Experimental Evaluations of the Aerodynamics of Unlimited Racing Hydroplanes Operating in and out of Ground Effect

Experimental investigations have been conducted to evaluate the aerodynamic performance and control of Unlimited-class hydroplanes racing at speeds exceeding 200 mph. These vehicles operate in very strong ground effect and may encounter unexpected disturbances such as wind gusts or waves, which can cause uncontrolled pitch-up and destruction. Specific test techniques have been developed in a modified subsonic wind tunnel to simulate these conditions, allow evaluation of the vehicle's aerodynamics and develop novel control surfaces. The paper presents details of these facilities and test techniques, associated wing-in-ground-effect tests, and characteristics of the pitching hydroplane as it transitions between in- and out-of-ground effect.