Phase 2 of SYRF's Downwind Aero Project.

Modern racing yacht semi-planing hull forms provide a number of complex challenges for designers and other professionals involved in yacht rating. The SYRF Wide Light Project was initiated as a means of (1) providing data with which to assess a range of alternative computation methodologies to analyse sailing yacht hydrodynamic forces and moments, (2) making this data available to the entire sailing yacht research community and (3) demonstrating how this type of study can be used to inform the rating process. This paper presents a comprehensive set of tank test results in both canoe body only and appended configurations to be used as a benchmark for a defined geometry of a modern semi-planing hull. Five different CFD stakeholders carried out ‘blind’ CFD analysis on the same test matrix using a range of different computational codes and approaches. The results are presented here along with feedback detailing the software, methods and resources used to generate the results. This project offers a comprehensive set of public domain data which researchers may use to validate and develop their numerical tools as well as highlighting how successfully commercial CFD codes may be used to confidently predict the variation of the forces on a sailing yacht hull as speed, heel and leeway change. Finally, discussion will be made on how this first phase of the project may be used to inform handicap rule makers.

In a sailing yacht match race —a duel between either identical or almost similar yachts— strategy plays a major role and sailors continuously have to make their decisions according to the wind variations and the opponent’s position and actions. This paper focuses on the issue of strategic decision-making during a match racing upwind leg, considering the skipper’s reactions to the opponent’s position and actions in a dynamic and stochastic wind. We address this decision-making problem with a stochastic game approach and propose a new formalism to model both yachts’ decision sequence and the resulting outcomes in terms of advantages to win the match. A first model of the proposed formalism is implemented on a simple racing scenario to illustrate the method. This paper shows how the strategic decision-making in sailing yacht match racing corresponds to the settings of stochastic games, considering the wind fluctuations and the opponent’s actions. Even if the model is simplified with strong assumptions with respect to the real game of match racing, the new proposed formalism with a two-player stochastic game approach permits some insights into strategic decision making and will be helpful for sailors training after some future developments to get closer to the real race.