Spitfire Sport (oz8047)

About this Plan

Spitfire (Sport). Radio control sport model. For .60 power.

Quote: "Paul Bennett's scale-like sport and competition multi is one of the year's best looking aircraft. Designed for .60 to .80 engines, the plans include details for the author's twin-cylinder .80 engine.

Is your mind open today? If not, just look at the pictures, decide to build one, and have a good time with it. It's just another airplane and anyone who has built and flown an R/C multi ship can build and fly this one. If your mind IS open, then I would like to present a few ideas in an effort to make things easier in this hobby. My interest in R/C is based on progress; I'm looking for the day when an airplane can be designed, built, equipment installed and you know it will fly. You can expect to bring it home. In short, do away with our all too familiar disasters. The equipment manufacturers have done a wonderful job. Now it's up to the designer-builder.

In what I'm about to say, please remember that I'm NOT trying to persuade or convince anyone of anything. I'm at a certain stage in the hobby and I'm only presenting my thoughts for you to consider. Some may disagree violently. That's all right, I've learned a lot from other people. But I may help a few, and that I'd like very much.

In studying aerodynamics, and reading everything written by my contemporaries, I've reached the conclusion that there is a common denominator in applying all this information and arriving at a successful airplane. Unfortunately that common denomiator is not simple. It comes down to the airplane and its relationship to the guy who is flying it. We have all seen guys who could fly anything. Their denominator is simple: an airplane, an engine, and radio gear. Nothing more specific than that. But there are many flyers slowly working up.

In motorcycle racing you have to 'throw it away' to see how fast you can really go. In flying, we are trying to find an EASIER way. Imagine someone just starting in multi flying something like this: 800 sq in, 6 lbs, good .45, and long, thin full-span ailerons. An experienced pilot would be completely relaxed and feel this a perfect combination for the beginner large, slow, and graceful. But back to the beginner. No conditioned reflexes. One wing is low: he notices this, decides which win it is, decides which lever corrects for it, decides which way to move that lever and then does it. The wing has dropped a little lower by then. He doesn't know how much control to use so he pushes gently on the lever. Nothing happens. Those nice gentle ailerons take a while to start moving that nice big slow wing. Now he pushes harder. But by now that wing has already overcome inertia and with the added control really comes up quickly. Usually the next thing is a crash.

With an airplane so easy to fly a chimpanzee could do it, our beginner has crashed in the first excursion of a pilot-induced oscillation. Why? Pilot reaction time, a treacherous ingredi-ent in our formula for success probabi-lity.

With an experienced pilot, that reaction time is a fairly stable item and he can fly anything. But for a beginner, reaction time varies considerably. Did someone cut in front of hint on the way to the field? Did he eat breakfast? Are there one or five people trying to help him, etc, etc?

Now we come to the question of what kind of wing does the beginner need? Hold tight, here it comes! A short span, medium area wing with large control surfaces of restricted movement and absolutely zero tip mass. I would suggest control movements that won't even allow a full roll in a normal flying area! Now whether the beginner pokes gently at the lever or jams it into the stops, the airplane will respond instantly but gently; and believe it or not, a beginner is on his way to a successful flight.

This airplane with the twin K&B's is not for the beginner, but this same
airplane configuration with a single 60 is being flown by several beginners who were suffering severe distress with so-called trainers.

The engine is just a step along the road of engine development. If built as shown, it WILL work and WILL fly an airplane. The rotor timing is not symmetrical and new ones should be made. Relocating the shaft in order to spread the bearings would increase bearing and gear life. Using spiral gears and thrust washers would also be an improvement. But here is a working device from which to start. I am not blind to the design's faults. I classify it liberally as - state of the art as restricted by time.

The airplane is strong, manueverable, and easy to fly. Aileron response is positive at all speeds without being vicious at full deflection. Pitch response is very smooth. By starting at 0° down thrust and increasing this quantity in small steps, an ideal power on to power off transition will be found. I like a setting that allows a slight nose down, moderately fast glide without changing trim. The air-plane has a smooth rate of sink that allows very predictable landing char-acteristics in most weather (wind). A lifting airfoil is used to allow lower landing speeds and does detract slightly from inverted flight characteristics. But inverted flight is still smooth and predictable and for Sunday flying it is more than adequate..."

Supplementary file notes

Article pages, text and pics, thanks to Cavitation.

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