Astro Flight Cobalt 25 Powered 1/6 Scale J3 Cub

This page was last updated on January 7th, 2003; Thanks for visiting!

Here are some design details on my 1/6 scale SIG J3 Cub kit conversion, which I first started building for an ASTRO-FLIGHT 25 Super Ferrite motor back in November of 1984. Photos were taken on a cold & intermittently snowy November 12th, 2000, (after it's first flight on skis) at Ron Teke's "Lost Creek RC Air Park", a private RC air field at about 8200 feet elevation in Summit County, Colorado.

I recently installed a new Astro-Flight Cobalt 25, 8 wind motor, and a 15 cell 2200maH SANYO NiMH battery system, and did a couple of modifications to the JOMAR SC-4 speed controller that's been flying this aircraft for many years. Static thrust testing done a few years ago showed that a Master Airscrew 10x5 brown 'Old Timer' prop produced good thrust with less current draw than many other props I'd tested at that time, so it's the prop I'm using for this Cub for now. With a separate 370mAH NiMH receiver battery, it's flying at about 83 ounces on wheels, for a ~16 ounce per square foot wing loading. Performance is impressive when the throttle is wide open, to say the least! It performs aerobatic maneuvers as well as any .46 powered glow fuel 1/6 scale cub I've ever seen fly here in the mountains. The takeoff on skis was predictable and effortless on the new wide track landing gear. And it's very stable and predictable on landings, too. I expect this aircraft will see a lot of air time from now on!

A key to having this aircraft handle sweetly lies in the wing strut length, and how they can affect the wing incidence. I built the wing struts with adjustable clevises on each inner end, so that they could be precisely set to hold a 2 degree wing tip washout, in reference to the wing root next to the fuselage. (This is an airfoil that you can't simply 'eyeball' to get this setting right.

A major modification that was needed for all of these years was to design a better handling landing gear setup. This Cub was the single plane most prone to ground looping on takeoff that I have ever built. WAS is the proper term. I recently built a new wire landing gear, increasing the tire tracking center distance from the kit stock 12-1/2", up to 18-3/4". (I'd also previously replaced the tail wheel with a tail skid wire, for use on our dirt & grass runways here in the mountains.)

Wow, what an incredible difference! On Friday evening, November 11th, as the light was beginning to fade, I & a friend went to SPARCS field just north of Fairplay, CO, to fly the 'recomissioned' Cub. The takeoff run was as smooth as any I've ever experienced; it's no longer a ground-loop-prone aircraft! Huray!

The Astro Flight Cobalt 25 motor (direct drive) was purchased for $120.95 from NEW CREATIONS RC at

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