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

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    #61
    Hooray..! The new compressor arrived today. Here it is, 'installed' (read 'poked'..!) under the work table...



    It's a far cry from the second-hand one that died on me; much quieter, and with all the gauges, filters, doodahs and wotnots that befit a decent bit of gear. I lost no time in trying it out on the patch inflicted on the Kirby...



    With any luck, this Saturday will be fine, with little wind, so I'll see about popping over to the flying field with both the Kirby and the Aeromaster. Fingers crossed, then..?

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      #62
      Hoping for fair skies and gentle winds.....

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        #63
        An afternoon at our local Flying Club, site shared with the ULM club as will be seen. An opportunity to 'maiden' the SFV 2019 Kirby Motor Tutor, and my Lou Andrews Aeromaster. I've edited out the really duff stuff, but it's still some 14 minutes in all, so get a cup of tea on hand first, with a biscuit or two.
        No, not much flying, but valuable lessons learned, and no broken bones, so a worthwhile session...

        https://youtu.be/dTm0K9Z71ZM
        For the Kirby...
        I had been warned that a steerable tailwheel could cause problems, and I now see why. Fine for taxying on tarmac (it worked at home...), but far too sensitive on grass when trying to lift off. I'll see about cutting it off and fitting a fixed wheel instead.
        I had neglected any check on lateral balance; the starboard wing has a definite weight penalty. Easy enough to redress, though, so not too worried about that. It's just dumb on my part that I'd not picked up on it. Never mind.
        At one moment, the rudder became stuck 'hard left'. Again, entirely my fault; I'd allowed a RX cable to foul the rudder servo. Simple enough to clear on the ground, but fatal in the air..! I must be more careful in attaching all this stuff in these cramped quarters. A lucky break, and a warning for another time.
        I'll have to check again the wing incidence compared to the tailplane, and probably shim the LE a bit.
        The motor has, on paper, enough power to fly the 'plane, and the prop is, in theory, correct, but there may be a lack of power just the same. Jérome was wary of opening the throttle too far too soon (rightly, seeing how she 'squirrels' on rolling...), but I'll see how to check for static thrust by some means, and maybe even 'up' the prop a notch. We'll see...

        For the Aeromaster...
        Again, steerable tailwheel issues; not much use on grass, so I think I'll render it rigid.
        After a couple of tentative runs, Jérome finally gave her enough throttle to lift off, but she keeled over to the left, and gently dived into the long meadow grass beside the strip. No damage, thanks to both the low speed and soft stems, and also the rubber bands releasing the top wing easily. Why the dive..? Probably bad motor alignment, not enough right thrust. I'll have to double-check lateral balance there, too. She did lift off, but I can't really claim that as being a First Flight. Maybe next week-end, if the weather is clement.

        Friday afternoon and evening had me setting up and playing drums with our rock group for the French 'Fête de la Musique' at our local pub. It went down very well (we played for twice as long as had been planned...). That, plus the energy spent at the flying field, has had as a result inordinately high blood suger levels this morning, so I'll have to take things easy for a while. Luckily enough, there's a few decent football matches on t'telly today, so I'll just relax and pick things up another day. That's all, then; bye for now...
        Last edited by Dad3353; 06-23-2019, 02:47 PM.

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          #64
          No damage, lots of lessons learned.........beautiful aircraft............ you did a glorious job.....I am proud to have played a small part in their creation.

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            #65
            Well, after the First Flight attempt, it's back to the den for analysis. I've checked the incidence of the tailplane to the fuselage, and it seems good (level with the cockpit edge...). Checking the wings shows a different story. The port wing has a reasonable incidence of around 2-3°; the starboard wing has none at all..! This would explain why she tries to lift off on the left and then tips over. I had a look at the struts, to see if they'd been badly fitted, but found that it's rather the wing itself which has taken a nasty warp. Here's some photos to try to illustrate. Here the wing is flat on the table, looking at the railing edge...



