Super Bison 220 (oz16384)

About this Plan

Super Bison 220. Radio control glider tug model. Wingspan 220 cm.

Direct submission to Outerzone.

Update 10/11/2025: Added article, thanks to Pit.

Quote (google-translated): "Super Bison 220, by Pierre Muller.

Like most sports and parasports, aeromodelling has a few stars whose names are known to almost all practitioners. Thus, the Bison, or rather the Bisons and Super Bisons created by Pierre Muller, have become synonymous with towing our gliders. It was therefore with great interest that we listened to Pierre Muller when he offered us the plans for his new model: the Super Bison 220. In addition to towing gliders, this model can perform other tasks: aerial photography, training for piloting large aircraft, banner towing, carrying payloads, etc... In short, thanks to its size, robustness, and powerful engine, this workhorse will provide many services.
P.G.

The Bison Saga: The first-generation Bisons, dating back to 1973 (yes, already!), had a wingspan of 1.80 meters and were designed for 10 cm³ engines. The evolution of gliders was such that it quickly became necessary to design a more powerful tow plane. To this end, some replaced the 10 cm³ engine with a 15 cm³. This was satisfactory, but when towing fairly heavy gliders, a certain instability of the aircraft was still felt, especially in turns. All the dimensions of the Bison were increased by 11%, and thus the Super Bison, 2nd generation, was born in 1978.

But glider pilots still want more! 5 meters, 6 meters, and even 8 meters wingspan for 14 kilos (Marc Hauss)! But where are we going, you might ask? Oh well! Let's play the game. Let's take the Super Bison, increase its wingspan to 220 cm, and power it with a 20 cm³ two-stroke engine. The cost is similar because the Super Tigre isn't much more expensive than a good 10 cm³ engine (Editor's note: provided it lasts!!). This is how the third generation of Bisons was born, with the Super Bison 220.

The S.B. 220 Prototypes: I acquired a fiberglass-epoxy fuselage molded by a friend, and built the wing and tailplane from balsa-covered polystyrene. Given the weight of the engine, 1200 grams, I had to add 60 grams of lead to the tail. Note that I centered it at the rear limit to optimize performance. This model had a fuselage similar to that of the second-generation Super Bison, and a wingspan of 220 cm. Jacques Grégoire, on the other hand, built an "all-wood" fuselage whose rear lever arm is 8 cm longer than mine.

He increased the wingspan to 232 cm and also opted for the 20 cm³ Super Tigre 2000. He didn't need to add any ballast to the tail. His Super Bison weighs 6.4 kg for 77 dm2, while mine weighs 6.250 kg for 72 dm2. These two 'prototypes' made it possible to define the design of the Super Bison 220, the plans of which are reproduced in reduced scale opposite (3 m2 wing area).

Specifications: Recommended engine: 15 to 30 cm³ two-stroke. Wingspan: 220 cm Wing area: 72 dm² Asymmetrical biconvex airfoil of 13.5%, extrapolated from NACA 2415 Aspect ratio: 6.7 Taper ratio: 0.68
Aileron area: 8 dm² Tailplane span: 78 cm Tailplane area: 18 dm² Elevator area: 5 dm² Tailplane airfoil: symmetrical biconvex of 11% Weight: 5.5 to 6.5 kg, i.e., a wing loading of 76 to 90 g/dm².

The Engine: As with any utility model, the choice of engine for the S.B. 220 is wide and depends on the intended use. If your needs are limited to 'training' flights or towing 'small' gliders, a 15 cm³ two-stroke engine is more than sufficient. To optimize towing capabilities, the 20 cm³ Super Tigre, which offers exceptional value for money, is perfect. Note that this 20 cm³ engine weighs 1200 g, the same as the 25 cm³ engine from the same manufacturer, and that the 30 cm³ version weighs only 1280 g. Installing a 25 or 30 cm³ Super Tigre two-stroke engine in place of a 20 cm³ engine therefore poses no practical problems (size and balance). My 20 cm³ engine, equipped with the Super Tigre resonator, turns an 18 x 6 inch (45 x 15 cm) propeller at 8000 rpm with non-nitrated fuel. Grégoire's engine turns a 16 x 8 inch (40 x 20 cm) propeller at a similar speed. In flight, we did not notice any significant difference between these two propellers..."

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