The E-FOX : By Bruce Stenulson

This page was last updated on June 11th, 2004, now showing this original design E-powered aircraft on floats, ready for float flying; thanks for visiting!

The Latest Photos, May 2004: Here is the E-FOX on the shorline of Dry Lake near Fairplay, ready for it's first flight from floats. It handled very well, both on the water, and in the air.

The floats are 35.5" long, set up with dual water rudders; (this set of floats was recently re-covered, and were originally mounted on one of my Wild Hares- the float mounting strut system is the same. ) While the complete aircraft weight increased 15 ounces form it's weight when flying with wheels, the wing loading is still only 17 ounces per square foot; the flying characteristics are very good; it gets up on step easily, tracks very well on the water on plane, accellerates quickly, and lifts off of the water effortlessly with only very slight up elevator input- just the way you would want a float plane to handle!


Wingspan : 63"

Wing Chord : 13.4"

Wing Flying Surface Area : ~810 square inches = 5.62 square feet

Airfoil: Custom Designed for this Aircraft : 0 Dihedral; Full Strip Ailerons

Fuselage Length : 48" from prop line to Rudder Trailing Edge

Flying Weight : On Wheels = 80 Ounces ; On Skis = ~84 Ounces; On Floats = 96 Ounces

Wing Loading : ~14.22 ounces (on wheels); to 17.08 Oz per square foot when mounted on Floats

Motor : 20 sized Cobalt (Brushed) motor, geared (to ~440 watts) : CERMARK CEM2008, with Astro Flight 2.38:1 Gearbox

Propeller : 13x8 APC

Battery Packs: 12 cell GP 3300 NiMH (and previously flown on a 12 Cell 3000maH NiMH)

Speed Control : Custom Built JOMAR SC-4 ESC design, Opto-isolated

Airtronics Radio ; Onboard System Rx & Servos powered by a separate 4 cell 300mAH NiMH battery (1.1 Ounce)

This design might be called an electric powered cousin of the SKYFOX, one of my highly sucessful 60 sized wet powered designs. It shares the long tail moment and tail group shape, and has the same wing span. This is a very smooth flying aircraft!

The wing airfoil on this E-FOX, however, is a different custom designed lifting airfoil, with a nearly symmetrical airfoil fore section. The performance of this airfoil / wing (flying with the present power system) is beyond expectations- it will hold inverted flight (and climb inverted) with very little negative pressure on the elevator, and easily pulls through from there into a half outside loop.

The excellent power-off-glide characteristics were also part of the original design concept objectives, but the performance is far beyond expectations. (I'm sure that the wing tip plates also contribute substantially to this dynamic characteristic.)

The one piece wing is built with an aluminum arrow shaft leading edge, designed to be strong, yet light weight.

I actually started designing and drawing the plans for this aircraft in early January of 1993. The project was framed up and then set aside, worked on occasionally, and finally completed and first flew in late June of 2001. It was originally designed and flown with a different large motor in a 15 cell (1250SCR) direct drive power system setup. Performance was good, but the flight duration was too short for comfortable flying.

The present 12 cell geared cobalt power system setup was installed on January 1st, 2003. It is 4 ounces lighter overall, with over twice the flight duration using the 3000 maH NiMH batteries (two Radio Shack Sub-C car packs rebuilt into one pack). It's now in the 10 minute flight duration range- much more reasonable.


In May of 2004, I built up two new battery packs of the GP 3300 NiMH cells. These cells have an extremely low internal cell resistance (< 4 milli- Ohm) and this definitely shows up in their performance! Flight performance is noticably stronger than with the previously used Radio Shack cells, using an APC 13x8 prop. I'm finding that after about twelve to fifteen minutes of flying repeated takeoffs & landings from water with the floats, that the battery pack is only modestly warm.
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With the 3-1/2" x 13" skis, it handles very well on the snow. The trick is to get the E-FOX to settle down on landings- it will glide a long ways, and land at very low speeds.

When flying from skis and wheels, the black air scoops on either side offer more cooling air flow for battery cooling; in setting up for float flying, I removed the forward intake air scoops and covered the openings to keep water from possibly coming in when taking off or landing in higher wave conditions. (The wing saddle area also needs to be sealed so that spray on the underside of the wing from the floats does not get inside to the servos. The radio receiver is wrapped in plastic wrap & sealed, so that it stays dry- essential for water flying!

In 2003, I changed the Aileron servo setup, going from the single servo setup that was originally designed & used, to a two servo setup which allows spoileron mode use on the Airtronics RD-6000 transmitter. This allows the plane to be landed in a much more reasonable amount of space!

May 2004 Updates: The 12 cell Sub-C Battery packs are now quickly changable through the top forward hatch, so they can be swapped out and charged outside of the aircraft. The GP 3300 NiMH cells definitely increase the performance!


I love night flying from water! So I made new wing tip plated for the E-FOX's wing from lightweight 1/4" thick balsa, and wired in 4 LEDs on each wingtip. The first photo below shows the plate with LEDs & wires & current limiting resistors glued in place; the second photo below shows the inner surface covered & the wire connectors coupled, so the wing tip is ready to be mounted in place with 4 screws.

More technical information on this night flying lighting setup is now included on the NIGHT FLYING PAGE.

For further information on float flying events, setups, and the float flying photo gallery, CLICK HERE.

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