You’re back to cylinders again, guys. The Superfoiler model (top) illustrating differences in pressure loading with a solid platform (left) providing endplate effect and traditional netting (right) where pressure leakage drastically changes the airflow and the aero efficiency
performance advantages to explore within a given design space. Over the past few decades a quiet revolution of integrating mast and sails has trickled down from America’s Cup campaigns, to their now being commonplace on any new high-performance programme. It started with ourselves, moving beyond just pure sail design by integrating the mast and sail design inside our design software. Here the individual mast and sail designs were coupled so that the stiffness of the mast could be matched with the stiffness of the sail, to find the best aerodynamic solution through the range of apparent wind speeds for a given target sail shape. Today this coupled solution is being combined with the hull/platform model to come up with a combined aerodynamic package that more closely matches what is happening on the water . CFD (RANS) solutions are expensive and time consuming to create, and can easily consume an entire design budget if several of the possible solutions are to be simulated. So care must be taken in doing enough simulations to understand the primary drivers within the design space, and then the designer’s solution is derived from the knowledge gained through the data provided. With the Superfoiler (more on this next month) one TWS was targeted and a mini-matrix was constructed sweeping through
42 SEAHORSE
AWA, trim and heel settings. The full model of the boat was then analysed in this matrix including the platform/hull, rig, sails and crew (the crew was simplified to ‘cylinders’ to capture their effect without over-complicating the model – sorry, boys). As a result of this type of melded approach designers are now able to understand the influence of the complete aerodynamic package and better balance the boat in a VPP, using a refined or more realistic aerodynamic package from the outset. With the advent of modern-era apparent wind sailing, interfer- ence drag and the proper way in which to calculate it soon started to become a factor in performance design. And as we now enter the new world of flying boats, interference drag moves up the hierarchy from being a factor, to being a significant factor. Interference drag refers to the aerodynamic drag of protuber- ances, rather than the baseline drag of the structure (objects that are generally on deck: winches, sailors, daggerboard and foil appa- ratus and so on). These items are embedded in the platform flow field and so should be incorporated into windage calculations. This study took a big a step in analysing the rig and sails in conjunction with the platform; most of the key items included in the baseline model, standing rigging and sheets and so on were
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