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.

Slamming is a pervasive issue for marine vehicles, few of which are composed entirely of flat panels. Experimental and numerical data from flat panels and wedges are often extrapolated to handle other shapes because much previous work has focused on flat panels and wedges. Though correction factors and other strategies have been employed to achieve satisfactory correlation, curved shapes behave in a fundamentally different way. The current work seeks to investigate the effect of curvature on slamming loads through the use of constant velocity experimental testing and coupled Finite Element-Smoothed Particle Hydrodynamics numerical simulations. Experiments and numerical modelling conducted in the current work show that curved bodies experience a much higher initial loading than rigid wedges, which then abates to a quasi-constant residual load. This load profile varies significantly from that found in flat panels. Peak impact force and impulse plots generated from simulating a range of geometries indicate rigid cylinder slamming represents a more severe load case than rigid wedge slamming. Correlation between experiments and simulations is evaluated by comparison of the time-frequency domain representations of the respective transient signals which results in a single goodness of fit value. Once correlated, numerical simulation techniques can be used to further investigate the influence of curvature on slamming loads. Understanding this relationship between curvature and slamming loads has the potential to increase design optimization resulting in more failure resistant structures.