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Aileron Counterweight Tube

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  • Aileron Counterweight Tube

    Getting ready to pour lead for the aileron counterweights. The BH BAM and Eric Newton's wing manual have the length for the 3/4in AL tube, but I can't find any reference for the counterbalance length using a 1in AL. Any thoughts? Also, looking to put in 5lbs 4oz of lead per the manual.Any input on this amount of lead?

  • #2
    The amount of lead will depend on how much shiny paint you squirt on your elevators. There is a bit of variation from Oratex to shiny PolyFiber Aerothane with 8 coats of the different covering materials.

    Bob gives a formula for how to calculate the weight of the fabric and paints. But as a practical matter - I suggest filling up the main long tube. Then insert it and actually balancing it using Bob's guidance for the fabric weight. See where you stand. If you need more use the little short section for more lead. But I would bet the long 1" tube will be adequate. Mark

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    • #3
      I haven't done the ailerons yet, but I did actually balance the elevator with weight. Oratex is a know quantity. Painted fabric less so.
      My plan is to tape a piece of 1" tube to the bottom of the aileron at the same fore and aft location of the hinge bolt. I will use that as a pivot. The leading edge will be hanging off the edge of a table. I will put the calculated weight of the Oratex at the centroid of the fabric, which is super easy to calculate on an aileron. I will then hang enough weight from the open end of the tube until I get it to balance. I will use a gallon jug of water as weight on a string. Add or subtract water until it balances. Then weigh the jug.

      Very light fabric painted is around 10 oz/sq yard. Heavy is 20 or more. That is the plan. The ailerons and flaps are the only thing still wrapped in bubble wrap.

      You could also stick a long bolt into the hinge plates (if installed) and hang the aileron from the ceiling, and then use the water jug. Or, if the ailerons are installed, just do the whole thing with the ailerons installed.

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      • #4
        Where is that formula? All I saw in the 1996 Beartracks is the 0.1lb/sqft number. A value of 0.1lb/sqft doesn't do much for me except make my head hurt. I don't know how to translate that into a weight centered somewhere on the control surface as in the picture.

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        • Mark Goldberg
          Mark Goldberg commented
          Editing a comment
          I suggest you just fill up the long tube, insert it, and then actually try to get as close as you can with the weight (per Bob's number) in the center of the elevator. Getting close is good enough for your purposes. You can always balance the control surface again after fabric & paint. If you need more weight you can add the little short section. Mark

      • #5
        I didn't know you could balance them after covering. Seems like the best way. I just unwrapped one and measured, and did a rough balance. I have a B model. The bottom chord of the aileron is 19", the top is 22" (curvature, measured with a tape measure). Span is 66.5". 18.9 sq feet or 2.1 sq yards. "Light" fabric is 10 oz/ft, required 77 oz of balance. "Heavy", 20 oz/sq ft required 111 oz. Oratex should be 67 oz.

        This is rough as it is a bare, kit aileron. No hinges, covers, hardware etc. But most of that is within 1/2" of the hinge line. I will do it again when it is covered.

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        • #6

          Very light fabric painted is around 10 oz/sq yard. Heavy is 20 or more. That is the plan. The ailerons and flaps are the only thing still wrapped in bubble wrap.

          This talk about fabric weight got me curious. For practice I made a 3' x 4' frame and finished my fabric through top coat to practice spraying. Did three before I was happy.I finished it exactly like I have done my fuselage and tail feathers. I cut one of the pieces to a square yard today and it weighs 8.9 oz. I used 2.8 oz polyfiber HD 2x2 cloth which hasn't been available for a long time, supposed to be as puncture resistant as heavy weight fabric. Used two cross coats of Ekofill instead of 3, top coat I used just enough fog coats to get color saturation and 1 wet coat for the gloss. I'm happy with the way it came out. The tapes are very visible but I like that look, glad I made the effort to get them straight. I thought my elevators would be balanced but now think they will be somewhat nose heavy which is probably better.

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          • #7
            on a side note,, For Lead weight, I used the BB's from Scuba diving ankle bands. just used a funnel and poured them in and capped with Epoxy. can't recall how much

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            • Mark Goldberg
              Mark Goldberg commented
              Editing a comment
              I have used lead shot used for shotgun shells. The diving lead is probably more available than lead shot. MG

            • svyolo
              svyolo commented
              Editing a comment
              For the elevators I used 5 lb lead balls from a local commercial fishing store. It was the cheapest I found to get lead. I want to say about 4 or 5 bucks a pound. I have some of the bagged lead diving weights, and they were only slightly more if I remember right. I didn't price the lead shot, yet.
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