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Re: [Dragonflylist] Elevator Control Horns

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  • terrence o'neill
    Chris in Canada, Did you balance yoor elevators? Up until mid-1930s the US Army AIr Force required their planes, which flew in the same speed range as ours, to
    Message 1 of 17 , Sep 1 9:42 AM
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      Chris in Canada,
      Did you balance yoor elevators? Up until mid-1930s the US Army AIr Force required their planes, which flew in the same speed range as ours, to have 100% static balance of flight control surfaces, top prevent flutter. It is fairly easy to do. The DBFN had one example, for internal balance. Another way is to add an external balance at the tip of each elevator. A third way but less effective due to flexibility of the surface, is to add the balancing weight inside the fuselage. Balancing results in the elevator staying at the same deflection where it was, when bumped up or down by a gust or vibration, because it has the same mass ahead of and behind its hinge line. Tightening things up is good, but really just moves the critical frequency to a higher velocity.
      An interesting question for the group weould be:
      What is the fastest your DF has flown, IAS? Ours has been to about 165 knots.

      Terr O' in humid So. IL
      Subject: Re: [Dragonflylist] Elevator Control Horns


      Dave and Jack--------- I built my Dragonfly with the original elevator
      setup and flew for maybe sixty hrs. I always checked the elevators for
      up and down as part of the preflight and started to notice a bit of
      slop. Maybe 1/8 up and down. My wife and I went flying one day in pretty
      turbulant conditions and was going a bit fast when flutter set in and
      the entire canard was ossilating severley. Having read of flutter I
      quickly pulled power and yanked back on the elevator to put some
      positive pressure on the system. It slowed down and the flutter stopped
      , but on the way back to the airport anything over 110 and I could fell
      it starting up again. After landing the elevator would move up and down
      1/2 inch. I grounded the airplane and did the mod as recommended by
      Hapi. Now I have a three inch hole in the side of my fuselage.
      If you look at the original setup, they have a fixed phenolic bearing in
      the fuselage side and one in the center of the fuseleage.
      My concept was to have the same fixed bearings, so you only have a 5/8
      hole in the fuselage side. The bearing in the center of the fuselage
      also has a 5/8 hole.
      The control system is almost the same as the new one you have except it
      is in two pieces. The piece that goes to the center of the plane has a
      sleave welded on it so the piece entering from the outside can slide in.
      This is the place that after everything is tight and in place you
      install a small pop rivet and then drill out another hole to the 3/16
      undersize that I had mentioned earlier.
      I you use the new system as it is, in order to get it into the fuselage
      with the control horn in place you need to have a large hole in the
      fuselage. You also need to install the phenolic hold down pieces and
      that's not a simple chore.
      The most critical part of the entire assembly is the attachment o the
      elevator. If you glass in the plywood piece with the nutplates and use
      the two small bolts along with the one through the torque tube you will
      have no slop. This is the place where most of the slop occured.
      Originally , drilling the hole exactly tight on the torque tube was a
      challenge, but with the new setup the other two bolts on the control
      horn add to the stiffness.
      If I had it to do over, it would have the bearings in the fuselage side
      and the center of the plane with a two piece assembly that slides into
      each other secured with one, properley installed 3/16 bolt.
      With this setup you also need to make the elevator trim and pasenger
      side control horns with a sleave and have it attachable by a bolt.
      Look at the old setup and the new setup and hopefully I explaned it
      well enough. Either way you decide you definitley need to do the mod at
      the elevator for sure.
      Your understanding of how I have my two inch wide filet attached to the
      elevator is correct. I also went to the airport and measures my contol
      horn that are connected by pushrods to the pilot and copilot sticks.
      They are 4 1/8 inches from the center of the 5/8 tube to the hole for
      the 3/16 bolt. I still need to bend my contol tubes slightly to give
      clearance for the fuel tank. With this length I still have lots of
      movement in the stick and it is not as sensitive. Clear as mud??? Hope
      I helped-------- Canada Chris--- Mark 2 turbo Subaru Dragonfly.


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    • Dorothea Keats and Chris Walterson
      Terry -------- No , my elevators and ailerons are not mass balanced. I have only flown to 170 mph indicated and only in calm air. I usually cruise at 140-145
      Message 2 of 17 , Sep 1 1:24 PM
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        Terry -------- No , my elevators and ailerons are not mass balanced.
        I have only flown to 170 mph indicated and only in calm air. I usually
        cruise at 140-145 indicated. I fly my little Quickie at 150 mph and it
        isn't balanced either. I know I should and some day I will, but when my
        flutter occured , it was largely due to the slop in the system.
        ------------Canada Chris
      • P Hildebrand
        I have flown KPG frequently at speeds over 180 knots even in some light turbulence. Controls are solid. After reading comments from some folks getting flutter,
        Message 3 of 17 , Sep 4 1:26 PM
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          I have flown KPG frequently at speeds over 180 knots even in some
          light turbulence. Controls are solid. After reading comments from
          some folks getting flutter, even at low speeds, I think the mass
          balancing is critical. I put 1/2" x 12" 4130 tube (I had it handy)
          full of lead on the leading part of each control. I glassed them on
          as far outboard as I could without interference. Then I built
          balance arms for the inboard similar to the news letters. I poured
          in enough lead into the buckets unto they balanced, then added a bit
          more. My controls feel light and solid.


