I um’d and ar’d over how to hinge the flaperons and eventually decide not to – to just let the film be the hinge. Multi-tasking was never my strong point so rather than try and wing-cover and hinge all in one go I decided to top-hinge the flaperons with a narrow strip of film first, I also covered the fuselage fairings before the whole wing:
Covering went well. The wing and tail undersides are dark blue. I was surprised to find that the cheap white Hobbyking went on better than the expensive dark blue Oracover. The winglets had 2 coats of sanding sealer, 2 of white enamel, and 2 of red:
The radio installation had been planned for from the outset so seeing it all fit – and the servo slide working – was all very satisfying. Working out all the angles to achieve ‘more up than down’ was fun too:
The flaperon horns needed to sweep forward:
…and the elevator horn had to sweep backwards to be 90 degrees to the control cable:
I was pretty pleased with my first attempt at signwriting with Oracover after asking for advice on the Model Flying Forum.
Close-up of my first attempt at function mixing with a sliding servo:
The wing-mounted fuselage fairings hold the wing halves together:
And the finished model – the DR 420 – ready for her first test flight. She balanced at 1/3 of her root chord without any ballast needed – pure luck!
From John H.
Hi Everybody, here is a forwarded message from Rob Oats of the Okehampton Model Flying Club. It would seem the best option as suggested, is to just hold just one event at the most suitable venue Sunday the 11th Oct.
Good Morning Everyone,
Storm Alex has scuppered our plans for the aerotow at 18 Acre this
Sunday. We have next Sunday as the reserve, however this clashes with
the aerotow at Little Haldon. If the weather conditions favour Little
Haldon we will cancel. If weather conditions mean an aerotow in Exbourne
is more favourable than Little Haldon then we will consider holding the
event in Exbourne.
The K7 continues to grow slowly and the bags of laser cut parts are starting to diminish. After doing all I could to the fuselage I started on the tail end. The fin is integral to the fuselage so a rudder was next and fairly straightforward of balsa and 0.4. ply. A double horn was made from G10 2mm fibre board; very hard but files well. The closed loop cables will connect to this.
Lots of laser cut parts went together to construct the tail plane and this was covered in 0.4 ply as is the fin, all very strong but getting heavy! Elevators x 2 of built up structure are driven by 2 servos in the tail plane.
I made a mistake with the hinging and got the hinge line in the incorrect axis but hope to address this later.
As it is quite thick at the hinge line and the elevator needs to swivel rather than just move up and down.
I have now begun the first wing, will be in touch! (Robert: I look forward to seeing more pics of this stage John)
If anyone is subscribed to Scale Soaring UK, more pics of John build can be found. Click here – UKJilles Smits 1/3 K7 Build
Stuart Chambers recently sent in a photo of this build by his No. 1 son. Does anyone recognise it? (of course Stuart knows the answer) Feel free to post your answer comment here or if more convenient over on our Facebook page.
We have had a couple of enquiries lately about whether powered flight is allowed on Dartmoor. The simple answer is No. As there may be visitors to our area intending to fly on Dartmoor and use our website to search out the best sites to soar, John asked for a statement to be added to our home page to reinforce our constitution and the advice given in our Dartmoor site guide.
“It is worth reminding club members and others visiting Dartmoor to fly RC that whilst non-powered flight is allowed, any form of powered flight whether electric or combustion is banned by the Nation Park Bylaws. Due to this importance this bylaw it is written into our constitution and included into our guide on flying on Dartmoor.”
An electric palm sander is a wonderful thing! If only I’d had one in the 70’s I could have filled the whole bungalow with balsa dust rather than just my little bedroom. Oh and the wonderful smell of cellulose dope… those were the days. And mixing my own diesel fuel… I regularly bought Amyl Nitrite and Ether over the counter in the chemist at just 15 years old! Anyway, back to the build…
After quite a lot of sanding:
Adding the fuselage fairings to the wing roots:
Then the wings had their final sand:
What you can’t quite see behind the winglets is, what was going to be the outer 4 cm of flaperon is now a short section of trailing edge with built-in washout. Will that prevent the nasty tip-stalls I’ve been warned about? We’ll have to wait and see.
To help achieve ‘more up than down’, the flaperons needed horns that were raked forwards. I couldn’t find any for sale so made my own using bits of plastic from an old bucket:
So here she is with her control surfaces pinned on just for the photo…
I don’t know about you but I always like to start with the wings.
