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Written by Don DeLoach Free Flight Sport As seen in the August 2020 issue of Model Aviation.

IN APPROXIMATELY 2001, there was a need to have a simple and small "formula" event for small, electric-powered Free Flight (FF) competition. E-36 was the result. It was the brainchild of Vic Nippert, Rex Hinson, and other electric enthusiasts.

The specified power was six NiCd battery cells, with a minimum airframe weight of 120 grams and maximum wingspan of 36 inches. With NiCd batteries and inrunner motors, the event didn’t produce much excitement. The models climbed slowly—roughly as fast as a Sport rubber model—and clocked roughly 90 seconds without thermal help. It was clear that the event could be improved, so in 2010, the National Free Flight Society (NFFS) formed an electric committee to reimagine E-36.

The "new" E-36 class debuted in 2011. The new rules kept the wingspan and weight restrictions but allowed two LiPo battery cells. This enabled the use of outrunner motors with much faster and more exciting climb performance.

That first year, at the 2011 Outdoor FF Nats, there were four fliers. The ensuing years saw an explosion in popularity. By 2014, the E-36 class was the most popular event at the Nats with 28 participants. To outsiders, this was a bit shocking—a new event was more popular than historic events that had been flown at the Nats since the 1920s—but for those of us who had been with E-36 since the beginning, it was not a surprise.

E-36 is a nearly perfect event. The models are inexpensive and generally simple to build. The motors and batteries are inexpensive and easy to find, yet they perform well. The models can be easily flown by novices on small- to medium-size fields. Motor runs of 10 seconds get the models high into thermal territory, and 2-minute max flights limit the required field size.

the late john oldenkamp was the designer of the original joulebox
The late John Oldenkamp was the designer of the original Joulebox E-36. Photo courtesy of CB Model Designs.

Build an E-36

There are copious options for kit-building. The two most commonly seen designs are the CB Model Designs Joulebox, which is available as a full kit or short kit, and the DeLoach Super Pearl, which is available as a short kit. Both have primarily balsa construction, tissue or plastic covering, and utilize an inexpensive kite spar for a fuselage/tailboom.

Other kit options include the Satellite, Witch Hawk, and Starduster from BMJR Models and the WeeDevil from Retro RC. For scratch builders, visit the NFFS plans store and search "E-36" for the original Joulebox and two elegant winners by FF Hall of Fame member Hal Cover.


There is a dizzying array of brushless motors that are suitable for E-36. Look for motors of approximately 20 to 30 grams and in the range of 2,500 to 3,000 Kv (rpm per volt). The most popular motor in recent years is probably the Cobra 2203/28. At 2,800 Kv and only 20 grams, it will swing a 7-inch to 7-1/2-inch propeller with a 4 × 6-inch pitch.

A recent move toward the heavier and more powerful 2205, 2306, and 2207 drone racing motors has gained a lot of attention. This style of E-36 is quite a bit faster in the climb but requires a larger, heavier ESC and stiffer, larger flying surfaces, so the glide performance is reduced because the model is significantly heavier.


In the 2,500 to 3,000 Kv range, you’ll be able to run 6-inch to 7-1/2-inch propellers with pitches of 4 to 6 inches. Popular choices include the Graupner folders that are sold by Texas Timers, as well as the standby APC 6 × 6E, 7 × 5E, and 7 × 6E propellers. Some claim that the fixed-pitch APC propellers have superior climb performance compared with the Graupner folders, although folding propellers clearly have an edge in the glide.


The C rating is the discharge rate of the battery. In electric FF, with a limited-motor runtime, we want a maximum continuous discharge rate. Look for 2S (two-cell) LiPos (7.4-volts nominal) with continuous C ratings of 60 or greater and a capacity of 300 mAh to 500 mAh. The capacity of the "fuel tank" is the mAh.

You don’t need more than 500 mAh for the 10-second maximum motor runs in E-36. The battery weight should be in the 20- to 30-gram range. Texas Timers sells Thunder Power RC LiPos in 70C, which is good. Other good brands include the HobbyKing Turnigy Bolt in 75C at 500 mAh and GaoNeng GNB 80C at 300 mAh to 450 mAh.

clint brooks is shown with his kit built joulebox
Clint Brooks is shown with his kit-built Joulebox E-36 during the 2016 Outdoor FF Nats at the International Aeromodeling Center in Muncie IN.


BMJR Models, Roger Morell, Texas Timers, and Starlink Flitetech all sell reliable electronic timers. The one from Texas Timers is a bit more expensive, but it’s the easiest to program via rotary switches. All but the BMJR Models timer offer an optional pigtail for hookup to a radio dethermalizer receiver.


For most E-36 motors, a 10- to 12-amp ESC is adequate. Retro RC sells the Cobra 11-amp ESC that many top fliers swear by. If you are running heavier 2205, 2207, or 2306 drone racing motors, you’ll be drawing 25-plus amps and will need a 20-to 30-amp ESC, such as the Castle Creations Talon.


It’s quick and simple to rig an inexpensive, 3.7-gram submicro servo to run off of your motor timer to give you precise 120-second dethermalizations.

Thousands of RC pilots who fly electric power have the skills to branch out into FF via the E-36 event, and many already have. Beware though—once you try FF, you might be hooked for life.

eleven year old skilly deloach set a junior
Eleven-year-old Skilly DeLoach set a Junior AMA record with her Super Pearl 202 in February 2020.


Model Aviation

July 2012: "FF Scale" by Louis Joyner

Review of Super Pearl 202-E

CB Model Designs


BMJR Models

(321) 537-1159


Retro RC

(248) 212-9666

Texas Timers

(423) 282-6423

Starlink Flitetech

(858) 231-4994

Stan Buddenbohm

Thunder Power RC

(702) 228-8883



GaoNeng Battery

APC Propellers

(530) 661-0399

Castle Creations

(913) 390-6939


But just like our SAM models...where can you legally fly them? Far as I can tell, without a waiver, which takes a long time to get approved, over 400 feet outside of Class B airspace is a high as you can legally go.

E-36 is strikingly similar to ½A Texaco: 36" wingspan on same type of model and speed 400 electric instead of a ½A glow engine. RC control of rudder, stabilizer and motor can be turned off at a designated time (3 minutes) and allow the thermals to take the model up and bring it back. My first experience with this method was a ½ hour almost out of sight flight on a hot August day. Had difficulty bringing it back down! A very satisfying flying experience with a simple model and equipment.

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