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Scratch built Slingsby King Kite 1/4**

Posted: 12 Nov 2020, 13:45
by Bovin
Hello everyone,

To start with, English is a foreign language for me,sorry for the mistakes!
Its almost winter again and it started to itch, what should I build? Whilst building the Slingsby Gull I had the possibility to read the book “ Slingsby Sailplanes ” by Martin Simons, writing about the development of all their gliders. There was a wonderful story about the Slingsby King Kite T- 9. This was a innovative design from 1936/37 with the aim of participating in a major international competition at the Wasserkuppe in July 1937. It was said that gliding would become Olympic. This glider was equipped with flaps and built to be able to fly fast. Because there was little time 3 prototypes were built simultaneously. During the test flights , the aircraft unfortunately turned out to be extremely sensitive to spins . As an emergency measure, all kinds of enlarged vertical stabilizers were built and with such an enlarged vertical stabilizer he finally flew and did reasonably well. Afterwards it turned out that there was a mistake in the building of the wings. Which mistake has never become completely clear, but what I understand is that the wing twisting was not well built (in all 3!) And that the center of gravity was quite far back. It is a wonderful story , it can also be found on this website : articles / rise and fall ., wonderful to read!
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Because this glider was covered with plywood (I like that) was innovative and had good flying possibilities, I decided to build it in 1: 4 scale. The wingspan will then be 3875mm and I hope to keep the weight below 4.4 KG
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Now the making, a different story. I grew up with pencil and drawing board and now I wanted to draw this glider digitally. I bought the drawing programs Devwing and Devfus4, just affordable . It took me quite some time to learn to work with it, but gradually I managed to do useful things sometimes with frustration, but in the end gave me a lot of satisfaction.
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I also had a problem what to use as wingjoiner. After breaking the carbon 8mm round wingjoiner (it was designed for a steel rod, which is has it now) of my Nemere 1/6, 330cm wingspan and with some warnings on the Retroplane forum, I had my reservations about carbon wing joiners . A steel wing pin is quite heavy and I really wanted to keep the weight down. Due to the gull wing there is quite a bit of dihedral in the middle part of the wing , which did not make it any easier.
On the Dutch modelbouw forum and on the Retroplane forum I stumbled in an excel sheet with wing spar and wing joiner calculations. That was nice, I'm educated in Kilogrammes , later Newtons and finally Mpa's , and I was afraid to make a mistake by a factor of 10 or something. With this program I could calculate the wing spar and also a wingjoiner.
http://voiletech.free.fr/Modelismeplane ... ngeron.htm
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I realized that if I made a wing joiner of UD glass/epoxy myself I could make it with dihedral built in . This means , moreover, that the wing joiner could only be held in place by the (reinforced) skin of the fuselage, a tube is not possible because of the built-in V . I bought 20 X 20mm square aluminum tube which will fit nicely between the 20 X 4 mm upper and lower girder of the main spar . Now I had to make a 17 X 17mm square glass rod so it would fit into this square tube . I thought let's try to make that. From spruce battens and a board (covered with packing tape to get a non sticking surface) glued together with hotglue, I made a simple mold.
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I took four pieces of UD glass tape, 7.5cm wide (600gr / m). Impregnated that with epoxy resin and folded lengthwise twice double (4 thick) , placed on the bottom of the mold, and after that the two upright sides in a similar way. In between those upright impregnated glass tapes,I first put 2mm balsa strips of 11mm, each against one side and then I put 1mm balsa strips between the other balsa strips to get the impregnated glass in place without touching it. Thereafter, the last layer of glass on it, and closed it with a batten with the tape to get a flat surface. Now I got a square glass / epoxy tube with a balsa core.
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The wall thickness turned out to be more than 4mm, making the joiner much stronger than the wing spar , it should stand 27G according to the above calculation program
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The weight of this joiner is 168 g, 60 cm long. I was glad with this experiment, now I could start the building of glider itself.
There is very little info of this glider, all info is very welcome!
To be continued.

Vincent.

Re: Scratch built Slingsby King Kite 1/4

Posted: 28 Nov 2020, 17:58
by Bovin
Hello everyone,

I thought it would be most convenient to start with the tail surfaces, I wanted to make the plans digitally, for me completely new. I had already played around with the drawing program Devwing last summer and I started to understand a bit how that worked
3D view of the vertical stabilizer
3D view of the vertical stabilizer
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. In addition, I had to try to understand how the real glider was constructed. Unfortunately, things went wrong in those two learning processes, it turned out that the horizontal stabilizer of the King Kite was more complex than I had realized. I also managed to make entire drawings disappear. Finally I managed to send the files as DXF. A good friend,Adri CNC'd the ribs and I started to build the horizontal stabilizer. Because I had misinterpreted a few construction details the result were unsatisfactory. Adri suggested it was better to CNC a new set of horizontal stabilizer ribs. In the meantime, I started on the vertical stabilizer. I wanted the rudder itself to be easily detachable, which is convenient for storage and transport.
The fin in construction, the laminated edge arch is already in place, as are the hinges
The fin in construction, the laminated edge arch is already in place, as are the hinges
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The top and TE of the rudder are completely curved, so I laminated the top of 3x1 spruce, bent after being poured over with boiling water and glued with thin CA. The rear of the TE is made up 3 pieces of 0.4mm plywood, scarfed joined, on both sides, filled with balsa, forming a sandwich.
right half of the py TE glued on and holes already drilled where rudder must be detached
right half of the py TE glued on and holes already drilled where rudder must be detached
TE rudder under construction
TE rudder under construction
The two hinge pins are made 1mm steel in 1mm epoxy/glass, so I can slide the rudder from above over these pins. It is secured with a sliding steel wire at the lowest rib
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I covered the front of the rudder with curved 0.4mm plywood, together with the main spar of the rudder this becomes a light and stiff plywood tube.
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basic structure of the rudder finished
basic structure of the rudder finished
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With the rest of the plywood covering I wait until a later stage of the construction, first I will built the horizontal stabilizer.

to be contimued,

Vincent.

Re: Scratch built Slingsby King Kite 1/4

Posted: 28 Nov 2020, 20:53
by Max Wright
Hi Vincent

Not to worry. Your English is fine and easy to understand.

Thank you for posting. It is a very interesting thread.

Cheers

Re: Scratch built Slingsby King Kite 1/4

Posted: 28 Nov 2020, 21:59
by Bovin
Hi Max,

Thanks a lot, glad you find it interesting :). The real glider was quite ahead of its time, hopefully I get the model flying well.

Cheers,
Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 28 Nov 2020, 22:21
by BrianF
Very nice, and you make more sense than some native speakers.
I have the same experience with DevFuse/Wing, a bit frustrating initially, gets better as you get used to it and figure out workarounds.

