The Slingsby King Kite
Part VI: Final Building Steps and the First Flights
This is the sixth and final part of this series. Readers may want to the review previous parts before proceeding with this article.
The pilot would be very visible so it was a challenge to make a proper job of it. My sister offered to make clothes but then I had to have a body first. I used my own measurements (only slightly Photoshopped!) and made parts from 10mm balsa. In the elbows and knees I fitted Robart hinges, the hips and shoulders were fixed with shock cord. In this way you get a figure that can be positioned naturally. To attach the pilot’s balsa boots I glued a piece of M2 threaded rod fitting into a plastic tube (that is, the control rod stuff) in the poor man’s lower leg. A small bend in the M2 wire provided some friction. The hands were fastened into the arms with 1mm copper wire and the head was adjusted into the chest with a 10mm beech dowel and some Velcro as friction. Hands, feet and head remained removable to make it easy to get him into his clothes.
The pilot’s head was made from Sculpey a kind of clay-like plastic, which must be baked at 140C to harden it. The tutorial Sculpey 101 (see Videos below) gives a wonderful explanation how to do that, but it still was a time consuming job.
I started with a beech dowel of 10mm and wrapped aluminium foil around it. The head could not be solid as it might crack when baking. I formed the head adding thin layers of sculpey. It took a while but I liked to work on it and seeing how it really started to look like a person.
The instrument panel, just like the pilot, would be in plain sight. The problem here was that information about it was nowhere to be found. One photo showed a tiny piece and the panel seemed to be white. I also detected a white panel on a photo of a Petrel, so that was feasible. I decided to make a good job of it. Looking at the other gliders of Slingsby I had already ordered a set of instruments in 1:4-scale from AeroCockpit (see Resources) but I could not use the dials. I still had pictures of the dials from the previous plane, the Slingsby Gull. On the photo of the white instrument panel of the Petrel, the instruments were countersunk and I decided to make something similar. The instruments from AeroCockpit were delivered as a superstructure, but could be cut off.
Now I could make the panel proper. It was is made of two layers of 0.6mm plywood. After having marked everything, I drilled all the holes with a 1mm drill, including the centre of the holes in the panels that were clamped together. Then I cut the plywood on the front and back with a cutting compass, cut segments in it and could break out the plywood. I glued the two panels together with a few dowel pins. Then the holes turned out to be just a bit too small for the instruments and with the tapered handle of a screwdriver and some sandpaper I made them fit exactly. I glued another plate behind it together with two magnets to secure it into the plane.
I cut off all the instruments that had been built up so that only the bezel with the glass was left. But the compass should actually be a sphere. On Retroplane Eric Spore had already done something like that and it was a nice detail. So I rounded off a handle of a file, clamped a piece of PET (clear plastic) on a board with a hole, heated the plastic, pushed the file up and a tube over it and — lo and behold! — a nice sphere. I glued a strip of a photo of the compass in it and painted the sphere black on the inside. I also made the screws from black pins, filed the heads flat and made a saw cut. Now I had all the parts. All that remained to be done was the fun part, gluing everything together with PVA.
The instruments also needed the pitot tube, which I liked to be demountable. I made it from solid 2mm wire which was lying around. I don’t know exactly what kind of stuff it was, but it was not magnetic. I took two pieces, bent them to look like the example and soldered them together with silver. I left one piece of wire sticking out and put a triangular brass plate on it together with a square piece of brass tube. Finally a piece of iron and soldered it all together with silver. The brass square tube fitted into just in a larger tube, in which I glued a magnet. The larger brass tube is glued into the fuselage nose with 5 min epoxy from the inside. I had to hold the fuselage upside down to glue it into place, good for my body flexibility!
I hesitated about the skid but decided to make it massive, not sprung. I glued 12 layers of 2mm balsa with PVA using the fuselage as a mould, separating with cling film. After curing, I took it off and planed it into shape and covered it with Diacov (see Resources) to imitate the sailcloth of the skid of the real glider. Then I painted it white and glued it all on the fuselage. On top of that I glued the skid itself, made from 0.6mm plywood and two layers of 2mm pine. Then 2x2mm pine strips in the corners, to imitate the battens holding the canvas.
