Sportster 20 (oz9169)
About this Plan
Sportster 20. Radio control sport model. 400 sq in area, for .19 - .25 power.
Quote: "It's small and docile, but it flies like a pattern ship if you want it to. Sportster 20, by Dick Sarpolus.
A .19-powered sport R/C aircraft offers many advantages: easier to transport, cheaper to build and operate, etc. But all these obvious advantages aren't worth much if the smaller aircraft does not perform well - it doesn't have to match the performance of a .40- or .60-sized bird, but it has to be good. In my mind, it should be able to handle windy weather and less than ideal flying field conditions, be fast and maneuverable enough to make flying it interesting, and be rela-tively easy, not demanding, to fly.
I believe a smaller R/C ship is tougher in some ways to design than a larger ship; it's harder to keep a favorable power-to-weight ratio and a reasonable wing loading in the smaller designs, while maintaining a relatively hot performance level. It can certainly be done; there are some .19 and even many .049 designs available which offer good performance.
The Sportster 20 is offered as a good .19- to .25-powered fun aircraft. It can handle just about any weather conditions you would care to fly in; it's maneuverable enough to do snap rolls and 3-ft high inverted passes across the field. But with its long moments and light loading, when throttled back it is docile and relaxing to fly. There are no aerodynamic breakthroughs or secrets to this design - just some good basic construction techniques applied to a properly sized and proportioned airframe, a good airfoil, and some styling ideas that appeal to me.
To discuss the design a little further, the wing area is 400 square inches. With a span of 50 ib, the aspect ratio is a fairly high 8:1. The wing planform is tapered, which I feel is amust for good roll performance. The airfoil is semi-symmetrical, 16% thick for good low speed flying..."
Sportster 20, MAN October 1979.
Direct submission to Outerzone.
Supplementary file notes
Article pages, thanks to RFJ.
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