What's New and Who's Doing It?
By: John Worth
Publication: RC Micro World Online Magazine – www.cloud9rc.com
Date: 8/1/2005

THE BEAUTIFUL BUTTERFLY
We’ve said a lot about Plantraco’s contribution to the state of the microflight art, via their RTF Butterfly and the 900 MHz RC control system. It reminds me of what happened with Petter Muren’s BladeRunner micro RC helicopter. Whereas two years ago Petter’s design was a one of a kind amazing achievement which had everybody buzzing at the 2003 NEAT Fair in New York, this year the design became available as a RTF, selling in toy stores all over the world.

But the BladeRunner was bought by many, many, modelers who recognized it as much more than a toy. They saw a tremendous technological advance that made it possible for many of them to successfully fly an RC helicopter for the first time—and in the house, too. Thus, where it took the genius of Petter Muren to advance the state of the art very dramatically so, too, are we seeing many modelers flying the RC Butterfly where only a few people like Henry Pasquet could fly such small and light model aircraft before—and in the home, too!

Until six months ago, I didn’t think I would ever be flying a 4 gram RC model and now it seems so ordinary and natural—thanks to the bright minds and “let’s see how we can do it” attitudes at Plantraco.

In just the first half of this year the microflight world had made a quantum leap in the number of people flying smaller and lighter stuff than ever before.

And, while Plantranco borrowed ideas from many other people regarding how to do it, what made it happen was the blending of such ideas and their own contributions to the state of the art. Furthermore, while much of what they have done has been pioneered by others, the outstanding contribution from Plantraco has been the introduction of the 900 MHz rc system. This exclusive development in our field has practically overnight made it possible for us to fly our own much smaller and lighter airplanes with state of the art commercial products; a dramatic advancement regarding what’s available to us now, compared to what was available last year.

The whole Butterfly package is remarkable: the model, the radio, the geared motor/prop combination, the tiny rudder actuator, the magnet-mount battery, the carrying case, etc. All this comes with a pricey cost factor, but the quality and performance involved makes it a reasonable investment when we consider that until Plantraco came along we were paying about $ 100 for the best receivers. And the Micro-Joule RC set—last year’s hot item in micro-miniaturization—cost about $ 150, with no model, transmitter, charger, or batteries involved. So, at about $ 230, the Plantraco package deal is not unreasonable.

The flight performance of the Butterfly is amazing. I was surprised to find that it had a lot of power, enough to have it zoom rapidly to the 24 foot high ceiling structure of the warehouse type building I was flying it in. I learned right away to launch at moderate power for a gentle initial climb and then to go easy on the rudder stick because the Butterfly turned so sharply. It did excellent figure eights with about five foot circles.

It was also obvious that a better pilot than I could handle it well in a very confined area. For me, I preferred gentle power and wider turns that produced slower flight. I was able to do this more easily by using the trim knob for power control rather than the control stick. I found that moving the stick against its spring centering required an extremely fine touch. For me, a ratchet action motor control stick would be preferable, to click in and hold various power settings.

Regardless, The Butterfly has lots of power and turn control. It can be flown fast or slow to suit the pilot’s preference and skill. I’m looking forward to more opportunities to fly it in a large space until I get good enough to fly it safely in a smaller space. It’s a revelation to find so much performance in such a small and light model. More about all this next month.

FREE FLIGHT TIMERS?
While this publication is intended basically for RC, much of our activity—especially as we talk about the smallest and lightest stuff—is related to Indoor Free Flight activity. We have learned much from the FF fraternity about construction materials and techniques, and the art of very slow flying. Furthermore, many of our microflighters do both FF and RC models; among the best are people like Don Srull and Ray Harlan.

Lately, a number of modelers who normally fly RC, including myself, have been using tiny electronic FF timers to control free flight electric motor runs, to tailor flight paths to the site available. A basic problem for electric powered free flights is to prevent the model from hitting the ceilings or building structure—electronic timers are ideally suited for this purpose.

Nick Leichty , among others, has been making tiny timers which operate off a one cell Lithium Polymer cell (that also drives the model’s motor). These timers allow preselection of the length of motor run and the amount of power delivered to the motor. Some timer versions also allow power programming to provide more power for initial launch and climb, throttling back for cruising close to the ceiling, then slowdown for descent and landing. I first reported on these timers in the July 2004 issue of RC Micro Flight.

John Krouse (Rockville, Maryland) has been one of the foremost practitioners of this kind of flying, with free flight models very much like his indoor RC models. These FF models have the used the geared 25:1 Solarbotics motor I have described previously (June RC Micro World) for possible RC use. Here’s a Krouse drawing of one of his models:

One of the nice things about using a timer like Nick’s is that extended flights in low ceiling buildings are possible. I have flown for over a minute with a half ounce indoor free flight model, staying under a 24 foot ceiling. Yet with the same model I have flown in buildings with 40 foot or more ceilings. The tailoring of the free flight patterns with programmable timers is a neat experience as equally enjoyable as flying RC. A nice sidelight to timed flying is that many flights are possible with one battery charge. When the timer shuts down and the model lands, a quick resetting of the timer allows an instant relaunch.

