I enjoy designing and flying R/C aircraft. I enjoy the possibilities that modern magnet and battery technologies open up. I like unusual models. I like to be original in my designs. I like to hear people say, "wow, that's neat" and "I can't believe this flies" about my designs.

Polyglot multiprotocol transmitter, 2009

I am developing a homebrew transmitter. I have four design goals for this project:

I am implementing this TX around an AVR microcontroller, using avr_libc. In this implementation, model memories are C functions. I want to explore a higher-level language for defining models, probably Lisp, if I decide to use a more powerful processor. I make GPL source code available for download. As of version 0.1.2, Polyglot supports PPM pulse train output as well as serial communication with Horizon Hobby's DSM2 2.4GHz RF decks. It also supports using accelerometers from a Wii Nunchuck as inputs. Additional photos, videos and discussion are in this thread on RCGroups.

2-foot Geobat, 2007

This is a bigger version of my carbon Geobats. 2 feet in diameter, it uses a Slow Stick fuselage and landing gear and employes wing wrap for elevons. The entire trailing edge deflects up or down and the model has no separate horizontal control surfaces as such. Elevator response is good; aileron is sluggish. It seems that the wrap is too close to the centerline to produce much of a rolling effect. The rudder is phenomenally effective though, and I end up reducing its area eventually. Like all my other Geobats, this one is very stable in both roll yaw and had a nice coupling between the two, so I mostly fly it with the rudder. This model is a good, slow flier, and its size makes it practical to fly it outdoors as well as in. Outdoors, the transparent model is hard to see. I lose it in a midair collision with a ducted fan jet. By the time its pilot notices the Geobat, he is too close to maneuver away. By the time I notice him, I am too slow to get out of his way. Thread and video on RCGroups

Multi-8, 220g, 2007

I think every man needs a Guinness World Record to his name. I may go for "most motors on a flying model." 8 motors is not a record, but as a first stepping stone this model does well. It's a bash of leftover parts: the fuse is from a Pico Stick, wings from a free-flight foam glider, RX with built-in ESCs from Blade CX. Multi-8 uses 4 channels--ailerons, elevator and differential throttle for yaw (aerodynamic rudder is stationary). The ailerons are very effective, flying as they are in prop wash.

Power is from 8 orange SuperSlicks 7mm pager motors which I wire independently on each wing as 2S2P. These motors do best on a single cell, so the 2S arrangement means that each motor sees 4.2 volts. I can also fly with a 3S battery, in that case each motor sees "1.5 cells," or 6.4 volts, which is about as high as these motors will run before they burn out. Props are GWS 2510. I initially try to get away without balancing them, but the vibrations are so bad I have to go back and balance every single one. Balancing a large number of props can be a hurdle if I build a model with more motors that this.

Thread on RCGroups. Photos and video by Mark Harms.

Single-plate flier, 18.4g, 2006

In November 2006, Greg "gbarc" challenges RCGroups members to build airplanes out of foam plates. Taking his challenge a bit too literally, I build a model out of a single plate--I cut it in half and turn it upside down. RFFS-100 and Plantraco HingeActs provide 3-channel control, while an orange SuperSlicks 7mm motor turns a GWS 2508 prop.

4 videos by Eugene Shimulinsky: 16 seconds, 8MB short flight; 6 seconds, 4MB shows elevons in action; 1 minute, 40MB; 1m46s, 50MB

5.25" geobat, 2.5g, 2006

2.5 grams is the weight of a US penny. If you squish one flat enough, and you get a geobat! I use 3-micron Mylar, 0.010" and 0.020" carbon rod for the airframe. Plantraco Butterfly RX with 30mAh battery and Didel MK04-10 4mm pager motor with an Estes/Cox 1.6" prop which I cut down to 1". Power train is the same as in an earlier foam model, but I use a smaller, 25mg actuator from Nick Leichty. With the heavier Plantraco HingeAct, I cannot balance the model--its CG is too far back.

I originally intend to make this model from floppy disk material. This proves too heavy, but the 5.25" size sticks in my mind. After I build the model, I realize that if I can find one, I can use an acrylic floppy disk case to store and display my geobat. It pays to follow standards!