Using root and tip rib templates cut from some old aluminium I made a couple of ‘rib sandwiches’ using up bits of scrap 1/16th balsa and new ply for the root ribs. It’s a method I used ‘in the old days’, does anyone else still do this(?) I have no idea but I do think tapered wings are well worth the extra effort.
Building semi-symmetrical wings on a flat board required quite a bit of careful packing but before long the wing halves (one left and one right – hopefully) were mostly done minus the full length flaperons, winglets, and washout. Oh, and minus the fuselage fairings that would eventually cover each root (what?? – more on that later).
The fuselage was even more fun to build. Again, the plan was to use up lots of bits of scrap balsa (I hate waste) through creating a sort of ‘exoskeleton’ whereby the hard/curved outer skin of 1mm ply was fitted first then the thickness built up by adding strips of soft balsa internally. Curvy parts of the top & bottom were strip-built too.
I don’t have any kind of jig so I glued on the fuselage sides back-half-first making sure the fin was truly vertical before pulling the nose together a few days later.
Then the strip-work began in earnest until of all of my short 3/32, 1/8, and 3/16 scraps had gone.
Clothes pegs are great!
Whilst waiting for glue to dry I made up the sliding servo tray using a scrap of plastic cable trunking, a bit of old ali carpet strip, a bit of 1mm ply and off-cuts of light mahogany. Much more fun than transmitter programming(!), well, I think so anyway.
Underside view showing the internal strips and bottom strips going on:
At this point I decided to find out about setting up the flaperons and posed a couple of questions on the Model Flying forum which proved most informative (https://www.modelflying.co.uk/forums/postings.asp?th=167572&p=1). More news soon.
I thought you might be interested to see my new slope soarer design which carries on from where I left the hobby in 1980. The repeated design/build/fly/crash, design/build/fly… cycle which dominated much of my spare time in the 70’s, culminated in this rugged 2-channel model I still have 40 years later.
My own design from the seventies
My new design uses the same boxy fuselage construction – full length thin ply sides, soft 1/4″ balsa top and bottom – but instead of 1/16″ all-sheeted wings I’ve copied the open-frame Kloudrider wing construction but with a semi-symmetrical section and higher aspect ratio.
I’ve designed things with ailerons in the past but not flaps. I rather fancied doing both this time but I’ve never really understood why control surface movements try to make different parts of the wing behave in different ways at the same time. So, I decided to go for full length flaperons (which I’ve also never done before) and to try the old ‘sliding servo’ way of mixing the controls which I heard about in the 70’s but never tried.
(By now you’ll have worked out that I’m some kind of weird old-timer who doesn’t want a foamie, doesn’t like programming, but does like a challenge!). “No wonder they used to crash” I hear you say.
The fuselage shape is influenced by the ASW 15 and 17 but I also like the way the 28 is concave on the underside of the fuselage. I also fancied having a go at a T-tail as I’ve never done one of those either. Oh and those little winglet things too – they look like fun. I decided to make the front end pretty big so I can get all four servos in and still have plenty of room for my fingers which don’t work as well as they used to. Anyway, that’s enough waffle for now. Here’s my hand-drawn plan which I’ve already deviated from slightly… (more in the next post):
My new design
Thanks to John for organising a ‘back to our roots’ slope soaring day at Black Hill last Sunday. There was a good turn out and we can see from the photos and video clips posted over on our Facebook group that members had a great time and demonstrated their skills of soaring without any power aids. Stuart Chambers has sent in some photos. Check these out on our Gallery page and the launch photo chosen to head up our home page. Thanks Stuart.
An an update on Johns 1/3 scale K7 build:
Progess on the K7 has been up and down yet quite a few more hours put in. The fin is virtually complete and covered in .4 ply and built integral to the fuz so nice and strong.
I have also finished the rudder which will be operated by closed loop and hinged with Robart Hinges. What has been apparent is the abundance of laser cut parts supplied with this short kit, comparatively little stock wood needed so far, and in the majority of cases they fit firmly together like a jigsaw. I have built nothing on the plan as the laser cut parts dictate positioning….brilliant so far!
Also nearing completion are the 2 elevators, again lots of precut parts. These will be driven by 2 wing servos in the tailplane, never be down that route before. Again the tailplane parts include a ply servo tray especially for this. As this build is so large things are made easier by big pieces that do not break in your hand and seeing what you are doing with older eyes much better. Onwards.