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1923 B3 'Charlotte II' in 1:3 Scale

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  • #31
    Thanks, Petr! Truss built ribs are pretty cool in appearance! The 'Hershey Bar' section ribs weigh 7 grams each. A similarly sized 1/8" medium density balsa rib without any cut outs or aluminum tube end weighs 6 grams. The truss ribs are stronger (or at least as strong?) in vertical loading but the balsa rib is stronger in lateral loading. Since the wing gets compression struts with drag and anti-drag bracing the ribs won't carry much in the way of loads so I'm happy with the weight of the truss ribs.

    Elevator and aileron construction begins! The 'Charlotte II' had some kind of as yet to be discovered coupled drive mechanism for the control surfaces. One was driven by a regular pull-pull cable(?) but the other was driven by an internal gear drive with bevel gears(?) at the control surface hinge line. Vince Cockett and I discussed possibilities via e-mail. The easiest route is good ol' 'artistic license' again! I'm gonna make each one operate via pull-pull cables. The horns were drawn, cables' angles determined, et al. They were cut from micarta and finished sanded in preparation for painting. Music wire was heated cherry red, their ends hammered flat, hinge pin holes drilled then they got a general filing and clean up in preparation for the painting and install. The hinge pin will allow the control surfaces to be removable. The LE of the control surfaces will be built up in layers to allow placement of aluminum tube bushings to guide the hinge pin. I'll start cutting wood for the control surfaces tonight.

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    • #32
      The micarta horns attach to bass wood 'rib' parts which are reinforced with 1/32" marine ply. I made a little jig to test fit the depth of the hinge so it can get epoxied into the rib. There are only two hinges per control surface so these have to be robust and accurate. When they were done they were test fitted to the control surfaces' spars. The elevators are the outermost control surfaces. Aluminum tubing was epoxied into a slot cut into the back of the spar. These tubes are spaced so that the control surfaces won't move or 'creep' laterally. These tubes also allow a 'piano hinge' pin to be removed allowing the control surfaces to be taken off the wing. All parts cut as 'doubles' at one time to ensure symmetry between left and right sides. The very last picture shows them all completed. The one in the lower right corner has its inside corners 'radiussed'. The other three need to be finished similarly. Once that is done then the wings get built!

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      • #33
        I forgot the diagonal braces on the elevators. They are the ones in pic above with aerodynamic counterbalances. I stuck a note on them so I won't forget! I got my train layout done! Looks like it, right? Actually, it was prudent to clear the bench to make spars. While bench was clear the 'twist' was measured at different stations along the wing span so the packing could be properly cut to hold the spars. The spars were fabricated. The fore spars are 1/4" square section spruce while the aft ones are 1/8" x 1/4" spruce. They have the same size shear webs of balsa. Mild sheet steel used to make strut attach fittings. These will bolt to 1/4" marine ply blocks properly placed as shear webs. One pic shows how the truss ribs 'thread' onto the spars.

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        • #34
          Michael, so true the statement its 80% Preparation, 20% Installation .
          Len Buffinton
          Team Horizon Hobby

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          • #35
            Yessir, Len! More time is spent preparing for activity and that doesn't even include my slow brain processing time figuring things out! The rib locations were marked onto the spars and the strut attach fittings bolted in place. The packing to hold the spars was pinned to the board. The ribs were slowly threaded onto the spars. This required lifting the spars off the packing multiple times then resetting root end alignment when the spars put back down. Not difficult but tedious. Ribs will get glued once the compression struts with their drag and anti-drag wires are installed. The ribs will get shimmed so the bottom of the rib contacts the spar. Music wire was threaded thru the TE 'eyes' for a quick check of alignment. Not bad alignment so far since the ribs aren't glued yet! Another pic is supposed to show how the noses of the ribs are pretty much in the same plane (pun intended ) to place the false spar and not induce twist. The extended portion of the wing that has the control surfaces gets built 'in the air' on spacer packing blocks. That'll really get tedious! I wonder how the 'real deal' was built?

