GROOVY 50 3A GOES ELECTRIC, THE

THE GROOVY 50 COMES IN TWO VERSIONS: the Groovy 50 3A and Groovy 50 3D. These models are very similar but play different roles. The 3A is more for pattern-type maneuvers and the 3D is more for-well-3D. The differences lie mostly in the wing; the leading edge of the 3A's wing has a lot of taper in it with a thinner airfoil and slightly less area than the 3D's wing for better wind penetration.

Since we had both models, I thought that it would be fun to convert the 3A to electric power. The 3A's design and light airframe (2.75 pounds empty) make it good for this project. Another key feature is that the top hatch on the forward fuselage is removable; no modifications are necessary for quick and easy battery access. With the accommodating servo layout in the fuselage, the battery can be placed with little effort where the fuel tank normally resides. The wide nose of the Groovy also allows easy motor mounting, and the cowl neatly covers the installation.

I built the Groovy 3A per the instructions, and all went very well. To power my modified Groovy, I used an Axi 4120/14 brushless outrunner motor, a Jeti Advance 70A Opto speed control and a Kool Flight Ultimate BEC that eliminated the need for an onboard receiver battery. I used a Kokam 4S2P (14.8 volts), 6000mAh Li-poly battery to make it all go.

A Southgate Aero custom motor mount made mounting the motor a piece of cake. I needed only to pop out the factory-installed blind nuts and reposition them for the new mount. This mount costs approximately $30 and can be made to the exact firewall-to-prop length needed. Spacer and hardware kits are available for other custom installations.

The biggest modifications I needed to make were adding cooling holes and slightly enlarging some of the fuselage formers to accept the battery. I secured the battery with strips of Velcro® that I glued to the bottom of the fuselage. The final weight of the model came out to be 5.5 pounds.

STATIC TESTS

With the Kokam battery fully charged by my AstroFlight Digital 109 lithium charger, I used a tachometer and an AstroFlight Whattmeter to perform the static tests.

At full throttle, the power system produced 810 watts of power while drawing 60 amps. The APC 14x10 electric prop turned at 8,600rpm. These numbers told me that a minimum of 144 watts per pound of power would be on tap. This should be plenty of juice for sparkling performance.

FLIGHT PERFORMANCE

Well, I certainly wasn't disappointed! My modified Groovy 50 3A gets airborne in a hurry from a grassy runway. When it flies, it's immediately obvious that this model lacks nothing in the area of vertical performance.

This Groovy 50 has a solid feel in flight, and basic aerobatics such as loops, rolls, Cuban-8s, spins and stall turns are a snap. Any pilot will quickly be at ease with the electric Groovy's flight characteristics. It can also stylishly perform more advanced pattern maneuvers such as Humpty Bumps, the Shark Tooth and inside and outside snap rolls. All in all, I'm very happy with the electric-powered Groovy 50 3A.

-Rick Bell

Copyright Air Age Publishing Aug 2005
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