Hoi-Choi - Biplane

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 Always wanted to build a biplane.. and here is one.. It flies beautifully.. awesome slow speed characteristics, amazing roll rate... it parachutes down with power off






Dimensions


A simple rectangular wing, box fuselage made out of 5mm XPS sheet/depron makes it very easy to build, and it can be built very quickly.

The research on CG of a biplane led to quite a range of literature, from simple to some very detailed ones (incl CLs of the airfoils)... finally KISS prevailed (keep it simple and straight).. The wing cord was taken as distance from the LE of the wing positioned ahead to the TE of the aft wing.. and it worked

Another aspect which went through a similar approach was .."whether to have ailerons in top and bottom wing or only one (bottom) wing"... here again, went with having the ailerons ONLY on the bottom wing.. and it works.

Electronics

Motor - 2212, 1200kv (even 980kv will do, used this as that is what I could spare). Prop 9x4.7, Servos - 4 x 9 gms , battery - 1500 mah 3S

CG

CG was calculated treating it as one wing having a cord of 23 cm (19 cm cord + 4 cm stagger), and was at 6 cm from the LE of the top wing. (@15% sm - 5.78 cm, at 10% sm - 6.73 cm )

Due to the available battery it required a few grams of additional weight in the nose. Also some down and left thrust

V 2 mods

The UC was changed and moved ahead. This also helped in doing away with the dead weight in the nose. The aileron, elevator and rudder throws were fine tuned to 40%, 70% & 50%... 

And a more colorful and visible color scheme  for visibility and orientation 




Here is a video https://youtu.be/BFWPhhyKY7w




 

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