power to continue hydrogen production. This ship is essentially a sailing yacht but
tasked with hydrogen production. As with racing yachts, minimising resistance and maximising driving force and sail propul- sion are crucial, making the successful opti- misation of the hull design, sail size and configuration crucial. Without modern CFD tools it is unlikely that such a novel solution would even be worth pursuing.
Hydrofoil catamarans Foiling technology, such as that used in the AC75, has garnered significant attention in sailing, with new foiling designs sprouting up in every direction. Using 100% foiling – where all the weight of the vessel is sup- ported by lift – requires very precise control of the foils, but offers the advantage of substantial resistance reduction. For large, high-speed passenger ferries, however, increased weight leads to higher loads on the foils and cavitation issues, making it challenging to achieve 100% foiling. The hydrofoil catamaran we are cur-
rently working on is a hybrid high-speed passenger ferry that relies on lift for about half of its support and buoyancy for the other half. This approach allows for much simpler foil control compared to 100% foil- ing and also reduces the risk of major acci- dents, enhancing safety. Inevitably, due to the wave-making of the hull, the resistance is greater than with 100% foiling, making hull and foil shape optimisation crucial, with CFD once again being indispensable. Additionally, stability in waves can now
be verified through CFD which marks an important step forward in the technology.
52 SEAHORSE
Racing yachts and dinghies As late as 2004 my involvement in sailing craft was still essentially limited to my work in the America’s Cup. Since then, however, I have been able to focus on a broader range of racing keelboats and dinghies. Given that racing yachts always attract attention for their performance, I find it very rewarding to enhance their potential using the latest tools available, CFD always delivering a compelling case for good design decisions. The original CFD code used for IACC
boat development holds many memories. Whether it was those times when it failed to deliver good results, despite numerous attempts, or moments when it produced a hull design that made a significant leap forward, it was always there underpinning everything we worked on. More recently, as that original code
became inadequate functionally, I have switched to using the commercial code FineMarine. This is used to model hulls with appendages, and to simulate planing plus more complicated shapes and condi- tions. It also supports VPP model calcula- tions, enabling more accurate VPP analysis. Our own original VPP uses a unique sail
trim model, which deforms the shape of the jib and mainsail using parameters including depth, twist and traveller positions, with sail forces modelled by CFD for the VPP. This model can now reliably reproduce optimal trim conditions for each wind speed and direction on the VPP. This enables estimation of values closer to actual sailing conditions than general VPPs. Racing yachts are created using each
designer’s best logical and scientific methods. Each designer pours their own thoughts and passion into their respective vessels. Hence my own most recent design – the 36ft Samurai 2 – represented the culmina- tion of some 30 years of work. Similarly, however, I have been applying the same dedication to dinghy and small craft devel- opment, with a particular fondness for the Snipe and 470 classes. For both the primary goal of my projects
was to develop new hull shapes with minimal resistance within the constraints of the class rules. For the 470, by conduct- ing numerous CFD simulations under various conditions, we achieved what we measured to be a drag reduction of up to 3% in some conditions compared to previ- ous ‘designs’. We also improved perfor- mance in waves and manoeuvrability, allow- ing the boat to handle more efficiently. For the Snipe, using CFD we also
studied aerodynamic performance, resulting in a new cut-away shape for the foredeck gunwale that does not contravene the rules. For our latest improved 470, we also
developed a radically different rudder shape, where the leading edge is slightly tucked in beneath the hull (Europe class sailors will quickly recognise the configu- ration). This modification proved able to smooth out waves coming off the transom, resulting in a significantly cleaner flow compared to the waves generated by conventional rudder designs, resulting in a further reduction in drag. Of course we always need to prove our
ideas in ‘real life’ at full scale, and in the case of the two dinghy classes discussed
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