Scratch built Slingsby King Kite 1/4**

[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.
After some bad moments, I thought better now, than much later in construction. So I cut out the curvature in the top spar

and with my powerfile I beveled both sides 1 in 10

I changed the angle in the build board (extensively checked now!) and glued two 1X10mm battens under the topspar to get a stable situation .

I fitted pieces of 2x10 mm spruce and glued it between the spar with 24h epoxy with wood dust as filler.

.
At least now The King Kite looks in proportion, just a few pictures in the garden.

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Vincent

[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..

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.

After cutting off the aileron from the wing, I realized how long and narrow it was, 115cm long and 4.5cm wide. .

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.

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.

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.

Then I added capstrips and the aileron was finished roughly, still needed some sanding.

Vincent

[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

[Bovin]

Peter,

This photo is a part of the one in Mark Simons book, you guessed that right. I know the other photo

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

[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

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.

Covered the structure with PVA

clamp it and with a 10X10mm batten en strips of 4mm ply with big clamps.

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

I smeared the top of the ribs with glue and clamp the whole thing together, just like before.

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

Vincent

[VinceC]

very interesting work and thanks for the video on how you bent the plywood

[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.

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I came up with very small horns, I drew them twice too big (by hand ..)

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My friend Adri was so kind to CNC quite a few. Afterwards the size seemed quite correct

First I made the dummy control at the top of the wing from 0.8mm steel wire, with a non-functional clip

. 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

. 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

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

[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 (74.95 KiB) Viewed 2817 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)

] and then saw off pieces. I started with the TE, narrow pieces

beveled with a Proxxon power file,

with which you can subtly shape those tiny pieces. They are glued to the end rib and fuselage with thick cyano

Where the curvature in the end rib decreases, I also take longer pieces

With a long round screwdriver I keep the pieces in place

Sometimes it goes wrong and then I have to cut out a piece. Finally it looks like this

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

[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.

Then I made them fit and sanded a bevel on it

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.

I smeared both surfaces to be glued with PVA

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.

It begins to look like a wing!

Vincent

[Peter Balcombe]

Very nice Vincent