Slingsby King Kite 1/4

[bocorvin]

Merci Sebastian, excuse, je continue en Anglais,
I have to make all the ply joints very, very carefully, they have to take all the strain. The advantage is that the tail"boom" becomes lighter, so much less ballast. Now the whole glider becomes lighter and hopefully there will be less chance on damage with bad landings. I have to wait and see........
I think that Etori Bugatti said ; "Si ca casse, fait le plus legere". I am not sure if he said that, but I like the way of thinking.

Vincent (DB)

[sebastian92]

Yes Vincent, you're right !
more weight = more inertia = more breakage… build light as possible ! good currency

[VincentB]

Il y a quand même un autre paramètre à prendre en compte, quand on atterri dur, ce qui arrive souvent, surtout à la pente, si on compare la même chose avec un grandeur il exploserait sans laisser aucune chance au pilote nous ça se solde par quelques réparations et c'est reparti.
N'empêche que si on devait garder toutes les proportions de section des grandeurs, ok c'est super beau, mais ce serait quand même fragile, et de toute façon, être trop léger ne permettrait pas de voler quand il y a un peu de vent, donc les compromis que l'on utilise sont pas si mauvais que ça. Après c'est vrai que plus c'est fin, plus c'est joli, et aussi, difficile à travailler.

[bocorvin]

You are right Vincent, hopefully I made it just strong enough.
Time will learn and I hope for the best!

Vincent (DB)

[bocorvin]

Bonjour a tous,
Before continuing with the cockpit, the remarks of Vincent BecanconI got me thinking 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 I pulled the dry roving wire through the holes and impregnated it with epoxy.




Just like the tool to pull a wire through the needle.

After curing, the girders feel much stiffer and not much weight is added. To get the cockpit right I first fitted the pilot (borrowed from my Gull) and after some fiddling he was neatly in place . Made a backrest, seat and floor from plywood / balsa sandwich, they are fixed with screws in plywood supports,







Enough space over the servos.


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.




Now I could start making the cockpit canopy. In that period it was not possible to make a bubble canopy's, so this canopy is made of curved panels, nice characteristic, beautiful (thanks to Thomas for the photo).



To make the supporting structure I laminated three frames.


and glued them together on the fuselage .



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?



. The canopy was quite a time consuming job, but now the frame is ready for varnishing and glazing.



Vincent (DB)

[sebastian92]

Hello Vincent,
great work and clever ideas
you speed to build !

[Sed]

Hi Vincent,

What a beautiful work !
The canopy is magnificent !

[bocorvin]

Thanks Sebastian, about the idea's; I can't stop thinking......

Vincent (DB)

[sebastian92]

So continue !
what kind of servos do you use ? they seems smaller… are there strong enough ?

[bocorvin]

Sed, thanks for your nice remarks

Sebastian, the servo's are Corona () from HK, type CS238MG, double ball bearing, analog, 4kg.cm
The weight of the plane is also about 4kg, so I think they are Ok. Dimensions 29x13x30mm.They are quiet and have lots of favourable comments. I Have thew same type for the wings, the only difference is the housing. Dimensions of the wing servo is 29x10x34.5

Vincent (DB)

[mainsd'or]

[bocorvin]

Hello Mainsd'or,

Thanks very much for your input .
To begin with, I have no theoretical education in this field, only the things I have learned myself and a lot of experience with wood and fibres.
From the (interesting) study you send me (in French,which is a foreign language for me) I found the E-modus of glass is about 5 times higher than wood, it means its 5 times "stiffer". Carbon has an E- modus about 13 times higher than wood.
So, in theory, the glass would take all the load till it breaks and the the wood should take all the load.
In full size small experimental sailing boats I reinforced some high loaded wooden parts with UD glass and had no ruptures or breakages in those parts. (I had other problems ).
Maybe you are right, time will learn and I hope it stays in one piece!

Vincent (DB)

[mainsd'or]

[bocorvin]

Hello Mainsd'or,

Thank you for the your well thouight out answer, I am not sure if I understand it all, sorry.
Maybe you can have a look at the fuselage,



The sketch represents about 1/4 of the side of the tailboom. The wood surface is; (from the ply taken only the innner and outer layer, parallel to the grain) 2/3 x 0.6mm x 90mm= 36mm2
the spruce stringer;
3mmx6mm= 36 mm2, total 54mm2
the glass is 2.4mmx .7mm= 1.7mm2.
I just estimate what I did, maybe you can tell me if I have to add more glass, or that it is in proportion

Regards,

Vincent(DB)

[sebastian92]

Bonjour,
merci mainsd'or pour le partage de ces documents !
in my opinion, sincerely, if you double the section of wooden stick… it will be quite rigid enough for… without complicated practice fiberglass.
The bending will make too the rigidity, well bonded in pressure.
Anyway, in case of a strong landing ... it will break the same

[mainsd'or]

[bocorvin]

Hello All,

Thanks for the reactions, it keeps me learning .
I ll leave it like this and I will try to land gently

Now I go on with the cabin of the King Kite.

Regards,

Vincent (DB)

[bocorvin]

Hello everyone,

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



and sand it smooth

I built the nose itself from 20mm balsa, sanded the side view first, then the top view

and then roughly into shape

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.

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.


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. This is done as follows, you smear both adhesive surfaces with PVA and let it dry. Then you put it together and press it together with a hot iron, the glue becomes soft due to the heat, and it is fixed. 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

then smear the glue surface with PVA and let it dry

. I could now place the piece exactly in place, fix it with clamps and iron it on

To be sure, I later applied extra glue on the inside, you never know, this technique is new for me.....

Vincent(DB)

[Sed]

Hello Vincent,
Good job and very nice, your tricky piece ! This iron technique is very interesting .
A little question : the nose will also be sheet with 0.6mm plywood ? I ask myself a lot of questions about this for the Pavelek P-2 ...

[bocorvin]

Hello Serge,

Thanks for your nice comments and yes its an interesting technique, I am still a bit afraid if its strong enough.....
About the nose, I will use veneer, thats 0.6mm wood, no layers, so sanding does not show . Its on my Nemere 1/6 http://www.retroplane.net/forum/viewtopic.php?t=4645&postdays=0&postorder=asc&start=0 and also my Gull 1/4.


The restauration of the nose of a real Petrel (almost identical nose as the Gull) took a year......

Vincent (DB)