Making Rudder Moulds from an America’s Cup Foil
The Valencia rudder build started with a stroke of luck. Rather than designing a foil profile from scratch, Shayne had access to something better — a rudder blade from the Spanish Ibedrola team’s 2007 America’s Cup campaign. Bright green, a proper grand prix foil, sitting in storage. The hydrodynamics in that blade represent a level of R&D that no cruising refit budget gets near. Using it as a plug to pull moulds meant inheriting world class foil geometry for the cost of materials and Kent’s time.
The Moulds
Kent handled the mould work. He’s a professional boatbuilder who has worked on Alinghi America’s Cup campaigns and builds high end racing yachts — the kind of person you want doing this. The release system was Teflon rather than traditional wax. Teflon release leaves a flawless surface on the inside of the mould with nothing transferred to it — every blade that comes out has a perfect outer skin straight from the tool, no post-mould polishing needed.
The mould itself was built up with polyester and chopped glass, with MDF flanges to keep everything flat and stiff enough to work from. Once released from the AC rudder the surface finish was exactly what they needed — clean, sharp, ready to use.
The Blade Construction
The rudder blades are built as a composite sandwich. Foam core with slits cut into it so it conforms to the mould shape, glassed over and weighted into place while it cures. At the base of each blade Shayne integrated a solid fibreglass insert — a deliberate design decision that will become clear shortly.
Paikea’s original stocks were reused. The port stock was the original Catana hollow stock that had been on the boat since new. The starboard stock was the solid SS replacement that came with the non-original blade — it had turned out to be the better of the two. New blades, existing stocks, properly sealed this time.
One adjustment mid-build: Shayne had planned to trim the rudder stocks and also planned not to — and cut them before catching the conflict. It meant rethinking the foam layout but Kent adapted the approach and it didn’t affect the finished blade. Real boatbuilding.
The Discovery
While planning winglets for the rudder tips something turned up in the workshop that changed the project. Tucked away were the original winglets from the bulbs of the 2007 America’s Cup yachts — the same campaign the rudder plug came from.
These winglets were designed to control tip vortices on the keel bulbs. That’s exactly what Shayne needed them to do on the rudder tips — stop low pressure bleeding from one face of the rudder around the tip to the other, which effectively makes a shorter rudder perform like a longer one. The solid fibreglass insert at the base of each blade was designed specifically to accept these winglets, bolted on at an adjustable angle of attack so the geometry can be tuned.
The winglets aren’t a straight wing — they have a curl at the tip, which makes pulling moulds from them more complex. They’re also handed, port and starboard, which means two separate moulds. More work, but Shayne planned to keep the moulds because the winglets are vulnerable and replacements will be needed.
Anna’s reaction on camera when she saw what they’d found — and what it would look like on the boat — is worth watching.
What Came Next
These blades went on Paikea in Valencia and stayed on through the Atlantic crossing — including the passage where the port stock failed mid-ocean and the blade was lost. The stocks from this build were visually inspected in Barcelona after the crossing. The starboard stock, the solid one, was reused again for the final rudder build in Valencia. The hollow port stock was not.
The winglets from the 2007 AC bulbs were never installed on these blades. That project evolved — Shayne eventually designed his own winglet geometry and had it 3D printed. The file is available to members.
Want to go deeper?
The full rudder series — design, build, winglets, and what we learned losing one mid-Atlantic — is documented in detail on the free resources page. If you want the technical detail behind the build, the members hub has the engineering deep dive including our forensic analysis of the failed stock and Shayne’s new rudder design from scratch.
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