Design
The Farr-designed Horizon F14 paddle board (below) is already winning races in Europe and the USA. Built by International 14 specialists Solent Boatworks in the UK, the thin-walled all-carbon board weighs in at just 13.5kg. Using CFD the fuller bow on this candidate design (top right) can be compared with the reduced disturbance of the final F14’s (below right) wave-piercing nose – placing greater emphasis on bow rocker to stop the finer bow digging in. Far right: the well finished final product (top) and a new deck in the mould (below)
New horizons…
The brains at Farr Yacht Design have always been ready to take on fresh areas of enquiry, a recent – successful – move into paddleboard design demonstrating that this enthusiasm for new challenges remains undimmed. Project lead designer Emerson Smith describes the process
The Horizon F14 Standup Paddle Board
Stand-up paddleboarding is one of the fastest-growing sports in the world today. Many of us here at Farr Yacht Design have boards and enjoy a paddle before or after work. Often lunch discussions among the team turn to what an FYD board would look like if we applied some of our yacht design tools to the problem. Then a few months back we were contacted by Andrew Thompson of Horizon Yacht Charters with interest in developing a new 14ft race board; all of a sudden we had the opportu- nity to see just what we could do… Our sailing yacht designs are focused on achieving the maximum aerodynamic and
52 SEAHORSE
hydrodynamic efficiency. While a SUP board doesn’t need to operate at heel and yaw, we are still on a quest to maximise efficiency; in this case the need to max- imise the transmission of paddler energy into the board’s motion.
Much as with sailing yachts, there are still a large number of design constraints that need to be balanced to develop a successful SUP board. Venue – a board optimised for big wave surfing in Hawaii is going to be completely different from one targeted at flatwater estuary races. Even in flatwater races, elements like slop and drafting from other competitors are still factors. And if there is even a small portion of downwind work with the waves, then the ability to surf easily can deliver huge gains. Stability – all parameters (hull radius, rocker, etc) being equal, a narrower board has less wetted surface and will be faster. That advantage is lost if these parameters are not balanced correctly and the paddler ends up swimming too much. The stability also needs to be carefully calibrated to the rider and range of conditions the board is to excel in. Directional Stability – bow volume is useful for preventing the bow from digging in, but too high a profile in a crosswind can knock the bow off course, requiring the paddler to expend energy to compensate. Therefore, crosswind airflow in part dic- tates the bow profile. An appropriately sized and placed fin is also essential for directional stability. Further significant
attention was given to the treatment of the high-drag area of the fin box. Manoeuvring – most races require turns around buoys, and this is certainly an influence on the design. For the most popular racing classes (14 and 12.5ft), the paddler needs to be able to shift weight aft, lift the bow out of the water and thus minimise the turn radius.
To understand the SUP design space, we developed a parametric model of a board that allowed us to easily make design changes, such as width at various points, rocker and rail hardness. This was ‘wired’ to automatically mesh the designs and run the boards in Fine/Marine software, which gives us our hydrodynamic force predic- tions. Over 100 designs were created in this way and the performance spread was considerable – the best candidate shapes demonstrating an advantage of some 15- 20% over our baseline reference shapes. Of course, these computer models only give a partial insight into the critical design drivers, so before moving to production we built three prototype boards to assess the many features that cannot be captured in the computer. How does the actual stability stack up against other boards already on the market? Are there particular sea conditions that a board favours? Does the cockpit drain? Can it turn at the buoy? Is the laminate robust and stiff enough? Building and paddling a prototype is the only way to answer these questions. It provided important design input that was then incorporated into the final design.
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