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

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

    A new Project, to be built before end of June, hopefully. Here's the plan and a picture of the original 'plane...



    I've now cleared a work top, laid out the plan and written out a wood list. Next step will be to check what I have in hand and what I'll need to order. I've plenty enough to at least start the fuselage or cutting out ribs, though.
    Speaking of which, I'm going to try an experiment. One method for producing ribs is to first create a pair of templates, sandwich balsa sheet between them and cut around. I've done this before, cutting the templates from ply, after marking the outline using carbon paper under the plan. Now, though, I've a 3D printer. Hmm...
    I have the Pdf plan, so I load it into Photoshop. I zoom onto the rib outline, copy it to a new page and fill it, black. This is saved as a Bmp file, and imported into 3D Builder, where I set its thickness to 5mm. I check the overall length against the paper plan, and save it as an Stl file. This is sliced by Cura and sent to the 3D printer. Here's the result...



    I'll see if they are any use as templates and report back...

    #2
    Continuing my folly, then, I've printed a set of 'soldiers'. Not really, of course (being rather more of a pacifist...), just a set of guides for holding ribs upright. I posted a full description on a 3D printer Forum, but there's what I've got, now...



    ... plus a dozen more, which will maybe replace the clamped Lego bricks I'd been using up till now for that task. I'll find out soon, as I 've ordered the wood that's lacking, notably the leading and trailing edges, and can now start laying wood onto the plan. I'll get going this evening, I hope, with the fuselage sticks; I'll also have a go at cutting and forming the ribs whilst waiting for the LE and TE to arrive (middle of next week..?).
    More, maybe, later on, then...

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      #3
      Here's my rib blanks, clamped between the rib templates. The odd shapes stem from trying to fit ribs onto the sheet in 'sardine' fashion, to waste less sheet. A fun exercise in itself...



      ... and the result of a couple of hours of notching (using hacksaw blades bound together...), whittling and much hand sanding...



      The templates did their job quite well, so I'm calling that a success. Improvements..? Maybe... I may try to incorporate pilot holes into the print, for passing skewers through. The PLA plastic is quite soft, really, so I had to be careful when cutting the notches to not saw the whole stack completely in half..! The sanding went off well, though, as there is a very different sound when rubbing down as far as the templates, and a different feel..
      I didn't get around to layng out sticks for the fuselage; best to leave something for tomorrow, eh..?

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        #4
        I'm plodding along, but slowly; oh, so slowly. Nevertheless, here's 'progress' so far...
        The first longerons are pinned in place...



        ... and preparations for a wing layout are ongoing, with 3mm hardwood spars...



        The 'soldiers' are waiting patiently their turn to spring into action. Meanwhile, a pair of root ribs have been formed, using the same 'printed' templates...



        They're very thick. I don't know why, but I'm doing what it says on the plan just the same. Normally I'd have made 'em from ply, but I had the balsa on hand, so...
        The red template has been 'printed' so as to make the series of ribs for the outer panels, which taper. I have to liberate the root ribs first, though, to re-use one of the blue templates. I still have the LE 'fish-mouth' notches to cut, probably this afternoon.
        There, now we're all up to date. More later, I hope, as the fuselage sticks get glued up...

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          #5
          Almost a 'blow by blow' account. The flank uprights are cut and glued in...



          ... then, when the Titebond is set, the diagonals put in place ...



          Leaving those to set, I turn to a wing panel. The TE is notched, with a 'Bruce' saw, after a guide cut is made, for better accuracy.. Here's the saw in place, with a rib to illustrate the nice fit of the notch. My 'Bruce' saw has two blades at one end, and three at t'other, to be able to notch two different widths. This is the 'two-blade' cut, for 1.5mm ribs...



          A dry fitting session, to be sure it'll all go together ...



          ... followed by 'the real thing', with the 'soldiers doing a fine job of holding the ribs true...



          I must say that I'm modestly pleased with these 'soldiers', as well as the rib templates. Much better than the Lego bricks, which are fine in themselves, but the clamping has always been an opportunity for extra clumsiness, as they need manipulation in a tight space, not my speciality. These 'soldiers' are simply placed over the rib, and do the same job.
          Meanwhile, the first fuselage flank is ready for duplication. A transparent film is carefully put in place, without disturbing the first part, and a second pair of longerons pinned down. The uprights follow, over the lower flank ...



          I'll leave that to set overnight, and add the diagonals to the upper flank tomorrow. I shall also see about making the tapered ribs; that'll be fun.
          More tomorrow then, hopefully ...

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            #6
            I cut a series of blanks for the tapered ribs; by a happy coincidence I was able to juggle the whole set from the strip left over from the parallel ribs. An 'interesting' exercise, fitting 'em all in without knowing what their shape should be, but it seems to have worked out well enough. Here they are, bolted between the 'printed' templates; first one side ...



            ... then 't'other ...



