Experimental Quantification of Drag Change of Commercial Coatings Under the Effect of Surface Roughness and Soft Fouling
Conference contribution, 2018
The performance of ships will be adversely affected by the excessive hull roughness to an extent where financial penalties will be incurred. It is beyond the bounds of possibility to achieve a perfectly smooth hull, as the ship building process and paint application will leave their “fingerprint” on the surface. The roughness of the hull may vary from fine to coarse according to the substrate finish, the coating application methods used and further driven due to exposure to aggressive sea environment.
The drag performance data of newly-applied and clean coatings is not sufficient to fully reflect the drag characteristics and efficacy of marine coatings over a typical period between dry-docking. Usually during this period, the increase in surface roughness and development of different fouling stages on marine coatings occur. Therefore, the study focuses on comparison of drag characteristics of hull coatings with relatively smooth, coarse roughness finishes and fouling conditions using time- and cost-efficient approach. The study describes experimental tests carried out to quantify the drag change of commercial coatings due to the presence of physical and biological roughness. Firstly, biocidal and non-biocidal coatings with relatively smooth and coarse roughness finishes are tested. Secondly, mentioned coating types and roughness ranges are exposed to fouling growth to explore the extend of algae fouling and its effect on drag characteristics. The results of the study may be useful to estimate the added drag and overall fuel penalty for ships with various coating roughness ranges and soft fouling.