No announcement yet.

1955 Kirby Motor Tutor, for electric RET RC ...

  • Filter
  • Time
  • Show
Clear All
new posts

    Time to think of wing struts. 3mm captive nuts have been inserted into the inner face of these 5mm balsa triangles, cut to fit into the fuselage structure...

    The struts will have electrical ring connectors at each end, which will be screwed to these captive nuts, probably using nylon knurled screws. I'm not sure about the wing end, whether to simply have hooks for the ring connectors, or install nuts there, too. I'm slightly worried that, with wing flexion, hooks will not give adequate support. Screwing into the wing would be more positive, but I'll have to re-cover a panel in the upper wing if I now, at this late stage, want to fit captive nuts to the waiting block in there. Another, less 'destructive' option would be to inset nylon nuts into the underside. I'm still not decided, but I'll have to jump one way or t'other soon.
    Meanwhile, it's also time, I think, to introduce Kirby, the young lass I've chosen to be the pilot of this 'plane...

    Fresh from the 3D printer, she weighs 12 gr, as she is hollow, and very thin-skinned. She'll not remain blue for long; in fact she has already two coats applied, with more tomorrow. Specifically designed for this build, using elements from several sources, she took over six hours to print. Now for the dashboard, and maybe (on option...), a pilot's seat...


      Progress, but slow; oh, so slow....
      The 'turtledeck being sheeted, one side at a time...

      And the fairing behind the pilot...

      The plan has this elegantly curved, in true aero manner; mine is resolutely straight-lined, as best I could.

      The 'contact' key is now fitted, and the electronics plugged in and tested. The ESC I had installed turned out to be duff, and I've nothing lightweight on hand, so I temporally replaced it with a massive 40A ESC, which is overkill. I could still fit it into the space below the battery compartment, though, so may be adopted, just the same. I've ordered a few more ESC's of suitable amperage, for this 'plane or future builds.
      Meanwhile, Miss Kirby has had a removable platform put in, so she can start to become familiar with the layout.

      Next step: fuselage covering...


        Time to bite the bullet and sheet the fuselage. Here's the underside being set up, with a few helpful clamps to hold the film roughly in place. The huge 40A ESC can be seen, now strapped in, under the nose bay...

        Not much point showing pictures of the fully-covered fuselage, as the film is transparent. Here, instead, is another inglorious shot of the first primer coat going on...

        Yes, I know; she's ugly like that. A necessary evil; t'will all become clear later, hopefully.
        On a side note, I've up-graded the compressor for the airbrush, and changed the nozzle and needle from 0.3 to 0.5, to get better cover with less clogging for lack of pressure. I'm still on the lower slopes of the painting learning curve, but it's starting to show promise. The final proof will be the finished 'plane, of course, so I'm still apprehensive and cautious. Another coat this afternoon or evening, probably, then she'll be set aside to 'cure' for a while. I'll get back to the wings at that point, and solder the wheels onto the undercarriage..
        Onward and upward..!


          Today's very modest exploit: fixing the wheels to the landing gear structure. Brass curtain fittings are 'adjusted' with my tin-snips, then soldered to the inner, then outer ends of the axles, aided by Our Eldest once again. The wheels have brass tubing inserts to make up the diameter difference...

          Not much, but I'm pleased of late with however little I can get done.


            I can never resist an opportunity to see how it's coming along, all together, so here's another 'teaser' ...

            Miss Kirby seems to be still optimistic; that's a good sign...

            Tomorrow, a quick look at wing struts, and more airbrushing, probably.


              I have on order carbon tubes for making wing struts, but I need to establish their length, as well as to find the definitive position for the wing. To this end, I've fitted temporary dowel struts into electrical ring connectors, screwed in place with nylon screws. Here's another inglorious photo of the poor thing having these fittings attached...

              It may (or may not..!) be noticed that she has taken on a different hue; the gloss black seen in previous shots was simply the recommended undercoat for the silver acrylic which she now displays. It doesn't show up so well in these photos, but she has now has a far more glamourous allure.
              Back to matters in hand... This is the second fitting of the tailplane, as, having glued it up, I checked back an hour or so later to find that it was askew, despite the clamping. Maybe I slipped, or knocked it accidently, I don't know, but I thought it best to cut it away and redress it. Once again carefully measured, for symmetry and alignment, it has now been glued back in place, assisted by Our Eldest this time...

              Yes, of course, the lump hammer is back, holding the piece firmly until the Titebond has set.
              Another small mod was deemed necessary, fitting a nylon bolt through the wing centre section, screwing into the pilot's headrest. Without this, the tension of the rubber bands had a tendancy to lift the wing trailing edge, altering the incidence. This bolt will insure that the wing is held down positively to the airframe.
              That's all for today.


                A final spray of Minwax Polycrylic Satin, a ray of sunshine; what more is needed for a few photos..?

                Miss Kirby enjoyed the outing, and is looking forward to rolling tests later on today or tomorrow, with maybe some glide testing in the pasture before the house, and, of course, a Maiden Flight at some future date, to be decided. No, those are the temporary struts; there are still a few details to sort out, such as the skinning of the landing gear, and battening down the hatch, but I think I can declare this 'plane finished, bar the First Flight. Videos will follow as and when they're shot.
                So, more to come, but thanks already to those who have contributed to this Build for their encouragement and (mostly humourous...) comments, and a huge 'Big Up' to Ken for the wonderful vinyl lettering and flashes that make all the difference.. Stay tuned...

