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:

Nose view:

Tail view:

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!

Hello DSSC.
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

David

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.
David

After the excitement of finishing The Plan I rather fancied celebratory drink and a sandwich. Not any old sandwich, a rib sandwich – two thick slices of aluminium filled with 13 balsa blanks. Once this aeronautical snack was rasped into shape (and the drink consumed), I finished it off with the sanding block, then repeated the whole process for the opposite wing. Hey presto! Two identical sets of 13 ribs.

‘Back in the day’ carbon spars hadn’t been invented, well at least I’d never seen one. We always used spruce. Seeing carbon amongst the balsa at my local store I thought why not? Not really having a clue, I went for two lengths of 6mm carbon tube with an 8mm joiner which seemed pretty light and remarkably stiff. Back at The Hanger I roughed up and epoxied the carbon tubes, then tapered and assembled the balsa trailing edge. So here we are with the spar, the TE, and two piles of sandwich filling:

I noticed that John said his laser cut K7 ribs had temporary little tabs sticking out that held each rib in perfect position above the building board. I had to devise my own way which was slightly complicated by my wing being not only tapered in both chord and thickness but also having a tip airfoil that’s different to the root airfoil. In the end I pinned tapered strips of scrap balsa to the board and pinned each rib to these. Theoretically this would hold each rib at the right height while the rib-spar joints dried. The aft strips remained pinned to the ribs until after the LE and TE were glued on. To make sure the ribs were equally spaced and vertical I cut all the bits of spar sheeting first and used them as temporary spacers. Just to make doubly sure the wing was ‘true’, at each critical stage I kept weighting it down with lead onto scraps of 18mm ply, packing the TE to take account of the tapers.

Next task was to try this new-fangled idea of sticking servos in the wings (well new to me anyway). In real terms, servos in the 70’s were more than twice the price they are today. More importantly, todays can be less than half the size. There didn’t seem any point using the fixing screws supplied as there’d be no way to access them so I just glued in a few scraps of balsa to hold each servo in place. I reckoned the necessary cuts in the LE sheeting would be weak spots in the wing so I beefed them up with tiny scraps of 1/64” ply. You’ll have realised by now, I ‘have a thing’ about using up scraps.

Looks like those exiting servo leads are going to be very vulnerable. I’ll have to address that later.

Next the center section sheeting went on. Then I ‘slotted’ the ends of the carbon spar to accept those distinctive ‘Peacemaker-style’ wing tips, fashioned the flaperons from 3/8” sheet, and cut the P-style tailplane from 3/16”. There’s something very satisfying about watching your own design gradually turn into reality (even if it was inspired by someone else’s).

Meanwhile, with Christmas looming, I’ve been making two chuck gliders as gifts – one for each of our elder grandsons.  I found a delightful little design called the Aleda by Joshua Finn on YouTube which I scaled up to 12” span. I added little bendable rudder trims. Here they are before being sealed and decorated: