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1:4 1928 RRG Professor

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  • #31
    Formers for the wing mount pylon structure were fabricated and let into the fuse 'box' structure. Paper patterns were drawn using the plans then fitted into the structure. The first former does not actually attach to the wing. It is for support of the others. It was made in halves using light ply. The second two formers were made from plywood. To fit each into the fuselage box a corresponding side diagonal had to be loosened one end to allow clearance for the former to be 'swung' into place. This wasn't hard work... just fiddly. You can see a wire piercing the pylon portion of the formers. This will be the wing retention pin. Tabs from the wing will hang down into the open pylon so that the wire can capture them. One end of the retention pin will be part of the headrest. At least this will eliminate some bolts! These strut braced birds have lots of nuts and bolts holding them together.

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    The two similar pics are a stereo pair. Cross your eyes to look at them and if you are binocular then a 3-D effect will occur rendering more detail!
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    • #32
      I was hoping to lay the keel on the bottom but no such luck. Making the top and bottom formers has been taking more time than expected. Second pic shows some of the formers before install. The forward most ones required a lot of angled sanding. You can see what is required by looking at the plan's side view as shown in first pic. I did get servo rails and servos installed. I'm using Hitec HS-525-MG servos. The third pic show ply being added to bottom nose section so that a skid mount block can be added later.Again, the last two pics are a stereo pair!

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      Time for supper!

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      • #33
        Some attention was given to the wing mount pylon. A maple block was drilled to receive the wing retention pin and its brass guide tube and this was epoxied in place. Spruce diagonals were epoxied in place so that they are attached to the maple block along with fuselage former. This combination should be pretty stout in tension (flying loads) and compression longitudinally (landing loads). So far this arrangement has worked well for the Eaglet! I started putting floors in place. The diagonals were removed wherever a floor was placed. Save weight anywhere, right?

        A schematic was drawn for the elevator input travel. The elevator pin moves a total of 11mm which isn't much. The schematic shows a triangle with the apex being the pivot for the 'servo throw reducer'. The servo arm, as configured, has 32mm total travel. The 'servo throw reducer' has to be ~100mm long to reach down to where the servo is located relative the the elevator push rod is located. So, I drew a 90mm eye-to-eye triangle with a base of 32mm then found where an 11mm width was located and constructed the 'reducer' from phenolic accordingly. The 'reducer' is pierced by an aluminum tube with a wood dowel inside it. A lite ply diagonal supports it. Larger aluminum tube segments act as bushings which are captured by gussets. All connections with push rods are interference fits. As said previously, slop in the system has to be minimal. If the servo was connected directly to the elevator push rod the servo wouldn't have much travel and the least bit of drive train play would be a cause for trimming issues and possible flutter (I guess)! If you spend time on making one control surface 'right' the elevator is the one!!!

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        Comment


        • Tango Juliet
          Tango Juliet commented
          Editing a comment
          And how are you making your pushrods? Are they wood dowel with threaded rod ends?

        • ARUP
          ARUP commented
          Editing a comment
          TJ, the push rods are 1/4 wood dowel. 'Z' bends are used where the push rod connects to 'servo throw reducer' and an adjustable clevis is at the servo end. There is a custom fitted connector at the elevator end as seen on the previous page.

      • #34
        Forward fuselage doublers were cut from 1/16" ply. More 1/16" ply put at the pylon. The pylon has a 'step' because the incidence was not proper when the fore sheeting was put in place. It'll be easily rectified with some filler pieces, later.

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        The rear third section of the pylon will be addressed, next.

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        • #35
          Work is done every day but there isn't a lot to show for it! The pylon as shown above narrows too much on the rear vertical so it had to be built up to widen it. The 3-views just won't 'flesh out'. Compromises and interpretations must be made. The pylon fairing was constructed pretty much 'by eye' since it was difficult to determine how it was made from photo evidence. The top wing platform 'teardrop' extension was added then the angled 'spine' from the tip of the teardrop to the fuselage was added. Verticals were added so the 1/64" ply sheet will have 'purchase'. Hash marks were penciled onto the rear portion of this pylon fairing showing how the angles/ bevels were sanded. I used a special 1/4" wide sanding stick that has sand paper on one end only... the other end of the stick maintains contact with other side of structure. Rubbing the stick to and fro gives the desired bevel to which the ply sheeting will contact. Fiddly stuff it was but it's done!

          I made the fore skid mount block from Bass. It is a custom sanded fit and will be drilled to receive a bolt to capture the skid. I have three more to make. I want to finish those then make the upper and lower keels. The last pic is my 'Tailored Pilots' pilot! He is looking pretty cool!

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          Gute Nacht!

          Comment


          • Tango Juliet
            Tango Juliet commented
            Editing a comment
            Looking good! I've ordered two pilots from Tailored. One in 1/3.5 scale to be my Flight Lieutenant and one in 1/4 scale to be my Cadet.

