Alpha
IN DESIGNING Alpha my objective was to come up with an easy-to-build, racy looking airplane having full aerobatic capabilities with a standard engine and nonretractable trike gear. The primary motivation was to provide a relatively inexpensive answer for those interested in developing their skills as aerobatic fliers. Note that I said aerobatic fliers and not necessarily pattern fliers. Even though Alpha will perform all maneuvers required by the AMA Masters pattern, I believe that there are lots of fliers who, like myself, have
True Dynamic Scaling and the Elyable RC Model
THERE HAVE BEEN numerous articles written on the subject of scaling down full-size aircraft to RC model size. The authors have often presented certain "rule-of-thumb" formulas or graphs which allow the designer to determine what weight and power goals should be set if the model is to be flyable. Note that I said "is to be flyable," and not "is to fly." The reason stems from the fact that a flyable model will have much more severe constraints placed on it than one which must simply fly. That is, the flyable RC model will be required to take off in a reasonable distance and land at a reasonable speed, whereas as airplane which is launch-assisted or has parachute recovery capability will not have those constraints placed upon it, but will still fly.
True Dynamic Scaling and the Flyable RC Model
IN PART ONE of this series, we discussed the meaning of dynamic scaling, and examined the basis for the laws of dynamic scale. We showed how these laws were derived in terms of the static scale factor. We will now compare these laws to the constraints imposed by the fact that the model must be flyable. Clearly, what one modeler considers flyable may be very different from another modeler's standards. This relates to the amount of experience and expertise of the flier. It also relates to the flying conditions he will encounter, especially the flying field.
True Dynamic Scaling and the Flyable RC Model
PARTS ONE AND TWO of this series presented the laws of dynamic scale and a discussion of flyability constraints. In this final part, we will look at two aircraft, and apply the laws of dynamic scale to each. We will also discuss a few prototypes that are not suitable for dynamic scaling, and explain why. In these illustrations, the quoted takeoff distance is the distance required to clear a 50-ft. obstacle. Horsepower and thrust are sea level (static) values. Bellanca Citabria 150S. Fig. 7 shows the dynamic scale figures for a model of this aircraft at three different scale factors (N); one to six, one to five, and one to four. Looking at these figures indicates that a model at any of these scales is well within the range of existing equipment and flyability.
