Velocity Prediction Program Development for Hydrofoil-Assisted Sailing Monohulls

Abstract

In the last decade the popularity of hydrofoil-assisted monohulled yachts has increased, especially for high performance racing crafts, as the ones used in the Vendée Globe. In the academic environment some research has been done to follow the industry evolution to better understand the behaviour of such vessels, yielding to the need of developing a tool able to predict the performance of such boats. For this reason, the present document aims to propose a simplified model that forecasts the velocity of hydrofoil-assisted monohulled yachts through the development of velocity prediction program (VPP). Due to the complexity of describing the behaviour of a complete sailing yacht, the developed tool uses empirical and analytical equations only, being a useful solution for a preliminary design stage. The aerodynamic model is based in the Offshore Racing Congress (ORC) documentation, the hydrodynamic model uses the Delft Systematic Yacht Hull Series (DSYHS) method, and the foil model is based in the Glauert’s biplane theory, corrected and adapted for hydrofoil with towing tank tests. The combination of the three models allowed the development of a VPP that balances forces and moments in three degrees of freedom: surge, sway and roll. The VPP includes three different hydro foils designs: Dali Moustache, developed for the IMOCA 60 class by VPLP and used in the 2016-17 Vendée Globe regatta; Chistera, also developed by VPLP but now for the new Beneteau Figaro 3; Dynamic Stability System, patented by Hugh Burkewood Welbourn and largely used in several different vessels for racing and cruising. Finally, the present thesis: compares the performance of different foils, pointing its advantages and drawbacks; discuss possible optimizations for the foils design and the precautions that should be taken; presents the limitations of the used models, which yields to the VPP limitations and suggests future works that should be done to better predict the performance of such yachts.