software is not cost-effective. ‘It makes much more sense to leave it to the program developers to conduct the constant research and development required to keep pace with progress, while we concentrate our research and development effort on our products.’
because of bridge heights on key sailing routes like Panama. To avoid going into the complications of hingeing or telescoping masts this has seen greater use of ketch rigs and even multiple mast
simulation are so accurate that physical testing is not required. However, Bouzaid, who has just returned from a week of testing at the Southampton wind tunnel, believes there is still a place for physical testing in sail design. ‘Airflow is much more random and complex than water,’ he argues. ‘Every shift in direction and strength has a direct influence on the flow over the sail. Then, adding to the complexity, the sail shape changes with every trim adjustment, making accurate modelling extremely challenging.’ Running CFD tests on every permutation becomes very time consuming. The computer may be more accurate in the end, but in two days at the tunnel Bouzaid says you can run hundreds of tests and get a pretty good idea of these sorts of issues.
Where computer modelling has advanced is in predicting how different sail shapes will perform, so less physical testing is spent on that aspect of design. ‘In the past we used the tunnel for testing shapes and how the sail would fly. Now the tunnel is used more for analysing interactions between multiple sail combinations and the impact on balance and helm loads.’ This is particularly relevant in superyacht applications, where more complex rigs are seeing greater use. As yachts become larger the sloop configuration has just about reached its limit
Top: one of Doyle’s
youngest sail designers, Stefano Nava, aged 29, has just finished his PhD in mechanical engineering. Nava works closely with Richard Bouzaid (above)
managing the considerable amount of CFD work now integral to all of this growing company’s output.
Bouzaid of course comes from one of the most
famous of all racing
dynasties. Father Chris and uncle Tony between them won two One Ton Cups, two Half Ton Cups and a Hobart and much, much else. And grandpappy Leo founded what is now Doyle Sails. Some family!
arrangements on vessels such as Maltese Falcon and Black Pearl. ‘On some of these big yachts you see sail plans with five or seven sails working at any one time, with lots of interactions going on between them. This has a significant impact on balance and helm loads and the tunnel is useful for analysing those forces. ‘In the old days this didn’t matter so much because superyachts tended to use hydraulic steering. Now superyacht owners enjoy sailing their boats and having the feel and feedback of manual steering, but they don’t want it to be so loaded up that you have to have two hefty crew swinging on the wheel.’
Already some of these very large yachts are using real-time load sensing and wind strength and direction inputs to automate sail trim and even reefing. As CFD analysis continues to become more adept and faster at modelling real-time airflow, Bouzaid predicts that it could become part of the management systems of more high-performance cruising yachts, even foiling types.
Whether the rulemakers of events like the America’s Cup, Volvo and Vendée Globe would allow any level of automation in sail management is doubtful, but real-time performance analysis programs might well be integrated with CFD to inform competitors on how to optimise trim.
At Doyle, Bouzaid says, the design team use CFD and FEA programs as well as a commercial sailmaking package called Sailpack. Developments in this field move so fast that he believes in-house
Sailmaking software has become so sophisticated that all the functions, from early-stage design to full structural engineering and aerodynamic characteristics to creating a file that will instruct machines on exactly how to construct the material, are now integrated into a single package. ‘It has progressed a lot in the past five years; there are incredibly accurate tools available on the market.’ At the same time he firmly believes that old-fashioned analogue values like experience and knowledge and a sailmaker’s eye remain an important part of the process. Along with the science there is still place for the sailmaker’s art.
The make-up of the Doyle design team reflects this combination. A number of the team members are graduates from the former Yacht Design programme at the Auckland University School of Engineering, where theoretical work in CFD and FEA played a major role.
David Le Pelley, who headed the university programme, is now also at Doyle as head of research and management for the Stratis product. Between them this group represent significant firepower in state-of-the art computer-based structural and performance modelling.
‘Then alongside them we have more experienced sail designers, who have been doing this for up to 30 years,’ says Bouzaid, ‘so they bring a more knowledge-based approach to the equation. It makes for a nice blend of talents and skills on tap for our projects and can advance new ideas very quickly. It has allowed us to not only develop our design processes, but also our Stratis product, which is under a continuing cycle of research and development.’
Uniting both the science and art sides of this equation is the fact that all the design team members are active sailors, bringing a passion for the sport and practical hands-on knowledge to bear on every aspect of their work. ‘When you are dealing with products like ours, which are very much custom, bespoke-type sails, experience and knowledge, alongside all the theoretical expertise and technology, are what it is all about.’
www.doylesails.com
q SEAHORSE 63
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