Slingsby Gull scale 1/4

[bocorvin]

Hello everybody,
After finishing a new fuselage for my Nemere 1/8 I started thinking about a new glider. First I wanted to build a Fokker FG 1, but that is very similar to the FG 2 that I had already built. Besides I like the period of varnished ply gliders! A fellow modeller mentioned the beautiful Fafnir. I talked about the flying characteristics of the vintage gliders. Because I do almost all my flying on flat fields, not on a slope (not much slope in Holland..) I realised that the thermal qualities are much more important. I thought building the wonderful Petrel, almost started with the frames when I realised that it has also a thick wing profile which cannot be changed without changing the “looks” of this glider. Luckily I found the Slingsby Gull,and a much thinner wing, but with struts. A development was the “cantilever” Gull, with a stronger wing (not thicker) and without struts. Fortunatly it has also spoilers, a great help for me with landings!
If I build this glider in scale 1/4 it has a span of practically 4 metres, which suits me well, with a relatively short fuselage, luckily in varnished ply. Also I wanted to build it light, hoping it will fly better .







I found a great drawing in the Martin Simons book about Slingsby. ;

The scale soaring Uk has also very usefull documentation
Because I (still?) can’t work with digital drawing programs I enlarged his drawing. The nasty thing is that the lines are also enlarged, so the frame plans are rather crude. In this case I started without a detailed plan, I just work from the original plans, often to find solutions while working. I also plan to make the fuselage with as few girders as possible. With good butted joints the ply should take all the loads. I tried that on a new fuselage of my Nemere 1 / 8,
http://www.retroplane.net/forum/viewtopic.php?t=4632 end of page 1, which seemed to work well.


The enlarged drawing of the fuselage.
So I started with the frames, I laminated them from 7 layers 1 X 5 mm spruce, dry bended, clamped and glued with thin cyano.





For the narrower frames I pre bended the spruce battens with boiling water and let them dry before laminating.





Next I made a building jig from a piece 20mm chipboard. 10 X 10 mm spruce battens screwed at a small angle on it on which later the frames are glued temporarely. So the frames are placed at that small angle, just as the plan, to achive the correct joints of the ply panels later. Because the inaccuracy of vthe frames it took some time to line it all up. Luckily its easy to thicken a frame with an extra 1mm batten. I sanded this setup with a long sanding block to get all the humps out. I had to remake one frames but in the end I was quite pleased with the result.








The batten on the inside of the frames will form a "sandwich " girder with the strip of the buttjoint of the skin panels (from 0.6mm ply)

Hopefully this scetch explains my intention!


To be continued

Vincent

[Johannes]

Hi Vincent,
schön das du wieder was baust
Die Konstruktion der Spanten gefällt mir sehr gut

Gruß Johannes

[bocorvin]

Hallo Johannes,

Danke, erst komt noch Ferien, dann sperrholz und dann gehts weiter

Gruss, Vincent

[caralp_laurent]

Hello Vincent,
It's a magnificent glider ! So you're building the Gull III without struts ant with brakes ? (I know one real sized Gull III still survives in GB, painted in blue and translucid).

I like your building method, (looks like mine , neither do I the drawings "computer made")
It will work and fly the same anyway

Have a good building, see you,
Friendly,

Lolo

[bocorvin]

Hello Lolo,

Thanks for your remarks and yes I build it with brakes and probably without struts. I hope to see the real one in Scotland soon.
Glad you like my building method

Amicalement,

Vincent

[Peter64]

Servus Vincent
bin schon gespannt auf deinen Bericht.
Viel Spaß beim Bauen .
Liebe Grüße Peter

[bocorvin]

Danke Peter ,

Wir haben erst Ferien, soll eben dauern for Ich weiter bastel .

LG Vincent

[Clifton]

Hello Vincent,

Very nice choice. I love this sailplane. I like your kind of building but I can't do that. It's terrific for me not having a good plan.

I'll follow your build with lot of interest.