          --- In Dragonflylist@yahoogroups.com, Dorothea Keats and Chris
          Walterson <dkeats@n...> wrote:
          > Terry -------- No , my elevators and ailerons are not mass
          balanced.
          > I have only flown to 170 mph indicated and only in calm air. I
          usually
          > cruise at 140-145 indicated. I fly my little Quickie at 150 mph
          and it
          > isn't balanced either. I know I should and some day I will, but
          when my
          > flutter occured , it was largely due to the slop in the system.
          > ------------Canada Chris
        • Dave Morris
          I put the wooden ribs into the inboard ends of the elevator today and found that the DBFN article with the mandatory mods does not mention a few other things:
          Message 4 of 17 , Sep 6 9:34 PM
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            I put the wooden ribs into the inboard ends of the elevator today and found
            that the DBFN article with the mandatory mods does not mention a few other
            things:

            1. You have to cut about 1/8 to 1/4 inch off the elevator tube in order to
            make it flush with the wooden rib. Otherwise the control horn will not lie
            flat against the rib.
            2. There doesn't seem to be a diagram anywhere of the bolt that you are
            supposed to put through the reducer and elevator tube.
            3. You have to be careful when you glass the rib into the elevator that you
            don't get any epoxy into the bolt holes with the nut plates on the back of
            the rib. It would ruin your whole setup.

            I've posted a few photos of what I worked on today at
            www.PlansPhotos.com Go to Chapter 6, page 11

            Dave Morris



            At 10:07 AM 8/30/2003 -0500, you wrote:

            >See
            >http://www.davemorris.com/elevatorchange1.jpg
            >and
            >http://www.davemorris.com/elevatorchange2.jpg
            >
            >Dave Morris
            >
            >At 09:42 PM 8/29/2003 -0700, you wrote:
            >
            > >O.K. guys, I know this is common knowledge but I dan't
            > >find the info right now. What is the new length and
            > >distance between centers of holes for the new control
            > >horns?
            > >
            > >Thanks,
            > >
            > >Jack
            > >
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          • Dorothea Keats and Chris Walterson
            Dave Morris ------ For the bolt that goes throught the reducer, follow the plans original plans installation. Grind your 3/16 drill bit down a bit at the
            Message 5 of 17 , Sep 7 10:54 AM
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              Dave Morris ------ For the bolt that goes throught the reducer, follow
              the plans original plans installation. Grind your 3/16 drill bit down a
              bit at the flutes to make it a few thousands undersize for a tighter
              bolts fit.
              I'm sure you realize this but just in case, did you drill your phenolic
              yet? When you do, Cut the phenolic out to size and then drill the holes
              for the 3/16 bolts. Then cut your phenolic at the center of where the
              torque tube will go. Bolt the two pieces together and then clamp the
              phenolic in the drill press and drill your hole for your tube. It is
              also a good idea to file a few thousands from your spade bit to allow
              for any wobble in the press. Hope this helps-------------- Canada Chris
            • CB Romero
              HI Why not just use a #13 drill. =.185 if you want an interference fit. How do you know what hole size you are actually getting when you grind flutes? CBR
              Message 6 of 17 , Sep 7 5:39 PM
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                HI
                Why not just use a #13 drill. =.185 if you want an interference fit.
                How do you know what hole size you are actually getting when you grind
                flutes?
                CBR

                Dorothea Keats and Chris Walterson wrote:

                > Dave Morris ------ For the bolt that goes throught the reducer, follow
                >the plans original plans installation. Grind your 3/16 drill bit down a
                >bit at the flutes to make it a few thousands undersize for a tighter
                >bolts fit.
                >I'm sure you realize this but just in case, did you drill your phenolic
                >yet? When you do, Cut the phenolic out to size and then drill the holes
                >for the 3/16 bolts. Then cut your phenolic at the center of where the
                >torque tube will go. Bolt the two pieces together and then clamp the
                >phenolic in the drill press and drill your hole for your tube. It is
                >also a good idea to file a few thousands from your spade bit to allow
                >for any wobble in the press. Hope this helps-------------- Canada Chris
                >
                >
                >
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              • oneskydog@aol.com
                Dave, I just bought a set of new elevator torque tube weldments. One piece I will be cutting the huge hole in the side of the fuse, and building a removable
                Message 7 of 17 , Sep 7 8:31 PM
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                  Dave,
                  I just bought a set of new elevator torque tube weldments. One piece I will be cutting the huge hole in the side of the fuse, and building a removable root fairing
                  to cover it. Bob has a nice set on his plane that bolt on with hidden bolts.

                  Cutting it and drilling for a bolt is going back to the original problem a 3/16 hole does not have enough bearing area even if it is a drive fit from my understandind of the problem.

                  I was in Dallas today on my way to New Orleans.

