Free Flight: Duration
Louis Joyner 4221 Old Leeds Road, Birmingham, AL 35213
Stamov's electronic-timer-equipped F1A model
A few months back we featured photographs of Matt Gewain's new "Smart System" electronic timer for F1A towline gliders (see Model Aviation, November 1996). Now it's noted Ukrainian glider flier Victor Stamov's turn.
After the Team Selection Finals at Lost Hills, Victor let several American glider fliers test-fly his electronic-timer-equipped model. At first glance it looked much like a familiar mechanical-timer model. The giveaway was a small vertically mounted disc at the rear of a pull-pull cable-actuated control system that moves the stab to its various settings for tow, bunt, and glide. (Matt Gewain's system uses a carbon-fiber pushrod to move the stab.)
A stab hammer is attached to the disc so that the hammer and stab move up and down as the disc rotates. For DT the disc rotates farther until a small pin pushes the hammer back, allowing the stab to pop up.
Up front, neatly concealed by a removable hatch, is the heart of the system. Like Matt's system, Victor's uses a servo to move the controls. On Victor's model the servo is fitted with a pulley to move the cable in the pull-pull system. Concentric with that pulley is a notched disc used to release two conventional arms: one operates a wing wiggler and the other shuts the timer off after DT to conserve the battery. The rudder movement is tapped off the swinging tow hook, as with any circle-tow system.
If you would like to know more about the system, check with six-time U.S. F1A team member Randy Weiler: 25 Winterhaven, Irvine, CA 92614.
Advantages of electronic timers
- Timing of functions is much more precise than with conventional mechanical timers. DT can be set to pop the stab at exactly three minutes rather than having to set it five or ten seconds over to be safe with a mechanical timer.
- Bunt duration and other intervals can be programmed accurately, to one-tenth of a second—precision impossible with typical mechanical timers.
- Amounts of movement are accurate and repeatable.
- Electronic systems allow tracking and storing of settings for different flying conditions. Instead of a notebook (or memory), you can use a pocket digital diary (for example, a Casio) to record exact settings. To change settings, hook the diary up to the model and download the desired configuration.
Free Flight News (FFN)
Free Flight News, the award-winning monthly British newsletter, now has a web site. According to editor Ian Kaynes, the web page will include a complete list of international free flight contests, World Cup standings, and more.
Web: http://ourworld.compuserve.com/homepages/kaynes
Mailing address: Free Flight News 7 Ashley Road Farnborough, Hants England GU14 7EZ
Subscription (airmail):
- One year: $33
- Two years: $62
Payment by international postal money order payable to Free Flight News.
Delrin and Small Parts
At the last Nats, Bob Hatschek showed a neat front end he uses on his Moffett and other small rubber models. It's a simple reverse‑Montreal stop that works from motor torque (not tension). This allows a tightly stretched motor and consistent prop folds, important for the high-aspect-ratio props Bob uses.
Bob uses DuPont Delrin plastic for the hub. Because Delrin's specific gravity is lower than aluminum, the same part can be made lighter by using Delrin; to keep strength, the part can be made larger. In the fight against weight, aluminum parts often end up with very thin, hard-to-machine walls that are somewhat fragile. With lighter Delrin, walls can be thicker and easier to make. Bob Hatschek's Coupe front-end photos are a good example.
Delrin is widely available from local plastics suppliers but they often have large minimum orders. For small quantities of Delrin rod and sheet try Small Parts Inc.:
Small Parts Inc. Box 4650 Miami Lakes, FL 33014-0650 Tel: 305-558-1255
Representative Delrin rod diameters available (one-foot lengths):
- 1/8 inch — $0.85 (natural)
- 3/16 inch — $1.02 (natural)
- 1/4 inch — $1.41 (natural)
- 1/2 inch — $8.90 (natural)
- 1 inch — $18.88 (natural)
Delrin sheet: natural (pale cream) and black. Example: natural one-foot-square sheet, 1/8 inch thick — $19.79. Black runs a few cents more.
Small Parts' catalog also offers many other useful items such as nylon and stainless steel machine screws.
Transcribed from original scans by AI. Minor OCR errors may remain.
