FARR YACHT DESIGN, PROJECT MANAGER
“New Horizons – The Horizon F14 Standup Paddle Board”
from SEAHORSE MAGAZINE, DECEMBER 2015
Stand up paddleboarding is one of the fastest growing sports in the world. Many of us at Farr Yacht Design have boards and enjoy a paddle before or after work. Often lunch discussions amongst the team turn to what an FYD board would look like if we applied some of our design tools to the problem. We were contacted by Andrew Thompson of Horizon Yacht Charters (and latterly Horizon SUP) with interest in developing a 14’ race board and it was a prime chance to see what we could do.
Our sailing yacht designs are focused on achieving the maximum aerodynamic and hydrodynamic efficiency. While a SUP board doesn’t need to operate at heel and yaw we are still in a quest to maximize efficiency; in this case the need to maximize the transmission of paddler energy into the board’s motion.
Much like sailing yachts there is still a large number of design constraints that need to be balanced to develop a successful SUP board.
- Venue – a board optimized for big wave surfing in Hawaii is going to be completely different to one targeted at flat water estuary races. Even in flat water races you need to deal with elements like slop and drafting from other competitors. If there is even a small portion of downwind work with the waves, then the ability to easily surf can be worth huge margins.
- Stability – all other parameters ( like hull radius, rocker etc) being equal, a narrower board has less wetted surface and will be faster. That advantage is lost if you either get other parameters wrong ( like hull radius, rocker etc) or you end up swimming too much!.. so the stability 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 cross-wind can knock the bow off course, requiring the paddler to expend energy to compensate. Therefore cross wind air flow in part dictated the bow profile. An appropriately sized and positioned fin is essential for directional and roll stability, and significant attention was given to the treatment of the high drag area of the fin box .
- Maneuvering – most races require turns around buoys, and this is certainly an influence on the design. For the most popular racing classes -14’ & 12’6”, the paddler needs to be able to shift weight aft, lift the bow out of the water and minimize the turn radius.
FARR YACHT DESIGN, F14 DESIGNER
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 curve and rail hardness. This was wired to automatically mesh the designs and run the boards in Fine/Marine software that shows us hydrodynamic force predictions. Over 100 designs were created in this way with the final design shape having an advantage of 18 percent over the original reference shape.
Of course these computer models only give a partial insight into the critical design drivers. Before moving to production, we built three full scale prototypes with further shape optimisation between each board before the plug and molds were built.
The lamination schedule and internal framing was perfected in the pre-production boards with the designers and builders working closely together. The production board is available with a range of standard and custom finishes.
How does the actual stability stack up against other boards in the market place?
Are there particular sea conditions that the 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 and provided important design input that was rolled into the final design.
Relative to the initial prototypes we added more volume throughout. The rail radius was tightened slightly aft and the beam increased slightly to achieve our target stability. Volume was added in the tail to provide additional buoyancy for buoy turns and a female mould constructed and a hollow carbon construction adopted to provide an exceptionally stiff, robust but weight efficient platform with optimized surface finish.
The final board is 14 feet long, 26.5” inches wide, with a fine entry and sleek profile. The rocker curve is a result of the target volume distribution that achieves the lowest possible wave drag and minimizes wetted surface to give an exceptionally smooth drag curve allowing the board to easily accelerate to hull speed and gives exceptional gliding performance. It also provides a good planing surface for paddling downwind in waves as well as allowing the paddler to minimize wetted surface area by shifting their stance slightly forward in calm conditions. We prioritized the shape to have the desired combination of low wetted surface and low wave drag while still having enough shape to the rocker curve to maximize gains when paddling in waves.
Unlike many boards, our designs maintain fullness through to the knuckle so that “effective” waterline length is maintained when paddling in chop but not so much that the board will trip over its own bow. We wanted to create shapes where the paddler can change how the board responds to different conditions by slight shifts in his or her position. The fine entry and additional rocker in the forebody will provide dynamic lift when surfing in waves but will not carry the same wetted surface penalty.
The wave piercing bow is probably the most distinctive feature of the board compared to many of the latest models. A full bow will be “excited” by the wave encounters (running into the back face of the wave in front). This will slow the board, requiring more energy to get up on the next wave. The wave piercing bow penetrates the wave in front without being dramatically excited and incurring a big drag penalty. It then relies on the buoyancy and shape of the rocker curve in the forward sections to lift the bow up before it begins to dig in. This, combined with a subtle peak along the centerline of the deck, allows the bow to quickly shed water and return to the surface. It’s a fine balancing act to get all aspects to work well together.
Hard, almost chine-like rails, are a common feature on many boards. This is one way to maximize stability for the lowest possible wetted surface area but this does not account for the drag associated with the vortices shed from the corners. Our shape, with much more gradual rails, reflects our flow analysis in this area, in an effort to find the right balance between wetted area, stability and total drag. Given the requirement to be able to complete mark turns, the rails harden significantly in the aft portion of the board.
The Horizon F14 hollow carbon board is being manufactured in the UK by carbon specialists, Solent Boatworks, who have been very involved in the development of the prototypes and the production build process as a whole. The board has already shown its pace in the UK Nationals winning a division in the 14-foot class and interest in the board has been substantial on both sides of the Atlantic.
The Horizon F14 is built to order, with a bespoke range of colour finishes, to complement the panels of clear coat carbon which highlight the build quality.