Lloyd’s Register (LR) has granted Approval in Principle (AiP) to Rondal for its Aero Wing Sail, a rigid wing-sail concept developed to deliver wind-assisted propulsion for large yachts and multihull platforms. The AiP was awarded during a ceremony at Metstrade 2025 in Amsterdam, following LR’s completion of a concept-level assessment carried out in accordance with its 2025 Guidance Notes on Wind-Assisted Propulsion Systems.

The approval confirms that the Aero Wing Sail has undergone a detailed review covering safety, structural integrity, aerodynamics and mechanical-system performance. LR’s assessment included CFD analysis, structural design evaluation and risk identification related to integration and operation. Moreover, Lloyd’s Register has also provided recommendations to support further refinement as the technology moves toward commercial deployment.

The Aero Wing Sail is an innovative rigid-wing system designed to harness wind power as a sustainable propulsion source. The design prioritises ease of use and integration, offering automated control that allows a vessel to be under sail within around 10 seconds. Unlike a conventional rig, the wing requires no stays, lines, or winches, reducing maintenance demands and eliminating the need for sail replacement.

According to Rondal, the system can deliver a lift coefficient of up to 3.1 and a lift-to-drag ratio of 20, while retaining a notable lift coefficient of 1.8, thereby enabling meaningful reductions in fuel consumption. The company also notes that the Aero Wing Sail increases vessel range without using interior volume and provides greater autonomy by reducing reliance on port-side fuel infrastructure.

Tom Wolodarsky, senior surveyor and lead specialist WASP at LR, said: "This Approval in Principle reflects Lloyd's Register's commitment to enabling innovative technologies that support decarbonisation and operational efficiency. Wind-assisted propulsion is a vital step toward reducing emissions, and we are proud to collaborate with Rondal in bringing this solution closer to market readiness."

Hermen de Jong, innovation manager at Rondal, commented: "This Approval in Principle is an important achievement for Rondal. It demonstrates the maturity of the Aero Wing Sail and that we are ready for application in new yacht projects."

The AiP reflects LR’s ongoing commitment to advancing wind-assisted propulsion technologies. Additional analysis on deployment and retrofit considerations is available in LR’s report Applying Wind-Assisted Propulsion to Ships, part of its wider Retrofit Research Programme.