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Jul 15, 2019, 11:03 AM
'Douglas' to his friends.
Thread OP
We had a power cut this morning (don't know why; it's rare...), so, by the light of a USB lamp, I made a servo tray of sorts. First, a platform between two handy longerons inside the cabin...



Then a longer piece, suitably pierced for the servos...



... with a hardwood strip glued in fore and aft of the servos, to better hold their screws...



... which will look something like this, once installed...



The power comes back on, so I can continue with applying the film. It looks very 'yellow' in these photos, but it has more of an orange-y 'Cub yellow' tint in daylight.
Time for a question, for those familiar with this 'plane, and similar builds. Is it reasonable to have the hinge line for the rudder further aft than the hinge line of the elevator..? Here's a desk-top mock-up, with the fin post behind the elevator joiner...



Here's the same mock-up, with the hinge lines aligned...



This second version pleases me more, but I can't see any way of realising it. Here's a mock-up on the tail end of the fuselage (the fin has to sink down, of course; the tailplane needs slotting for that...)...



The fin post is flush with the end of the fuselage, which seems reasonable, but the tailplane and elevator have to be more forward of the rudder hinge line. Is that correct, or is there some trick I've missed..? I 've not used the dowels for joining the tailplane halves, but I don't think that that affects the issue, as it's the elevator joiner that has to be somewhere. Am I over-thinking this..? The only plan I have is for the Berkeley kit, which is rudder only, and so neatly avoids the issue..! Thoughts folks, please..?



Edit : Hmm... In looking around t'web, and this Forum, I see that the obvious solution is the one adopted all over, with the elevator hinge line more forward than the rudder. It makes sense, of course; I'll go quietly and do it like that, then.
(... but I still prefer them aligned..!)
Last edited by Dad3353; Jul 15, 2019 at 11:16 AM.
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Jul 15, 2019, 01:33 PM
'Douglas' to his friends.
Thread OP
There, that's done...



Just a dry run, here, but it all fits together, and should be pretty sturdy. I'll not glue it all up, yet; I'll further the fuselage, and get the tail end covered, first. Meanwhile, I've still a wing and ailerons to cover, so, whilst I have the iron out ...
Jul 15, 2019, 08:48 PM
'Douglas' to his friends.
Thread OP
Profiting from the amiable cooperation of Our Eldest, the wing covering goes a-pace. Here's the start...



Trying it out for size, with only the centre panels left to do ...





... and shrinking of the completed wing being performed, attentitively...



It'll get another going-over tomorrow, and the ailerons will follow.
One gets an impression of the size of this thing now; it's the biggest (most voluminous...) 'plane so far, quite a chunk. That's not a Bad Thing in itself, but I'm going to have to re-think my storage options at some point.
As an aside... I'm minded of an old story of a bloke who wore shoes one size too small. When asked 'Why..?', he would reply : 'It's such joy when I take 'em off..!' In similar ilk, I have been building biplanes of late (Udet Flamingo, Curtiss Condor, Aeromaster...). It's such joy to know that, once done, there's not another wing to do for the Cub..!
(On the other hand, I've another Cub to build..! )
Jul 16, 2019, 02:33 AM
I like real wooden aeroplanes!
Sundancer's Avatar
Coming along nicely Douglas, should be a great performer and nicely docile like all Cubs. One of my ex-pat flying mates has just learned to fly on an ARTF Carbon Cub. I did the first flight when it had all sorts of technology installed - GPS, auto-land, AS3X, something called "virtual fence" etc. etc. and it was an absolute ANIMAL. I did get it back on the ground in one piece, just,but it really was most unpleasant as the technology was fighting me all the time. We whipped the innards out and installed a simple receiver for the next flight - what a difference, it was now a delight. We then set up the wireless trainer link on our DX6's and inside 3 flights he was doing take offs, after 5 he landed it successfully and now, two weeks later he is completely solo. One thing I will note is that this has the "tundra" wheels fitted which does make landing much easier, you can really "plaster it on" without it finishing up kangarooing down the runway. So I have high hopes for your Cub.

And oh yes, you were over-thinking the fin/tailplane business - but then I think over-thinking may be a personality trait of yours sometimes?
Jul 16, 2019, 03:44 AM
Bellanca Kruesair
epoxyearl's Avatar
here's the J-3 assembly on that 'location' question that you've already solved .
Latest blog entry: Ban Birds.
Jul 16, 2019, 05:39 AM
'Douglas' to his friends.
Thread OP
Cheers, Earl; thanks for that. My version is not so bad after all, then..!
Jul 16, 2019, 06:39 AM
So I'M meant to be in control?
Colonel Blink's Avatar
I'd advise 'tundra wheels' and a rigid (non castoring) tailwheel if my Jack Headley Cub is anything to go by..... it's a fight to try and drag it off the ground before it goes running off at some incongruous angle bearing no relationship to the intended direction of travel!

With a bit of rudder mixed in to the aileron, it is nice to fly though and has the 'tail high' flying attitude of the full size.
Jul 16, 2019, 06:58 AM
'Douglas' to his friends.
Thread OP


Check, CB. I'll definitely fix the tail-wheel (you've already seen what trajectories my previous Builds have taken; very few are straight..!), and go for Big Chunky Wheels. I've a few in stock; I'll try them first.
Jul 16, 2019, 06:40 PM
'Douglas' to his friends.
Thread OP
That's the ailerons covered ...



... and the empennage hinged and glued up, after checking for 'square'...