Re: Scratch built Slingsby King Kite 1/4

Posted: 29 Nov 2020, 13:33
by Bovin
Thanks Brian, I looked at your pics from Devwing, its helps me to learn what is possible with it.
In the meantime Thomas (on Retroplane forum) found a wunderfull photo of the Wasserkuppe event he wrote the following
"I found the list of participants, aircraft of the international competition of 1937 and the result in the book by Peter Riedel "Über sonnige Weiten" - Experienced Rhön history 1933-1939"
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P M Watt, placed 12th with a towel? on his head and a sigarette, cries out to be modelled!
He also has the participents
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and the results
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Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 09 Dec 2020, 10:29
by Bovin
In the previous construction report I had already written something about the horizontal stabilizer. I had completely overlooked something in the plans
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The front of the moving part is not only a semicircular plywood tube (which I was used to) but also a square box girder behind it. I think this is there to take up the bending and torsion of the balancing tips. In addition, the designers opted for a thin profile, which can be clearly seen in this photo
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(Thanks to Thomas from Retroplane who found this photo on an item about W Watt, here is the link to this info. https://benitz.com/Watt/WattPercyM1906_Photos.html) This also an enlarged rudder, to prevent spinning problems, due to an very unfortunate unknown wing (construction?) problem, it was an prototype.
Because the horizontal stabilizer is also very tapered, the profile at the tips becomes very thin. I also wanted to keep the horizontal stabilizer very light, I presume that the 0.5mm plywood covering and web plates, glued with 2 X 2 mm spruce, should be strong enough.
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I had to make sure that there was enough sheeting to keep the construction stable when removing it from my buildingboard, so I filled the space between the 2x2 beams of the rudder with balsa and glued all the web plates in. I glued diagonals in the nose, which together with the top sheeting should already form a kind of D box. The bottom sheeting can only be added when the stabilizer is off the building board. Top sheeting, scarf joints
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The TE, just like the vertical tail, is constructed from 2 layers of 0.5 plywood with balsa in between. The balsa ribs appeared to be very fragile at the TE, so I reinforced them with thin spruce battens Yet another problem caused by the balancing tips is the detachability of the rudder, it cannot be slided aside. I bent a hinge pin from 1mm steel wire, which I can later detach with a screwdriver or a similar tool from the bottom
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Nose D box bottom also sheeted, the prebent ply strips in the background are for the nose of the elevator itself. The outer ribs were to thin for the hinges, so I put them one rib to the inside.
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To be continued,

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 09 Dec 2020, 12:13
by VinceC
Nice and considered build. Well done

Re: Scratch built Slingsby King Kite 1/4

Posted: 09 Dec 2020, 14:31
by Bovin
Thanks Vince for your encouragement. The building of and reading about the King Kite makes me aware that the real thing was some project.
I hope to build a nice replica, it will take some time...

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 17 Dec 2020, 14:46
by Bovin
I went on with the elevator. First I cut the rudderhorn from 1mm epoxy sheet. I had to attach that to the extra box girder of the elevator
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To get a proper bond, I filled the inside of the web plates with spruce strips. I didn't want to glue the rudderhorn in its place yet and stored it .
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On pre-bent ply strips (with boiling water) I drew the ribs on the inside to make the various gusset plates in one piece. In reality it was different, but I want to keep it as light as possible. I glued these pre-bent strips over the main spar of the rudder to form a torsionally rigid and round nose. At the location of the hinges I milled openings in this
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and now the rudder had to fit the fixed part of the horizontal stabilizer. After some fiddling it did. However, once I had glued one capstrip in place , attaching and loosening the elevator with a screwdriver (to keep the spring hinge pins unlocked) turned out to be quite inconvenient. After a night's sleep I made a kind of angled screwdriver from 1mm iron strip, which I could temporarely fix with a piece of tape. Now all hinge pins were simultaneously “unlocked” and I could slide the rudder into place.
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Then I could turn the iron strips back and I could (combined with maximum deflection of the elevator) take the strips out. Now the pivot pins sprung back in place and the rudder was secured. I was very happy with this, because I could also apply this technique to the ailerons. Besides I like to have the rudders removable, its easy with varnishing and covering.
With some clamping the tips were sheeted with ply.
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Then I sanded all the triangular gusset plates neatly into shape and the stabilizer was more or less ready.
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It feels very stiff and weighs 118 grams, I can’t get it lighter....

Vincent.

Re: Scratch built Slingsby King Kite 1/4

Posted: 17 Dec 2020, 16:06
by Cliff Evans
Lovely build!

Re: Scratch built Slingsby King Kite 1/4

Posted: 17 Dec 2020, 17:41
by Bovin
Thanks a lot Cliff!

Re: Scratch built Slingsby King Kite 1/4

Posted: 17 Dec 2020, 19:06
by VinceC
Nice build

Re: Scratch built Slingsby King Kite 1/4

Posted: 17 Dec 2020, 19:13
by Max Wright
Very innovative. 8-)

Re: Scratch built Slingsby King Kite 1/4

Posted: 23 Dec 2020, 11:29
by Bovin
I went on with the vertical tail.
The fin was already ready with one side sheeted, but fortunately I saw that both on the drawing and on the photos that the vertical tail had a much rounder nose than the profile I had chosen, afterwards that was not the right choice. I had already sheeted one side, so I ripped that off. I glued filler pieces to the ribs
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and sanded them, along with those of the rudder, with a long sanding batten into a more rounded profile.
With the boiling water technique I was familiar with, I bent the plywood into shape and and sheeted both the fixed part and the rudder itself
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Finished it with capstrips on the ribs and sanded the gusset plates in shape
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The vertical stabilizer was now roughly ready, and weighs 50 grams.
With the tailplanes in this stage I can start with the fuselage.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 23 Dec 2020, 12:06
by Peter Balcombe
Very nice Bovin 👍

Re: Scratch built Slingsby King Kite 1/4

Posted: 31 Dec 2020, 12:07
by Bovin
After finishing the tail planes it was time to digitally draw the fuselage. I decided to having a go at it and bought Devfus, a program that is still affordable for a hobbyist.
After a lot of messing around with terms on the screen that I had never heard of, I got familiar with some things! Unfortunately, sometimes drawings were suddenly put (by magic??) in a different folder and I could no longer open them in the drawing program (Yes, laugh ...) Thats why I drew the hull about three times, practice makes perfect they say ... Gradually I found out what is possible, it is easier to make a hull straight in a drawing than to sand frames down or glue some extra material on.
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Here you see some of the drawings of the frames and
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the placement of the frames and the 3d view of the fuselage.
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I thought it would be convenient to use a central batten to align the frames. My friend Adri was kind enough to CNC the frames and he did it excellent. Just like with the Gull, I made a construction setup of a panel of chipboard to which I screwed 10 x 10mm battens at frame distances. I deliberately made a “jump” in it because I wanted to sheet parts of the hull on the construction setup. The tail at the top and the nose at the bottom.
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In this way, it stays nice and straight and the stringers can be as thin as possible, to keep the weight of the tail down. Aligning the frames took a lot of time and I would like to hurry up, but I know sadly that errors in the frame setup are difficult to correct later .
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One of the two main bulkheads is prepared so the wingjoiner can be slid through it.
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Here is the 3X3mm spruce batten which slides through the centre of the frames,. I first wanted to screw them on the jig, but clamps actually do it better.
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I first glued in both stringers left and right and then made the wide bottom (keel?) stringer, where the landing skate will be attached later.
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So nice that the frames were “aligned” ( Ican’t find the correct word for that), I didn't have to sand them much! Designing took quite a bit of effort, but this was very satisfying.
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It's starting to look like a fuselage!

