Carbon vs. Fiberglass: Building for Performance and Reliability
People ask often enough why some parts of Paikea are carbon and others are plain fiberglass — the rudder blade being the clearest example. The honest answer isn’t glamorous: it comes down to fit for purpose, what was actually available in the Caribbean at the time, and a fair bit of pragmatic engineering under real time pressure.
Carbon Where It Counts, Glass Where It Doesn’t
The tiller arm assembly back in the engine room is a good place to start, since it’s not all carbon even though it looks like it at a glance. It’s built as a cored, sandwich-style structure — carbon skins on the outside, with fiberglass making up the core in between. That’s a deliberate choice, not a compromise: the middle of a structural section, sitting close to the neutral axis, doesn’t need to be stiff or strong the way the outer skins do. Fiberglass there does the job perfectly well, and it’s cheaper and far easier to source than carbon when you’re working out of the Caribbean with a limited stock on hand.
The original plan for this assembly was actually more ambitious: fully isolating the steering system from the rudder electrically, to avoid an electrolysis path running from the hydraulic system, through the metal ram, into a fully conductive carbon tiller extension, and out into the water. In the end, time won that argument — the departure deadline for the Atlantic crossing arrived before that isolation work could be finished properly, and the tiller arm went on as a full carbon wrap instead. Stiffness needed to come from somewhere given the tight geometry around that clamp flange, and carbon was the fastest way to get there without redesigning the whole part under pressure.
Why Electrolysis Isn’t the Problem It Sounds Like
Skipping full isolation on the tiller arm doesn’t mean ignoring the issue entirely. The rudder blade itself is fully skinned in fiberglass, so the only points of contact with the water are the stainless bearing shell and whatever section of the stock sits below it — both isolated fairly easily where they meet carbon, by grinding the carbon back at the fitting and running a fiberglass plate through instead.
Fiberglass earns its name here, literally: E-glass stands for electrical glass, developed originally for the electrical industry precisely because it’s such an effective insulator. That’s also why it’s priced the way it is — high-volume industrial demand keeps the cost down for boatbuilders who benefit from the same property for a completely different reason.
Building the Blade in Glass, Not Carbon
The rudder blade itself came out fully fiberglass rather than carbon, and the reasoning was straightforward: not enough carbon on hand to do it any other way, and no realistic way to source more in a reasonable timeframe. Fit for purpose again — fiberglass does the job well, and the boat had already proven that crossing an ocean without drama.
Choosing a Stock: Aluminum, Stainless, or Carbon
The rudder stock was a genuinely open question, and every real option got considered rather than defaulting to carbon on instinct. Aluminum dropped out first — bearing wear against aluminum stocks is a known issue on other boats, and even with more electrolysis-resistant grades available, it wasn’t worth the risk.
That left stainless steel and carbon fiber, priced almost identically once the right stainless grade was factored in. The deciding difference wasn’t cost — it was bonding. Resin doesn’t bond well to stainless steel at all, even with the best structural adhesives available, which is exactly why metal rudder stocks typically need large tabs protruding into the blade: the tab is doing mechanical work that the glue bond alone can’t. Most production rudders compound the problem by using cheap urethane foam cores instead of proper structural PVC foam, meaning the tab-to-glue-bond ratio ends up doing even more of the load-bearing work than it should.
Carbon changes that equation completely. A carbon stock bonds directly into the same structure as the blade’s skins, which means the connection between stock and blade isn’t really a torque tab in the traditional sense at all — it’s closer to a proper shear connection, since the carbon tube is transferring torque through a genuine structural bond rather than relying on a mechanical tab hanging off the back of a stock that can’t otherwise stick to anything.
Testing It the Hard Way
The real test came without planning for it: time ran out before a second new rudder could be built, so the Atlantic crossing happened with a genuinely asymmetric setup — one older carbon-stocked rudder built in Valencia, one newly built in the Caribbean. The performance difference between the two was noticeable, and both held up without issue the entire way across.
Back in Spain, For Now
The plan heading into this stretch had been a proper refit in Trinidad — chainplates, rudders, blown windows, and the interior all queued up. That plan changed with a phone call: an offer to run rig and systems on an America’s Cup campaign, which meant packing up and heading back to Spain instead. It’s not the path either of us expected this season to take, but the trickle-down from working at that level — foil sections, systems thinking, reliability under real load — is exactly the kind of knowledge worth bringing back to a cruising boat once the dust settles.
This post is part of a Series
To understand the entire rudder project on Paikea, visit Paikea’s Rudders: The Full Story on our Free Resources page.
In the Members Library
For the deeper technical breakdown of the shear-connection versus torque-tab reasoning covered here, see Composite Rudder Evolution and Design in the Members area.