In the fall of 1901 the Wright Brothers doubted the published aerodynamic tables. They built a wind tunnel in the back room of their bicycle shop in Dayton.
They made between one and two hundred small wing models and tested them. By December they knew that a single constant everyone used was wrong. Lilienthal’s tables were largely right. The error sat elsewhere.
They rebuilt their glider on their own numbers. The 1902 glider was fully controllable. The 1903 machine flew.