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 Jan 2021, 15:48
by Bovin
Sorting out the tail.
First I had to make the tail shoe, I laminated the bottom girder and made two small frames, I had to deduct that from the photos how that was constructed, nice to find out, but sometimes it takes a while!
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I could not find any details of the fuselage to the horizontal stabilizer transition in any photo. I think the mounting method would be just like the Gull I built before. It was stuck with 4 horizontal pins that were inserted from both sides
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this gives an idea of how that was made in the real Gull.
In the model of my Gull I solved that with 2 continuous 1mm steel wire pins and that is how I want to do it for the King Kite.
The design of the fuselage at that location was not clear to me.
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First I made the frames at the stabilo position according to the drawing. Partly because I did not know the thickness of the stabilizer profile, this was not correct, so it did not work. I remade it 3 different ways before I felt that I had it right. For the fairing of the fuselage at the front of the horizontal stabiler I laminated a plate? from balsa and 0.4mm plywood on both sides, which I sanded in a in contour of the fuselage
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It turned out that there was also kind of infill in front of the vertical fin
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Unfortunately, I had made the vertical fin a bit thinner than the real one, so that now the elevator no longer fitted nicely to it, I also changed that a bit. So, after gluing the vertical fin
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and properly positioning the stabilo
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I thought that , when sheeted with ply, it will look just as the real thing.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 Jan 2021, 17:23
by Peter Balcombe
Very nice Vincent.
I admire your persistence in getting the nice result :)

Re: Scratch built Slingsby King Kite 1/4

Posted: 14 Jan 2021, 12:11
by Bovin
The placement of the servos was next. Before I started, I first made a tow coupling. On the Gull I had made one that worked well and took up little space inside. I soldered a piece of 6mm internal brass tube and another piece of 2mm internal brass pipe at right angles to each other with silver
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Drilled a 2mm hole through and through and made it a bit larger with a reamer,
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so that a 2mm iron round could move freely through it. Over that 2mm round I soldered a piece of brass tube, which I flattened at the end with a hammer and drilled a 1mm hole for the operating rod
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I glued the coupling in the front fuselage frame, reinforced it with some roving to take up the forces .
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(the 2mm drill is only temporary while the resin sets)
Now the servo’s. I wanted to have them in the front (good for the CG) and low, so I can make a scale interior , which I like to make... After some thinking I came up with a servo tray for the 3 fuselage servos
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The blue arrow points to the rudder servo that actuates the rudder with 2 pull-pull cables, the yellow arrow to the coupling release servo, the rod will go under the rudder servo arm to the coupling. At the red arrow is the elevator servo, that will actuate the elevator with a push-pull Bowden cable, fixed in the holder? (black arrow).
After figuring out the servo’s, I went on with the cockpit area of the fuselage. Cut through the two frames, adjusted the sloping frame and glued it in.
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Then I sheeted the inside with 0.6mm plywood. The front of the fuselage is now quite stable.
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Its my intention to sheet the top end of the fuselage while its still secured at the building rig to keep it in shape while putting the ply on.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 23 Jan 2021, 12:40
by Bovin
Before continuing with the cockpit, I got some doubts about the size of the stringers in the fuselage. They have about the same (scale) size as the example, but my landings are a bit rougher than the real ones. On the other hand, a light tail boom provides much less ballast and so on. I decided to put a single glass roving with epoxy on the inside of the left and right stringer, the stiffness of glass is closer to that of wood than that of carbon. I hope it works out well.
I drilled 2mm holes next to the beam and with a double folded 0.2mm steel wire
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I pulled the dry roving wire through the holes and impregnated it with epoxy. After curing, the girders feel much stiffer and not much weight is added.
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To get the cockpit right I first fitted the pilot (borrowed from my Gull) and after some fiddling he was neatly in place .
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Made a backrest, seat and floor from plywood / balsa sandwich, they are fixed with screws in plywood supports
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Enough space over the servos.
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Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 23 Jan 2021, 12:48
by Bovin
The planned receiver battery box had a conflict with the pilot's feet, so I changed it and now the pilot has room for his feet and there is space for a 2s 1700Mah LiFe and 4s 2000Mah eneloop, they will be connected with a Schottky diode. If all goes well I can read the voltage on my transmitter.
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Now I could start making the cockpit canopy. In that period it was not possible to make a bubble canopy , so this canopy is made of curved panels, nice characteristic, beautiful (thanks to Thomas for the photo)
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To make the supporting structure I laminated three frames
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and glued them together on the fuselage
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The canopy is secured at the front two pins (yellow arrow) and in the back with strong magnets, both in the hood as in the fuselage. The magnets are glued between layers 0.6 triplex (Black arrow). From 0.6mm plywood I laminated the longerons?
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The canopy was quite a time consuming job, but now the frame is ready for varnishing and glazing.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 30 Jan 2021, 12:59
by Bovin
Before I was able to sheet the fuselage with ply, I had to do some preparatory work; the topside of the fuselage ahead of the cockpit will be sheeted with narrow strips (like the real one) so I had to fill it with thick balsa
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, and sand it smooth
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. I built the nose itself from 20mm balsa, sanded the side view first, then the top view
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and then roughly into shape
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. I hollowed out the inside further (I had already partially done the gluing of the balsa together) and glued a plastic jar in it. That jar can hold 170 grams of lead.
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What I'm planning is this; when the plane is ready I put the 170gr lead in the jar, I measure how much ballast is needed and then fill the nose with lead snippets and epoxy resin. Then I have the option of removing ballast without cutting it out.
I glued in plywood reinforcements for the rear of the wing mount and 10mm balsa at the bottom of the fuselage where you grab it when you handtoss it.
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Now I could sheet the fuselage with 0.6mm plywood. Until now I glued the plywood with thick cyano, but this time I wanted to try the white glue and iron technique, which I picked up at this forum :) I had already made a few test pieces and it turned out to work.
Because the fuselage at this stage is still very flexible I put it back in the construction frame. I started with a tricky piece, first chamfer the edges with this set-up
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], then smear the glue surface with PVA and let it dry
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. I could now place the piece exactly in place, fix it with clamps and iron it on
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. To be sure, I later applied extra glue on the inside, you never know, this technique is new for me.....

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 05 Feb 2021, 12:58
by Bovin
After that tricky first piece of sheeting, I went on with the top of the fuselage, which was still temporarily attached to the building jig. Scarfing the thin plywood is a time-consuming job, especially if the panels are not straight. I made up a few sanding tools in the hope that I would make fewer mistakes
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By the way, the self-adhesive sandpaper “easy-touch” is really great!
Some pictures of the glueing of the panels, using the "iron" method, which I dared to do, thanks to this website.
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The fit with the scarfed joints, which are also curved, is critical and I don't know if I can work accurately enough. Another problem was that the horizontal (longitudinal) seam was difficult to straighten, I found it difficult to get each panel exactly in place. I temporarily fixed with it clamps
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and glued it with a iron (middle position, 150gr). I decided to make the remaining panels a bit too long and later sand them to the correct length, with another sanding tool
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On the same picture the connection horizontal stabiler / fin is done.
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A picture of the top of the fuselage,
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The fuselage is now stiff enough to remove it from the building jig.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 05 Feb 2021, 16:32
by SedB
Hi Vincent, what a piece of art you are building here!
Maybe a stupid question, but I was wondering why you will be using different voltages on your batteries? What is the gain or bennefit?

I'm looking forward to the varnishing process (and am curious what materials you'll be using), must be a rewarding part in the build to see all the wood come alive!

Dan

Re: Scratch built Slingsby King Kite 1/4

Posted: 05 Feb 2021, 17:45
by Bovin
Hi Dan,

Thanks for your nice words!
Surely its not a stupid question, I planned to put two big Lipo's in the nose, useful ballast! But, there wasn't enough space for the pilots feet, so I changed it. I put a 1700 2s Life and 4x 1.5 AA eneloop Nimh in the nose. They are going to be connected with a shottky diode (that knowledge is of a friend), so when the Life is really low, it wil switch to the Nimh cells. In this setup I don't need a voltage regulator, so it should be possible to read the voltage on my transmitter. Hope you like the idea....

