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Posted by Watty | Apr 21, 2017 @ 10:47 PM | 5,936 Views

I designed and built this 3 channel, 2-meter electric powered glider – which I call E-fficiency – in 2002. I designed it to be capable of soaring in weak thermal conditions, and for long-duration flights under power. The three-view drawing in Figure 1 and Photos 1 and 2 show the configuration and construction, and give overall dimensions. The configuration is uncommon, but I like to experiment and try different things in my original designs. Based on my design objectives, the twin boom, inverted V-tail configuration made sense. The glider flew well right off the drawing board, and I didn’t have to make any modifications to the airframe. However, the structure is very light, and if I were to make another one, I would use a stiffer structure less prone to flutter, and include spoilers to make it easier to descend out of thermals and to improve glide path control for landing. I did upgrade the power system, changing from a brushed motor to a geared brushless inrunner motor, and later replaced the NiCad and NiMH batteries with LiPo batteries. I have spent many enjoyable hours thermal soaring with this glider as well as relaxed puttering around in calm conditions. I instrumented it with an Eagle Tree Systems Flight Data Recorder PRO and associated sensors to measure performance, and then analyzed the measurements with techniques I developed. I learned quite a bit from that, and I believe the performance measurements are fairly accurate....Continue Reading
Posted by Watty | Oct 09, 2016 @ 12:10 PM | 6,597 Views
While deciding what to bring to the Horizon Indoor 2015 event, I got the crazy idea to put floats on my UMX Radian so I would have something to fly off Spektrum Lake. Unfortunately, other things took priority, so I didnít complete the float installation until early January 2016 - which isnít a great time for flying off water in New England. So, initial flights were in a sports dome and off snow. I was finally able to try flying off water during some unseasonably warm days in early February, when we had a lot of rain and large puddles at our flying field.

The float setup works well. The plane has taken off from artificial and real grass, snow, and water, so I guess it truly is an amphibian. Being slow, it can be flown in confined areas Ė possibly a large swimming pool if you are lucky enough to have one handy. The primary shortcoming is there isnít a lot of excess power with the stock motor. The plane requires a strong battery Ė a 200 mAh battery works best. The UMX Radian is very light and the wind can flip it over easily when on floats, so should only be flown off water in calm or light wind conditions.

I call the plane a Radiam, for Radian Amphibian. Early flights can be viewed here:

UMX Radian on Floats (3 min 37 sec)

My float installation uses a single center float and two outrigger floats. The center float is from an E-flite UMX Carbon Cub Float Set (EFLUA1190). The built-up outrigger floats are made from 1 and 2 or 3mm Depron sheet. The...Continue Reading
Posted by Watty | Jan 03, 2013 @ 10:26 PM | 9,782 Views
My first blog entry describes a method to make thin Depron sheet similar to Durobatics from readily available 1 mm Depron sheet.


In late 2007, I designed a small aileron, elevator, and throttle airplane around the radio system from a Park Zone Minium Cessna 210, and a more powerful GWJ 7mm Gearbox w/SS Blue motor from Bob Selmanís BSD Micro RC. The fuselage was built up from 1 mm Depron and a few pieces of balsa and plywood in high stress areas. The symmetrical airfoil wing consisted of a balsa root rib, tip rib, and a balsa spar covered with a single piece of 1 mm Depron wrapped around the leading edge.

The model flew satisfactorily and would perform basic aerobatics, but it was clear the wing was much stronger and heavier than needed, thus performance suffered. So, I decided to see if I could lighten the design by thinning the 1 mm Depron sheet wherever possible. Most of the weight in the 1 mm Depron sheet is in the skins, so removing one of the skins reduces weight significantly. I developed a simple method to machine and sand the 1 mm Depron to a thickness of about 0.025 inches. I used this material to build the next version of the plane, called the TinE Dancer V2. Performance was much improved due to the lighter weight. This plane is shown in Photo 1, alongside the PZ Cessna.

I received many positive comments about the plane, its flying characteristics, construction, and materials I made it from. More information and a video can be found...Continue Reading