Radio Control: Scale
PARIS FAI MEETING: The annual trek to Paris for rules and technical specifications is finished, and we brought back some rather astonishing results. For many years we have heard the lament from U.S. competitors that FAI model specifications were too restrictive, particularly on engine displacements. It was generally agreed that the day of a single .60 two-stroke engine in a Scale model was long since a thing of the past, and yet the FAI rule book persisted in this upper limit. The restraining limit was imposed originally because of the suspected unreliability of earlier radio equipment and because of a general regard for safety in the days when models could be lethal missiles in the hands of novice pilots. Actually, some of these conditions may continue to exist, but it has become increasingly apparent that the old restrictions were somewhat antiquated and were stifling competition.
Radio Control: Scale
SCALE MATH: Scale modelers who build from kits have some of their questions answered by the designer or manufacturer. The expected weight of the model and the suggested range of engine sizes is given on the drawing or instruction booklet. Scratch-builders ask searching questions on such important matters as a projected estimate of model weight and engine requirements, and the answer really is needed in the early stages of design. Once a model size has been decided upon, wingspan and area are a straightforward function of the scale ratio, that number which represents the difference between full-size aircraft and the model. We simply divide the prototype's span by the scale ratio to determine the model's span.
Radio Control: Scale
CABLE SYSTEMS: The use of cables to operate elevators and rudder is now rather common. The only real trick in assembling such a system is the matter of Scale realism. The visible, external portions of cables should enter through the fuselage side in proper locations, and when elevator cables cross (not unusual), the crossover point should be in the right spot relative to cable length and other external features. This requires a bit of planning. If at all possible, it is helpful to have some idea of the cable layout and routing in the prototype aircraft. Lacking this vital information, project the line of each cable on a photo, or on the three-view drawing, to help determine the location of the internal bellcrank where the forward ends of cables are connected. It is then a relatively simple matter to install the model's bellcrank assembly in the proper location.
Radio Control: Scale
THE SCRATCH-BUILDERS: Definitions of what is meant by the term "the true scratch-builder" have considerable variation. Most commonly, they build from published drawings made by another person who is the designer. A small group prefers to build their own designs to satisfy creative urge or in the quest for a truly different airplane model. An even smaller number design and build the ultimate examples of Scale model airplanes that are near perfection and achieve national acclaim. Only a small portion of the world's airplanes have been modeled, and some of the obscure types are among the most attractive. Lack of information, three-views, photos and general documentation can quickly sidetrack the modeler's desire to construct one of the lesser-known aircraft. Desire is the key element here. The modeler who really wants something entirely different will always find a way to pursue research of his selected prototype. There are those who would rather dig out buried information than build models (which tells us that a joint effort between researcher and builder may be worthwhile).
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.
