


                  • #49
                    Originally posted by Skyboom View Post
                    Oh my.
                    That's Wild Bill lol

                    Comment


                    • #50
                      Had a great photographer at the field today, shooting some extremely high res pics of our models :D
                      Attached Files
                      Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                      Comment


                      • #51
                        A couple minutes of messing around with the Mirage... What this little thing can do is quite amazing.

                        Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                        Comment


                        • #52
                          Originally posted by janmb View Post
                          A couple minutes of messing around with the Mirage... What this little thing can do is quite amazing.

                          Damn! That looked fun, the only time I really fly mine like that is on the approach to final and landing. Time to change it up! Mostly turns with rudder? And please tell me you're not using a gyro...

                          Comment


                          • #53
                            Originally posted by Phantom View Post

                            Damn! That looked fun, the only time I really fly mine like that is on the approach to final and landing. Time to change it up! Mostly turns with rudder? And please tell me you're not using a gyro...
                            Yes, in order to do high alpha turns, you essentially do a coordinated rudder turn (turn using the rudder, using elevator and opposite aileron to maintain the attitude you want). You cannot have excessive bank with this little energy.

                            A completely different, but equally fun meta is to use lots of power and do extremely tight high bank, high g turns at medium/slow speeds. The clue is that you need to pull a lot of g to keep from falling (imagine running on a circular wall)

                            And yes I use a gyro in normal damping mode. Not making an ounce of difference - as you can clearly see in this video, it has nowhere near enough authority to prevent wing rocking at these low speeds anyway, and in calmer conditions there simply isn't any wing rocking to fight anyway. As long as you get the cg aft, it is rock stable with gyro turned off even at 60 degree alpha.
                            Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                            Comment


                            • #54
                              Originally posted by janmb View Post

                              Yes, in order to do high alpha turns, you essentially do a coordinated rudder turn (turn using the rudder, using elevator and opposite aileron to maintain the attitude you want). You cannot have excessive bank with this little energy.

                              A completely different, but equally fun meta is to use lots of power and do extremely tight high bank, high g turns at medium/slow speeds. The clue is that you need to pull a lot of g to keep from falling (imagine running on a circular wall)

                              And yes I use a gyro in normal damping mode. Not making an ounce of difference - as you can clearly see in this video, it has nowhere near enough authority to prevent wing rocking at these low speeds anyway, and in calmer conditions there simply isn't any wing rocking to fight anyway. As long as you get the cg aft, it is rock stable with gyro turned off even at 60 degree alpha.
                              How much aft? What CG number are you running?

                              Comment


                              • #55
                                A couple posts up... I have my CG there, in that post, too. I don't run a gyro in most my planes and this definitely doesn't need one. Yes the high alpha is easy and quite precise.


                                Originally posted by Phantom View Post

                                How much aft? What CG number are you running?

                                Comment


                                • #56
                                  Originally posted by Phantom View Post

                                  How much aft? What CG number are you running?
                                  Currently flying at 515, but working on getting it a bit more aft.

                                  Definitely agree with Evan that the model doesn't *need* a gyro. Very few models really do. It is really stable, even when slow.

                                  But pretty much *all* models benefit from having one, in terms of looking better when windy. The challenge on this particular model, as with a few others, is that the speed envelope is so huge, that a gyro gain that is low enough to avoid oscillation on the high speed end will do next to nothing in the low speed end (as my video demonstrates fairly well). Optimally, one would have airspeed telemetry and let that drive the gain.
                                  Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                                  Comment


                                  • #57
                                    Some more French shenanigans :P

                                    Thanks to Frode for filming

                                    Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                                    Comment


                                    • #58
                                      Does nice off of grass strip. Even grease landing. lol

                                      Comment


                                      • #59
                                        Originally posted by Skyboom View Post
                                        Does nice off of grass strip. Even grease landing. lol
                                        It's not real grass though, it's the fake stuff you get on soccer fields. We inherited the old surface from the local club when it was too worn out for soccer. Perfect surface to fly from - perfectly even, slightly softer and more forgiving that tarmac, and provides perfect roll resistance to allow easy takeoffs yet lend some braking aid on landings.
                                        Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                                        Comment


                                        • #60
                                          Another fun day at the field. Got some nice shots in a brilliant sunset, and great filming from RC Tommy on YouTube.

                                          Attached Files
                                          Freewing A-10 turbine conversion: http://fb.me/FreewingA10TurbineConversion

                                          Comment

                                          Working...
                                          X