PONY 2
During flying of Plantraco’s MicroBlimb over the past several months I often marveled at the unique control system it has; somewhat different from those offered for airplane use. The MicroBlimp has three motors controllable in forward or reverse, with simultaneous proportional control of each motor in any combination. That’s six combinations of control, an extraordinary system, especially since it is very light—only 10.6 grams (7.5 for the radio, with motors, and 3.1 for the 90 mah Lipo battery!).

It’s a perfect system for a blimp but I wondered, how about for an airplane? Two of the motors could be used as for many contemporary models, with differential thrust for turn control, plus proportional speed control of thrust. But most such differential thrust systems simply slow one motor down while the other produces full forward thrust. With the Plantraco system one motor can be controlled to produce reverse thrust while the other has forward thrust, resulting in a more effective turn control.

Meanwhile, the third motor is mounted at right angles to the others to produce up thrust or down thrust, for effective elevator action, or pitch control. That action is definitely not typical and it would be interesting to see how it works with an airplane. We know that using a motor at the tail to produce right or left thrust, in what I call a rotor-rudder action, is very effective. It works even at low or no airspeed, since it does not depend on airflow from forward flight to push against a conventional rudder surface for turn control.

Would the up and down thrust motor be effective, too? Theoretically, yes, but in the case of the Plantraco control system package the third motor is close to the other two and in a typical installation would be very close to the c.g. of the model and thus probably less effective than a rotor-rudder with a long moment arm back at the tail to multiply the thrust effect. If the third Plantraco motor was physically separated from the package and mounted at the tail it surely would be more effective than a nose mounting.

But the simplest way to experiment was to simply take the Plantraco system assembly as is and mount it on the nose of a conventional model. When I was inspired to do this I had just gotten the all-foam Pony free flight model from Hobby Lobby. It was a very simple matter to remove the prop and rubber motor. I then mounted the Plantraco RC system to the nose of the Pony via an adapter balsa block. It was quick to do, only about 15 minutes.

Very interesting is the fact that the weight of the rubber powered version of the Pony is 55 grams and the weight of the model with the Plantraco multi-channel RC system weighed slightly less, at about 50 grams! The bare original model weighs 35.4 grams with the landing gear\and since the latter weighs 6.5 grams, if the l.g. is removed the bare plane weighs only 28.5 grams which suggested that the bare plane with radio, at xx grams, might be flyable with the three small pager motors in the Plantraco system.

Note: the rubber motor and prop together weigh almost 20 grams (19.7) and this fact alone indicates that an RC electric version of the Pony is feasible with many contemporary RC/electric motor systems, such as the one that Pete Carpenter installed in his Pony 1 model.

In trying to fly the Pony 2 I quickly found that the forward thrust was not strong enough for more than producing a prolonged glide from a hand launch. Obviously a model to use the blimp system needs to be much lighter to suit the thrust available, after all, only a small single cell Lipo is provided.

Why bother with all this? First of all, the system provides a lot of control for a very little weight. Also, the complete MicroBlimp system is only about half the price of the Butterfly airplane package. If the MicroBlimp system can be attached to about a ten gram model (not unreasonable) it might have enough power. So that’s phase two of this project to use the blimp radio in a model plane. I hope to report more on this project next month.

JOE’S MICROLIGHT BUTTERFLY
Inspired by his success with Plantraco’s 4 gram Butterfly, Joe Malinchak (Greenfield Township, PA) decided to try a half size (3.5” span) version. It uses Nick Leichty’s RC receiver (1/10 gram!), a 4.4:1 geared 4 mm Didel motor, 30 mah battery (which weighs 1 gram, half the total weight of the model ready to fly). Joe carved his own prop from lightweight contest balsa.

Here’s what Joe had to say about this project: “The Plantraco Butterfly is such a great flying model, I decided to build a 1/2 scale version. I was also looking for a good project to test Nicks new 3ch 100mg receiver. Didel had some new light gears, a 40 tooth spur and 9 tooth pinion that work well with the small 4mm motor. I could have made the model slightly smaller and lighter by going direct drive but I wanted the model to have good duration. I constructed a 1/2 scale contest balsa Butterfly prop that I mounted on a Didel removable hub. The model flies great on the 30 Li-poly cell. It’s a little fast to fly in the house, but maneuvers well for such a small model. The battery is the limiting factor which represents half of the model’s weight. With a 10 Li-poly cell (like the samples Henry Pasquet uses on his record breaking models) it could easily be flown in the living room. Hopefully new batteries are on the horizon that will make a model of this size more practical .“