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 Feb 2021, 09:49
by Bovin
Hello everyone,
After the fuselage was detached from the construction setup, I decided to do the rc part first. It's tempting to continue building, but now everything is much more accessible. I had already more or less made the servo tray and the battery box. To be able to get the latter one out easily I made a kind of clip from 2 layers of 0.6 plywood and a short piece of spruce, which you can unlock with one finger
IMG_2440.JPG
Next to the switch I placed the shottky diode, made two plugs for both receiver batteries and plugs for the lead to the receiver placed more to the rear of the fuselage.
IMG_2444.JPG
IMG_2444.JPG (31.65 KiB) Viewed 2905 times
. I ran this wire between the inner and (not yet in place) outer skin
IMG_2445.JPG
Behind the backrest of the pilot I made an “holder” for the receiver, antennas and space for the vario
IMG_2455.JPG
IMG_2456.JPG
I had already made the servo tray, I had to glue 2mm extra strips under the rudder servo to make enough vertical space between the actuation cables and rods.
The elevator actuation works with a 1mm steel wire pull / push rod, in a double plastic guide
IMG_2453.JPG
IMG_2462.JPG
To be able to mount and dismount the horizontal stabiler, I made the last 70mm of this rod hinged. I bent a very small eye in the 1mm rod, in which the pin of the quicklink fitted tightly. Just bend a slightly too big eye and carefully make it smaller with pliers until it fits exactly.
IMG_2227_367.jpg
IMG_2449.JPG
I can lift that moveble part and then attach the other quicklink to the rudderhorn of the elevator. Then the whole stabiler can be lowered in place and the moveble part of the actuation rod comes “in line” and operates without any slop.
IMG_2458.JPG
The rudder is operated with two pull / pull cables (20kg strong). They are attached to the rudderhorns of the rudder with self-locking steel wire hooks, so that the rudder can easily be disassembled for transport .
The controls are moving OK, now I can go on with sheeting the fuselage

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 Feb 2021, 11:42
by IanT-White
Bovin , It may be better to simply have two Life batteries , each with a schotky diode after its own switch.
This way you have still the redundancy of having two batteries , also same charging regime for both batteries , plus both batteries will share the load.
Its also dead easy to check each battery by only switching one battery on , waggling the sticks and looking at the displayed voltage from the receiver.
You can then switch that battery off and test the other battery . This gives a sort of load test .
To have a battery as a backup and not being normally used , creates problems of its own ,batteries are best used ,also how do you know its going to be ok when you need it ?
One of the big advantages of LiFe batteries is the precise reliable charge that is obtained with a decent charger , no false peaks that you get with nimb batteries and the charge voltage can be seen , usually all the way from about 6.8volts up to fully charged at 7.2 volts displayed on your charger.
Really useful to keep track of how many flights/duration of flights on a flying session , then charge the batteries when you get home and note on the chargers display , how many milli amps were required to fully charge each battery
These values can then be used to calculate say how many milliamps are used , say for a flight or an hour of flying , which gives a good idea of how far you can push your batteries , I use a value of two thirds of the capacity of the battery to have a safety margin and also avoid over discharging the LiFe battery which is something that really needs to be avoided.
I hope the above makes sense and really impressed with your modelling skills.
Best regards Ian Turney-White

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 Feb 2021, 15:37
by Bovin
Hello Ian,

Thanks for your very good and detailed explanation. This not an easy subject, backups can indeed give someone a false feeling of safety.
I had rather a spare battery in the nose than just lead to get the CG correct. I thought that it was a good idea to choose different batteries, because I can read the voltage on my transmitter (when there is enough thermal activity..) and so to know if I am using the Eneloops or the Life. I choosed the Eneloops because they stay very good loaded ( I don't know the correct term fot that, sorry), for years. So I check them with the start of the season and it has saved me my already one model.
I agree 100% not to decharge more then 2/3. So, I think your are right, but my battery box is just finished, so I leave it like this. Surely I will consider it with another plane, first built and fly this one :)

Bets regards, Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 Feb 2021, 18:41
by Peter Balcombe
Vincent,
Please note that connecting multiple batteries to a regulator, or direct to a receiver, via diodes is good practice as diodes pass the higher of the available battery supplies through to the load at any point in time, until they reach the same voltage - after which you will not know which one is being used at any time as they will each switch in and out.

If you are using two different battery types or differently charged packs, then you should be able to see the highest voltage one being used first, until it has discharged to the same voltage as the other. After that, the 2nd battery will start being used more or less in parallel with the 1st, so you are likely to see a slower change as the batteries are effectively working together.

The big advantage with the diode connected supplies is that if one battery is faulty & discharges rapidly or suddenly fails completely, it doesn’t also discharge the others as it is effectively automatically switched out of circuit by its series diode.
A downside is the voltage dropped across the diode, but this can be minimised by using a Schottky type & is outweighed by the redundancy benefit.

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 Feb 2021, 19:15
by Bovin
Peter,
Good to hear that. I feel the same what you mentioned in the last paragraph. It once saved a plane when the connector with the main battery failed.

Best regards, Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 21 Feb 2021, 11:56
by Bovin
Now I could cover the bottom of the fuselage. I came up with a sanding tool so I could clamp the panels, otherwise my fingers would get cramped
IMG_2485.JPG
A batten attached to my worktop with a screw clamp , a piece of aluminum angle and two large spring clamps. The sanding went a bit better now.
IMG_2478.JPG
. Fuselage and panel with glue
IMG_2480.JPG
IMG_2481.JPG
IMG_2479.JPG
, panel in position and secured with a hot iron. wetted with a sponge
IMG_2483.JPG
IMG_2484.JPG
bent and secured. After a few days it starts to become a fuselage
IMG_2492.JPG
IMG_2494.JPG
. Next is the nose, lots of panels ...
Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 06 Mar 2021, 10:32
by Bovin
The nose of the fuselage is a challenging job. It's important how the fuselage looks, so I hope to do well.
King-Kite-3.jpg
I had roughly sanded the nose into shape and I marked the strips on it with a pencil.
IMG_2470.JPG
At the connection to the cockpit cover they follow the round frame shape. Further forward, the strips flatten so that they can be bent towards the tip of the nose. There is no double bending .
IMG_2510.JPG
IMG_2513.JPG
IMG_2516.JPG
I came up with the idea to mark the strips with a small router, so you can sand some without sanding away the marking. On this picture you can see where the strips will come . Strip by strip, the nose is covered.
IMG_2516.JPG
IMG_2517.JPG
For these strips I use veneer instead of ply and I glued them with thick cyano
IMG_2526.JPG
The result
IMG_2530.JPG
IMG_2531.JPG
IMG_2533.JPG
Now I am starting the preparations for the wings and the fairing wing/fuselage.

Vincent.

Re: Scratch built Slingsby King Kite 1/4

Posted: 06 Mar 2021, 10:48
by VinceC
Nice detailed work. What glue are you using to fix the panels?

Re: Scratch built Slingsby King Kite 1/4

Posted: 06 Mar 2021, 11:04
by Bovin
Hello Vince,
Thanks for your nice comment!
In the past I used always thick cyano, but (thanks to the very instructive video I picked up at this forum) I use PVA with heat. I will use that mostly in the wings too. The small strips on the very nose of the King Kite I did with thick cyano, the others with PVA/ ironing. I still have some doubts about the strenghts, time will learn. Its certainly less stressfull.

Vincent.

Re: Scratch built Slingsby King Kite 1/4

Posted: 13 Mar 2021, 13:09
by Bovin
The wings, I started with the right one
The profile choice I found difficult, the real King Kite had a profile NACA 23021 which looked quite symmetrical. The profile and thickness determine the "looks" of the aircraft and so I ended up with HQ 2.5 with a thickness of 12% decreasing to 10 at the tip. With the flaps (and the ailerons, not prototypical) I can make more camber . With Devwing I drew the wing
vleugel.png
vleugel.png (70.03 KiB) Viewed 2961 times
My friend Adri was kind enough to mill the ribs and the web plates. The root ribs in 2mm plywood and the rest in 2.5mm medium-hard balsa.
IMG_2537.JPG
With the program “Calculdelongeron” I calculated the main spar, 24X4mm spruce on top and bottom at the root to 2x10mm at the tip. Should be able to take 10G, not including sheeting. By the way, the wing is completely sheeted with 0.6mm plywood, like the real one. I had previously made a glass / epoxy wing joiner with dihedral that fits in 20x20mm aluminum square profile. Because it has a gull wing, I made a building board with the gull angle and laminated the spars in that angle too.
IMG_2523.JPG
IMG_2555.JPG
building the wing
building the wing
IMG_2541.JPG
IMG_2546.JPG
Servo holder, all 4 made in one go
Servo holder, all 4 made in one go
IMG_2545.JPG (31.64 KiB) Viewed 2961 times
All the web plates glued, left open at the root. So the space between the aluminum square and the main spar can be filled with epoxy /micro balloons.
IMG_2553.JPG
IMG_2553.JPG (29.51 KiB) Viewed 2961 times
It's starting to look like a wing!
It's starting to look like a wing!
I'm going to build the other (left) wing now.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 13 Mar 2021, 19:29
by Max Wright
This is a nice build, Vincent.

