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  • Restart on an old bird

    Guys, I'm restarting work on an old bird I've had nearly forever, and never completed. It is a 1/3 scale Nimbus 4D by Rosenthal. Attended an aerotow event yesterday that got me all atwitter about getting the 8.8meter slipper in the air. My question is this: What size and torque of servos should I use in the fuse for the rudder (on pull-pull), tow release and retrac. I think I can go with 7.4 volts, using a 2S lipo system. I prefer HiTec normally, but open to other reliable brands as well. What would you "big kids" recommend?

  • #2
    I don't know much about what would be needed but I do know a lot of fliers use a separate battery to power the retract in case it binds and the servo stalls. That will safe guard against total system failure.Those wings will be pretty thin so a 'thin wing' servo of as much torque you can find would be prudent. A Hitec HS-125MG servo might be a good choice. The digital Spectrum and Hitec HS-5125 versions similar to the HS-125MG are on back order at Horizon Hobby. Hopefully, more knowledgeable folks will respond.

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    • #3
      Hi Larry.
      Sorry for a delay in jumping in here, we were in Georgia at an aerotow and just returned.

      This is going to be awesome, I'm looking forward to seeing the progress. I have a 10.6m Nimbus 4 so I may be able to help with some logistic questions.

      With modern radio equipment you will not need to run chokes on the long wires. I used a heavy gauge twisted wire when I built mine back in 2011. Crimp your connectors on, which takes a bit of practice with the heavier gauge wire. ( we can talk about that later)
      The servos used in these big floater models don't need monster torque since they're are so many servos operating small surfaces. Pay attention to the flap servos and maybe the inboard aileron servo's since they're the largest surfaces on the plane. As for flavor of servos, put in something you don't have to replace all the time. If you're planning on HV servos ( which I TOTALLY agree with you), Spektrum has a nice line, JR are excellent and some of the Hitec high end servos are excellent. ( 7955, etc) but check on the Voltage allowance.

      You'll probably have pretty good option since you don't need thin wing servos with a plane that big. I believe you can use a standard size servo on most surfaces of the wings, maybe thin servos in the elevator?
      Look at the JR 398 thin wing or MKS for thin wing too. ( I would not use the 5125 hitec, they have proven to have amplifier issues ) plus they're not HV.

      Rudder is another spot for a higher torque servo. 200+ oz

      Len
      Team Horizon Hobby

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      • #4
        ARUP, thanks for the advice. I understand the idea about using a separate retract battery. Good thought.

        Len, Thanks for the response, and hope you had fun in Georgia. I agree that thin servos aren't likely needed except for the outer ailerons. As an aside, can you share what the wing control surfaces are? At some point in the past, I thought the inner four surfaces (two per side)were flaps, but later thought I'd been told only the inner two surfaces were for flaps. Not sure so thought I'd ask someone that owns one.

        Larry Fitch

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        • #5
          I would agree that the inner 2 are flap, however I have it set up as flaperon in mine so they move with the ailerons, then I have them deflect down for flap when needed.
          Any combo is fine. Since the wing is so long, you'll need all the aileron you can get.
          Team Horizon Hobby

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          • #6
            Sorry for asking the question twice but, Len you are saying only one flap on each side of the fuse? I agree with your approach to using flaperons. Thanks for that. I take it you also have "speed" and "thermal" modes to some switch assignment? Both up or down about 1/16 to 1/8" across the full span of the wing? Thanks for all the insights. I'll likely need a lot more help as I make some progress.

            Larry

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            • #7
              I'll take a look at the wing setup I have, it depends on how big the surfaces are in your kit. Can you post the wing layout?

              Len
              Team Horizon Hobby

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              • #8
                Len, I will post the layout late this weekend fire we complete our week at the beach. Wife and I kicking back in Long Bach, WA and having some fun flying kites and my e-powered Bird of Time. Should be home late Saturday evening.

                Thanks,
                Larry

                Comment


                • LRFitch
                  LRFitch commented
                  Editing a comment
                  Len, I measured the wing control surfaces and find the following for each wing half:
                  Spoilers= 24"
                  Flap= 50.75 X 2.5"
                  Aileron 1= 40 X 2.5"
                  Aileron 2= 32.25 X 2.125"
                  Aileron 3=27.125 X 1.25"
                  Aileron 4= 10.75 X 1.5"
                  Aileron 5= 9.625 X 1.25"
                  Aileron 4 and 5 will be pinned together, and driven by one servo. The flap and spoiler are on the inner wing panel, and the ailerons are on the outer wing panels.