Philippe

[bocorvin]

Hello Philippe,

Glad that you like this plane!
I can't make digital plans, I make a kind of plan in my head and I am to lazy to work that out in detail.
Hopefully the construction idea of the fuselage works out OK.

Vincent

[bocorvin]

Hello everyone,

We went to Scotland this spring and my friend Rob found out that a Slingsby Gull was exhibited in the National Museum of Scotland, Edinburgh, what a coincidence . First time I could actually see the real thing before making it! Because the Gull was suspended onder a glass roof, it was difficult to make good shots, but I could figure out quite some details.


.
Back at home I went on, made the main spar of the fin,


and attached it with the frame of the fuselage.



Next I glued thick balsa on the inner spruce stringer, sanded it flush on the outside.

To align all the frames I had to sand them with a very long sanding block and on one frame I had to glue an additional batten.
On the outside of the balsa went a strip of 0.6mm ply, 12mm wide to stiffen the girder and later be a joiner plate for the skin.


To my relief this girder appeared to be very stiff, so I thought; when I put some diagonals between the two girders it can be taken of the jig.



With caution I unscrewed the fuselage from the building jig and it was pretty stiff, so I could take away the temporary battens.

I glued a 10mm wide 0.6mm ply strip with cyano at the "keel" and reinforced this joint with a fillet from thickened epoxy.



to be continued,

Vincent

[Fotor]

Very nice Vincent, great job again.

I can't wait to tow this one into the air with the Eco Boomster.

[bocorvin]

Thanks very much for your nice comment Raymond, I am also looking forward to be towed, please have some patience
By the way the weight of this backbone? is 330 grams.

Vincent

[bocorvin]

Hello everybody,

After all the heat I started to build was the horizontal stabilizer. I hoped to make the ribs in the conventional way, but there appeared to much taper in this packet of ribs

it just was not acceptable. I didn't like to ask my friend(s) to cnc the few ribs (I already asked to do the wingribs..) so I choosed a bit more basic approach. I cut a lot of 2mm balsa at the same width, pinned them down on the drawing with my ply endribs in place and sanded the tophalf in shape with a very long sanding block.




Made some sanding tools for the nodges in the ribs






Took both halves of the building board and sanded the other side into shape. Joined both halves and made some reinforcements in the middle



The real thing



I tried to make a similar way of attaching the stabilizer to the fuselage.

from epoxy print board and drilled 1 mm holes.






To be continued.

Vincent

[bocorvin]

Hello everybody,

I now had the basic structure of the horizontal stabilizer. The nose had to be covered with 0.6mm ply. I thought prebending the ply; started pouring boiling water over one side of a strip of ply, wide enough for the nose

turned the strip around and folded it a "U" shape. Poured again boiling water through this "gutter"

now I could easily fold it further and put some clamps on it

Now I poured again boiling water through this almost closed gutter

through the pressure of the clamps this gutter closes itself further

After some drying it stayes nicely in shape.

This is a sharp bend, for wider bends I fold he ply around a pipe or a wooden dowel with a suitable diameter.
Now it was easy to glue the ply. The LE with cyano and the other parts with PVA.

Made the hinges from epoxy sheet (like the hinges Vincent Besancon uses).


I also wanted to make the rounded front of the moving part of the elevator from ply, forming a ply tube which is very stiff in torsion.

I added capstrips and gusset plates. The gusset plates are glued on top of the ply covering as Hans Jacobs put in his book

the stabilizer almost complete, it has become very rigid with the ply parts and capstrips.


Next was the rudder;





Made the rounded front of the rudder from prebent ply, using some big clamps trying to bent the ply in a nice half circle

almost completed

The fixed part of the rudder

The real glider had a demountable part of the fin, I tried to make it in one piece





I wil cover the massive balsa piece with ply or veneer. Its a complicated spot on this glider with the actuation of the elevator, which is also demountable, I hope the pictures explain it....

The elevator and rudder will be activated with steelcables







To be continued

[CHAUSSEBOURG]

beautiful work, congratulation!
Pierre