Free Flight
Duration
Jim Haught 3069 Sovereign Drive Cincinnati, OH 45251
A TRULY SHEETY IDEA
The June 1991 Duration column contained a photo of the latest in a series of re-entry models I've built in an attempt to re-acclimate myself to Nordic flying. Since a number of people have expressed interest in the design, I'm presenting it here.
As the FF Team Finals approached last fall, I needed an additional model to give me a reasonable fleet to take to Lost Hills. I became interested in the possibilities of all-sheet wings when doing some catch-up reading of old NFFS Symposium reports, which showed a number of models, particularly those of Peter Allnutt, using this construction.
Another factor in my trying sheeted wings was that here in the Midwest we often face somewhat rugged terrain at our flying fields. I felt that sheeted wings might be a little more puncture-resistant than traditional coverings. Since I view my first few comeback models as trainers, I wanted something fairly tough to help me negotiate the re-learning curve.
Naturally, when I presented the idea of sheeted wings to some of the current Nordic hotshots, snickering was evident; so were some less delicate remarks about what a sheety idea such a model would be. Of course, this provided the impetus for me to begin construction immediately.
Airfoil: CH407 variant, with increased trailing-edge thickness to alleviate concerns about strength in that area. The panels were laid up on jigs and mated just prior to covering. All wing spars are spruce with carbon-fiber reinforcement and Kevlar wrap on the inner panels. Covering is a single layer of tissue with unplasticized nitrate dope.
Sheety Idea makes extensive use of items from Bradley Model Products: carbon-fiber sheets, tailboom, electronic timer, tow reel, towline and tow hook all come from the BMP catalog. Many-time Nordic team member Jim Bradley runs a garage-shop operation, and I highly recommend his products. Quality, service and support are all excellent. A SASE to 1337 Pine Sap Court, Orlando, FL 32825 will get you the latest information.
Despite being conceived as a quick model and whipped together in a few weeks prior to the Team Finals, Sheety Idea has exceeded expectations. It serves very nicely as a fly-anytime model and may be worth a serious look by those needing a trainer-type model or a quick-building replacement airplane. Easy to build, adjust and fly. A national/world record-holding model has brought great pride and pleasure; I hope it will do the same for you.
High-dollar 1/2A
The emergence of the Shuriken and CS engines raises questions about what the future holds for 1/2A Gas as an AMA event. While a better product is a form of progress, the arrival of these engines threatens the nature of this event. The fact that these engines drastically change the economics of the event could have an ominous effect.
I do not see this as the same situation which developed when the Tee Dee came out in the early Sixties and virtually eliminated the Holland from the scene. After all, the price of those two engines was nearly the same. Thus the same flier who used Hornets could afford Tee Dees as well. With a Shuriken priced at roughly four times the price of a Tee Dee, I don't see the same affordability.
My initial reaction to 1/2A becoming a pocketbook event was to circulate a letter calling for the banishment of ball-bearing engines from 1/2A. This met with considerable negative reaction, and some words of wisdom from Rudy Kubicek, my district's Contest Board representative.
Rudy's thought was that while he agreed with the idea of keeping the big bucks out of 1/2A, to ban existing engines would be troublesome, especially considering the rules change cycle time. What may be needed, then, is an alternative event: Classic 1/2A, or something similar. Here, only plain-bearing engines would be permitted, thus providing an affordable alternative while keeping the spirit of the event alive.
Many AMA Power events have suffered reduced participation recently in all but the larger contests, particularly with the rise in popularity of Nostalgia. With the popularity of simpler Nostalgia models increasing, doesn't it make sense to have one regular AMA Power event? Or will 1/2A become an experts-only event, with no chance for the newcomer or younger flier? Voice your comments!
Two-position stab ("streaker") — What a stroke!
A learning-curve problem I encountered returning to Nordic flying was my models' pinning on circle-tow when multiple circles were attempted in windy conditions. My testing at home had been done under relatively calm conditions; at Lost Hills, where there was more breeze, I bound two or three models off the deck before seeking help.
It turns out there's a simple solution: a "streaker," or two-position stab, to add incidence for the tighter turns required during circle tow. Paul Crowley is widely credited with innovating and developing this system. He explains its workings (taken in part from the 1976 NFFS Symposium):
- The stab has two positions: tow and glide. If a trim change is not made after the turn is tightened up for circle tow, a spiral dive will result. The two-position stab allows a much tighter circle during tow.
- I use approximately three degrees more decalage during circle tow than in the glide. A single line is used to pull a movable rudder stop forward and to set the auto-stab mechanism for tow. This line is released by the unlatching of the hook.
Crowley's later models have used a timer-operated release, allowing a brief (0.5 second or less) delay between release and auto-stab activation. It's important to note that the up position on the stab lever must be angled slightly so that normal DT-line tension will push that stab to the down position. It's easy to add this system to existing models with minimal effort, and it gets the job done.
Partial-motor testing — finding motor length and size faster and safer
Partial-motor testing uses a simple concept. As an example, a quarter-size test motor requires a test stick exactly three-fourths the distance between hooks, weighted exactly three times the lubed weight of the quarter motor. Since one-quarter of the full motor turns can put the model up, it should climb one-quarter of its previous altitude and fly one-quarter of the time. Good news: four times the test flights can be made. Bad news: errors induced through inaccurate procedure or faulty estimation of altitude will be compounded.
Most modelers overrate their ability to estimate aircraft altitude; using a helium balloon up-beam and marking the line at exactly 50 percent and 25 percent locations helps make better height estimates.
Once I'm fairly certain of the optimum length and size from the quarter-motor, I prefer to verify with a half-motor when time permits. At the 1985 US Team selection finals in Akron, Ohio, pressed for time, I went directly to a 1.05 quarter-motor test flight and then the full-motor official flight of 4:31.7 — still three seconds away from perfect correlation. Finding myself in the same situation flying Top Cat 90 at the 1990 Nationals, I went straight to a 1.023 quarter-motor test and the winning full flight of 4:12.9 — again deviating from perfect correlation by just three seconds. Partial-motor testing has great merit.
Often full-motor flights will be slightly higher and longer because of warmer air near the site's ceiling.
Recommended Indoor Suppliers
- Indoor Model Supply, Box 5311, Salem, OR 97304
- Micro-X Products, 5200 Seven Pines Drive, Lorain, OH 44053
- FAI Model Supply — FM tan rubber, Box 3954, Torrance, CA 90510
- Erv Rodemsky microfilm, 1600 Rockspring Place, Walnut Creek, CA 94596
- Bob Oppegard rubber cutters, 140 East Golden Lake Lane, Circle Pines, MN 55014
Duration — Jim Haught, 3069 Sovereign Drive, Cincinnati, OH 45251
Transcribed from original scans by AI. Minor OCR errors may remain.