                  Regards,

                  One Sky Dog
                  Dave Morris ------ For the bolt that goes throught the reducer, follow
                  the plans original plans installation. Grind your 3/16 drill bit down a
                  bit at the flutes to make it a few thousands undersize for a tighter
                  bolts fit.
                  I'm sure you realize this but just in case, did you drill your phenolic
                  yet? When you do, Cut the phenolic out to size and then drill the holes
                  for the 3/16 bolts. Then cut your phenolic at the center of where the
                  torque tube will go. Bolt the two pieces together and then clamp the
                  phenolic in the drill press and drill your hole for your tube. It is
                  also a good idea to file a few thousands from your spade bit to allow
                  for any wobble in the press. Hope this helps-------------- Canada Chris
                • Dave Morris
                  The reducer is a weird choice. The DBFN mod says to use a 7/8 OD steel tube. The inside diameter of the tubing inside the elevator is 1 minus 0.035 wall
                  Message 8 of 17 , Sep 7 9:06 PM
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                    The reducer is a weird choice. The DBFN mod says to use a 7/8" OD steel
                    tube. The inside diameter of the tubing inside the elevator is 1" minus
                    0.035 wall thickness, which is 1.00 - 2x0.035 = 0.93". The 7/8" OD is
                    equivalent to 0.875", which leaves a gap of .0275" all the way around. It
                    means there is basically nothing connecting the torque tube with the
                    elevator tube except that AN3 bolt. Seems a little odd to me. And if
                    that's the way the original plans design has it, then I fully understand
                    why they wanted to add a plywood rib with 2 more AN3 bolts to hold the
                    thing on there!!!

                    I just get infuriated every time I look at the plans for this plane. They
                    are so under-illustrated and poorly written. Aarrrghhhh. I estimate it
                    takes me 3 hours to read, re-read, re-re-re-read the plans for every 1 hour
                    of actual construction.

                    I also discovered that the elevator trim plate on the LH torque tube
                    assembly hits the canard drag bulkhead, so I'm going to have to cut off the
                    forward half of it. No big loss, because I plan to use a Strong servo
                    motor to control the trim anyway, and it uses a self-centering spring, so a
                    single attachment point is OK.

                    Dave Morris


                    I made my bearings last weekend. I don't have a photo of them yet, but
                    they look pretty nice.

                    At 01:54 PM 9/7/2003 -0400, you wrote:

                    > Dave Morris ------ For the bolt that goes throught the reducer, follow
                    >the plans original plans installation. Grind your 3/16 drill bit down a
                    >bit at the flutes to make it a few thousands undersize for a tighter
                    >bolts fit.
                    >I'm sure you realize this but just in case, did you drill your phenolic
                    >yet? When you do, Cut the phenolic out to size and then drill the holes
                    >for the 3/16 bolts. Then cut your phenolic at the center of where the
                    >torque tube will go. Bolt the two pieces together and then clamp the
                    >phenolic in the drill press and drill your hole for your tube. It is
                    >also a good idea to file a few thousands from your spade bit to allow
                    >for any wobble in the press. Hope this helps-------------- Canada Chris
                    >
                    >
                    >
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                  • Dorothea Keats and Chris Walterson
                    CBR--------- The trouble with drilling the elevator control, you haven t got it clamped in a drill press and any movement with the drill will open up the
                    Message 9 of 17 , Sep 8 2:12 PM
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                      CBR--------- The trouble with drilling the elevator control, you
                      haven't got it clamped in a drill press and any movement with the drill
                      will open up the holes too big. You can use any size drill bit you want
                      as long as it's a bit smaller than 3/16. Upon final assembly I insert
                      the bolt in the top hole and then brace the elevator and give the bolt a
                      good wack with a hammer. This makes for a tight fit. The control horns
                      take most of the load and this bolt is just added security.--------
                      Canada Chris
                    • Dorothea Keats and Chris Walterson
                      Sky Dog------- As I said in the other post, the bolt in the elevator tube is the last resort bolt. The other two in the contol horn thats attached to the
                      Message 10 of 17 , Sep 8 2:15 PM
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                        Sky Dog------- As I said in the other post, the bolt in the elevator
                        tube is the "last resort" bolt. The other two in the contol horn thats
                        attached to the plywood in the elevator take most of the
                        load.----------- Canada Chris
                      • Dave Morris
                        The article also does not mention glassing the rib in place, but that would have to be assumed, else there is nothing really holding the rib in place against
                        Message 11 of 17 , Sep 8 4:47 PM
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                          The article also does not mention glassing the rib in place, but that would
                          have to be assumed, else there is nothing really holding the rib in place
                          against the inside of the elevator except the "last resort" bolt, and we're
                          back to the original problem.

                          Dave Morris

                          At 05:15 PM 9/8/2003 -0400, you wrote:

                          > Sky Dog------- As I said in the other post, the bolt in the elevator
                          >tube is the "last resort" bolt. The other two in the contol horn thats
                          >attached to the plywood in the elevator take most of the
                          >load.----------- Canada Chris
                          >
                          >
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