Sunday, August 28, 2011

Dandy E205



This is not about a high-performance sailplane but about building something that you knew about maybe 30 years ago...

Graupner used to have a glider kit called "Dandy". I found a new-old-stock Dandy kit offered on eBay, but it went for what I considered way too much. So I decided to build something similar to the Dandy, and luckily found the web site http://www.koralpe.biz/dandy.html which has nice pictures of the original kit and a plane built from it.
I had also read about the Eppler 205 airfoil, both good and bad, so I decided to try that.
Finally, the "glider" should have an electric motor because using a high-start is somewhat cumbersome. The motor and prop combination was determined by trying various things in online motor calculators and by comparing with off-the-shelf models of similar wingspan, weight and type.




Wingspan170cm
Length105cm
AirfoilE205
StabE193, 50 x 11cm
Wing Area39.1 dm2
Weight1156g
Wing Loading29.6g/dm2
Decal FontOptima Extra Black
MotorTurnigy C3530-1100, Kv1075, 73g, 15A Max, later MVVS 10 2/1120
Prop9x5 Folding Prop
Speed Controller25A max
Battery2200mAh 3S LiPo


The center of gravity came out somewhat too far in the back unless two batteries are packed into the front of the plane. The total weight of about 1.2kg includes the two batteries and radio gear. The original plane had a slightly smaller wingspan, weight of 1.0kg, and a wing loading of 16-29g/dm2.

First flight was on the morning of August 28, 2011. Two brief flights before breakfast. It flies nicely! I was surprised how slow. Current draw is 13A at full power, and about 5A when cruising around.

--

17 July 2016: Axis of Turnigy snapped off (!) during climbout. Managed to land ok, but prop vanished in the woods.
Replaced with MVVS 10 2/1120. On summer evenings using about 400 mAh for 10 minute flight.

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