I'm learning a lot. 8-)

Re: Scratch built Slingsby King Kite 1/4

Posted: 13 Mar 2021, 20:27
by Bovin
Hello Max,

Thanks a lot Max and I am learning also lots from all the build reports :)

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 14 Mar 2021, 08:43
by john greenfield
Hi Bovin

Can you tell us more about the program With the program “Calculdelongeron” please? This is not a program I have heard of before but it sounds very interesting.

AEB

Re: Scratch built Slingsby King Kite 1/4

Posted: 14 Mar 2021, 10:26
by Bovin
Hi John,

Glad that you are interested! Funny, I found this French program on the Dutch "Modelbouiwforum" and later I also found it on the forum "Retroplane".
I am not familiar with basic computor programs, but I managed to get my values in it and get sensible results.
Calculdelongeron (bois) - king kite.xls
I get the impression that I can't send it as an attachment, so I send an PM to.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 19 Mar 2021, 18:51
by Bovin
The assembly of the left wing went without a hitch and I could fit both wings on the fuselage. Then I discovered a huge mistake!!! In a kind of having a blind spot I had made the dihedral in the wing equal to the dihedral of the wing connector; ERROR, that had to be half of that , oops. :shock: :shock:
After some bad moments, I thought better now, than much later in construction. So I cut out the curvature in the top spar
IMG_2559.JPG
and with my powerfile I beveled both sides 1 in 10
IMG_2560.JPG
I changed the angle in the build board (extensively checked now!) and glued two 1X10mm battens under the topspar to get a stable situation .
IMG_2561.JPG
IMG_2562.JPG

I fitted pieces of 2x10 mm spruce and glued it between the spar with 24h epoxy with wood dust as filler.
IMG_2565.JPG
IMG_2566.JPG
.
At least now The King Kite looks in proportion, just a few pictures in the garden.
IMG_2567.JPG
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IMG_2571.JPG
IMG_2571.JPG (30.92 KiB) Viewed 3103 times
Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 27 Mar 2021, 19:06
by Bovin
Now that the basic structure of the wings was ready, it was time for the ailerons and flaps. First the ailerons.
I found differences between the ribs in the drawing and the photos..
vleugel KK.jpg
IMG_2577.JPG
In the drawing, the aileron even seems to consist of two parts, of which nothing can be found in the photo. I therefore decided not to divide the aileron in two parts. Another problem was that the aileron was “enclosed” on both sides. I therefore chose the same hinges as the horizontal stabilizer. The aileron remains removable. With the help of a curved strips you can unlock all hinges at the same time, place the aileron, and then remove the strips.
IMG_2599.JPG
After cutting off the aileron from the wing, I realized how long and narrow it was, 115cm long and 4.5cm wide. .
IMG_2583.JPG
The profile choice did not help either, unfortunately. The aileron was therefore only 6-7mm thick. I also became convinced that I had to control the aileron in two places and luckily was able to find place for an extra servo in the wing.
The balsa ribs in the aileron were very thin and fragile. So I replaced the balsa ribs with 2mm solid spruce, took out one, replaced it with spruce, went on to the next, so that I kept the dimensions.
IMG_2584.JPG
IMG_2590.JPG
I wanted to make a plywood D section for the nose of the aileron. With boiling water I bent U profiles of 0.6 plywood around a 6mm tube and let them dry. I slid the aileron skeleton into this profile and clamped it to a plate with a batten. I had covered both the batten and the board with tape, in order not to get adhesion with glue. I also built in some twisting. I set the plank upright and dripped thin cyano between the rib skeleton and the plywood U profile.
IMG_2577.JPG
Now I had a much firmer unit. I further built up the rear frame with 0.6mm plywood and sawed, cut and sanded the U profile and the TE into shape.
IMG_2592.JPG
Then I added capstrips and the aileron was finished roughly, still needed some sanding.
IMG_2593.JPG
IMG_2598.JPG

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 27 Mar 2021, 19:36
by Peter Balcombe
Vincent,
The 3 view drawing in your latest post looks the same as the one on page 66 of the Martin Simons book Slingsby Sailplanes.
The photo on page 70 of the same book shows a King Kite being moved at the Wasser-kuppe in 1937. This photo clearly shows 2 upper surface aileron control horns.
It may be that the long, narrow ailerons needed to be split into 2 pieces to avoid warping over their length, much as you thought necessary.
Peter

Re: Scratch built Slingsby King Kite 1/4

Posted: 27 Mar 2021, 20:43
by Bovin
Peter,

This photo is a part of the one in Mark Simons book, you guessed that right. I know the other photo
IMG_2173.JPG
and it has indeed two rudderhorns.
On the drawing (and my model) you can see two places where the aileron it strenghtened for the rudderhorns and even the pulleys for the aileron actuation are in the drawing.
I guessed the designers thought it was neccesary to split the aileron, but at the same time quite some big gliders (20m span) used ailerons in one piece.
I tried on my model to move the aileron while I bent the wing at the same time, and worked OK. I presume that the aileron is horizontally not that stiff, so it won't "straighten"the wing when flexed.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 09 Apr 2021, 19:04
by Bovin
9-4-21
After I built the second aileron, I went on with the flaps. These are much shorter (56cm) than the ailerons and completely sheeted. They are even thinner than the ailerons, less than 6mm thick. So I liked to sheet them in one go. I took a strip of 9cm wide, 0.6mm plywood, and bended it around a 6mm round rod, whilst pouring over with boiling water, see also this video (sorry, Dutch subtitled). Then I clamped and let it dry
IMG_2617.JPG
Also on the photo is the backbone consisting from the ribs, main spar, back frame with balsa filler strips. It is a very weak skeleton. By fitting this skeleton into the folded plywood, I could mark, cut and sand the plywood.
IMG_2622.JPG
Covered the structure with PVA
IMG_2623.JPG
clamp it and with a 10X10mm batten en strips of 4mm ply with big clamps.
IMG_2624.JPG
After the glue had dried I could fold the plywood “open”, and I drilled 1mm from the inside pilot holes so that I could make the openings at the hinges and rudderhorn later
IMG_2618.JPG
I smeared the top of the ribs with glue and clamp the whole thing together, just like before.
IMG_2626.JPG

With a Dremel I made the openings for the hinges and after some adjustments it fitted neatly into the wing.
IMG_2628.JPG
Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 Apr 2021, 09:26
by VinceC
very interesting work and thanks for the video on how you bent the plywood

Re: Scratch built Slingsby King Kite 1/4

Posted: 22 Apr 2021, 12:51
by Bovin
Thanks Vince for your encouraging comment.
I wanted to keep the operation of the ailerons and flaps simple, this time not with pull / pull wires, as with the Gull. The pull / pull cables in the wings are nice, but weigh a bit more and there is a bit more friction which is not good for the precision, unfortunately. I thought to make a pull / push rod on the bottom and a dummy control on the top. Unfortunately I couldn't figure out how the flaps were operated, so I also chose a pull-push rod on the bottom of the wing. On the basis of a photo I tried to estimate the size of the rudderhorns.
IMG_2173.JPG
IMG_2173.JPG (36.16 KiB) Viewed 2791 times
I came up with very small horns, I drew them twice too big (by hand ..)
IMG_2651.JPG
IMG_2651.JPG (36.96 KiB) Viewed 2791 times

