ABS reviews bound4blue's Pwind method, easing the compliance case for wind propulsion

A review of the method, not just the sail

Wind propulsion specialist bound4blue has secured an ABS review of the methodology it uses to build the force matrix behind its Pwind values — the figures that quantify how much thrust its eSAIL suction sails deliver. According to Cyprus Shipping News and MarineLink, the review covers how the company generates the aerodynamic polars that feed those calculations, and adds to a growing set of classification-society assessments of its approach.

The methodology combines RANS-based computational fluid dynamics (CFD) with wind-tunnel-validated tools to produce vessel-specific force matrices, accounting for both sail-to-sail and ship-to-sail aerodynamic interactions. Because it avoids expensive, time-consuming full-scale testing, it aims to deliver both confidence and speed. ABS said it assessed the method against applicable IMO regulations and ITTC guidelines.

Turning wind into a countable compliance benefit

The practical value is regulatory. Verified Pwind values can be used within EEDI and EEXI calculations and help determine FuelEU Maritime’s Wind Reward Factor — so a credible, third-party-reviewed number lets owners count a wind installation toward compliance rather than leaving its benefit unquantified. bound4blue’s José Miguel Bermúdez said independent review from a class society such as ABS gives stakeholders confidence that the aerodynamic methodology is “robust, credible, and suitable for regulatory use,” while ABS’s Michael Kei framed the work as providing “a clear and consistent framework for evaluation of wind-assisted propulsion systems.”

The company says its eSAILs generate forward thrust up to seven times greater than conventional rigid sails of the same size, and that the mechanically simple, non-ATEX units suit tankers, bulkers, ro-ros, cruise vessels, ferries, gas carriers and general cargo ships. It reports installations on eleven ships with seven more on order, representing more than 50 eSAILs.

Apeks view — The news here is not the sail; it is the verification. Efficiency technology only scales in shipping when an independent class society signs off on how its benefit is measured — that is what turns a promising installation into a bankable, compliance-ready decision for owners, financiers and charterers. Wind-assisted propulsion has long had a credibility gap between vendor claims and audited performance. Third-party review of the calculation method is how that gap closes: in this industry, trust is earned with evidence, not asserted with brochures.