FREE FLIGHT DURATION
Louis Joyner, 4257 Old Leeds Road, Birmingham, AL 35213
LIGHTWEIGHT TIMERS
As flying fields shrink, the need increases for accurate, reliable timers to dethermalize (DT) the model after it makes the max, but before it gets to the trees or corn. A fuse DT works every time, but the accuracy can leave something to be desired. The clockwork timers used for power models range in weight from about 12 grams to more than 20 — too much for light models such as Coupe and P-30.
The lightest alternative is the Badge timer from Wheels & Wings. This is a small and very light (1.2 grams) device made from black Delrin plastic. It's really quite simple. Instead of an escapement and gears to regulate the speed, it uses a rotor turning in a viscous liquid sealed inside the timer body. And instead of a wind-up spring to power the timer, it uses a stretched rubber band. The unwinding time will depend on the size and stretch of the rubber band, and to a lesser extent, the ambient temperature.
Baton Rouge modeler Lewis Roussel uses one of the Badge timers on his new Coupe. Rather than run a direct line back to the stab for DT, he uses a simple lever mounted on the side of the pylon to hold the stab line down without putting too high a load on the timer. A close look at the photo should explain everything.
The Badge timer and the similar, but even smaller Button timers are available from Wheels & Wings:
- Badge timer (Badge Lite shown in the photo): $13 each
- Button timer: $18 each
- Shipping: $1 per order
Wheels & Wings, Box 762, Lafayette, CA 94549-0762.
Another lightweight alternative that has been popular for almost 20 years is the various homemade adaptations of the Tomy wind-up toy. In the early 1980s there were many articles describing ways to modify the Tomy for use as a timer. A ready-to-use version was made in Australia for several years but has been discontinued. Now a British-designed and Polish-made version is available through F.A.I. Model Supply.
Like the earlier Fletcher timers from Australia, these new timers feature an aluminum faceplate and a turned Delrin DT scroll. The works are the familiar Tomy gear train. The Mini DT Timer, as its name implies, is strictly a single-function dethermalizer timer. It sells for $17.50. The Super Mini Timer ($19.50) can handle two additional functions, such as VIT (Variable Incidence Tailplane) and auto rudder. Weight is about 6 grams. Order direct from F.A.I. Model Supply (address below).
ANDRIUKOV STAB
Starline International's Sal Fruciano loaned me one of Alexandre Andriukov's new Wakefield stabs to examine.
The first thing I noticed is that there really isn't much to notice. This thing looks more like a piece off an indoor model than like a part from an outdoor rubber model. There's a leading edge, a trailing edge, and some very thin ribs in between.
The leading edge forms the main structure for the stab. It consists of a 3.5 mm diameter carbon-fiber tube that provides both torsional and bending strength for the entire stab. While carbon tubes have been popular in Europe for stab spars, this is the first time I have seen one used as the leading edge. The tube appears to be rolled from a single layer of Russian unidirectional carbon. Quoted weights for similar tubes are in the 1.2–1.5 gram range.
The ribs are very thin (about 0.6 mm) and carbon-capped. In fact, the carbon capstrip extends completely around the front of the stab and is attached to the tube leading edge. My best guess is that the ribs were carved from a thick block of balsa, carved and sanded to the exact airfoil shape, covered with a single layer of unidirectional carbon, and sliced to the desired thickness using a diamond saw. The 3.5 mm hole for the tube was carefully drilled out, leaving the carbon capstrip undisturbed. The ribs were then slipped over the tube and the carbon-fiber trailing edge was added.
The trailing edge is very small — about 5 x 10 mm — so Alex reinforced the center with a small piece of molded carbon cloth much like a wing D-box skin. Uncapped false ribs help preserve the rather thick airfoil. It looks like the popular Wobbeking stab airfoil. To stiffen tips against bowing inward, Andriukov uses 3 mm-wide balsa ribs capped with carbon. The stab measures 78 x 370 mm (3-1/16 x 14-9/16 inches), which comes out to 288.6 square centimeters (44.55 square inches). Weight of a Mylar-covered stab is about 42 grams.
A finished covered stab is $35 plus shipping; it would be a good idea to write Sal first to check availability.
Starline International 6146 E. Cactus Wren Rd. Scottsdale, AZ 85253 Tel: 602-948-5798
MODEL ENGINE WORLD
Richard Palmer sent along a copy of the British magazine Model Engine World. As you can gather from the title, this monthly publication focuses on model engines of all types, from the early (and very collectible) ignition engines of the 1930s to the engines of today. Edited by John Goodall, it is similar in size to the NFFS Digest and includes many black-and-white photographs.
The copy I have includes a review of a Webra .61 converted to diesel; step-by-step instructions for building a 13 cc side-valve four-stroke engine; a review of the O.T.C. .19 (Brown Junior copy made by students at a Missouri technical college); and an in-depth article by Gordon Cornell on the mechanics of model engines. Previous issues have included articles on the O.K. Cub and on reworking the .05 Oliver replica. In the works is a piece by Doug Galbreath on the MP Jet .061.
If you are interested in engines, especially the history of model engines, this magazine should provide a lot of good reading. You can also look at the pictures and mentally kick yourself for unloading that Dooling .29 for $10 back in the '60s.
Subscription information:
- US: Send $45 for one year to Richard Palmer, Box 609, Palisades, NY 10964-0609.
- Outside the US: Subscribe directly to Model Engine World, Barton Model Products, 34 Barton Gate, Barton-under-Needwood, Burton-on-Trent, Staffs., DE13 8AG, England. Prices range from 24–35 pounds Sterling.
- Australia: Contact David Owens, Box 264, Fairy Meadow, NSW 2519, Australia.
SHOW-OFF PLANS
In the June and July 1996 Duration columns I mentioned Frank Ehling’s Show-Off power model. It was an early 1950s FAI power model that looked like a good possibility for Nostalgia Gas.
Jim O’Reilly, now back in Kansas after a year in Georgia, wants everyone to know that he has full-size plans available for the Show-Off. The wing area works out to 406 square inches, projected. Sounds about right for a good greenhead Torp .15. Like Jim’s other plans, these are CAD-drawn. This will allow Jim to eventually scale the design up or down easily. Check with him about the availability of other sizes.
To order a set of the 406-size Show-Off plans, send a check for $9 ($8 for the plan, plus $1 postage) to: Jim O’Reilly 4760 N. Battin Wichita, KS 67220
Throw in a dollar third-class mail and Jim will send you his list of more than 100 cottage-industry free flight suppliers.
NEW SIZE FOR TAN II
F.A.I. Model Supply owner John Clapp called recently to tell me about the new size available for Tan II rubber. In addition to the sizes already available for Tan II, John is now able to supply 3/32-inch in one-pound boxes. This new, smaller size should be popular with Coupe and P-30 fliers who are limited to 10 grams of rubber. Using 1/8-inch rubber, the smallest previously available, you were often forced to choose between making up 10-strand or 12-strand motors, when you really needed just an 11-strand motor. The new 3/32-inch size will allow a little more flexibility in fine-tuning the rubber-prop-model combination for maximum performance.
The price will be the same as for the other sizes of Tan II — $17 per pound postpaid. Write F.A.I. Model Supply at: F.A.I. Model Supply Box 366 Sayre, PA 18840-0366 Tel: (717) 882-9873
Transcribed from original scans by AI. Minor OCR errors may remain.
