Free Flight Duration
Louis Joyner [email protected]
An overview of the 41st NFFS Symposium Report
Also included in this column:
- British Free Flight Forum 2008
- Trimming the Dixielander
- Smoothie timers
- Instead of balsa ...
- Witch Hawk
- AMA Gas info
THE NATIONAL FREE FLIGHT SOCIETY (NFFS) annual Symposium Report, better known as the Sympo, serves as a source of the latest technical information and provides a historical record of the evolution of free flight. For the 41st edition, editor Rick Pangell pulled together articles covering a wide range of free-flight topics.
Daniel Petcu continues his F1E Sympo series with a piece about bunting. The F1E class, long popular in Europe, has gained interest in this country. The models are large, Nordic-size gliders that are hand-launched much like RC slope-soaring aircraft. F1E models use a forward-mounted fin fitted with a magnet for steering.
Peter McQuade explores the effect of bank angle on towing stability of F1A gliders. Brian Eggleston and Peter Allnut teamed up to prepare a paper about the use of Internet tools to design an F1A airfoil; Brian did the theoretical work and Peter built the test model. Rubber guru Fred Pearce looks at the effects of stress-induced crystallization on rubber strip.
George Mansfield’s “Systems Approach to Design and Build an FAC Scale Model” offers suggestions for optimizing construction methods and material selection. Although geared toward the popular Flying Aces Club scale models, the information should be helpful for non-scale types. Texas Timers owner Hank Nystrom looks at the mechanical timer’s history and future.
The 2008 Models of the Year, selected by Bill Booth and committee, include Mark Benn’s Spin-Up 36 tip-launch glider, Tim Batiuk’s record-holding Turn-Up tip-launch glider, and Reid Simpson’s R60 A/B gas model.
In addition, special awards go to Roger Morrell for the Southern California Aero Team Electronic News (SEN), to Ray Harlan for his extensive line of indoor tools and supplies, and to Jim Parker, Walt Ghio, and others for the Junior F1P Program. See the May 2008 Duration column for more about this worthwhile endeavor.
Free Flight Hall of Fame inductees for 2008 are Alexander Andriukov, Rex Hinson, Herb Kothe, Reid Simpson, Roger Simpson, and the late Walt Rozelle.
You can order your copy of the Sympo from NFFS Publication Services. The price is $30 for NFFS members and $35 for nonmembers. Postage is $5 within the U.S. Postage for orders from Mexico or Canada is $9. Only check or money order will be accepted for domestic orders. For more information, contact NFFS Publications Coordinator Bob Stalick or visit the NFFS website.
British Free Flight Forum 2008
In the last quarter century the annual Free Flight Forum has provided a useful mix of practical and theoretical material, all with a delightful touch of British humor. The 2008 version, chaired by Mike Evatt and edited by Martin Dilly, includes more than a dozen articles.
Peter King’s “Beyond Rubber Stretch Testing” factors the traditional rubber-energy test into a computer analysis of model performance. He also looks at the optimum VIT (variable incidence tailplane) timing for F1B models.
Bob Bailey’s “Selection and Testing of Balsa Wood for Indoor Duration Models” illustrates test methods that assure both adequate strength and low weight. In “Measuring Success,” Mike Woodhouse shows a variety of special fixtures he uses to set up his F1B models with accuracy and repeatability.
Phil Ball looks at the new British Rubber class that was introduced last year to replace Open Rubber. The new category limits rubber weight to 50 grams. For many contests the new class is combined with Vintage models (100 grams of rubber) and Classic models (75 grams). “A Review of the 2007 BMFA and Combined Rubber Contest Season” illustrates typical models and explores the best options for contest flying.
Chris Strachan’s “Small Rubber Models as an Introduction to Free Flight” suggests both the P-30 class and the popular 25-inch-span British kits from the past, such as the Keil Kraft Achilles, as good starting points.
In “The Lottery of Winning,” George Seyfang looks at the variables of contest flying. His conclusion is that the more skilled flier with the better model is usually unbeatable; the methodology he uses is interesting.
In a second article, “Transportable Wind Tunnels,” George proposes two wind-tunnel designs: a small garage-size wing test of 800 x 400 mm test section and a trailer-mounted tunnel that would accommodate models exceeding 8 feet in span.
