Radio Control: Electrics
Bob Kopski 25 West End Dr. Lansdale, PA 19446
This month's topics
- Electric Connection service
- Trainers and flight instructors
- Thrust measurements
- More on the Futaba Electric receiver
REMEMBER: The "topical table" above is a new column feature that began with last month's issue. The idea is to provide an easy lookup scheme for readers who saw something somewhere. Aside from the above, the table will forewarn you of what's ahead when you first open MA each month. Please give it some time, and then let me know if you like the idea.
The Electric Connection service was also introduced last issue. The idea is to help electric modelers meet. If you're a loner, a small group, or a club that wants to let folks in your general area know you exist and are looking for more modelers of similar persuasion, just let me know in writing and I'll list your info here. Since this service is new, it will take several months for initial offerings to appear. After that it will still take a few months for your input to appear. As an example, I just received a December-dated issue of our favorite model magazine as I prepared to write this column for the February issue!
Trainers and instructors
Trainers bring in a lot of reader mail and are one of the dominant model types at the local flying field. Given all this interest, I'd like to share some thoughts about instructors, trainers in general, and some electric trainers in particular.
Sometimes (heck, it's all the time with me!) when going through model magazines and advertising I get the feeling that RC "trainers" account for 99.9999% of the total model hobby market. It seems that just about everything advertised is a "trainer"—no matter the configuration, size, shape, etc. This is an exaggeration, of course, but there are a lot of so-called RC trainers out there. I suspect many an unwary beginner pilot was tempted by some flashy ad or a pretty picture and wound up with deep regrets about his supposed trainer selection. I believe some manufacturers have no consciences!
Beginning pilots need two things:
- A good, honest basic trainer (electric or glow-powered).
- A good instructor pilot.
These two in combination can make a big difference.
What is a basic trainer? What makes a good instructor?
Opinions differ, but to me a basic trainer is a relatively slow, stable, forgiving model that, if properly set up, would be capable of a sustained safe flight and landing on its own—with no RC guidance. In effect, it could behave like a docile sport free-flight model. This is not to say it would actually be flown this way, but it could be.
Good examples of this concept are many Old-Timers. Such a model typically has a high-wing "cabin" appearance, a flat-bottomed or undercambered airfoil (perhaps a Clark Y section with a slightly raised leading edge), no ailerons, sufficient but not excessive dihedral, and is constructed mostly of balsa. It's reasonably light and thus capable of relatively slow flight.
A good instructor is someone accomplished at flying the kind of model described above and who understands the needs of a beginning pilot. I've seen many hotshot pilots who can dazzle with high-powered aerobatics but have little ability—or interest—in teaching "on the wing." A good instructor is safety conscious, will stick closely with you, and will rarely allow a mishap—so your plane will last much longer.
Electric trainers I've flown and recommend
I've flown several electric trainer-type models and helped students with them. The following models (in no particular order) are ones I recommend considering, assuming they are equipped with rudder, elevator, and motor control (speed control preferred) and that the power system provides adequate flight power:
- Great Planes ElectricCub
- Great Planes PT Electric
- Astro Viking
- Goldberg Electra
- Goldberg Mirage
- Leisure Amptique
- Leisure Playboy
A basic trainer—wet or dry—needs only three channels (rudder/elevator/motor) and adequate power. I've seen more beginners get into trouble from a too-high-powered, too-fast so-called trainer with ailerons than from almost any other cause, other than a poor instructor who allows such a model to be used in the first place.
On average, the planes above that are capable of the slowest flight are the Viking, Playboy, and Amptique. These give a beginner the most time to think—a critical advantage when everything seems to be moving very fast at first. The Viking and Playboy are Old-Timers that began as free flights; the Amptique is not an OT but is a slow flier because it is typically lighter (about eight ounces less than many others), has generous wing area and a moderately thick, flat-bottomed airfoil. The Amptique is one of my all-time favorite kits.
I consider those three the best choices for beginning pilots who have some model-building background. Note a subtle distinction: a beginning RC pilot and a beginning model builder are not necessarily the same. Old-Timers have a lot of sticks and tricky features like undercambered airfoils, which makes them relatively more difficult to build and cover—exactly the wrong thing for beginning builders.
Building and equipment notes
- If you have little or no previous building experience, get experienced help with construction before flying an OT-style trainer.
- The easiest to build for most beginners seem to be the Electra, Mirage, and PT Electric lines. These include extensive, highly detailed, illustrated instruction booklets and plan sheets, making them good choices for beginning builders. These models usually have heavier wing loadings and thus fly somewhat faster, but they still make good basic trainers for many people.
- The Electra Club is more scale-detailed, somewhat more complicated and fragile, and can be less tolerant of rough handling and novice landings. I recommend it as your next plane after you have gained some basic experience.
- Of the models listed, the Electra differs in that it is a sailplane and is also the largest. It is one of the best of the bunch for carrying conventional radios with standard-size servos, 500 mAh receiver battery packs, and large receivers because of its large wing area. In general, I recommend using micro-sized radio systems for trainers unless you really need larger gear—micro gear is lighter and simpler to install.
Finding an instructor if your club won't help
I get letters where "the guys in the local club" won't help a new member with an electric. Reasons vary: some are intimidated by motors and batteries, others are suspicious of electrics, and some clubs simply lack members experienced with electrics. If you run into this, consider:
- Find someone locally who likes and is experienced with sailplanes or Old-Timers. Even if they lack electric experience, they can usually do a good job checking out your plane and getting you in the air.
- Use the Electric Connection service (see above); it may help you find local electric flyers.
Thrust measurements
Thrust measurements (propeller pull) interest many electric modelers. I receive letters, photos, and thrust-measurement data from readers. Some test setups are impressive, and I plan to pass along useful information and suggestions in a future column.
Typical homemade test setups affix a motor/prop combo to a mechanism that displays thrust (propeller pull) in ounces. Provisions are usually made to vary and measure power input, rpm, and to swap motors and propellers. The usual purpose is to determine the best combination of motor, battery, and prop.
A key point: motors and batteries do not develop thrust per se—a spinning propeller does. If a given prop at a given rpm produces a certain thrust, it will produce that thrust at that rpm regardless of what turns it (electric motor, gas engine, or any other source of torque). What differs is how easily and efficiently different motor/battery combinations can reach and maintain that rpm under load. I understand the convenience of using electric motors to evaluate and compare props and thrust; what I object to is the impression that a particular motor/battery magically changes the prop's thrust at a given rpm. If anyone pursuing thrust measurements thinks I've missed the point, please let me know and I'll pass the information along in a future column.
Futaba receiver and speed control
Speed controls have been covered in recent columns; here is a brief follow-up. The Futaba Electric receiver with the built-in speed control uses a frame-rate speed control design. I personally borrowed one and measured it to confirm this.
This receiver has become popular locally and seems to work well. It is, however, limited to relatively small motor battery packs and small motors. One feature I don't particularly like is the automatic motor shutdown built into the BEC (battery eliminator circuit) design, which can catch you by surprise. For that reason I prefer a separate receiver battery. I hope Futaba's marketing success with this set leads to more and better receiver/speed-control combos in larger sizes—simpler installations would benefit many folks.
Closing
The beginning of a whole new flying year will be on the scene just about the time you're reading this. Happy quiet landings to everyone throughout 1990!
Transcribed from original scans by AI. Minor OCR errors may remain.
