What material did the Wright Brothers primarily use for the frame of their aircraft?

The Wright Brothers primarily used spruce wood for the frame of their aircraft due to its ideal balance of strength, weight, and flexibility. Spruce is a lightweight yet strong type of wood that provided the necessary structural integrity while minimizing the overall weight of the aircraft, which was crucial for achieving flight. Their choice of material was informed by their careful experimentation and understanding of aerodynamics and weight distribution, which were critical factors in the design of the first successful powered airplane. Additionally, spruce wood was readily available and relatively easy to work with, making it a practical choice for their pioneering efforts in aviation.