For F1A towline glider fliers, Chris Edge presented “Aborted Launch Solutions,” to deal with the problem of a premature hook unlatch. His solution is to modify the circle-tow and timer hardware and software to allow relatching. If you think the modern F1A is simple, take a look at this article.
Indoor flier Nick Aikman looks at new building techniques in “Lutz Schramm’s F1D.” Instead of bent balsa, Lutz uses Kevlar thread wetted with epoxy resin and formed in a fixture to create the propeller-blade outline. The latest versions use carbon fiber instead of Kevlar.
British F1C team member Alan Jack explores thermistors and the difficulty of finding good air in “Comments on Thermal Picking and Related Matters in Odessa ’07.”
“Balsa for Indoor Models” by Mark Benn explains the difficulty of selecting the best wood and cutting it accurately. After reading this, you'll understand why indoor balsa is the most expensive lumber in the world.
For electric free flight, Jonathan Crossley offers “The Zombie Flight Profiler: Advanced Motor Control for Electric Free Flight.” The Atomic Workshop Zombie Flight Profiler is a lightweight electronic module that functions as a motor-run timer and voltage-cutoff device.
In “Safety and You!” Manny Williamson focuses on what the individual can do to reduce the chance of both property damage and personal injury. Roger Morrell's “Electronic Timers” takes a look at this increasingly popular means of flight control. He includes practical tips for installing, setting up, and caring for electronic timers.
The 2008 Forum report is available from Martin Dilly. The price, including airmail postage to the U.S., is £14.00 (approximately $30, but the exchange rate fluctuates). Make checks payable to "BMFA F/F Team Support Fund." Since checks must be in pounds sterling only and drawn on a bank with a branch in the UK, it's much easier to pay by credit card.
Contact Martin by fax or e-mail. Back issues of previous Forums are also available.
The 2008 Forum is also available from NFFS Publications (Bob Stalick). The price is $25 plus $5 postage. Checks or money orders only on U.S. orders; international orders can pay by credit card, but a service fee is charged.
Dixielander Trim
The NFFS Nostalgia Committee recently approved George Fuller’s Dixielander for use in the Nostalgia Gas event. The original design was a compact, 350-square-inch model with an undercambered wing airfoil based on the NACA 6409, a high pylon, and an aft-mounted rudder. Power was a 2.5 cc engine, and the flying weight was roughly 15 ounces.
The design, kitted by Yeoman, was among the most popular power models in Great Britain during the late 1950s, but it was seldom flown in this country. The only one I ever saw was George Fuller’s own E-Type Dixielander, which he flew at the 1961 Nats in Willow Grove, Pennsylvania.
The E-Type was a stretched Dixielander powered by an ETA .29. The wingspan was almost 60 inches, compared to the standard Dixielander’s 50 inches, producing a wing area that just exceeded 400 square inches.
Before you get too excited, George developed the E-Type Dixielander in 1959—well past the 1956 cutoff for Nostalgia Gas. Only the original Dixielander is legal for Nostalgia.
After witnessing the incredible climb of George's model at the Nats, I decided to try my own 1/2A variation on the "smaller is better" theme. I came up with essentially a scaled-down Dixielander with a flat-bottom airfoil and a rudder on the bottom.
The wing measured 6 x 36 inches, giving it an area of slightly less than 200 square inches, which was considerably less than the typical 1/2As of the early 1960s. Power was a Cox TD. This design is also too late for the Nostalgia event.
Luckily I had a copy of George’s Aeromodeller article about trimming power models. I followed his suggestions religiously. The secret to the Dixielander’s success was the built-in settings. The wing and stabilizer are both set at +3°, both wingtips are washed out 2°, and the right main panel is washed in 3°.
The stabilizer is set parallel to the right inboard wing panel to give a right glide turn. The CG is located at roughly the wing trailing edge. Glide adjustments are made by slightly shifting the CG—never by shimming the stabilizer. If necessary, adjust power trim by slightly shimming the wing leading or trailing edge.
