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www.sname.org/sname/mt April 2013 including all the major geometry using Fluent requires around 15 million grid cells. Accurately modeling the detailed geometry of a yachts rig and sail conguration is one of the biggest advantages of this type of analysis. Designers are able to accurately set the boats rig and sail geometry up virtually and dene loading scenar- ios likely to be experienced in real life. e starting point for a computational load analysis of a yacht is a detailed three- dimensional (3D) CAD model of the yacht and rig. If 3D CAD les are not available for the project, step one is to dene the CAD model starting from 2D drawings. Sails are then designed by a sailmaker to t the rig and incorporated into the 3D model of the yacht. Sail sets are dened to choose the sails to be used in specic apparent wind conditions. Load case de?nition Its not just the pure size of the new sailing mega yachts but how they are sailed that also contributes to the huge loads they expe- rience. ese yachts are pushed hard by their owners and crews with the emergence of competitive super yacht regattas around the world. Early sailing mega yachts were designed primarily with comfort in mind and thus were not pushed to the strength lim- its of their designs. e super yacht regatta series has raised the bar for the performance of these boats and now they are being designed with racing in mind. ough the yachts will spend most of their lives leisure sailing, they have to be designed for the loads encountered while racing. Load denitions for mega yachts are now similar to race boat programs with the rig power usually being limited by the boats maximum righting moment. e next step is to determine at what apparent wind angle and wind speed the load calculation will be performed. Often in the design stage yacht designers use a velocity prediction pro- gram or a VPP to predict the speed, heel, yaw, pitch, and roll The fact that sails are only stable structures when set properly to the wind adds to the challenge of properly designing for the maximum loads. RANS CFD surface mesh for a 125 ft. sailing yacht. THE MEGA MODEL