Super Clean (oz11033)

About this Plan

Super Clean. Radio control sport trainer model. Wingspan 56 in, for .19 engine.

Quote: "Good looking trainer designed specifically to overcome many beginner's problems such as landings, slow flight, cross wind flight and the other intangibles that plague the beginning pilot. Designed for a .19 size engine it is still snappy enough for maneuvers! Super Clean, by RC Remington.

How many times in the last ten or 15 years have you witnessed the following episode? A fellow modeler (or yourself) arrives at the field with a new model. Obviously, from its appearance, a great deal of time and effort has been spent building the model to the designer's specification. A last minute check is made of proper balance and alignment. The engine is started and the controls checked for proper operation at all engine RPM and aircraft attitudes. The air is calm, the sky is clear and no one else is operating on the same frequency; therefore, having exhausted all excuses for not flying, the pilot is committed.

With engine idling (and flyer praying), the model is taxiied to the end of the runway. Slowly the throttle is increased and the model starts to roll. Increased throttle and up elevator is applied, and to everyone's surprise, the model takes off and climbs cleanly into the sky. The pilot, who is capable of flying trainers like the Falcon (oz2424), has little trouble flying the model through straight and level flight, turns and simple aerobatics. Fuel is now running low and the moment of truth is at hand - as the pilot turns onto the final approach at reduced speed, it becomes apparent that the model requires flying right down to the ground. Slight changes in attitude are violently over-corrected and recorrected, resulting in partial or total disaster.

What causes so many models to be damaged on landing, after obviously successful flights? Is it the aircraft design, or the pilot's lack of skill? In reality, it is a combination of both. Today's Pattern designs, with full symmetrical airfoils and zero incidence angles, aggravated by high wing loadings, do not perform well at low speeds. While the expert Pattern flyer has little or no difficulty handling this type of bird, it's completely beyond the capabilities of the novice to intermediate flyer.

'Super Clean' is the result of trying to bridge the gap between the trainer and the pure Pattern machine. Since I like the general appearance of Mr Clean (oz14909), I decided to use this basic configuration in a slightly larger model and to include some design changes.

Since low speed stability was the prime prerequisite of this design, a semi-symmetrical Davis airfoil with 2% camber was chosen. Wing root is a 14% thick section while the tip section is 15%. This variation, coupled with slight adjustment of the ailerons up from true zero, gives exceptional low speed characteristics and practically eliminates tip stall. To compensate for the obviously reduced lift in inverted flight due to the semi-symmetrical airfoil, 2° downthrust (which becomes upthrust with the model inverted) was built in. With the wing and stab set at 0° incidence and the model balanced as shown in the plan, down elevator during inverted level flight is reduced to a minimum.

The original calculation for wing loading came out to 20 ounces to the square foot, based on flying the model with a Veco .19 and fixed landing gear. Sketches of the plane, prior to construction, with the landing gear retracted looked so good that I couldn't resist the temptation. The model is now flying at a wing loading of 23 ounces per square foot using an OS Max H4OP swinging an 11 x 4 prop. The wing was moved up into the fuselage, just to keep Art Schroeder happy.

Early flights of Super Clean were actually made from a grass field using a Veco .19. While takeoffs were a bit hairy, performance in the air with the gear up was exceptional, considering the power. In fact, if l were flying from a paved strip I probably would never have changed to the larger engine. This airplane, more than any other I have ever designed, fulfilled the design specifications set forth prior to construction. Its aerobatic capabilities are exceptionally good while it retains superior low speed characteristics. Landings are made in a nose high three-point attitude with no fear of instability.

As a matter of interest, all photographs of Super Clean accompanying this article were made after an entire season of flying! This attests to the inherent strength of the airframe construction, and not, I assure you, to the pilot's skill!

Construction. Fuselage: The fuselage is constructed in a somewhat unique manner. All formers and the keel are 1/8 plywood. When cutting the plywood parts, he accurate. Mark the thrust line on all formers and the 3/32 balsa sides and align them during assembly. The formers are assembled on the keel. All formers aft of the cockpit slide on from the rear..."

Super Clean, MAN, December 1973.

Direct submission to Outerzone.

Supplementary file notes

Article pages, thanks to RFJ.

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