To further improve the design and operation of modern sailing cargo vessels, additional knowledge of the interaction between multiple sails in combination with the hull is needed. This study investigates the aerodynamic performance of a fully sailing car carrier through an experimental test campaign with a large, fully instrumented model of the complete ship at the Volvo Cars Wind Tunnel in Gothenburg. The ship design is based on the latest version of the Orcelle vessel deigned by Wallenius Marine,which is a 217 m long car-carrier, equipped with six two element wingsails. The campaign focuses on evaluating multiple sail trims under varying apparent wind angles and different hull configurations. All tests are done at a chord based Reynolds number of approximately 0.9 × 10⁶. The evaluation involves measuring the aerodynamic forces through individual force measurements for each wingsail, combined with the overall force generated by the integrated hull and wingsail system, all measured in six degrees of freedom. The results highlight the importance of the sail trim and demonstrate how hull design influences wingsail performance. For apparent wind angles below 30°, reduced flap angles, a slender bridge, and trimming strategies that maximize forward thrust while minimizing yaw moment are favorable. At apparent wind angles closer to 90°, larger flap angles are preferred, bridge design becomes less critical, and maximizing forward thrust remains the primary trimming objective.

The in-situ measurement of aerodynamic parameters on a boat evolving in natural conditions can be challenging. Nonetheless, the development of wind assistance and propulsion for cargo vessels calls for new methods to ensure the broadest possible evaluation of the aerodynamic interaction effects between the wind propulsion units and between the units and the hull. This paper proposes an experimental approach based on a scaled model of the Oceanbird concept car-carrier sailing at sea, in real conditions. A pressure measurement system was developed at KTH Royal Institute of Technology, which consists of 66 differential pressure sensors installed inside one of the four rigid wings. The capabilities and limitations of this sensor suite are explored in this article. With the implementation of specific experiments with the wings, we show that the system can detect stall and its hysteresis loop, as well as wing-wing and wing-hull interaction effects. The main limitation for the full aerodynamic characterisation of the boat comes from the lack of simultaneous measurement on all wings, which will be addressed in a second part of this paper. 

Reducing the impact of shipping on climate change is a must and new regulations try to enforce this. The technological development to allow for wind propulsion or wind assistance for ships are numerous and new methods need to be developed to ensure accurate performance prediction but also efficient and safe control of these ships. The interaction effects between the multiple wind propulsion units and the influence of the hull on the performance are still not well understood. The unsteady effects due to the fluctuating wind or the ship motion are seldom investigated and are also not fully understood. In this paper, we present experimental measurements of the aerodynamic performance of a 1:30 scaled model of a wind powered cargo vessel in real conditions, thus accounting for all interaction effects and unsteadiness of the wind. The results highlight the potential benefits of different trimming strategies, and also show the influence of unsteadiness on the aerodynamic coefficients and the overall performances.