My friend Adri was so kind to CNC quite a few. Afterwards the size seemed quite correct
IMG_2635.JPG
First I made the dummy control at the top of the wing from 0.8mm steel wire, with a non-functional clip
IMG_2633.JPG
IMG_2634.JPG
. This rod can move freely in a plastic tube glued to a rib. I made the functioning pull / push rod from an M2 threaded rod with quick links
IMG_2636.JPG
IMG_2639.JPG
. To remove the aileron (to put the Diacov on) I disconnect the quicklinks, unlock the hinge pins and then I can detach the aileron with dummy rods and all. The flaps only have pull-push rod at the bottom
IMG_2662.JPG
IMG_2663.JPG
I make these from 1mm steel wire with a guide tube against bending. After some soldering I could check the working of the flaps and ailerons, they worked nicely.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 30 Apr 2021, 10:28
by Bovin
29-4-21
The fairing from the wing to the fuselage had to be made. In the original there was a gap between the wing and the fuselage of about 10 centimeters, just big enough to mount the wings. After assembly a strip of plywood went over it,
Schermopname (160).png
Schermopname (160).png (74.95 KiB) Viewed 2688 times

I also wanted to make it like that, seemed nice to me.
In the fairing, the grain of the plywood must run the length of the wing and thus be bent transversely to the grain. I made a small video how I managed to do that

After bending I let the plywood dry, cut 1 side (which was needed for the bending)
IMG_2689.JPG
] and then saw off pieces. I started with the TE, narrow pieces
IMG_2681.JPG
beveled with a Proxxon power file,
IMG_2686.JPG
with which you can subtly shape those tiny pieces. They are glued to the end rib and fuselage with thick cyano
IMG_2680.JPG
Where the curvature in the end rib decreases, I also take longer pieces
IMG_2685.JPG
IMG_2687.JPG
With a long round screwdriver I keep the pieces in place
IMG_2692.JPG
Sometimes it goes wrong and then I have to cut out a piece. Finally it looks like this
IMG_2699.JPG
IMG_2703.JPG

Here the roughly finished fairing with the gap to the wing, which will be covered by a detachable plywood thing. I have to do the sheeting of the wing first.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 09 May 2021, 19:59
by Bovin
I always find it difficult to sheet the wing nose with ply . I enjoyed gluing by securing semi-dried PVA with a foil iron. I was unable to bend the plywood sharply enough with water and a foil iron. This is also due to the profile, which has a sharp nose. An additional problem is that the panels have to be skewed to keep the seam parallel to the longitudinal axis. That is why I then tried to pre-bend the panels, as with the aileron, with boiling water and then let them dry.
IMG_2708.JPG
IMG_2709.JPG
Then I made them fit and sanded a bevel on it
IMG_2714.JPG
In order not to get cramps in my fingers, I came up with an attachment, a thin aluminium profile, attached to the worktop with a G-clamp and covered with sandpaper as anti-slip.
IMG_2713.JPG
IMG_2720.JPG
I smeared both surfaces to be glued with PVA
IMG_2715.JPG
IMG_2716.JPG
The glue has to be spread out still. After drying I put such a panel in its place, it can still slide and I heated it with a foil iron to set the glue This turned out to work fine, and the wings got a quick start.
The bend in the gull wing also succeeded with two narrow panels.
IMG_2731.JPG
IMG_2732.JPG
It begins to look like a wing!

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 09 May 2021, 21:44
by Peter Balcombe
Very nice Vincent :)

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 May 2021, 10:36
by Mike F
Hi Vincent

Thank you for your highly detailed build log with great photos and explanations of your building techniques.

Much appreciated!

Mike F

Re: Scratch built Slingsby King Kite 1/4

Posted: 10 May 2021, 16:15
by Bovin
Thanks Peter and Mike for your kind words!
I also learned a lot from all the info on this and related sites or fora, for example the PVA with a foil iron technique, so I am glad to do something in return. (my parents used to be teachers ...)

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 16 May 2021, 19:41
by Bovin
The wings are completely sheeted. Again a lot of panels, glued with the same technique, dried PVA and fixed with a foil iron.
IMG_2736.JPG
IMG_2737.JPG
IMG_2738.JPG
I have some doubts how that sticks to the balsa ribs, I think I should apply 2X PVA on them, now that the wing is still “open ”, I can apply some extra glue, but when the top goes on, that will no longer be possible. As I got closer to the wingtip, I found that an extra pivot point for the aileron was needed. First drilled an oversized hole and then glued an epoxy bearing plate to the rib.
IMG_2739.JPG
IMG_2739.JPG (16.59 KiB) Viewed 3162 times
IMG_2740.JPG


With a long batten with sanding paper I sanded the edge of the sheeting straight .
IMG_2741.JPG
IMG_2742.JPG
IMG_2743.JPG
IMG_2745.JPG
The sheeted wings look very strong!

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 22 May 2021, 11:00
by Bovin
I now sheeted the topside of the wing, pre-priming the balsa ribs with PVA, that seems to work better.
IMG_2750.JPG
IMG_2751.JPG
Next I had to trim the back of the sheeting for the ailerons and flaps. By the way, I had already done that with the bottom sheeting before applying the top sheeting. I did this by drilling a few 1mm pilot holes with the hinge pins as guidance and cutting the plywood along these holes. Of course there was still a lot of sanding. When the top of the wings were sheeted, I just repeated the process.
IMG_2753.JPG
The ailerons and flaps remain demountable, just like that of the horizontal stabilizer
IMG_2260.JPG
IMG_2262.JPG
I plugged in the leads and to my relief it all worked.
The wings are now roughly finished weigh 936 and 942 grams.
IMG_2754.JPG
IMG_2755.JPG
Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 23 May 2021, 11:53
by SedB
A very nice build so far, I enjoy to see is all come together!
The wings look great, I wonder how you achieved so little difference in weight between the two? Did you weight them in between, or is this the result of working precise?

