Fly Electric!

Dragon Fly

Closer view of front section
53 kb
The wings are 2 piece
44 kb
Access hatch
35 kb

'Dragon Fly' caught my eye as an unusual 'old timer'. Designed in 1938 and built by me from plans in 1993. It started out with an OS48 four stroke engine but has now been converted to electric. The model turned out to be a bit tail heavy with all the planking and sheeting, and the glow version had 15oz of noseweight to correct the CG. Removing this, the motor, mount, fuel tank, firewall and bits and pieces saved enough weight to convert it to electric without increasing weight significantly. The model does not need the power of an Astro40 and 20 cells, but it does need this weight to achieve a correct CG. I have now detuned the motor to improve duration, and it has the lowest power to weight ratio of all my models. It is nevertheless still quite sprightly for a vintage model (enough power to pull it through a loop from cruising speed) and is reasonably controllable with rudder/elevator control only. 10 minutes in calm conditions is pleasing.

Wing span: 83"
Wing area: 864 sq"
Wing loading: 23 oz/sq'
Weight: 9 lb
Motor: Astro 40 Cobalt #640
(minimum advanced timing)
Gearbox: Astro standard 1.63 : 1
Prop: Master Airscrew 11x7.75 Kavan
Prop speed: ? RPM
Batteries: 20 x RC2400
Motor current (full power): 23A
Motor power: 500w
Power loading: 55 w/lb(input)
Flight times: 10 minutes (8 on 2000's)
Receiver: Futaba 8ch dual conversion
Servos: 2 x Futaba 3001
Speed control: Anything - I've used a Jeti JES80, 40 and Astro 204D.
Rx battery: 350-700 mah 4 cell nicad
Aircraft design: John Pond plans
Airfoil: Slight undercamber
Wing construction: Traditional spruce spars and partial balsa sheeting
Fusalage construction: 1/8" balsa planking over formers
Undercarriage: Fixed
Covering: Silk and dope
Extra features: Conversion from Glow

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