The stability and the dynamic behaviour is an integral part of designing hydrofoil supported sailing vessels, such as the America’s Cup (AC) 50 class. The foil design and the control systems have an important influence on the performance and stability of the vessel. Both foil and control system design also drive the maneuverability of the vessel and determine maneuvering procedures. The AC50 class requirements lead to complex foil control systems and the maneuvering procedures become sophisticated and multifaceted. Sailing and maintaining AC50 class yachts is a complex, expensive and time-consuming task. A dynamic velocity prediction program (DVPP) for the AC50 is therefore developed to assess the dynamic stability of different foil configurations and to simulate and optimize maneuvers. The goal is to evaluate certain design ideas and maneuvering procedures with this simulator so that sailing time on the water can be saved. The paper describes the principal concepts of developing a AC50 model in the DVPP FS-Equilibrium. The force components acting on the yacht are defined based on physical principles, computational fluid dynamics (CFD) simulations and experimental investigations. The control systems for adjusting the aero- and hydrodynamic surfaces are modelled. Controllers are utilized to simulate the human behaviour of performing sailing tasks. Maneuvers are then defined as sequences of crew actions and crew behaviours. In the paper examples of utilising the DVPP in preparation for the 35th America’s Cup in Bermuda are described. The DVPP is for example used to investigate the effect of different boat set-ups on stability and handling during maneuvers. With the sailing team, maneuver procedures are developed and tested. Procedures such as dagger board and rudder elevator movement and crew position are investigated and evaluated to minimize the distance lost during tacking and gybing. The DVPP is also employed for trajectory optimization during maneuvers.

Recent breakthroughs in the America's Cup have put hydrofoil technology in the focus of high-performance sailing. This paper describes the performance assessment of two different centreboard hydrofoils designed for a C-class catamaran. Regarding the numerous design criteria resulting from sailing on hydrofoils, a reliable performance assessment tool helps to find the best compromise [1]. A Velocity Prediction Program (VPP) has been developed in order to facilitate the analysis of numerical simulation results obtained for appendages and the wing-sail in terms of speed potential of the C-Cat. The approach used to model the hydroand aerodynamic forces on the catamaran is described, along with the challenges peculiar to a VPP model for sailing on hydrofoils. Different optimization schemes for trimming the wing-sail and hydrofoil configurations are tested to obtain the theoretically most efficient trim settings and to evaluate the different hydrofoil designs. Using the developed VPP model, realistic velocity prediction can be carried out. The catamaran flying on hydrofoils sails at up to 2.8 times the true wind speed in many conditions. Records and observations made during the International C Class Cup (ICCC) of 2013 confirm the predicted performance of the modelled C-Cat. Some remaining challenges in velocity prediction of vessels equipped with hydrofoils are highlighted.

In upwind sailing conditions, bulbs of canting keel sailboats operate close to the water surface and therefore induce non-negligible changes in the wave system, thus influencing the wave making resistance of a sailboat. The bulb could produce relatively positive as well as negative effects, and therefore its design is suitable for optimization. A case study for a modern 100-foot canting keel sailboat is presented. The design space was explored to determine the bulb shape that would produce favorable interference with the hull wave system, reducing the total resistance of the sailboat for an upwind sailing condition, using the Response Surface Optimization (RSO) methodology developed by the authors. In the 1,000 bulb variations that were performed using an advanced parametric modeler, the volume and location of the center of gravity of the bulb were fixed so that the stability of the sailboat was not altered and, therefore, the computed total resistance became a direct measure of merit of the bulb design. An outlook is given to a combined optimization of hull and bulb in order to gain optimum improvement.