Aerodynamics of High-Speed Sponsons

Abstract Research undertaken at Lehigh University into the design of sponsons for high speed racing boats is described. Sponsons from a commercially available RC racing boat, the Eagle SGX-45, along with custom built sponson designs underwent wind tunnel testing. The aerodynamic stability of these sponsons was examined particularly as related to "ground" effects near the water surface. Two different concepts for sponsons for high-speed boats were conceived with two overarching objectives - low drag and vehicle stability. The two different sponson concepts had very different behaviors, each benefitting a particular usage.The goal of the first type of sponson design was to minimize lift gradient (lift force as a function of angle of attack) to effectively increase the longitudinal pitch stability of the boat. The results show that a new, more aerodynamically "neutral" sponson (with a lift coefficient nearly independent of angle of attack) could be made, and that it had considerably better aerodynamic performance than the commercial sponson.The goal of the second type of sponson was to provide substantial aerodynamic lift, but only in ground effect. The boat would then be able to "fly" at an essentially constant height above the water surface, thus eliminating hydrodynamic drag and accordingly have very low total drag. Results from wind tunnel tests showed that a sponson in the shape of a small aspect ratio wing equipped with end plates had the desired characteristics.