Analysis on the Key Parameters Driving the Mast Stiffness Accuracy to Improve Sail Design using Fluid/Structure Simulation with Beam Elements

_ The masts of racing yachts are generally designed considering a discrete list of load cases which are prioritized according to their margin of safety. Masts are subject to two main loads: mast trimming (docktuning) and sail forces, typically accounting for 30% and 70% of compression loads respectively. Mast design must ensure that for any sailing configuration, mast deflection matches the sails shape to maximize the boat’s performance. Loads on the sails are quantified in sail design tools using Fluid/Structure interaction approaches. Such methods use simplified beam models for the mast definition to reduce computation time. However, these simplified beam mast models do not reveal the instability of the structure (buckling), which is key parameter driving the mast design. More detailed shell models, capable of predicting the local buckling modes to validate the final stiffness, can only be built when the manufactured configuration is finalized. This disconnection between the initial beam models and the as-manufactured shell models means that the on-board measured curvature of the mast can be very different from that calculated with the beam model, leading to a significant error in the actual shape of the sail during sailing. To reconcile the mast and sail design processes, a new methodology has been implemented to generate automatically an updated beam model directly from the shell manufacturing model as it is developed to provide much greater accuracy, earlier on in the rig development process. In this work, we use a series of twenty different loading cases that correspond to an IMOCA mast design and a D-mast section (typically for AC75 boats) to quantify influence of the refinement of the composite definition and related beam model generation. Keywords Mast engineering; beam model; composites modeling; mumerical method; mast bending