        • #36
          TJ, you'll like those pilots as they are very nice and ... poseable! I drove my '59VW around. Gotta get the engine 'broken-in'. My buddy, Bill, and I put a new engine, tranny, disc brakes-lines-dual circuit master cylinder in it not too long ago. On to the Professor! Paper patterns were made in order to cut the fore upper and lower 'keel' parts. The parts were cut from 1/16" marine ply. The rear portion of the keels were made from 3/8" balsa. Two 12 degree bevels was put on the edge. It is a simple thing to do. Measure the angle of the fuselage formers (12 degrees from horizontal), set the table saw blade, push the wood through, flip over end for end then push the wood through again to get a nice 'V' bevel that has twelve degrees each side! There is a pic showing my 'fancy' half sand paper sanding stick. I used to to true the bevels. Two more skid mounting blocks were installed. Only the rear-most left to go!


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          Buenas noches!

          Comment


          • Tango Juliet
            Tango Juliet commented
            Editing a comment
            Now I'm hungry for Nachos!

          • ARUP
            ARUP commented
            Editing a comment
            You didn't get hungry for schnitzel on the previous page?

        • #37
          Mmmmm..... nachos!
          Deer Sanny Klaws, al I wan for Crismiss iz Dwimill kut tof weelz. I bin uh good boy an it wuz dat bad kid Len hoo pulld on Luisas har not me!

          The wing strut carry through mount was fabricated from 3/16" music wire. Heat the ends cherry red, hammer flat, drill for 4-40 bolts to pass, dress and shape with Dremel, sand, clean mask and paint... whew! When the paint dries it can get mounted tonight.

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          Have a great day!

          Comment


          • Tango Juliet
            Tango Juliet commented
            Editing a comment
            What the heck kind a bit is that in yer Dremel? Whatever it is, it looks like it's been worn to a nub!

          • ARUP
            ARUP commented
            Editing a comment
            Yes, TJ. That's why I'd like Santa Claus to bring more cut off discs to me! I wore that last one I have on hand down to the nub all right!

        • #38
          The Professor should be a fine flying model, Fred China built one at the same scale and I flew it when I was up his way, I was tempted to take it home with me.

          Comment


          • ARUP
            ARUP commented
            Editing a comment
            Mr. China sure built some pretty sailplanes! Dave Smith has shown me some YouTube vids, too!

        • #39
          The strut carry-through wire/rod mount was cut to length from bass wood. It was grooved on the table saw then the groove was finished using the off-cut 3/16" music wire. Just scrape the groove with the music wire edge until it nestles perfectly! Balsa needed to be relieved on the fuselage to clear the strut attach wire/rod. Epoxy does the job to attach the assembly to the fuselage.

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          Gotta get to work!

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          • #40
            Michael. Got a question for you. What’s your source for long sheets of 1/32 and 1/64th plywood? I’m working on a 1/3 ASK-14 and will need ply skins eventually.

            Comment


            • ARUP
              ARUP commented
              Editing a comment
              Dennis, Aircraft Spruce and Specialty has 4 x 4 sheets of 1/64" ply. http://www.aircraftspruce.com/catalo...nnishbirch.php It is the Finnish Birch Ply (metric) Balsa USA used to sell 4 x 8 sheets and they would send them rolled. I can't find a source for 4' x 8' sheets of 1/64" ply anymore.

          • #41
            A 1/4" marine ply block was epoxied into the rear of the fuselage for the tail skid which will come later. The mounting blocks and hardware for the skid were put onto the fuselage. The front mount has a 'T' nut to firmly attach the skid. The next two mounts have a brass tube bushing to let the bolts travel up/down during takeoff/landing. A Nyloc nut secures the bolt. The skid was ripped from a block of Ash. I had to make multiple passes on my Microlux table saw to get the width and thickness needed. The skid was sanded, soaked in hot water (absolutely use no ammonia unless you don't mind the wood becoming brittle and easily broken) then clamped onto a jig to set the curve to follow the fuselage contour. When dry it was drilled for the mounting bolts then stained H.Behlens 'Nutmeg Brown'. This is a water based stain so it is perfect for staining wood before gluing assemblies. Oil based stains won't work in this regard. The skid is slotted at its rear mounting point to allow movement as the skid rubber hose segment shock absorbers are compressed.

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            Comment


            • #42
              More pics of skid stuff. The picture showing the Nyloc nut isn't great but you get the idea. The nut just keeps the bolt from dropping out of the airframe. The auto fuel tubing serves as shock absorbers. You can see the slot at the skid's end. There is a thin piece of auto hose under the front end of the skid, too. It's a good idea to allow the skid to 'move' otherwise the mounts might get 'torn asunder' during landings..

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              More to come!

              Comment


              • French1
                French1 commented
                Editing a comment
                Skid is always a difficult compromise to balance avoiding it to be removed at each landing or been to heavily fixed to the fuse and on a hard landing to rip all the bottom fuse.
                Third option is always to have good landing but quality my vary...at least on mines...
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