Author: Bob Aberle
Edition: Model Aviation - 2008/09
Page Numbers: 71,72,74
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Frequently Asked Questions

Bob Aberle | [email protected]

Indoor model airplanes: a credit to FF modelers

Please write in with your questions, since that is the only way we can keep this column format going. When referring to already published Q/As (for follow-ups), provide the number as a reference. Also note that addresses and websites are now placed in a group, separate from the text, at the end of this column under "Sources."

Q364

Q: "I see a lot of references in model publications to micro indoor RC flying using electric motors for power. Years ago I flew indoor rubber-powered aircraft. In other words I did not use RC or electric power. Are some modelers still flying this type aircraft and if so can you recommend any general form of reference material?"

A: Many dedicated and experienced modelers are still flying indoor rubber-powered aircraft. Indoor rubber power is one of the many events included in the annual AMA Nats.

An old friend and fellow Long Island Gas Monkeys club member, Ron Williams, has specialized in indoor rubber-powered models for years. He wrote an excellent book about the subject and published it himself in 1981 with a second printing in 1984. Ron recently made a third printing, titled Building & Flying Indoor Model Airplanes (ISBN 978-0-615-20203-7). It contains more than 200 drawings, sketches, and photographs. Aero Craft is selling the book; the company’s website contains a good write-up along with several sample drawings. The book is $24.95 plus shipping and handling.

Q365

Q: "Many of my local modeling friends seem to be using the FMA Direct Cellpro 4s balanced Li-Poly and A-123 battery charger. I understand that FMA has recently introduced a new Cellpro 10s charger and was wondering what’s the difference in these chargers?"

A: The FMA Direct Cellpro 4s balance charger can charge as many as four cells at up to a 4-amp current. It has a single output intended to charge one battery at a time. The new Cellpro 10s is a more powerful version than the 4s, and it will cost you more, but the new features are worth exploring.

With the 10s, you can charge two separate battery packs, up to five cells each, and at up to a 5-amp current each (a total of 10 amps). The special balancing software that FMA Direct developed will allow you to charge batteries at up to a 3C rate. This means that instead of taking an hour to fully charge a battery, you can do it safely in about 20 minutes.

Another big plus of the Cellpro 10s is that internal software can be downloaded through a PC at regular intervals, and charging data can be stored and graphed using a PC. If you haven’t already bought a Cellpro 4s, think hard about moving up to the new 10s. I also wrote a detailed 17-page review of the Cellpro 10s charger for AMA’s Sport Aviator webzine.

Q366

Q: "I just purchased a new Airtronics RDS8000 2.4 GHz spread-spectrum RC system. After checking it out and getting ready for my first flight, I turned on the transmitter and heard a continuous beeping sound and noted a message on the LCD screen indicating 'TH-Hi.' I didn’t see any screen like this in my owner’s manual. What am I doing wrong?"

A: Nothing is wrong, but when you look through a new owner's manual, read the text as well as look at the illustrations.

On page 11 of the manual is a chapter titled "Throttle High Warning." The RDS8000 has a built-in warning system that will not let you operate the transmitter unless the throttle control stick is in the dead-low or idle position. At any other stick position, the alarm will sound and the message "TH-Hi" (throttle high) will appear on the screen.

As soon as you move the stick to the idle position, the alarm stops, the message leaves the screen, and the transmitter operates normally.

If you have an electric-powered aircraft, most of the new ESCs will not let you start the motor until the throttle is at the idle position. Therefore, this warning feature may be redundant for electric flyers. But glow-fuel pilots can benefit from this feature, because you certainly don't want your engine starting at anything but idle speeds. It's a worthwhile safety feature for any modeler, regardless of the power system.

Q367

Q: "When you employ electric power your ESC will, most of the time, have a BEC that allows you to power your RC system from the main battery pack. Since this pack is charged often (sometimes before each flight) there isn't much concern as to the power left in the battery. There will always be some power remaining to operate the radio until a safe landing is made.

"But I have several larger electric-powered models that don't have a BEC and require a separate battery. I also fly glow-fueled models that require an airborne battery pack. How can I quickly determine at the flying field that my battery still has enough power to operate the airborne RC system?"

A: To quickly determine battery capacity at the field, you need a voltmeter that applies a load to your battery pack. Simply attaching a digital or analog voltmeter will not make a valid test; a simulated load must be applied. Through the years I've seen several meters that do this job, but the problem has often been too little of a load or not enough choice of loads.

Peak Electronics now sells the Custom Electronics Loaded Digital Voltmeter (item CEL-1530) for $59.95. This handy little tester can plug into the charging jack on the side of your aircraft fuselage. You can measure pure voltage with no load or select "Load" and choose 250 mA, 500 mA, or even 1000 mA for larger-capacity battery packs.

The instructions that come with the meter cover, very carefully, how to analyze the readings you obtain and give you an idea of when it is time to stop flying and recharge the battery. So please don't guess—measure the voltage under load.

Q368

Q: "I've noted the big explosion in micro indoor RC electric-powered aircraft. I suspect with the high cost of automobile gasoline, traveling to distant flying sites may require some 'cutting back.' The thought of flying in a local gymnasium or sports dome now seems like an excellent idea.

"However, I still like doing aerobatics and would very much like to see indoor micro RTF models available with full four-channel control, including ailerons for roll maneuvers. Do you see this happening in the near future?"

A: I've seen website information indicating that at least one company—Kyosho of Japan—is thinking along these lines. I found its new Piper Cherokee that comes as a ready-to-fly (RTF) with a 2.4 GHz spread-spectrum RC system, a brushed/geared motor, an ESC, a Li-Poly battery, and a charger. The model is set up for full four-channel operation, including ailerons. Total flying weight is 24 grams (0.85 ounces).

Kyosho will also introduce a full four-channel-control electric-powered helicopter called the Caliber 120, also with 2.4 GHz RC and including a gyro. Its flying weight is expected to be only 30 grams, and it should come with training gear. These products were expected roughly midsummer.

Q340 Follow-Up

After the Q/A concerning Fiddlers Green paper aircraft published in the April 2008 column (page 88), I received many e-mails from readers. One from Joe Mielnicki mentioned another source for paper aircraft. Even if you don't build these models, they still offer excellent three-views from which you can construct micro and park-flyer-size aircraft.

Joe referred me to Paper Models International (PMI) of Beaverton, Oregon, which has a 60-page online catalog available. The company even carries the line of Fiddlers Green paper aircraft that I mentioned in the column. It's well worth your time to scan through this catalog.

Since Joe knew I am interested in unusual airplanes for various model-design projects, he also referred me to the excellent Encyclopedia of the World's Commercial and Private Aircraft (ISBN 0-517-36285-6). This large-format book contains more than 250 pages that include 143 diagrams, 113 color profiles, 230 color photographs, six color three-views, and 25 cutaway drawings. It is a treasure for any aviation enthusiast, and especially for scale-model designers and builders.

Such a reference, when new, might have sold for close to $100. Joe suggested trying Amazon.com for used copies. I did and found quite a few, with conditions varying with the prices. I ended up with a clean copy that arrived in approximately a week for less than $10. Try this for yourself.

Sources

Transcribed from original scans by AI. Minor OCR errors may remain.