Free Flight: Duration
TIPS: The shape we give the wingtips of our Free Flight models is based a bit on aerodynamic theory, some on the practicalities of construction, and-perhaps more than we care to admit-on fashion. The tip of a wing, or any flying surface for that matter, is an aerodynamic special case. At the tip, the air is not flowing straight from front to rear, as it is over the rest of the wing. Instead, it is curling up from beneath the wingtip, rolling and wrapping itself into a spiraling vortex trailing off the tip. This vortex produces quite a bit of drag. (That is why wind-tunnel test airfoils extend the full width of the tunnel.) For generations, modelers, as well as designers of full-scale aircraft, have tried a number of things to reduce the size and effect of the tip vortex.
Free Flight: Duration
AS CAN BE EXPECTED, my remarks about the Builder of the Model rule in the January column aroused considerable interest. I've included excerpts from some of the letters I have received on the topic. Most of the letters were long-three or four pages-so I have had to edit things down a good bit. I hope that what remains is the essence of what the writer intended. John O'Leary and 10 other members of the Minneapolis Model Airplane Club sent along these thoughts: "I view our hobby/sport as a combination of design, construction, trimming, flying, and contest strategy skills. In my opinion, the design and construction elements share equal weight with the flying phase. I find great satisfaction in ever-improving construction skills over the years. I have learned something from every model I've built.
Free Flight: Duration
SOGGY STABS: Flying in the rain is not my idea of fun. I doubt that anyone really enjoys getting soaked through-and-through while having to deal with wet equipment, slippery models, and trim changes. But the rain falls equally on everyone at the contest, so we muddle through. At the last team selection finals, held at Palm Bay, Florida, it rained most of the first day, when I was flying Wakefield (FIB). Experience had taught me that the extra weight of raindrops on the tail will cause the center of gravity (CG) to shift to the rear. If it shifts far enough, the model will stall.
Free Flight: Duration
LOCKED UP POWER: With all of the proposals being discussed for a new Slow Open Power event (SLOP), it might be useful to take a look at some of the ways that a power model can be controlled without the use of timer-actuated auto surfaces. But first, a quick refresher course on the basic problem. Lift increases the faster a model goes. Lift is a good thing, so wouldn't more lift be even better? Not if it's going to cause the model to loop. The tendency of a model to loop (or at least nose up excessively) as its speed increases can be counteracted in several ways:
Free Flight Duration
THE 1999 FREE FLIGHT World Championships will be held August 24-31 in Beer Sheba, Israel. The United States will be represented by Brian Van Nest, Jim Parker, and Steve Spence in F1A towline glider; by John Sessurns, Bob Piserchio, and Vladi Andriukov in F1B Wakefield rubber power; and by Faust Parker, Ron McBumett, and Ed Keck in F1C power. Team manager will be George Batiuk Jr.; assistant manager is Blake Jensen. Texan Steve Spence will be representing the US for the first time at this World Championships. But he is not the first Spence to make the team. His dad Henry was on the Power team in the 1960s and 1970s, and made it to the flyoffs at the last finals.