This model comfortably flies figure-8s in my 13'x15' living room. Video credit--Eugene Shimulinsky; photo credit (right)--Mark Harms. Thread on RCGroups

Picnic Plate, 14.2g, June 2006

Foam plates have a cross-section that, if you look at it from the right angle, is practically a reflex airfoil. This model is about as simple and inexpensive as they get. It uses AeroAce electronics for differential steering and has no moving surfaces. The model is not a trainer, but is quite predictable in its flight characteristics. It can probably do even better with a truly proportional radio system. One of the drawbacks of AA gear is a noticeable lag between transmitter and receiver as the system only transmits between 4 and 6 control packets a second, compared to about 50 for hobbyist FM systems.

I like the expression of disbelief on Martin Newell's face (right in the first photo). Martin builds some of the most amazing indoor models anyone has ever seen. His carbon fiber techniques are an inspiration to me and many other modelers. Photo credit left two photos: Mark Harms.

Update (August 2006) - I now fly the plate using my Python modulator that generates 20 frames per second and has 16 steps in the rudder channel, and it's indeed easier to control, as this video by Mark Harms shows. I make no modifications to the AA receiver.

Tailless Wonder, 19.6g, 2006

This is not really my own design, but rather a mod to a very popular model. SpinMaster AeroAce biplane sells for around $30 at Toys-R-Us and Target, and is a popular platform for hobbyists to modify. Many modelers build their own airframes around the inexpensive, "almost proportional" receiver that comes with the plane. Some have also modified stock airframes (many examples here and here). I want to see how far I can get from the original while still using only parts of the stock airframe. How about a flying wing? The modification requires a minimum of changes to the original. I pull the tail off, remove the bottom wings and attach them to the top wing's tips. A video shows the model in flight outdoors; another video indoors. Thread on RCGroups

Foam LRF, 2.8g, 2005

My lightest model up to then. Plantraco Butterfly receiver, Didel MK04-10 4mm pager motor, Estes/Cox 1.6" prop cut down to 1", direct drive.

This model turns out to be ridiculously sensitive to trim changes, especially motor thrustline adjustments. Half a degree right or down thrust makes the difference between a mellow, slow flier and a wild aerobatic monster with a mind of its own. First flight video and another video taken a week later after some trimming (video credit both: Chris Sorensen); photo credit (left): Mark Harms; thread on RCGroups.

Plantrénalyn, 15.6g, 2005

A 1/3 scale version of the famous Drénalyn, for Plantraco equipment. More information on the full-size original, is available at La page officielle de la drenalyn; more information on my rendition is available in this thread on RCGroups.

Carbon geobat, 4.4g, 2005 / 3.5g, 2006

I base this on the geobat.com design. Doesn't look like much, but it flies much better than I expect. Here's a video of its first flight. 7.5" diameter. (video credit: Chris Sorensen); thread on RCGroups.

I rework the model for the SmallRC Living Room Flyer Cook-Up the next summer. (Sadly, SRC forums become unavailable when DWE goes out of business in 2006) I replace some of the heavier carbon fiber with thinner rod and the Saran Wrap covering with 3-micron Mylar, reducing the weight almost by an entire gram. The object of that cook-up is to build models that were slow enough to fly in a living room 24'x24'. With the occasional bump into a book case, I can now fly figure-eights in my 13'x15' living room. More photos and videos by Mark Harms on his site. I later build a smaller version, see the 5.25" geobat above.

Slow-G autogyro, Apr 2005

This model is popular enough that it makes economic sense to produce a kit. The kit now has its own website.

Kitbasher Twin autogyro, Mar 2005

This is my first successful autogyro. I build it on the GWS Pico-Stick fuselage, with Penni helicopter blades. Thread on RCGroups.

Carbon Skeeter, 20.5g, Jan 2005

My first carbon-fiber model, and my first sub-ounce design. RFFS-100 receiver with KP-00 motor and U-80 prop. Tail surfaces come from a DWE Skeeter.