Investigating sailing styles and boat set-up on the performance of a hydrofoiling Moth dinghy

The adoption of hydrofoils in the International Moth class of dinghy has posed new challenges to sailors both in terms of the set-up of the boat and hydrofoils, and their sailing techniques and styles. The experience of sailors in the class indicates that the height above the water surface at which the boat is flown (ride height) and the amount of windward heel (heel angle) are critical factors affecting performance, particularly in upwind sailing. The fore-aft position of the helm affects the stability of the craft and, in conjunction with the aft foil settings, alters the pitch orientation of the craft and offers potential for significant gains in performance. A four degree of freedom velocity prediction programme (VPP) with the capability to investigate these factors is presented and used to demonstrate how the fore-aft position of the helm and the aft foil may be used in conjunction to maximise speed. Nomenclature α Incident flow angle [rad] c Chord of foil [m] X CB ∂ Movement of centre of buoyancy in X-direction [m] D Drag [N] α ∂ ∂ L C Lift-curve slope of foil [rad 1 ] Spray D Spray drag [N] Z Y X i , , ∆ Distance along X, Y, or Zaxis, between centre of effort of i th component of force and centre of mass of craft [m] W D Drag due to windage [N] air ρ Density of air [kgm 3 ] e Oswald efficiency factor [-] ρ Density of water [kgm 3 ] Z Y X i F , , Force in X, Y, or Zdirection, acting on i th