Back to the interior for a moment: I covered the seat with leather from an old wallet and made a control stick from aluminium tube, which slides over a piece of installation wire so that the stick could be bent into the desired position.
Apart from some details of the interior, the model was now ready. I had calculated the centre of gravity (CG) with cgCalc (see Resources) and it had to be 79 to 90mm from the front frame. I had to use 450g ballast, of which 130g could be removed in the white jar. In this way the CG could be adjusted between the two values without having to chop or break. Epoxy resin was poured over the loose lead pieces. And, yes, the weight of the epoxy was deducted.
Some more data of the model: span 3875cm, weight 4800g, wing area 85dm² and that gives a wing loading of 56.4g/dm².
My model was now almost ready to fly. I did some paint work on the pilot and some details on the interior, found with some searching and help from Scale Soaring UK (SSUK), the right lettering which my friend Adri Brand was able to cut the lettering which went on easily.
And then, suddenly, there was the opportunity for the first flight. The weather forecast was good, Rob Ten Hove offered to tow, Adri would coach me and Raymond was at the ready to do the photo and film work. That Friday there was quite some wind at the field. It was chilly and the sun to weak to break through completely. Rob’s Eco Boomster had no trouble with the King Kite. I had to trim the aileron quite a bit because of the strong wind.
After releasing from the tow and elevator trimming there was the moment of truth: the plane flew really well, tight and responsive, stayed on altitude fine and was a pleasure to fly. Of course there were no thermals, but I think that will be fine, too.
Another thing about the flying characteristics of scale gliders in particular: on a slope there is usually enough lift. However we don’t have slopes here and, incidentally, not many thermals close to the coast either. That’s why it is very nice that it has a decent sink rate.
The real King Kite had a pretty modern profile, which is why the HQ 2.5 airfoil of this model is not very noticeable. After a few minutes we had to land with flaps and ailerons slightly up — the real one didn’t have the latter.
The maiden flight of the King Kite was captured by talented videographer (and frequent contributor to the New RCSD!) Raymond Esveldt in a short film entitled Slingsby King Kite 1/4-Scale First Flight (see Resources). The video shows how happy I was that it flew well because the aerodynamics are sometimes hard to predict.
Apart from a few minor details my King Kite is ready. I would like to thank everybody who provided assistance and Modelbouwforum (MBF), Retroplane and SSUK for all the help. Especially a big thank you for Adri for all the milling and lettering, to Rob for towing and to Raymond for the photos and videos.
Additional build details can be seen on MBF in Dutch as well as on Retroplane and SSUK in English. Also, the King Kite flew on a tow meeting in Kampen, Netherlands and performed very well. All are linked in Resources and Videos, below.
I am really pleased with this scale glider and I thank you for reading about it these past months.
Good luck with your projects and see you all again soon!
©2022 Vincent de Bode
Resources
- AeroCockpit scale cockpit accessories. — “Products…are first of all intended for model-builders…make a high quality equipment of RC model aircraft cockpits…”
- cgCalc — “calculates and evaluates the center of gravity (CG), neutral point (NP) and mean aerodynamic chord (MAC) but also visualizes your design of conventional aircraft…”
- Diacov — Product page from the Sarik Hobbies website, based in the UK: ” Extra-lightweight iron-on polyester fabric! DIACOV 1000 is ideal for covering scale model aircraft, from…with high tear resistance and temperature stability…”
- ModelbouwForum — Forum discussion thread with additional build details of the King Kite in Dutch.
- Retroplane and Scale Soaring UK — Forum discussion threads with additional build details of the King Kite in English.
Videos
- Sculpey 101: Tutorial on How to Sculpt a Head with Polymer Clay on YouTube. — “We start with building the basic structure for a humanoid head. I tried to come up with a way for beginners to be able to get the proportions correct…”
- Slingsby King Kite 1/4-Scale First Flight — by Raymond Esveldt on YouTube. “First flight of a 1/4-scale Slingsby King Kite, designed, built and flown by Vincent de Bode…”
- Slingsby King Kite at Kampen — by the author on YouTube. “Scale glider Slingsby King Kite at Kampen tow meeting. The glider is sratch built…”
All images by the author unless otherwise noted. Read the next article in this issue, return to the previous article in this issue or go to the table of contents. A PDF version of this article, or the entire issue, is available upon request.