It'll be glued into its place when I've installed the control rod 'windows' at the rear of the fuselage. Meanwhile, the servos have been screwed in, and the servo platform attached to the fuselage, with a pair of nylon bolts going through to captive 'claw' nuts below...



Tomorrow, the control runs, then, and trial fitting of the electronics. Maybe aileron hinging, too, if all goes well...
Jul 17, 2019, 04:56 PM
'Douglas' to his friends.
Thread OP
If there's one thing that's as bad as hinging (and there is...), it's control runs. A real pain in the [insert anatomical part here...]. Here's a pre-loaded exit window, covered in advance to simplify the task later on...



The tubes for the control runs have been installed, despite everything, but it's slow, laborious work, a real chore, lining it all up while the plastic tubes bend, the holes bind, the CA glue used for the port exit window won't hold... The list continues. The reward, in the end, is the fastening of the empennage to the fuselage...



That'll set overnight; I'll see what there is to do next in the morning. Probably not hinging.
Jul 18, 2019, 04:36 AM
'Douglas' to his friends.
Thread OP
Before covering the fuselage, some detail stuff needs to be painted, so ...



It's not an exact colour match, but close enough for me, and changes with the light in any case. Not enough surface to warrant the airbrush, so the more traditional paintbrush did the job, first with grey surface primer, then yellow acrylic. I primered the landing gear, too, basically to stop it going rusty from handling with my fingers..!
Jul 18, 2019, 08:46 AM
'Douglas' to his friends.
Thread OP
The aileron servos have been installed, with Ohio 'Snug-A-Plug' joiners keeping the connectors safe from coming apart...



The hinging will wait; I'll need extra hands for that delicate operation.
Meanwhile, on with the control runs. The elevator is done, here's the setting up of the rudder cable. The servo has been centred, and the rudder clamped 'streight ahead'. The rudder clevis is in place, so the cable has to be cut at exactly the right spot...



...marked with a black dot...



... then cut to length with the tin-snips. A harassing moment, with no room for error. There's about a centimeter of adjustment available in the clevises, and, of course, Tx trim, but it's always better to be as close as one can get first of all. Here's the result, a short video of the controls being cycled...

SIG Cub Servo Test (0 min 50 sec)


I've checked the throws; the elevator has twice the recommended travel (1" up and down instead of 1/2"...), but can't be reduced more in the 'plane, so I'll do the rest in the Tx. The rudder is fine (1" each side...), and has scope for more or less if required. I'll probably re-link the rudder servo, to reduce the 'twist' we see, which will give more throw, so may need reduction at the rudder end if there's too much. Best to have slightly more than slightly less, I reckon, as excess can be dialled back. Next up : ESC, Rx and battery, aileron hinging and coupling, fuselage covering and tests for C of G. Tout un programme...
Jul 19, 2019, 08:46 AM
'Douglas' to his friends.
Thread OP
I had the extra pair of hands needed yesterday evening for applying the laminating film hinges for the wings, so that's another chore done ...



This morning saw me soldering the electronics for the Cub's innards. The contact key has been set into the port flank, a 40A ESC chosen and the whole shebang poured into the cabin, connected up and tested. A short video, to illustrate..? Why not...

SIG Cub 02 (2 min 0 sec)


Not that much longer to wait before rolling tests, then..!
Jul 19, 2019, 09:18 PM
'Douglas' to his friends.
Thread OP
Meanwhile, there's cowls to paint. I thought about covering with the same film as the 'plane, for colour match, but decided that I'd probably not be best pleased with the result, given the curves. I have a good compressor now, and a decent airbrush, so...
First a coat of grey surface primer...



Then some yellow...



No, it's not 'Cub Yellow', at least, not yet. Once I've played around with the bottles I have, I may be able to roughly match the film. I'm not looking for exact, anyway, just close enough to not be too shocking. More tomorrow, then, and maybe fuselage covering.
I've weighed the 'plane, fully equipped, wheels an' all, and the total is around 1k600 or so, depending on which battery I choose. She's heading to be well under 2kilos, in any case. I played around with the C of G whilst I was at it, and she balances at 60mm from the LE with the 4S Lipo against the back of the firewall. The doc I have says to never fly with C of G further back than 72mm, so I've a bit of margin there, I think. The motor is rated at 388W, drawing 35A. I've a 40A ESC (burst 55A...), and the thrust with a 10x6 is given as 1k580, so I should be in some sort of ball-park there, too. Enough to potter once around the field, I hope..!
A visit from Our Daughter and The Littl'un tomorrow, for a week, so things may slow down a bit. That'll give the paint time to dry..!
Jul 25, 2019, 12:35 PM
'Douglas' to his friends.
Thread OP
A fixed tailwheel is screwed, then glued, in place. Here, the backing film is used to restrict the growth of the Gorilla Glue, inducing it to go further down instead...



The cowl only goes so far over the nose; a curved sheet is needed to fill the gap just in front of the cockpit/dashboard. I have no sheet of the required width, so I'm gluing two sheets together. I've cut a diagonal over both pieces, to ensure a fit, taped 'em, then opened the fold to accept Titebond. They'll be laid flat over more backing film, to avoid sticking to the table, and will have the black set-squares to keep 'em flat...



Once set, it'll be curved to shape and fitted to the nose. I'll probably paint it black, as anti-glare for the pilot.
Meanwhile, covering has continued, and can, I think, be declared 'Finished'.



There's really not that much left to do, just some tidying up inside, make a cabin plate for the pilot and passenger, then ssee about a rolling test or two. S'getting close...

Oh yes, struts. I'd forgotten them. Hmm... I'll look into it...


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