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Needing help with method for balance my 4.3m sailplane

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  • Needing help with method for balance my 4.3m sailplane

    I'm getting close to the point of thinking about how I'm going to balance my 4.3 meter sailplane and would like some suggestions on how to go about doing that. My fingers aren't strong enough to hold it up like I do my much smaller airplanes. Ouch. I know a lot of you guys have the really large sailplanes and I was curious how you go about setting the CG on them. If someone could help me with that I would really appreciate it. I've been working on this project forever it seems and now have time to work on it and anxious to finish it up and get it in the air. Thanks!!

  • #2
    Jack - Is it a scale model? If so, what is it a model of and what company manufactured it? What kind of wing joiner is used - steel blades, round steel rod or rectangular carbon?


    • #3
      Thank you for responding to my question. This is the Rödelmodell ASK-21 4.2m model from Icare-Icarus . The wing joiner is a round steel rod. It is a fiberglass fuselage with obechi covered foam wings.


      • #4
        Make two 1/16”plywood plates that fit over the wing rod and rear pin……make the plate come above the wing/fuse by about 1”…….drill a small hole at the balance point……assemble model with a ply plate on each side of the fuse between wing/fuse…….make a loop of mason twine or similar string and hang the airplane from overhead……add weigh as needed to balance.


        • #5
          Tom's suggestion works great.

          You can also drill two very small holes in the wing roots of the fuselage sides (3/32 - 1/8" or less to match a piece of music wire), bend a piece of music wire into an "L" just slightly more than a 90 degree angle and then insert into the fuselage extending inside about 1.5 inches and then extending upward high enough to clear the wing top and add a small loop on the end into which you'd tie cord.

          Insert these "L's" into each side, slide the wings on, secure the wings, and similarly hang the fuselage from the two loops with some stout cord. Your "recommended" CG will always be there marked on the fuselage sides hidden when the wings are on and the two tiny holes are meaningless. You'll also then have a CG rig to use on any future sailplanes regardless of wing root dimensions.

          If you really get into this scale stuff, making a CG stand on your own or purchasing one of the commercially available ones will be worth the expense in the long run.

          This totally adjustable puppy has paid for itself many many times and has held a 45 pound sailplane. YMMV

          Click image for larger version

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          Team PowerBox Systems Americas... If flying were the language of men, soaring would be its poetry.


          • mlachow
            mlachow commented
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            No digital one yet steve?

          • Steve P
            Steve P commented
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            Digital? I just found out the internet is now available on computers!

          • when2fly
            when2fly commented
            Editing a comment
            That adjustable puppy looks really handy. Where do you get them in the US?

        • #6
          Thank you very much!. You guys are awesome. These are the kinds of things I haven't thought much about with the larger aircraft. I'm sure there are other things I will learn later. Where can I find information on the commercial CG stands? I guess they will be listed in one of the links on the home page. Sorry i will look there. Thanks again. This is a really great site and lots of friendly folks. I look forward to meeting some of you at one of the future events. Happy flying.


          • #7
            You could use two scales, one on the wheel and one at the tailskid. Measure those distances from a reference point and do the math.


            • #8
              Kit type balancing stands. 5 different sizes.

              Team PowerBox Systems Americas... If flying were the language of men, soaring would be its poetry.