My model flew right off the board with no adjustments whatsoever. With an all-up weight of approximately 5 ounces and less than 200 square inches of wing area, the climb was very fast, yet surprisingly safe. I credit all this to George Fuller’s trim system and recommend it without reservation if you try a Dixielander for Nostalgia.
Full-size plans for the Yeoman-kit version of the Dixielander are available from Whit Russell at NFFS Plans. The price, including postage, is $8 for NFFS members and $9 for nonmembers. Rolled plans in a mailing tube are $5 extra. See the NFFS website for information about Canadian and overseas orders.
If you are an NFFS member, be sure to read Bob Stalick’s article about the Dixielander in the December 2007 Digest. You can also take a look at the NFFS plans in the January–February 2008 Digest.
Smoothie Timers
Tim Goldstein has upgraded the Smoothie DT timer in his Sting Aero line of hand-launch and catapult gliders.
As do other viscous timers, the Smoothie utilizes a rotary damper. Line tension slowly turns an arm while a thick liquid sealed inside the timer case offers resistance. But line tension is critical: if there is too little, the timer won't rotate at all; if there is too much, the timer turns too quickly.
Now the Smoothie timers come with an assortment of sleeves that fit over the rotating hub, allowing you to adjust the leverage and rotational speed. Timers are $9.95 each plus shipping. Also available are the stock viscous rotary dampers for $3.95 each; these require drilling and fitting a pin (not supplied).
Visit the Sting Aero section of the Peck-Polymers website for more information about Smoothie timers.
Instead of Balsa
For some reason, plastic foam, which was introduced a half century ago, has found surprisingly little use by the free-flight community. I was pleasantly surprised to see junior flier Miles Johnson with a foam-winged catapult glider at the 2007 Nats.
His model has a wing cut from blue insulation foam using the hot-wire method. Since hot wiring works only with straight tapers, the wing had to be cut in four sections and then hand-sanded with 320-grit paper to shape the curved tips.
The wing was then covered top and bottom with lightweight fiberglass cloth wetted out with epoxy resin. The assembly was vacuum-bagged while the epoxy set.
Foam is approximately half the weight of balsa, and it requires a surface skin for stiffness. “The foam by itself isn't that strong,” said Miles.
The fiberglass cloth he used is the most popular skin choice for light models, but there are other options. Some years back, Ramrod designer Ron St. Jean developed a simple system using tissue applied to foam with diluted white glue. Larger RC models often use foam skimmed with balsa sheet or even hardwood veneer.
If you are interested in giving foam a try, there is a wealth of information in back issues of both the Free Flight Forum and the Sympo. An excellent place to begin is Len Surtees’ “Composite Wings for Outdoor and Indoor HLG” in the 2002 Sympo, available from NFFS Publications.
One method Len describes uses stacked phone books instead of a vacuum bag to attach the fiberglass skin. You can't get much easier than that.
Witch Hawk
In the May column I mistakenly credited Ralph Prey as the designer of the Witch Hawk. Bob Watson, who has a fleet of five Witch Hawks, e-mailed to let me know that Jim Clem designed the model.
Ralph Prey is the author of an excellent two-part series, “How to Adjust that High-Powered AMA Gas Free Flight,” which was published in the July and August 1979 issues of Model Aviation.
AMA Gas Info
AMA Life Member Huston Gruen e-mailed requesting information about getting started in AMA Gas.
Since I haven't touched a power model in more than 30 years, I did an Internet search that turned up an excellent piece by Don DeLoach entitled “Beginning Free Flight Power.” You can find it on Bob Beecroft’s website, which contains several other interesting articles and dozens of links to other free-flight sites.
Sources
- NFFS — www.freeflight.org
- NFFS Publication Services / Bob Stalick
Box 1775 Albany, OR 97321 [email protected]
- The Atomic Workshop — +44 (0)1493 369317
- Martin Dilly
20 Links Rd. West Wickham, Kent BR4 0QW UK Fax: +44 (0)20-8777-5533 [email protected]
- Whit Russell at NFFS Plans
1375 Ridgefield Dr. Roswell, GA 30075
- Peck-Polymers — (720) 833-9300
- Bob Beecroft — www.theaerosmith.com
Transcribed from original scans by AI. Minor OCR errors may remain.