Daniel

Re: Scratch built Slingsby King Kite 1/4

Posted: 23 May 2021, 17:21
by Bovin
Thank you for your nice comments and yes I am also looking forward to see it as a whole (I had a small preview :) ).
The weight of the wings is purely a coincidence, what helped that not much balsa is used, ply for sheeting, spruce for spars? only the ribs are from balsa, but it was selected balsa, all medium.
I found it difficult working with balsa ribs and the spruce, sanding is very tricky, but I am very pleased that the wings didn't turn out heavy.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 24 Jun 2021, 14:33
by Bovin
In the real glider there is a gap between fuselage and wing to get to the connecting gear.
Schermopname (158).png
Schermopname (158).png (91.85 KiB) Viewed 2183 times
This gap is covered with a curved strip of plywood
Schermopname (156).png
Schermopname (156).png (81.04 KiB) Viewed 2183 times
King-Kite-3.jpg
I tried to replicate this. The wing of my model slides over the square glass epoxy wing connector and is secured with a nylon M3 bolt in plywood lips on the fuselage and wing.
IMG_2801.JPG
I made a constructing aid consisting of 2 ribs (equivalent to the root rib). On this I clamped plywood with two rows of 3mm holes. On the inside I put first 2mm balsa and another strip of plywood.
IMG_2642.JPG
IMG_2643.JPG
Holding the inner plywood in place with my fingers, I ran thin cyano through the holes on the balsa. I made a nose piece
IMG_2646.JPG
and also an upper and lower piece up to the TE. Then I glued the three pieces together, and cut it lengthwise forming the two filler pieces. I glued magnets to the rear to secure it .
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,
This piece now fits exactly in the gap and I glued 5mm wider strips on top, that fit just over the wing and fairing on the fuselage. You slide it over the wing
IMG_2804.JPG
and click the magnets
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To my relief It suddenly formed a visual unit with the fuselage.
Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 24 Jun 2021, 14:44
by Bovin
It was time for the interior, first the pilot
The pilot is very visible, nice to make proper job of it. My sister wanted to make the clothes, but then I must have a figure first. I used my own measurements (a bit photoshopped....) and made the parts from 10mm balsa
IMG_2757.JPG
In the elbows and knees I fitted Hobart hinges,
IMG_2760.JPG
the hips and shoulders I fixed with shockcord
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In this way you get a figure that can be positioned naturally.
IMG_2759.JPG
To attach the balsa boots I have glued a piece of M2 threaded rod in, which fits into a plastic tube (control tube stuff) in the lower leg. A small bend in the M2 wire provides some friction, just bend it carefully a little. The hands will come with 1mm copper wire in the arms and the head with 10mm beech dowel in the chest. Hands, feet and head remain removable, much easier to get him into his clothes.
IMG_2761.JPG
In the meantime I started with the head, made of sculpey (a kind of clay-like plastic, which is baked at 140gr). This tutorial gives a wonderful explanation, but it is a time consuming job


I start with beech dowel of 10mm, wrap aluminium foil around it (the head may not be solid, it might crack when baking) and then I build the head from layers sculpey
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It takes me a while, but it's nice work and it starts to look like something (I hope a pilot...)
IMG_2768.JPG
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Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 24 Jun 2021, 17:54
by Phill Tadman
Fantastic work!

Re: Scratch built Slingsby King Kite 1/4

Posted: 24 Jun 2021, 22:28
by Bovin
Thanks for your nice words Phil, it is also a remarkable glider, nice to work at it!

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 02 Jul 2021, 10:38
by Bovin
The instrument panel is, just like the pilot, well in sight. However, I had a problem, nowhere I could find information about it. On this photo I could see a tiny piece and there the panel seems to be white.
Schermopname (154).png
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I also found a white panel on this photo of a Petrel, so it did occur.
IMG_2812.JPG
I decided to make just something out of it, looking at the other gliders of Slingsby. I had already ordered a set of instruments in 1:4 scale from Aero Cockpit, 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 it likewise. The instruments from Aerocockpit were delivered as a superstructure, but that can be sawn off. On the photo on the right the sawn off altimeter and on the left the clock that was not sawn off.
IMG_2815.JPG
Now I could make the panel proper.
It is made of two layers of 0.6 plywood, because that can still be cut. 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. After this, I cut the plywood on the front and back with a cutting compass, cut segments in it and could break out the plywood.
IMG_2821.JPG
I glued the two panels together with the help of a few dowel pins. Then it appeared that the holes were just a bit too small for the instruments and with the tapered handle of a screwdriver and some sandpaper I could make them fit exactly.
IMG_2824.JPG
Then I glued another layer of ply behind it, with 2 magnets to secure it in the plane. Now back to the instruments. I sawed off all the instruments that had been built up so that only the ring(bezel?) with the glass was left. But the compass should actually be a sphere. On Retroplane Eric spore had already done something like that, nice detail. I rounded off a handle of a file (I use everything within reach...), clamped a piece of PET on a board with a hole, heated the plastic, pushed the file up and a tube over and to my relief got a nice sphere.
IMG_2834.JPG
I glued a strip of a photo of the compass in it and painted the sphere black on the inside.
I made the screws from black pins, filed the heads flat and made a sawcut.
IMG_2822.JPG
Now I had all the parts.
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All was left was the fun part, gluing everything together with PVA .
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Vincent
===============================================

Re: Scratch built Slingsby King Kite 1/4

Posted: 05 Aug 2021, 15:27
by Alex Tankink
Hey Vincent,

Just wanted to drop a line and say thanks for the inspiration!

Am planning a nice 1/4 grunau or similar and always wanted a nice looking detailed pilot. No plastic fantastics for me.

During our recent lock down with parts to finish another glider delayed, I thought I would just have a try at making a pilot bust for my future project.

My wife is and the RAAF so a 1930’s aviatrix was the model for my first ever sculpt. The photos attached show progress to date with a barnstormer leather jacket, goggles and other details yet to be sculpted.

When finished it will be cast as in epoxy as a hollow and painted (hopefully) ah la aces of iron style

Has been a great project and learned some great modelling skills.

Next project will be a modern pilot for my first scale glider a 1/4 ASK 18 hopefully arriving soon 👍🏻

Cheers

Alex

Re: Scratch built Slingsby King Kite 1/4

Posted: 05 Aug 2021, 17:29
by Cliff Evans
Very nice Alex.

Re: Scratch built Slingsby King Kite 1/4

Posted: 06 Aug 2021, 00:03
by Alex Tankink
Cliff Evans wrote: 05 Aug 2021, 17:29 Very nice Alex.
Cheers Cliff,

Is a very interesting road this forum and scale sailplanes has led me down 😁. Never thought I’d sculpt anything let alone be able to sculpt.

It’s not a glider but hey it’s at least in the genre while I wait for my covering and parts to arrive.

We shall see how it finishes up.

Cheers

Re: Scratch built Slingsby King Kite 1/4

Posted: 06 Aug 2021, 11:35
by Bovin
Hey Alex,

Glad you got some inspiration from my efforts, your sculpture surely is looking nice!
Funny where hobby's can lead you in, surely it inspires the creative part of the brain.
I am interested how you make the impression and the casting, like to hear that.

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 09 Aug 2021, 12:50
by Bovin
The instruments also include the pitot tube, which I like to be demountable. I made it from solid 2 mm wire, which I had lying around, I don't know exactly what kind of stuff, but it was not magnetic. I took two pieces, bent it 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. Finally a piece of iron nail and soldered it all together with silver. The brass profile fits into a somewhat larger profile, into which I glued a magnet
IMG_2847.JPG
IMG_2847.JPG (32.63 KiB) Viewed 933 times
I glued the larger brass profile into the fuselage nose
IMG_2848.JPG
and glued it with 5 min epoxy from the inside. I had to hold the fuselage upside down and glue it in place, which keeps you flexible...
IMG_2853.JPG


I hestated with the skid, I decided to make the supporting structure massive. I glued 12 layers of 2mm balsa with PVA using the fuselage as mould, separating with cling foil.
IMG_2840.JPG
After curing, I took it off and planed it in the shape
IMG_2845.JPG
and covered it with Diacov, to imitate the sailcloth of the real glider. Then I painted it white and glued it all on the fuselage. On top of that I glued the skate itself made from 0.6mm plywood and two layers of 2mm pine. Then 2X2mm pine strips in the corners.
IMG_2846.JPG
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Back to the interior. I covered the seat with leather from an old wallet
IMG_2843.JPG
and made a control stick from aluminium tube, which slides over a piece of installation wire
IMG_2857.JPG
So that I can bend the stick in the desired position.
IMG_2856.JPG
Some details still missing in the interior….

Vincent

Re: Scratch built Slingsby King Kite 1/4

Posted: 21 Aug 2021, 12:02
by Alex Tankink
Bovin wrote: 06 Aug 2021, 11:35 Hey Alex,

Glad you got some inspiration from my efforts, your sculpture surely is looking nice!
Funny where hobby's can lead you in, surely it inspires the creative part of the brain.
I am interested how you make the impression and the casting, like to hear that.