            Yes, I heeded the advice given concerning holes in the templates, and learned how to do that using the 3D software. The delicate part is not the editing itself, but 'knowing' how to align the two different forms. I used the lower spar notch as a reference, as all the tapered ribs will sit on that. The blanks were clamped between the templates, ensuring that they were all flat to the board and lined up with the LE, then two holes carefully drilled through the stack, and bolts run through. Half an hour of whittling and sanding produced this ...



            This stack contains the ribs for both outer wing panels, which implies that, because of the curve between the templates, the resulting pairs of ribs will not be identical. I'll trim them to the lesser of the pair once they're parted from the templates. They are numbered, so I will know which go together. They are all slightly long, too, to be trimmed to the TE once on the board. The TE strip I ordered is a little wider that that on the plan, which is handy, as it makes even more sense to notch it to accept the 'tail' of the ribs. This evening, probably; this afternoon will be spent watchin g the rugby. Back later, then ...

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              #7
              A lousy photo, but my eyes have gone, so... It's supposed to show the tapered wing panel, ribs now glued down, 'soldiers' on duty...



              Tomorrow, possibly, a Leading Edge and upper spars; perhaps even a wing-tip. There's another match in the afternoon, though...

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                #8
                There will be a slight delay in the next instalment, which was to be the cutting and fitting of the fuselage formers. I've found files for 'printing' a fuselage jig, so will get that going first; it should look something like this (but different colours, probably...)...



                Slight complications, of course, as the hardware store have in stock every imaginable type and size of bolts, except for those I need for this. Web order made; awaiting delivery in a few day's time.
                The square profile aluminium, too, is not in the 25mm size, either (23.5mm..? Why..?), so I'm editing the files to suit the profile. Mustn't have things too easy now, must we..!
                I'll cut the formers just the same, and maybe (just maybe...) lift the half-wing off the board to start the other one. That shouldn't be too hard, as the ribs are now already prepared. Hmm... Maybe...

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                  #9
                  The Leading Edge has been glued on ...



                  ... and the fuselage flanks unpinned from the plan. They'll be continued upside down, to benefit from the straight edge of the upper longeron, in this fashion ...



                  ... but, hopefully, mounted in the fuselage jig, once it's made (parts are 'printing' as I type...). Before lifting the half-wing, I still have the tips to do; here they are ...



                  ... and mighty beefy, too. Why the plan calls for 3/8 (9mm...) I don't know, as they'll be sanded down to much thinner later, but I had some gash pieces, so used them anyway.
                  No more this evening; bed-time. More tomorrow...

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                    #10
                    The cross pieces of the jig are being 'printed' as I type...



                    ... three by three (no more space on the machine's bed...). I'll do this three times,as I've nine rail blocks done (20cm rule to show scale...)...



                    Five hours for each set of three, after which I have to print the arms. Meanwhile I'm awaiting the nuts and bolts later this week, I hope.

                    I'll be lifting the half-wing this evening, hopefully, to start the second one...

                    Comment


                      #11
                      Not so good these days, so little gets done. However, there are still things that can go on without much active participation on my part. Here's one: the fuselage jig has been printed, and most of the nuts and bolts delivered, so I was able to sit in my armchair and assemble the stuff, then do a mock-up assembly to see how it'll work with the Kirby fuselage...





                      It's not fully adjusted, and won't be before the articulations receive their washers, yet to be delivered. It shows promise, though, albeit with a period of adaptation on my part.
                      Inspection will reveal a red 'printed' part; this is a template for the firewall, or, in my electric build, the motor mounting plate. The plan calls for 3/8 ply for this, and the template will serve to cut this out. It has also inspired thoughts of an experiment: I have ordered a reel of 'wood' PLA, which contains microfibres of real wood mixed in with the plastic filament. I shall print another firewall with this material, and see if there's any scope for making 'plane parts from it, such as formers. My off-the-cuff calculations indicate a weight penalty of about two to one, but I'll do one or two just the same, to see if there's milage in the notion or not. The ply piece is, of course, solid, but the red template has been made hollow, and printed flat, with supporting ribbing between the faces. Here's the print in progress; the ribbing may be seen (with a little imagination...)...





                      I'm sure that there are ways of optimising a piece of this nature; indeed, there are whole 'planes printed in various plastics these days. Is it possible to have a hybrid solution..? Will Titebond work well enough on 'wood' PLA..? I'll know next week, if health improves a bit. It's going to be a long week-end, I'm afraid, with little progress and lousy weather weighing on one's morale. Never mind; it'll pass. Onward and upward..!
                      Last edited by Dad3353; 03-14-2019, 03:36 PM.

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                        #12
                        The second half-wing has now been glued up, and is setting, watched over by my set of 'soldiers' ...



                        Later, perhaps this evening, the upper spars will go on, then the LE. It's advancing, slowly but surely...

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                          #13
                          Very nice use of 3d printing

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                          • Dad3353
                            Dad3353 commented
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                          #14
                          Upper spars fitted ...

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                            #15
                            LE is done, and wing-tip on, awaiting trimming...





                            Both wing halfs are now off the board; the centre section is next on the list to be built.

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