An experimental study was carried out to compare the drag characteristics of a tin-free self-polishing co-polymer (SPC) and a foul release coating. Rotor measurements were carried out using different cylinders coated with both paint types. The experiments showed that the frictional resistance for the foul release test cylinders was lower than for the tin-free SPC cylinders. The drag characteristics were related to the roughness parameters of the tested surfaces measured with an optical measurement system. The measurements indicated that the texture of the foul release surface was significantly different from SPC systems. The findings show that the drag of a foul release coating will only correlate with a characteristic roughness measure that takes both the amplitude and the texture of the surface into account, and that is calculated at bandwidth parameters which depend on the degree of roughness.

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Turbulent boundary-layer measurements have been carried out on flat surfaces coated with two different new generation marine antifoulings. The coatings were applied on 1-m-long test sections that were fitted in a 2.1-m-long flat plate setup. The measurements were carried out in two different recirculating water tunnels by means of two-component laser Doppler velocimetry and were compared with measurements of a smooth steel reference surface and a surface covered with sand grit. Both coatings exhibited an increase in frictional resistance compared to the reference surface, but the increase was significantly smaller for the Foul(ing) Release coatings than for the Tin-free SPC coating. The coatings did not significantly affect the boundary-layer thickness. When expressed in inner variables, the coatings did not have an effect on the turbulence intensity profiles, but when expressed in outer variables, the coatings affected the near-wall turbulence intensities.

Due to the phase-out of TBT-SPCs imposed by the International Maritime Organization, new-generation antifoulings are set to replace 80% of the existing antifouling market. Two types of coatings are claimed to offer satisfactory performance over five years: tin-free SPCs and foul-release coatings, which were both commercially introduced in the mid 1990s. This paper gives an overview of the research at the University of Newcastle upon Tyne which compares the drag, boundary-layer and roughness characteristics of both coatings when newly applied. It was found that foul-release coatings offer less drag than tin-free SPC, by an amount which depends on the quality of application and which has been related to the respective differences in roughness characteristics. Assessments have shown that foul-release surfaces are very effective against macrofouling organisms, but that the surface is covered by slime films when the vessel returns to drydock. A literature review on the effect of slime films on ship resistance shows that slime films have a significant effect on drag, but in turbulent flows the effect is likely to remain limited because of detachment processes. Further research is underway to investigate this.

The maneuvering characteristics are highly affected by the under‐keel clearance. In shallow water, the results of standard maneuvers reveal a decreased maneuverability and an increased straight‐line stability. This modified behavior is mainly to be ascribed to the modified flow around the hull, but also the control forces exerted by rudder and propeller are different compared to the deep‐water case. Besides the effect of vertical limitations, a ship navigating parallel to the horizontal boundaries of navigation areas will also experience the so‐called bank effects, that is, disturbing forces and moments due to the asymmetry of the flow around the hull. In some harbors and their approach channels, the bottom is covered with a layer of fluid mud. This not only complicates bottom survey, but also affects a ship's propulsive performance and maneuvering due to the specific rheological properties of the mud layer and to the generation of internal waves in the interface between water and mud. Finally, different types of hydrodynamic interaction between ships may take place in restricted waters, due to encountering and overtaking maneuvers, the effect of passing ships on moored vessels, lightering operations, and ship–tug interactions.