Adjustable Fins Replace the Rudder.

Inside his Västervik workshop, Swedish solo sailor Sven Yrvind inspects a scale hull model to evaluate an unconventional steering system. Rather than installing a traditional stern rudder, the design relies on twin lateral foils fitted along the hull. As Yrvind explains, “So, the plan is to use fins instead of rudder.” The submerged foils are configured to serve multiple roles, stabilizing the double-ender while running before heavy following seas and providing directional steering force as their immersion changes.

The lateral foils operate in conjunction with a dedicated bow daggerboard. By adjusting foil immersion alongside the forward centerboard, the hull balance shifts dynamically to meet varying sea states. Modern offshore cruisers typically rely on electronic autopilots or windvanes, but Yrvind discards both systems in favor of foil and sail balance. Reflecting on his early voyages, he notes, “When I started in the ’60s, those things were very expensive and autopilots didn’t exist for small boats.”

Reversible Fin Angles and Hull Balance

To adjust the steering foil angle without mechanical complication, Yrvind developed a simplified mounting system. “This is just a two-dimensional thing. So, what you do, you lift it up like a gate, and then you turn it, and you put it down on the other side.” Once adjusted, the foil angle allows the 5.6-meter cruiser to track cleanly through head seas rather than drifting off course.

Adjusting fin angles is central to Yrvind’s planned voyage toward Dunedin, New Zealand. Near the equator, adverse headwinds and counter currents demand close-winded performance. He recalls an earlier passage from Ireland to Newfoundland where a small boat faced 11 days of continuous gale conditions. By fine-tuning lateral resistance, the craft could reach forward against head seas toward coordinates 60 and 89.

Workshop Fairing and Hull Assembly

With the desktop model verified, workshop focus turns to the full-size hull. Built from Divinycell foam core and NM-epoxy sandwich laminate, the cruiser spans a beam of 1.45 meters and carries a three-masted lugger rig totaling 9 square meters of sail. Yrvind sets up framing blocks along the hull bottom to confirm fair curvature across the laminate before bonding. Acknowledging the experimental nature of the steering foils, he admits, “Will it work? Oh, I don’t know. It’s a long shot.” After sighting down the hull line, he concludes, “Check the fairness. Oh. Looks good to me.”

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