By using rotor apparatus torque, measurements on rotating cylinders with and without coatings have been done, and roughness function ∆u/uτ has been evaluated. Drag measurements in the rotor cylinders are carried out using differential length technique (40, 80 mm) to avoid the end effects of the cylinders. In these study three kinds of coatings that are suggested for use in marine industry is evaluated: 1) Self polishing systems with tin compounds as a biocide containing 2) seal coat systems as a fiber system and 3) Silicon elastomers systems as a biocide free and non-stick system. The results of experiments have been shown that the coefficient friction related to silicone elastomer coatings is lower than two others. The experiments demonstrated that the Foul Release systems exhibit between 9 and 20% less frictional resistance than the Tin-free SPC system. The difference resistance has been related to the respective differences in roughness. In comparison with two systems silicon coatings have been shown better results in reduction of frictional drag
in downward shift of the velocity distribution.