For example, he was convinced that over a certain speed, the amount of air flowing into the engine vents in the hull sides decreased rather than increased. He performed his own "wind tunnel“ tests by attaching tiny telltales all over one of his hulls before running it. He was right: Above a certain speed, every hull experiences a detachment of laminar airflow, the separation being as much as several inches off the hull's surface. This prevented air from being scooped into the engine room vents in the hull. When he pressurized the engine room with an air-handling system, the performance improved substantially.