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In the last decades, the use of foils on sailing yacht has highly increased. Whether they are mono or multihull, yachts are using foils to reduce their drag forces and then, to increase their speeds in a large range of wind and sea conditions. Several CFD-based studies have already been carried out in order to optimize the foil’s shape and location on the hull, but feedbacks on the yacht’s behaviour is mainly given by the crew when sailing at sea. The aim of the presented paper is to propose a complementary and faster approach that could help to predict and quantify the yacht behaviour in calm water and in waves while sailing under foil’s action. This approach is well known as a system-based modeling and is a mathematical method that leads to understand the complexity of a system from the study of its interactions in their entirety. The paper will present the ability of the system-based approach to predict the attitude of a catamaran while performing maneuvers such as turning circles with 35 degrees of rudder deflection and zigzag tests 10-10 and 20-20 shapes.
Velocity Prediction of Wing-Sailed Hydrofoiling Catamarans
The paper presents a Velocity Prediction Program for hydrofoiling catamarans with solid wing sails. Starting from a description of the mechanical model, suitable models are identified for the forces that act on the boat components. The study is deliberately limited to means for restricted methods where computational resources and budgets are limited. Enhanced lifting line approaches are described for the wingsail and appendages. Windage is calculated from force coefficients and dynamic pressure while hull resistance is determined by means of a potential flow solver. The description of the implementation is followed by the presentation of the results including a comparison to measured data. Additionally significant findings in terms of overall force composition and distribution as well as loading on specific components of the catamaran are presented and discussed. Finally, some of the challenges encountered during the study are discussed. It was found that the VPP predictions compared favourably with measured data from the 34th America’s Cup in San Francisco in 2013.
Unlocking Hydrofoil Hydrodynamics with Experimental Results
Hydrofoil sailing has been able to unlock performance characteristics previously confined to speed records, making them available to multiple racing fora. The America’s Cup is now regularly sailed at 40 knots, Moth sailing dinghies and A-Class catamarans achieve up to 30 knots on standard race courses. The systems employed to achieve these speeds have been refined to such an extent that high speeds are regularly attained. However, there are still large gaps in our understanding of the fundamental hydrodynamic phenomena to enable safe control of these machines and continued increases in performance. For example, arbitrary ventilation pathways have been noticed and yet are not fully explained. This paper provides the means to unlock the methods of quantitatively establishing a pathway for arbitrary ventilation and for measuring the flow regime complexity around such foils. These two methods have been developed over many years by the collaborators mentioned in this paper. The result is a valuable contribution to capability available to the sailing research community. An additional two methods of experimental analysis have been detailed within the paper.
Hydrofoiling Catamaran Experimental Research Platform
This paper outlines the development of a hydro-foiling catamaran experimental research platform. The platform was designed to allow the configuration to be easily adjusted to assess the effects of various parameters on the performance and stability of the craft. In order to determine the performance of the craft, a data acquisition system was developed to record wind, speed, heading and IMU data. A hydro- foiling velocity predicition program was written to provide a comparison tool between the physics and data collected on the water.
Prediction and optimization of aerodynamic and hydrodynamic forces and boat speed of foiling catamarans with a wing sail and a jib
This paper describes a method to calculate the
aerodynamic forces generated by a rigid two-element wing
together with a jib. Additionally, investigations of
hydrodynamic flow forces generated by water-piercing Lshaped
foils are introduced. The aerodynamic and
hydrodynamic flow force prediction methods are combined
in a velocity prediction program featuring a constraint
optimization method in order to predict boat speed and wing
and foil trimming parameters for its maximization.
A velocity polar calculated by applying this method to a
50-foot catamaran is shown and the result of some studies
are presented, varying design parameters of the catamaran.