If you’ve been following along, you’ll know that losing a rudder mid-Atlantic and building a replacement at anchor in the Caribbean was not the plan. But it did give Shayne something invaluable: a reason to design the right rudders for Paikea from scratch, with real data to work from.
This post walks through the design process — the hydrodynamics, the 3D modelling, the decisions behind the new foil section, and why the winglets you might have expected to see aren’t going on straight away. The video above covers the highlights. If you want the full in-depth version, that’s over on the members section of the site.
It Started With Bubbles
Before the design work, there was a moment that made the whole project worthwhile. Sailing upwind in 14–16 knots, we caught underwater footage of what was happening at the rudders — and what we saw was extraordinary. Bubbles. Lots of them. Streaming off the blade in a way that told Shayne, immediately, more than years of number-crunching could.
For a designer who spends enormous amounts of time trying to get the criteria right for rudder design, real-world footage like that is gold. It fed directly into the decisions that followed.
Designing the Foil Section
The first job was designing a new aerofoil section — the cross-sectional profile of the blade. Shayne didn’t pull one off a shelf. He designed his own, using historical data collected from Paikea over years of sailing: what speeds the rudder sees, what angles of attack it operates at, how the loads are distributed. That data defined the parameters.
For reference points, Shayne looked at a number of known profiles — the EPL E836, the NACA 63012 (a laminar flow section that he describes as a bad rudder section, useful mainly as a guide for where not to go), and the well-known NACA 0012. The section he ended up with is close to the NACA 0012 in character, but with specific tweaks to improve performance within the tolerance zones that Paikea’s data showed the rudder actually operates in. The historical data is what made those tweaks possible — without knowing precisely what the rudder sees in real sailing conditions, you’re guessing.
From 2D to 3D
Once the 2D aerofoil section was right, the work moved into 3D analysis. This is where things like aspect ratio, taper ratio, tip shape, and load distribution come into play — all the factors that a 2D section analysis can’t capture.
One point worth clarifying here, because it’s widely misunderstood: the goal is an elliptical load distribution, not an elliptical planform. A rectangular or tapered rudder can be just as efficient as an elliptical one — what matters is how the lift is distributed along the span, not the outline shape. A lot of sailing commentary gets this wrong.
In the 3D analysis, Shayne modelled three rudders side by side for comparison: the original rudder designed with the boat by Lock Crowther, the Valencia-built rudder using the AC moulds, and the new design. The results showed a meaningful step up in efficiency with the new design — better lift-to-drag ratios across the operating range.
The Winglet Question
The new rudder design includes provision for winglets at the tip — inserts built into the blade so they can be added later. But they’re not going on straight away, and the data shows why.
Winglets reduce tip vortex losses and effectively extend the working span of the blade. In the right conditions they improve efficiency. But the key question is: at what angle of attack does your rudder actually operate?
Shayne’s data shows that Paikea’s rudders spend most of their time at two to three degrees angle of attack — lower than the five degrees where winglets start to show a clear advantage. At those lower angles, the new rudder without winglets is actually more efficient than the same rudder with them. The crossover point — where winglets become worthwhile — sits around three to four degrees for Paikea at typical sailing speeds. Close, but not enough to justify the additional complexity right now.
There are other potential gains from winglets, including reduced pitching, and the option is built in for the future. But for now, the cleaner blade is the faster blade for the way this boat actually sails.
The Structural Design
Once the hydrodynamics were resolved, the work moved into 3D modelling for fabrication — translating the foil design into something that could actually be built.
This meant modelling the existing bearing housings in the boat, designing the blade geometry for hand-shaping (CNC would have been preferable, but that wasn’t an option in the Caribbean), and specifying the carbon stock that C-Tech in New Zealand would build. The stocks were designed with stainless steel shells bonded on, so that in future the existing nylon bearings can be upgraded to Scheffer self-aligning roller bearings without having to replace the whole stock assembly. Future-proofing built into the design from the start.
From the 3D model, full engineering drawings were produced — blade geometry, laminate specifications, carbon fibre orientations, and machining details for the stainless shells. Those drawings went to C-Tech for the stock build and guided the blade construction in Antigua.
Want More Detail?
Explore our The Full Story of Paikea’s Rudders
This post covers the overview. The full in-depth version — including Shayne’s complete foil analysis, the CFD results, and the design drawings — is on the members section of the site.
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