Author: Bob Kopski
Edition: Model Aviation - 2004/06
Page Numbers: 114,116,118
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RADIO CONTROL ELECTRICS

Bob Kopski, 25 West End Dr., Lansdale PA 19446

This column includes three meet announcements, reviews several recurring reader questions and advisories, reminds you of a SIG that is growing in popularity, and describes a how-to videotape that should be of particular interest to the Scale modeler—electric or otherwise.

Meet announcements

  • Old Time Eagles Electric Fly-In
  • Contact: Joe Beshar, 198 Merritt Dr., Oradell NJ 07649; Tel.: (201) 261-1281
  • Event: Eighth annual Old Time Eagles Electric Fly-In
  • Date: Saturday, May 15 (rain date Sunday, May 16)
  • Notes: A fun, low-key gathering with open flying for all and an Elexaco event for the competition-minded. If you plan to attend, contact Joe for more information.
  • Loudoun County Aeromodelers Association 5th Annual Electric Fly-In
  • Contact: Brian Allen, 47036 Berwick Ct., Sterling VA 20165; Tel.: (703) 430-5849; E-mail: [email protected]
  • Event: 5th Annual Electric Fly-In
  • Date: Saturday, July 24
  • Location: Club flying field at Banshee Reeks Park, several miles south of Leesburg
  • Notes: AMA-sanctioned, offers lunch, a raffle, and vendors. More info at www.lcaa.org.
  • Cocalico Prop Busters Electric Fun Fly
  • Contact: Karl Benson, 28 Cheltenham Dr., Wyomissing PA 19610; Tel.: (610) 678-1447; Fax: (610) 678-7017
  • Event: Cocalico Prop Busters Electric Fun Fly
  • Date: September 11
  • Notes: Also open to CO2 power. Fun events include GWS Moth pylon race (mass-launch), Wingo endurance contest, Zagi combat, and other events/judgings. Karl can provide a mailer with map.

If you have an electric event planned, share the information with me and I'll pass it along in an upcoming column. Please provide the facts more than four months ahead of the event date so everyone can benefit from adequate publication lead time.

Reader questions and common topics

Many readers send repeat or recurring questions—often because new people continually enter the hobby or because some details are hard to remember. Two frequent themes:

  1. Direction/orientation of passive components
  • Resistors: Resistors have no direction; you can install them either way. The color code indicates resistance value and related info, not orientation.
  • Inductors/chokes: Like resistors, these typically have no direction.
  • Capacitors: Some capacitors are polarized and must be installed with the correct orientation. Polarized caps are marked accordingly; I indicate polarity in my electronics-construction articles.
  • Semiconductors and batteries: Components that require polarity/orientation include diodes, LEDs, transistors, ICs, and batteries—these must be wired correctly.
  1. Chargers and the concept of "constant current"
  • Many chargers are designed as constant-current sources: they deliver a specific charging current regardless of the number of cells, as long as the pack is within the intended design/application range. This is true for every charger I've published.
  • Measuring charger output voltage with no pack connected can show an extremely high "open-circuit" voltage. For a properly working constant-current charger, this open-circuit voltage measurement means nothing except to indicate the maximum number of cells allowed. What matters is the charging current when a pack is connected.
  • If you want assurance, connect an ammeter in series with your pack and observe the charging-current value.

All my published electronics projects include a necessary-parts list. If a suggested supplier discontinues a part, you can substitute a similar component only if you are fully knowledgeable about what you're doing. If not, stick with the parts called out in the article or consult the referenced supplier.

NiMH packs and premature ESC shutdown

A common problem with the growth of small-model interest and NiMH batteries is premature ESC shutdown. Many pilots report shorter-than-expected flights because the ESC cuts power midflight. In most cases, the cause is not the ESC itself but the pack's inability to sustain terminal voltage under the motor current drain.

  • NiMH packs often have higher internal resistance than similar Ni-Cd packs. Under heavy load, the terminal voltage drops enough that the ESC's low-voltage cutoff "thinks" the pack is nearing empty and shuts down to preserve power for the radio. The ESC is doing its job—but for the wrong reason.
  • This issue is common in six- and seven-cell systems with ESCs that cut off near 5.5 volts. Everything may seem fine right after charging or at reduced throttle, but at high throttle the ESC may cut out a minute or so into the flight.
  • Solutions:
  • Add another cell (for example, replace a six-cell Ni-Cd with a seven-cell NiMH) to raise nominal pack voltage.
  • Use higher-capacity or better-quality cells with lower internal resistance.

If you are getting short flights due to premature ESC shutdown, investigate pack internal resistance and nominal voltage options.

Vintage Radio Control Society (VR/CS)

The Vintage Radio Control Society (VR/CS) is an AMA Special Interest Group dedicated to early RC model designs—RC designs predating January 1, 1970. Many participants fly electric-powered versions of these classic airplanes. VR/CS activities are nostalgic and appeal to many veteran aeromodellers.

Representative vintage designs include:

  • Hal deBolt's Live Wire series
  • Esquire
  • Trixter Beam
  • Square Haze
  • Many others

VR/CS meets include challenging events such as Rudder Only (an old AMA RC event). Many of these vintage designs are now flown with contemporary radios; one photo I recall shows an early single-channel super-regenerative receiver (Citizen-Ship) operating on 27 MHz—complete with a glass-bottle look and relay output.

For more information:

  • Contact: Scott Wallace, Membership Chairman, 3621 Matthews Dr., Endwell NY 13760; E-mail: [email protected]
  • Website: www.vintagercsociety.org/
  • Notes: The society publishes a bimonthly magazine; membership is $20 annually. VR/CS rules allow electric power.

Scale highlight and balsa-molding video

A photo this month shows a gorgeous 1/5-scale Bugatti racer built by Keith Shaw of Ann Arbor, Michigan. Highlights:

  • Custom-built "transmission" (gearbox) coupling an Astro 40 motor to counter-rotating propellers
  • 65-inch wingspan
  • Approximately 800 sq. in. area
  • Energy storage: 24 CP1700 cells
  • All-up weight: 9.5 pounds
  • Finish: MonoKote
  • Construction: Balsa molding techniques

If you've been stalled on a curvaceous Scale project, consider the how-to video Balsa Molding Techniques from Robin's View Productions:

  • Producer: Robin's View Productions, Box 68, Stockertown PA 18083; Tel.: (610) 746-0106
  • Length: 105 minutes
  • Content: Detailed processes for molding balsa in straight and compound-curve applications (yes, balsa can bend both ways at the same time).
  • Robin's View also offers tapes on Lost Form wing building and covering with Japanese tissue.

Closing

Thus ends another column. Please include an SASE with any correspondence for which you'd like a reply—everyone who does so receives one. In the meantime, many happy electric landings, everyone!

MA

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