            Even allowing for camera angle, it looks to be twisted. Upon measuring, I find, with the centre section flat, 30mm at the LE wing break (where the struts are attached...), both sides, but at the TE, there's 15mm port and 30mm starboard...





            Question: Any suggestions for bringing the wing back to symmetry..? I'm pretty sure this warp was not present before filming, and didn't notice anything amiss after, either, but the evidence is there. Should I strip the film off, maybe just the starboard wing..? I don't think that playing around with the struts would do much; I'd rather the wing was good first, then strut it. Any takers..?

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            • COCHISE99
              COCHISE99 commented
              Editing a comment
              TWO MAN JOB with a twist that severe...........Perhaps one fellow keeping the un-warped side stable,.......... then another twisting the warped side and reheating the covering with an Monocote iron or a heat gun on low heat to stretch it back taunt. I have had this issue and this seems to remove as much of the warp as possible........hold in place until the film has cooled....DO NOT HIT THE VINYL I SENT WITH A IRON OR MUCH HEAT FROM A HEAT GUN.....baby steps until the majority of the twist is out......Google search this issue for other opinions.......good luck.
              Ken
              Last edited by COCHISE99; 06-28-2019, 10:11 PM.

            #66
            Static thrust check done, using a new digital fishing scale. The Kirby on the floor, without her wings, tethered to a table leg with the scales. I've three props, two 8x4, and a 9x6. The first 8x4 (the one used last week-end...) gave 300 gr at full throttle. The black 8x4 gave 280 gr flat out, and the 9x6 wooden prop gave just under 220 gr. The Lipo is 3S; we tried a 4S with the wooden prop, which gave 315 gr, but this fell away rapidly, and I stopped it. Just as well, as the motor was getting very hot, even with this short run of a few seconds.
            Result..? The 'plane weighs around 700 gr, so the best prop would appear to be the first one tested, with its 300 gr. Enough for Small Field Vintage flying, hopefully, but I think she'll need full throttle to Rise Off Grass, or maybe even a hand launch. Useful info, though, showing me that the motor is at its limit. If any more power (thrust...) is really needed, it'll mean using a different motor.
            We did the same test for the Aeromaster; results in the appropriate topic...

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              #67
              Understood, Ken, I'm doing this in stages. There's no danger of affecting the vinyl; my modest, low-power heat-gun gets hot alright, but not enough to burn the film nor strip paint, and I'm moving it over the surface all the time. I can see the shrinkage going on, and this treatment is not as invasive as it may appear. It's had it's third treatment so far, and is in much better shape. It'll rest again, now, overnight, so I'lll see tomorrow if it's going to hold the incidence equally each side. Fingers crossed...

              Comment


              • COCHISE99
                COCHISE99 commented
                Editing a comment
                I am glad to hear it seems to be correcting the issue......good on ya!

              #68
              I found an 8x6 prop today, so thought to do another 'tractor pull' thrust measurement. Here she is, tethered to the table by the digital gauge...



              ... and this is the reading at full throttle (275 gr...)...

              .

              If there's not enough 'oomph' with this motor, I have a Prop-Drive which will fit which, according to e-Calc, shuold give about 30% more.

              Meanwhile, I must confess to not having painted the fullest of pictures concerning last Saturday's attempts at flight. In the video, it can be seen that, following a blocked rudder, I removed Miss Kirby from the cockpit, and cleared the obstruction. Rather than put her back in place, I chose instead to stuff her into my pocket. Bad move. When adventuring into the wilderness to recover the fallen Aeromaster, I bent down, and felt (and heard...) an ominous 'Crack'. Yes, I'm sorry to admit that, by clumsy inadvertance, I had decapitated Miss Kirby. Can she be repaired..?



              Indeed she can, and that's what I've done this evening. Here, we see her in, once again, ignominious posture, head down in a jar, 'watched over' by her headless torso...



              'Why this incongfous pose..?', I hear you ask. Here, in video, is the explanation...

              https://youtu.be/uBqDr8h_JdM

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