The Wrights actually found that Lilienthal's glider data, especially the specifics about airfoil design, was terribly inaccurate (the closer they got to replica

The Wrights actually found that Lilienthal's glider data, especially the specifics about airfoil design, was terribly inaccurate (the closer they got to replicating his designs, the worse their gliders performed). It was only after they built a wind tunnel and used it to validate the performance of various airfoil shapes that they could stabilize their gliders enough to think about making them powered. In many ways, the Wright's greatest advancement was abandoning the established knowledge of the field, including Lilienthal's, and validating their design experimentally from base principles.