SL 33 Information, Review, Specs

Sailing Performance & Handling

The sailing characteristics of the SL 33 are defined by extreme acceleration and a sensitivity to trim that borders on the aeronautical. With a Displacement/Length (D/L) ratio of approximately 20, it sits firmly in the "ultra-light racer" category. The original design featured curved C-foils (daggerboards) providing significant vertical lift to reduce drag and increase speed in light air, though it was not initially a full "flight" platform. According to editorial tests by Sail-World, the boat was specifically optimized for light-air performance (under 15 knots), where its high power-to-weight ratio allows it to outpace almost any other multihull of its size.

As the class evolved, the SL 33 transitioned into a fully foiling one-design. These "Turbo" versions utilize asymmetric L-foils and T-foil rudders, allowing the hulls to leave the water entirely at speeds as low as 17–18 knots. Handling at these speeds (often exceeding 30 knots) requires an elite four-to-five-person crew and a dedicated "flight controller" to manage foil rake and ride height. Owner anecdotes describe the experience as "riding a raging bull," with G-forces during downwind maneuvers being significantly higher than those found on traditional displacement catamarans.

Popular Mentions & Media

The SL 33's cultural footprint is inextricably linked to the America's Cup. It was the primary test bed for the foiling revolution that changed the face of the sport in 2013. ETNZ famously used their SL 33s to secretly develop the foiling geometry that would later be scaled up for the AC72. Notable owners include Mike Sanderson, a two-time Volvo Ocean Race winner and World Sailor of the Year, who campaigned the foiling SL 33 Stratis in Auckland. The boat has been featured extensively in Catsailingnews and various grand-prix racing journals as the "genesis" for the modern foiling era.

Known Issues & Buyer’s Checklist

Prospective buyers of a used SL 33 must approach the vessel with the mindset of an aircraft inspector rather than a traditional boat owner.

• Carbon Delamination & Slamming Damage: Because these boats are pushed to the absolute limit, the bow sections and longitudinal stringers are prone to fatigue or delamination from high-speed slamming. Inspectors should use ultrasound or "tap testing" on the hulls, especially forward of the main beam.
• Foil Trunk Integrity: The massive loads generated by foiling (particularly in converted models) put immense stress on the daggerboard trunks. Check for stress cracks around the hull-to-trunk joins and ensure the foil rake adjustment mechanisms are not seized or eccentric.
• Rigging and Chainplates: The 16-meter rotating carbon wing mast places significant point loads on the chainplates. These areas should be inspected for signs of electrolysis or hairline fractures in the carbon laminate.
• Nomex Core Moisture: While the Nomex honeycomb core is incredibly light, any puncture in the carbon skin can lead to water ingress. A moisture meter is essential to ensure the core remains dry and the structural integrity of the "sandwich" is intact.

Community & Resources

The primary technical authority for the class remains the designers at Morrelli & Melvin, who maintain archives on the boat’s evolution from curved-board racer to full foiler. While no formal owner association website remains active for the class today, technical discussions and maintenance logs are frequently updated within the high-performance multihull sections of major sailing forums and through specialized composite repair shops in New Zealand and Germany that originally serviced the ETNZ and Luna Rossa fleets.

The Verdict

The SL 33 is a historic, high-adrenaline platform that offers America’s Cup-level technology for a fraction of the original development cost. It is not a boat for the casual weekend sailor, but for a professional-grade team, it remains one of the most exciting tools for mastering the art of foiling.

Pros:

• Blistering speed; capable of 30+ knots.
• Elite pedigree as an America’s Cup development platform.
• Advanced carbon/Nomex construction provides incredible stiffness.
• Highly responsive and rewarding for skilled crews.

Cons:

• High maintenance; requires specialized composite knowledge.
• Physically demanding and potentially dangerous in high winds.
• Unforgiving of handling errors, with a high risk of capsize or "pitch-pole."
• No interior or creature comforts; strictly a day-racing machine.