Vincent

Vincent,

I’ll keep you posted on the progress and results’

Am enjoying following you build thread and best of luck with it 👍🏻

Cheers

Alex

Re: Scratch built Slingsby King Kite 1/4**

Posted: 07 Nov 2021, 13:28
by Bovin
I'm a bit behind with my construction report, flying and working at the house...
The structural work progressed well and with some sunshine I took some pictures outside
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Here all parts ready for finishing
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I applied bister (an organic water-soluble dye, available at the art materials store) with a sponge. Then I applied two layers of porienfuller and finishing it with PU yacht paint. The shed was full of it and it smelled quite bad
IMG_2876.JPG
The horizontal stabiliser, rudder and ailerons were sheeted with Diacov.
IMG_2880.JPG
IMG_2882.JPG
Vincent

Re: Scratch built Slingsby King Kite 1/4**

Posted: 07 Nov 2021, 13:33
by Bovin
The cockpit canopy in the original was made of bent (perspex?) sheets over a wooden frame
Schermopname (156).png
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King-Kite-3.jpg
I glued 0.5mm transparent plastic panels with canopy glue on the frame, two panels at the same time,
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finishing with the big front panel. And also cover strips over the fore aft seams
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Not to forget very small "screws", pins with a sawcut I the heads
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(just as I made for the instrument panel)

Vincent

Re: Scratch built Slingsby King Kite 1/4**

Posted: 07 Nov 2021, 13:40
by Bovin
Except for some finishing of the interior, it was ready now. I had calculated the centre of gravity with Ecalc and it had to be 79 to 90 mm from the LE. As the fuselage is too wide for my new digital CG scale, I got my old contraption from the attic, 3 sheets of plastic coated chipboard screwed together in a sort of U
IMG_2907.JPG
The wings rests on slats with a 2X2 mm rounded slat (see arrow)
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where the plane balances on.
I had to use 450 gr lead, of which 130 gr can be removed. I put that in the white jar
IMG_2913.JPG

In this way I can adjust the CG between the two values without chopping or breaking. I poured epoxy resin over the loose lead pieces (although I deducted the weight of the epoxy).
Some more data of the model, span 3875mm, weight 4800 gr, wing area 85dm2 and that gives a wing loading of 56.4gr/dm2
I made some pictures in the sun.
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It is now almost ready to fly, just some painting of the pilot, some details of the interior and the lettering.
Question; I can't find any documentation how the flaps are actuated, I mean what kind of handle the pilot had in the cockpit, can anyone help me with that?

Vincent

Re: Scratch built Slingsby King Kite 1/4**

Posted: 07 Nov 2021, 17:02
by VinceC
I have acquired a few more King Kite photos from the 1937 Rhön Contest which may interest you

Re: Scratch built Slingsby King Kite 1/4**

Posted: 07 Nov 2021, 17:08
by VinceC
....and some more.

Re: Scratch built Slingsby King Kite 1/4**

Posted: 07 Nov 2021, 21:18
by Bovin
Thanks very much for these nice pictures, they are very useful.
I think its very rewarding to make history a bit alive again. and I think this was a very special glider!

Vincent

Re: Scratch built Slingsby King Kite 1/4**

Posted: 15 Nov 2021, 13:02
by Bovin
After some searching and help from this forum to find out the text, Adri was able to cut the lettering and I put it on quickly. The model was now practically finished, some interior details missing.
Then suddenly there was the opportunity for the first flight, the weather forecast was good, Rob could tow, Adri came along for some coaching and Raymond liked do the photo and film work. On the field there was quite some wind, it was chilly and the sun unfortunately didn't break through completely.
Ready
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pilot also ready ,
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Rob's Ecoboomster had no trouble with the King Kite
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I had to trim the aileron quite a bit, so the first tow was not perfect. It was almost against the sun

vlcsnap-kb5 2021-11-12-15h15m55s240.jpg

After uncoupling and elevator trimming there was the moment of truth, fortunately it flew really well, responsive, stayed well at altitude, a pleasure to fly.

Of course there were no thermals, but I think it will be perform fine in them.

(Because it is so flat here in the Netherlands, we cannot fly on the slope. With scale planes on the slope there is usually enough lift, but we don't have that here and unfortunately not many thermals either, we fly a few kilometres from the sea. That's why it's very nice that it doesn’t sink fast)
The real King Kite had a pretty modern profile, hence the HQ 2.5 of this model is not very noticeable.
vlcsnap-kb62021-11-12-15h20m51s835.jpg
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After a few minutes we had to land
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with flaps and ailerons slightly up (the real one didn't have that)
IMG_kb100887.jpg
I was very happy (to see on the video), that it flew well. Apart from the technique, I find the aerodynamics hard to predict, that's why.
The link to Raymonds video;
Apart from a few small details he is ready, I would like to thank everyone and MBF. Retroplane, SSUK for all the help, especially Adri for the CNC work and the lettering, Rob for the towing and Raymond for the photos and videos.

Vincent

Re: Scratch built Slingsby King Kite 1/4**

Posted: 15 Nov 2021, 16:29
by Mike F
Hi Vincent

Congratulations on your maiden King Kite flight. The surface finish of the King Kite looks very authentic; well done!

Mike

Re: Scratch built Slingsby King Kite 1/4**

Posted: 15 Nov 2021, 16:53
by chris williams
Excellent job, Vincent, nicely done...

Re: Scratch built Slingsby King Kite 1/4**

Posted: 15 Nov 2021, 17:15
by Cliff Evans
Well done Vincent. Looks very good both on the ground and in the air. So, What is your next project?

Re: Scratch built Slingsby King Kite 1/4**

Posted: 15 Nov 2021, 18:07
by Bovin
Thanks a lot for your nice comments!
I am very glad that it is also performing nice (that shows in the video :D )

Well Cliff, next project, that looks like a job!
First I am going to build a new tow plane, the kit is already on my attic. Its the Eco boomster S. and I keep you informed whats coming after that...

Vincent

Re: Scratch built Slingsby King Kite 1/4**

Posted: 30 Mar 2022, 12:27
by Bovin
Saturday we had a tow meeting close to the IJsselmeer. The weather was very nice, so this footage is a bit more sunny, not as good put together as the previous one, which Raymond did (I am a beginner in video editing..)
I also changed the camera (mobius) position, more like Chris Williams.

By the way, my Eco Boomster S is ready and flying, I am doing some small gliders at this moment.

Vincent

Re: Scratch built Slingsby King Kite 1/4**

Posted: 30 Mar 2022, 18:33
by simon_t
Looks lovely - have you been to Maasvlakte, as the large dunes at Slufterstrand should be enough to fly a 1/4 scale?

Simon

Re: Scratch built Slingsby King Kite 1/4**

Posted: 30 Mar 2022, 18:55
by Bovin
Hi Simon,

I feel a bit ashamed, never been at the Maasvlakte, should do that once. I live between Leiden and Haarlem, very close to the beach with dunes, but only flyable with NW winds. There is another issue, salt and sand aren't very good for electronics, so I have a special planes and transmitter for that use, don't dare to fly these big scale planes over there.
But I should try the Maasvlakte once with my salt & sand glider!

Vincent

Re: Scratch built Slingsby King Kite 1/4**

Posted: 30 Mar 2022, 19:24
by simon_t
Nice area - Noordwijk and Katwijk beaches are lovely - I stayed at Katwijk on my last visit to ESA near you. You might be surprised by the dunes at Maaasvlakte - they are man-made, but big enough and with enough lift that they now that they attract many paragliders.

Simon

Re: Scratch built Slingsby King Kite 1/4**

Posted: 30 Mar 2022, 20:29
by Bovin
We used to fly at Langevelderslag, just a bit north of Noordwijk, but not often last years. Maybe we can have a go at the Maasvlakte, thanks for that suggestion!

Vincent