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            • #36
              Looks like "somebody" figured out how to post his pictures!!!
              Nice layout and fantastic work...
              Len Buffinton
              Team Horizon Hobby

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              • #37
                Yeah, Len! I think I have the pics at a size my ISP can handle. No more 'activity wheel' spinning in the top left corner of the page after I post!
                Spruce compression struts were let between the spars. 1/4" marine ply triangles cut and got epoxied to the compression struts. Drag and anti-drag cables get attached to these. Triangles of 1/16" marine ply added to spars. The angled extension spars attach to these.

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                • #38
                  The front spar is parallel to the board but the rear spar isn't. The shear webs get custom fitted into the rear spar incrementally as the spruce was bent to be level with the board for the outer extended portion of the wing. It wasn't a difficult thing but just tedious. The 'angled' spars were fitted and measured for shear webbing. Again, another simple but tedious process. There was a lot of measuring going on to keep everything aligned! The TE with gussets got installed. The false LEs with gussets got installed. The tip with gussets got installed. Epoxy used here. CF tow will get added later.

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                  • #39
                    Looks great Michael, I am looking forward to following along!

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                    • #40
                      Hey... thanks for checking in here! Can't wait to get the Klemm and build it for motor-gliding and towing. I have a remote starter unit that can get fit to the gasoline powered engine that I'll put on it, too!
                      Here is the basic left wing structure... all 87" of it!

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                      • #41
                        Here are construction pictures of the right wing. Spar anchors are marine plywood. These hold the diagonal spars for the extended portion of the wing. Once done both wings will get some glassing of these joints to really tie the diagonal spars to the main spars. The root rib is 1/4" marine ply and has to be hand fitted to the spar ends. They are left removable for now so the bell cranks for the control surfaces can get fitted to them later. After a nice long meticulous 'T' bar sanding session the false LE strips got attached. The straight edge was used to insure they remained fair.

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                        • #42
                          Thanks Michael. Looks like the Klemm will be going to a good home! Very interesting wing shape, I like it, a lot! I think I may buy a glider kit to build once we get settled. I may never fly it, but it sure would be fun to build! Talk to you soon! Keep up the great work!

                          Jason

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                          • #43
                            Jason, I hope you build AND fly a scale sailplane soon! It's so much fun! I hope I can do the Klemm justice. A little more work has been done on the Charlotte II. A jig for setting the hinge height off the table has been made along with a jig to set the gap of the LE of the control surfaces from the TE of the wing. A center rib was reinforced to carry the hinge more robustly where the control surfaces horns are located. Cap stripping has commenced. Once they are on and the paint dries on the hinges and horns then they can be installed so the pull-pull cable exits can be fashioned.

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                            • #44
                              Kelly, you and I continue down this strange long lost brother path. I have more websites and documentation saved for a planned Klemm build than you can imagine. I've temporarily shelved the plans to focus on the Sparmann mainly because I found so many Klemm-modelled examples already out there I started to want something even more different than the Klemm. However, I still love the design and think one would make a great tow plane - and you know we need a good one around here.

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                              • #45
                                Ain't it the truth! We need to get the aerotowing fever started around here. I'll have to have a look at some of your Klemm documentation. That's easily worth a family pizza night out and beer, right?
                                I have been busy! Fairleads for the control cables were made from brass tube, bent and support structure cut and everything epoxied. The rib that these attach was re-inforced with 1/32" ply. Cable exits were built. I used short segments of fishing line connected to the control surface horns in order to get the exits placed correctly. Fiddly but easy enough!

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                                • ingrahal
                                  ingrahal commented
                                  Editing a comment
                                  I did the same thing on the Cherokee. N72DG had the rudder cables coming out through slits in the covering. I used string to determine where the exits would be and noted the measurements. Then after covering I new exactly where to cut the slits.
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