POU- Tandem - 30"

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A pivoting wing design in the lines of Mignet's Flying Flea

Front wing :
Span : 755 mm
Cord : 155 mm
Airfoil : NACA 23112
Dihedral

Rear wing
Span : 510
Cord : 155 mm
Airfoil : NACA 23112
No Dihedral

Motor : 2204, 1400kv, 3s 1500 bty, 30A ESC, 7x4.8 prop, 2x 9gm servos. All these are reused components , and specially the motor/bty/esc combination could have been much smaller and lighter

Horizontal separation of wings 15 mm, Vertical Separation of wings 85 mm

Wanted to keep the construction  simple

  • Both the wings have the same cord and airfoil. This makes construction easy in terms of hotwire airfoil template / ribs> The wings are hotwired out of EPS, and the leading and training edge have been laminated. There is a 3/4 span 3 mm CF road in the front wing. 
  • Two thin Aluminium "L" section have been epoxied at 20% of the cord, on the bottom surface of the front wing. The lower prong of the "L" have holes through which a bolt attaches it to a hole in the pylon.. .....this is also the pivot for the angle of incidence of the wing.. and controls the pitch of the aircraft. IMP : The hole.. i.e the wing pivot point is 10 mm ahead of the 25% of the cord. This is a balance between auto stabilization of the wing and the force on the servo
  • Fuselage is a block of foam shaped to allow mounting of the wings, rudder, motor and electronics... length of fuse 400 mm
  • The front wing pylon is made out of balsa, and so is the motor mount
The construction is fairly straightforward.. pics below











The thin line perpendicular to the cod is the 25% cord line and the pivot hole of the wing is 10 mm ahead of it. Also note the wing incidence control through the servo linkage at the rear part of the front wing

The BLACK line in the fuselage and wing is the CG

It is a 3 channel plane. Though the controls are a bit 
Throttle : motor rpm
Pitch : Wing incidence control
Bank & Yaw : Rudder.. ( the front wing has a slight dihedral at the tips)


After the initial flight the rudder throws were trimmed down to 40%.. Does ROG at @ 70% from standing start. She is very stable , and flies hands off  when trimmed.. best part is NO STALLS.. tried a number of times by yanking the nose up  at very low speeds but she does not stall.. also tried the parachute decent and it works.... for landing and takeoff into-the-wind is better (the typical characteristics of Flying Flea)... a nice effortless flyer


A video link to the first flight ( after reducing rudder throws).. pardon the bad quality of the video

https://www.youtube.com/watch?v=y0tVnx9UkVE&feature=youtu.be

the excellent photos are courtesy my friend Ranga








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