Although later aircraft designers had a better understanding of fluid dynamics, the Wright brothers did not. In fact, most early aircraft pioneers failed to understand that air should be treated for mathematical purposes as a very very non-viscous fluid. Bernoulli's principle was based on hydrodynamic studies of water flow.

Instead, the main R&D tool used the Wright brothers was a wind tunnel. The Wright brothers were both skilled machinists, and spent several years testing and refining sucessive wing designs and layouts in a wind tunnel of their own design using carefully-constructed scale models. The Wrights kept very careful records of the dimensions of which wing layouts worked better than others a producing lift for a given range of speeds of airflow in the wind-tunnel.

However, the real innovation that allowed the Wright Brothers to be successful was not their airfoil shapes, but the idea of control surfaces, the idea that the shape of the airfoil must be a changed in predictable and controllable ways to control the flight of the aircraft. The Wrights aircraft patents in fact were not for a "flying machine" but for a "system of aerodynamic control" aka a 3-axis control system.