Advanced Construction Pioneer
The Strojnik S-2 represented a significant leap forward in homebuilt aircraft construction methodology when it debuted in 1980. While most amateur-built aircraft of that era relied on traditional aluminum or wood construction, Strojnik employed a sophisticated mixed-material approach that combined fiberglass skins over carbon fiber and aluminum wing spars, with carbon fiber tail surfaces covered in fiberglass. This advanced construction technique, relatively uncommon in experimental aviation at the time, enabled the aircraft to achieve performance levels typically associated with high-end manufactured sailplanes.
Designer and Development
Aleš Strojnik designed the S-2 with a clear focus on maximizing soaring efficiency while providing reliable auxiliary power. The aircraft's pod-and-boom configuration placed the single-seat cockpit in a wooden structure covered with fiberglass, while an aluminum tail boom extended beneath the folding propeller. This layout optimized both powered and unpowered flight characteristics, allowing pilots to fold the propeller during soaring to minimize drag.
Strojnik's engineering philosophy proved successful in practice. He personally earned his silver soaring badge flying the S-2 prototype, demonstrating the aircraft's competitive soaring capabilities. The design's commercial viability became evident when Strojnik sold 22 sets of construction plans by 1983, indicating strong interest from the homebuilding community.
Technical Excellence
The S-2's specifications reflect its designer's commitment to aerodynamic efficiency. The 49.2-foot wingspan generates a high 19:1 aspect ratio, enabling the exceptional 34:1 glide ratio at 55 mph. With an empty weight of just 617 pounds and gross weight of 980 pounds, the aircraft achieves a wing loading of only 7.7 pounds per square foot. The Wortmann FX 67-170/17 airfoil contributes to the aircraft's impressive minimum sink rate of 132 feet per minute at 42 mph.
The 28-horsepower Kohler single-cylinder engine, mounted in pusher configuration, provides a modest but adequate 350 feet per minute climb rate. The engine's primary role as auxiliary power rather than primary propulsion reflects the aircraft's soaring-first design philosophy. With a stall speed of 38 mph and never-exceed speed of 149 mph, the S-2 offers a comfortable operating envelope for recreational soaring and cross-country flights.
Variants and Records
Strojnik developed the basic S-2 into an improved S-2A variant, which aviation observers praised as "very well engineered, with some significant cleverness in the aerodynamics of the wing." The design spawned additional variants that pushed performance boundaries further. The one-off S-4 "Laminar Magic," registered as N85AS, featured a shorter wingspan optimized for speed rather than soaring efficiency.
In 1987, the S-4 achieved a notable milestone by setting a United States national aviation speed record in FAI Category C-1a/0, the European microlight category for aircraft under 300 kilograms gross weight. This achievement demonstrated how Strojnik's design concepts could be adapted for different performance objectives while maintaining the fundamental efficiency advantages of the original configuration.
The S-5, registered as N51152, represented another evolutionary step with slightly increased wingspan compared to the S-4, balancing improved soaring performance with recreational flying characteristics. These variants showed the flexibility of Strojnik's basic design approach across different mission requirements.
Production and Current Status
Production of the S-2 remained limited, reflecting its specialized nature and homebuilt market focus. At least eight examples were constructed, with the design available to amateur builders through plans rather than kit production. This approach was typical for innovative homebuilt designs of the era, allowing builders to source materials locally while following proven construction techniques.
By July 2011, six S-2 variants remained on the United States aircraft registry, including three original S-2s and three S-2A models. The original prototype is no longer registered, though several examples continue to demonstrate the design's longevity and continued airworthiness decades after introduction.
Legacy in Motor Glider Aviation
The Strojnik S-2's influence extends beyond its modest production numbers. Its successful integration of advanced composite materials in homebuilt construction helped establish techniques that later became standard in experimental aviation. The aircraft proved that amateur builders could successfully work with carbon fiber and achieve professional-level performance through careful engineering and construction.
For the soaring community, the S-2 represents an important bridge between pure sailplanes and more conventional powered aircraft. Its ability to achieve competitive soaring performance while offering the flexibility of powered launch and retrieval made cross-country soaring more accessible to pilots operating from airports without dedicated soaring infrastructure. The design continues to influence modern motor glider development, particularly in the experimental and light sport aircraft categories.