                Ah... I forgot tyhe 'cockpit' view; sorry ...

                Last edited by Dad3353; 05-31-2019, 09:53 AM.


                  Added detail...
                  All-up weight : a fraction under 700 gr (1.5 lb in Old Money...).
                  Power drawn from 3S, flat out, tethered to the table : 65 W

                  Enough to potter around the park, maybe..?
                  I may have a problem with the elevator, as it turns out to have stacks more 'Down' than 'Up', despite best offset, rate change curve and what-not on the Tx. As all is sealed up inside, I may have to practice some 'keyhole surgery' (ie : cut a panel of film away...) to access the linkage. I'll see how she glides, first, then decide whether to attack the servo end or the clevis end (both enclosed...). I do have some deflection, which I can even out between Up and Down, but it's little. Little may be enough, of course, but I usually bank on having some 'spare' in hand, which is definitely not the case here. We'll see after gliding, then.


                    First 'mod', as I'm not convinced of the way I've done the detachable wings. They're fine 'static', but I haven't built in enough of a means of having 'em stay together; they rely too much on the struts. My 'knee-jerk' solution ... Glue 'em up...

                    It's handy that Our Eldest built his luthier's workbench so long. Exactly the right length, in fact, for holding the wing structure in place while the Gorilla Glue does its job. The wings are dowelled into an aluminium tube through the centre section, with a pair of locating dowels towards the trailing edge. Already a pretty nice, binding fit, the glue should hold all of that together with no issues. I'll probably wrap tape, or laminate a ribbon, around the joins, then paint 'em. That'll keep the wing in one piece, at least during a hand launched glide..!


                      Following on...

                      The joining of the wings went off quite well, but was not without issues. Despite precautions being taken, the Gorilla Glue seeped out, and it's a swine to clean up cleanly..! I did my best, and it looks worse in the photos than up close ...

                      I've received the fibreglass cloth I'd ordered, in order to 'glass' the wing centre section and joins; this was applied this evening, again with assistance from Our Eldest ...

                      It's now setting overnight; I'll probably give it another coat of paint once the resin has fully cured.
                      As usual, I'd mixed twice as much resin as was needed. It's difficult, I find, to dose in such small quantities; here I weighed 10 gr of resin and 6 gr of hardener, and it was still twice what's required. Anything else need 'glassing', then, whilst I'm at it..? Hmm... Maybe. I've also received my carbon tubes, so I've dipped one end into the goop and fitted on the ring crimps...

                      ... hoping that it will be enough to secure them in place. I've only done one end, as I need to fit the wing to the fuselage to trim these struts to their final length. I'll then glue on the other crimps, probably with CA glue.
                      I suppose others are like me, and 'hoard' stuff, just in case it shows a future use. Such is the case of the pot seen holding these struts in regal manner. It's original contents were black peppercorns, and the lid has several appertures, one of which just happens to have four holes, just right for holding the carbon tubes aloft. Unfortunately I've many other 'odds'n'sods' that have yet to bring to fruition their potential. Such is Life.
                      As there was still resin in the jar, we also cut another couple of strips of cloth to 'glass' the nose of the Bixler, which had yet again fallen victim to my mis-handling of the sticks, and had split open again. With these bandages around the nose, maybe she'll resist better my attempts to drill a hole through to China. Still, I'm learning, and better to bust the Bixler than the Kirby, no..?
                      Once the glassed Kirby wing is ready, I'll fit a new method of fixation, as I'm not too happy with the piano-wire 'cabane' I made. A bit simpler, I think, with an elastic hooked from below, just behind the windscreen. More of that later, though...


                        A Charming Lady for certain........I am proud to be a part of her charm.


                          I've fitted the definitive, carbon tube, struts ...

                          ... The wing is now very solidly mounted, and rigid. I've also changed the wing attachment, with a ring screwed into the underside of the wing, in the cockpit, and a brass hook at each inside lower corner of the cabane struts/firewall...

                          ... which hold a pair of elastics in place. Almost 'scale', as the full-size Kirby has a triangular wing strut at the fore..! These elastics are not just black for scale appearance, they are thin slices of a bicyle inner-tube, with less 'give' than normal rubber bands, and hold the wing down very tightly. All we need now is a suitable week-end's worth of decent weather; no chance of that this week, and the next looks no better for now. Patience, then; I'll get on with renovation of a SIG Piper J3 Cub in the meantime.
                          To be continued, when a First Flight becomes possible...


                            Your patience and attention to detail is wonderful. I used to have both qualities but have misplaced them.


                              Originally posted by COCHISE99 View Post
                              ...I used to have both qualities but have misplaced them.
                              The lettering and decor on the sides of the Kirby are proof enough to the contrary, my friend..!


                                By error on my part, I had to adjust the elevator control rods after they had been sealed up inside the fuselage. I chose to do this at the rear, hoping that it would be easier to patch up than a cesarian in the side of the 'plane. Now that the control centring has been finalised, I had to repair the wounds. I had simply sliced through the painted skin to allow access, but not removed it completely, simply folding the panels to one side. Rather than re-cover with new film, I decided to glue a piece of thin card in place, then fold back the panels, gluing them down to the card. In the photo it looks far worse than in daylight...

                                ... but a touch-up with the airbrush should sort that out, once the clamps are off (and the new compressor arrives..!). I'll post pics of that when it's done, but otherwise, there's only waiting for a flying window; I can't think of anything left to do, until First Flight shows up any mods that need attention.