Composite materials are good candidates for hydrofoils manufacturing, ensuring a good balance between strength and weight. In the high performances sailing yacht domain, hydrofoils are thin structures, highly loaded that experience sig- nificant displacements. This study investigates experimentally and numerically the influence of the laminate layup on the hydrodynamic performances of a surface piercing hydrofoil. Four hydrofoils with a constant chord, geometrically identical with different composite layups are mechanically characterized and tested in a hydrodynamic flume. The foils are designed to have a significant tip displacement of 5 to 10% of the span. Experimental results highlight a bending-twisting effect that leads to significant change in the hydrodynamic performances of the structures. Two different FSI numerical approach: from a potential code coupled with beam theory to the full coupling of a shell structural code and a VOF hydro model with free surface are presented and the first one is compared to the experiments with great results. The two approaches are two com- plementary bricks in the design process to compute the effect of passive deformation on hydrodynamic performances of the foils and therefore the yacht stability.

This paper presents an advanced and accurate integrated system for the design and performance optimisation of fibre reinforced sails, commonly named string sails, developed by SMAR Azure. This integrated design system allows sail designers not only to design sail shapes and the reinforcing fibre paths, but also to validate the performance of the flying sail shape and have accurate production details including the overall sail weight, material used, which means costs, and length of the fibre paths, which means production time. The SMAR Azure design and analysis method, extensively validated and used to optimise several racing and super-yacht sailing plans, includes a computationally efficient structural analysis method coupled with a modified vortex lattice method, with wake relaxation, to enable a proper aeroelastic simulation of sails in upwind conditions. The structural analysis method takes into account the geometric non-linearity and wrinkling behaviour of membrane structures, such as sails, the fibre layout, the influence of battens, trimming loads and interaction with rigging elements, e.g. luff sag calculation on a headstay, in a timely manner. Specifically, this paper presents an optimisation of a real fibre reinforced membrane sailplan of an aluminium super yacht, carried out in collaboration with Paolo Semeraro (Banks Sails Europe). The optimisation process of the fibre layouts led to a sensible reduction in maximum stress, strain and displacement compared to the initial designs, keeping the same fibre weight or slightly increasing it. The results have been confirmed in the sailing tests, although no exact measurements have been performed.

Out-of-autoclave prepregs are the construction material of choice for high performance marine craft, due to their high material properties, and relatively low processing costs compared to traditional autoclave prepregs. Because of the low compaction pressure, voids are not collapsed by external pressure; therefore air must be removed from the laminate prior to cure to ensure a low void-content, high quality laminate is produced. This work presents the development of experimental techniques to accurately measure the as-laminated void content, compaction response and in-plane and through thickness air permeability of two prepreg materials. The material models developed were implemented into an air removal model, and compared against experiments. Excellent correlation was observed for the cloth material, whereas the unidirectional material exhibited complete closing of air pathways, which was not captured well by the current model.