Anemoi Marine Technologies and Nantong Cosco Khi Ship Engineering Co. Ltd. (NACKS) have received Approval in Principle (AiP) from ClassNK for two rotor sail integration designs for Ultramax bulk carriers.

The approval covers wind-assisted propulsion system (WAPS) arrangements for 60,000-65,000 deadweight tonnage (DWT) vessels. Both configurations use Anemoi’s latest-generation rotor sail design, measuring 3.5 metres in diameter and 24.5 metres in height, offering a larger sail area than the company’s pilot Ultramax installation in 2018.

One design places a single rotor sail on the forecastle deck, while the other uses a longitudinal rail system to deploy three sails on the upper deck. According to the companies, the two arrangements are intended to suit a range of common operational requirements for Ultramax vessels.

Nick Contopoulos, chief commercial officer of Anemoi, remarked: “Ultramax vessels have been early adopters of WAPS technology, going back to Anemoi’s installation on the world’s first bulk carrier with Rotor Sails in 2018, the M/V Afros, and the AiP represents an opportunity to apply all those lessons to optimise installations for maximum efficiency on our generation 3 products.”

Anemoi said the project strengthens its cooperation with Cosco-owned shipbuilder NACKS and broadens its reach in Chinese yards, where bulk-carrier newbuilding activity has grown significantly in recent years.

The AiP confirms the feasibility of the concept designs under ClassNK’s guidelines for wind-assisted propulsion systems. The assessment covered sail particulars and arrangement, foundation and supporting structures, initial trim and stability calculations, fire and safety arrangements, and energy efficiency calculations under the International Maritime Organization’s Energy Efficient Design Index (EEDI) framework.