Radio Control: Scale
UNEXPECTED STALLS: Warped wings are deadly. Warps that result in a greater angle of incidence at the wing tip than at the root are the worst. This condition is known as washin. A model with this type of warp on one wing needs lots of aileron trim control at the transmitter to keep the model from rolling into a turn. The condition worsens when we add a high angle of attack, as when using elevator to increase climb or during a steep turn. It affects the model differently at various speeds. The elevator is the trim control. It is used to trim the wing's angle of attack-the angle at which it meets the oncoming flow of air. A warped wing, with a tip that is already near stall, will suddenly stop flying when Up elevator is applied, since its angle of attack is increased beyond the critical point at which lift is lost.
Radio Control: Scale
LIQUID COOLING: Engine cooling in Scale models can be a serious problem, particularly for the modeler who values his engines and searches for ways to extend their lives. The tightly-cowled engine is vulnerable to excessive wear due to overheating damage. Adding extra lubricant to fuel can help avoid the wear, but this introduces another variable, with the possibility that it may be forgotten when the model isn't flown often. A letter from a reader requested information about liquid cooling for tightly-cowled engines. Almost any prototype that has a liquid-cooled engine, for example WW II fighters or those aircraft with pusher propellers, presents a problem to the Scale modeler when there are no suitably large openings for ventilation.
Radio Control: Scale
DESIGN YOUR OWN. Building Scale models from kits or plans can be very satisfying, but there are modelers who prefer something more rewarding: an airplane that hasn't been done in quantity or in the size desired. These persons follow another path to satisfaction in designing, building, and learning to fly an outstanding aircraft that attracts attention. Original-design models also have better-than-average contest-winning potential. For example, more than half of the top-placing Nats RC Scale entries were originals. Any number of Scale enthusiasts have thought seriously about building a rare bird but aren't quite certain of methods and procedures. The project is forever postponed for lack of information, and incentive is lacking because there are an overwhelming number of kits and plans waiting to be built. Some of us have gathered photos, books, magazines and three-view drawings for most of our lives. There will probably never be enough time to build models from all of these sources.
Radio Control: Scale
FACT OR FICTION? One of the fictional theories about model flying is the importance of scale effect, our bugaboo of the past that supposedly kept a model from flying in a manner somewhat similar to its prototype. We have been asked whether scale effect makes changes necessary in airfoils or tail surface areas. Our answer is that present-day RC Scale models don't need these changes. There is no doubt that scale effect is a factor on very small, light, and slow-flying models such as Peanut Scale, rubber-powered, or Schoolyard Scale RC types. However, in the size models we are now flying, with .40, .60, or 1.20 engines, the effect isn't evident. This is really accentuated in our experience when we compare flight of our models with that of the exact full-size counterparts and find remarkable similarities. Giant Scale models are even more like their prototypes.
Radio Control: Scale
NEEDLE VALVES, again: Our recent column item about needle valve extensions sparked a letter, with sketches and photos, from Sam Abdow showing his method of reaching a hidden needle without making a hole in the cowl. He begins by making a spring approximately 11/4-in. long using 1/32-in. music wire. This is roughly 40 turns of wire, closely wound on a mandrel that will produce an inside diameter of 3/16 in. One end of the spring is then soldered over a 3/16-in. brass tube which is cut to the proper length to reach the open rear edge of the cowl. He then solders a short 8-32 socket-head Allen screw into the other tube end. The music wire spring is then soldered to the needle. Adjustment of the needle can now be made using an Allen wrench.
