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Archive for March, 2011
Posted by A Useless Geek | Mar 06, 2011 @ 10:57 AM | 7,684 Views
Unit B is a much better implementation of the Longhorn II Lunatic than the first pass. Hanging the control surfaces out the back and getting some real surface movement made this a completely different plane. I also reshaped and added some anhedral to the horizontal stabilizer/elevator. The results were far closer to what I expected.

I was able to construct this plane without the typical wood or carbon fiber structural bracing in the back because the moving surfaces left a clean fuselage for taping. So far the 3M Extreme tape is all that is needed to keep the back end held together. We'll see if that is true over dozens of flights.

(As a side note, I plan to attach a pinhole camera to the plane to watch the rear end in flight and look for flex.)

The Lunatic is a radical departure from the performance of the "normal" Longhorn with its conventional control surfaces. Death spirals, for instance, look like the airplane is chasing its own tail. Rudder spins are stupidly tight. Invert loops happen in the blink of an eye and almost within the airplane's own length. Outside death spirals are possible with this plane, something I haven't managed to do with anything other than a real 3D plane.

The 24 gram motor is bigger than this plane really needs. I can cut back to a 19 gram motor and 8A ESC and shave another eight grams or so off the front end. As it is the C/G is a little far forward of optimal for maximum flight stupidity, so moving the C/G rearward with component selection is actually a benefit.

I'll post up some video when I get a chance.

Specs:

Length: 840 mm
Span: 560 mm
Mass: 177 grams (dry)
Motor: hexTronik 2730-1700; 24 gr, 1700 KV
ESC: TowerPro 12A
Servos: hexTronik HXT500 (2)
Battery: 2S Turnigy 500 20C