Having built a 60" Depron pusher I wondered how small I could go using the same layout & 3.7g servos. The object was to create a plane that could be flown outdoors.
I selected a 20" span.
On another small plane I had used pull/pull cables using fine (7lb) mono-filament fishing line.
Such a system has the advantage that a single servo can work both ailerons with virtually no weight penalty. I then went a bit further and adopted an 'elevator only' V tail layout with separate pull/pull cables to each half of the elevator.
Everything is quite a tight fit.
The 4 channel Corona and the 3.7g elevator servo.
The front of the fuselage is sized to hold a 420mAh 3s.
420mah3s.JPG  The pylon mounted aileron servo.
The pull/pull cables on the aileron horn go forward to an eye and then to the servo.
The elevator cables also have to go through an eye to clear the prop.
EleCables.JPG  And then on to the V tail
It weighs 3.5oz with nearly that much thrust.
At the very small loads required mono-filament line works well and the lines can be stretched a bit on assembly to make sure there is no slack.
It took some modifications before it could be even considered controllable but now it flies quite well - on calm days - but it is still pretty twitchy!
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Those little plane are fun in a protected area, or on a calm day. But if a good wind comes along, you get to watch it carry your plane away. That fishing line is a smart way to save weight.
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I actually developed the idea of a fishing line pull/pull for my scale 24" Sopwith Pup - not Depron this time but balsa & tissue.
The object was to make all the control runs scale with the line running inside the wing. Not too much of a problem for the elevator & rudder but the ailerons used a rather complex closed loop system to work all four.
From the fuselage, out inside the bottom wing then 90 degrees to the aileron horn, over the horn to the aileron trailing edge, up to the upper aileron. over its the horn, 90 degrees, right across the inside the upper wing, repeat the same thing and eventually back inside the lower wing to the servo horn.
I used ballpoint pen inners steam bent round 90 degrees. It was smooth enough that the 7lb fishing line could be pushed along the control run - just!
To say it all took a long time would be a bit of an understatement!
The finished article.
With a 500mAh 2s it weighs 4.5oz.
It 'piece de resistance' is the Gnome rotary. The 2805 out runner bell is the crankcase with the 9 cylinders glued to it, so it is a true rotary! i have flown it once but it is impossibly delicate. It really should be for indoors only.

ps The Pup normally had an 80hp Le Rhone in a full cowling but for UK defence duties the 100hp MonoSoupape was substituted as it gave a faster climb rate.
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