                  Thanks for your time,
                  Larry

              • #9
                Guys, Something different here. I'm thinking about using SBus to control the servos, at least in the wings. This old Rosenthal airplane wing is obechi over foam, and I will need to run wires out to the tip aileron servos, and am concerned about getting dozens of wires out in the 14' wing half. There are some wires in the wing, installed by the factory, but not at each servo location. All are glued to the surrounding foam, and I'm not sure how to get them out, or really what options I have to deal with controlling the servos. This is partly why this glider is 13 years old, and still not in the air. Has anyone else dealt with this type of issue?

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                • #10
                  Guys,still working on my Nimbus,and hit a bit of a question/issue. The inner wing sections each have a spoiler that are about 24 1/2" long and made up of two sections connected together. The longer section is 14 1/2" long and the shorter ones are about 9 13/16" long. Each spoiler is made up of one long and one short section. The top aluminum caps have been off for years, and in safe storage. I attempted to install the caps on one inner panel, and all went fine (after watching the video on the website--thanks Len). When I tried to do the other side, I found the the long section was fine, but the remaining short section was backwards in relation to the long one. My questions are : 1) will the spoilers work OK if the one side has the "different hand" sections used? and what and how do I attach the wood that still needs to be applied to these top caps? I'd guess I should use this balsa, and glue them on somehow?

                  Thanks,
                  Larry

                  Comment


                  • #11
                    Hi Larry,

                    I don't understand why the spoiler was installed backwards. It seems like there must be a mistake somewhere.
                    The spoiler should still work fine I guess.
                    As for glueing the tops on, I use G-10 and make the caps myself, then paint them white before installing. The process for doing that is as follows.

                    build the spoiler cap

                    test fit into the opening

                    Sand the top of the spoiler

                    Apply an 1/8" bead of epoxy, ( thickened with micro balloons to a firm past )

                    Squish the cap onto the spoiler and use a few Popsicle sticks across the top to set the correct height. The sticks will span the spoiler opening and hold the cap down while the glue sets.

                    After the glue has firmed up, buy before it really hard, open the spoiler to be sure there is no glue in places you font want it.

                    Clean off any issues and let it fully cure.

                    Hope this helps
                    Team Horizon Hobby

                    Comment


                    • #12
                      Len, Yes it does help. Thanks. As I've stated, the kit is quite old, so don't know all the history. The spoiler parts that are in the wing were mounted by Rosenthal when the wing was built. I don't think the cap pieces were ever mounted, until yesterday. The pieces that are in the wing are all oriented, interconnected, and glued in correctly. I'd guess the top caps were mixed up with others when they were wrapped in bubble wrap, and placed in the fuse for shipping.

                      How thick a piece of G-10 do you use? I will be covering the wings with white sign vinyl, and had expected to cover the spoiler tops as well.

                      Len, thanks for your continuing help with this build.

                      Larry

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                      • #13
                        the g-10 just needs to be thick enough to not be too flexible. I don't know how its measured, but maybe 1/16th?
                        Team Horizon Hobby

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                        • #14
                          Len, Spent some time with Wil Byers before he moved his belongings to his new home in Moses Lake. He happened to have the spoiler piece I needed to make a right and left handed pair for the Nimbus. All is good now, in that regard. It's really good to have friends that collect glider stuff.

                          Currently working on the tail, and getting ready to make the mount for the pitot tube in the stab leading edge. Then will make a mount for the speed sensor electronics right near the tube. Then I can epoxy in the rudder post. I've cut several access holes in the post to allow access to the pitot tube, it's electronics, and the tail wheel. Making progress, but it's slow. On nice days I have to fly a while, and attend a couple aerotow events over the next 6 weeks. Will be in Salem OR to fly and watch the total Solar eclipse in August. Likely the last time I'll be alive to see one.

                          Larry

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                          • #15
                            Folks, I'm in need of a wing rod for my Nimbus build. I have the outer rods that go between the inner and outer wing panels, but missing the longer one that connects the inners to the fuse. The missing piece is made of solid fiberglass, is 25mm in diameter, and 32.5 inches (825mm) long. It's quite a club! I emailed Bruce Devisser who was importing Rosenthal, but he said once again they were not in business, and looking for a buyer. So, no luck there. Anyone know of a source/supplier for a rod this size?

                            Larry

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