Propeller surface finish
A propeller surface finish has big effect on fuel consumption. A surface finish of 70 microRa will add over 4.5 per cent to the fuel consumption bill compared with one of 10 microRa. A super-smooth surface (1 microRa or better) is inhospitable to marine organisms as well as beneficial to the efficiency of the propeller. Most propellers have a finish between 2 microRa and the 6 microRa laid down in the ISO specification.
It is desirable and cost effective to polish the entire surface of the propeller blades, but 75% of the benefit is obtained by polishing the outer half and leading edges of the blades. UMC International has introduced an underwater polishing technique to produce the surface finish of 0.5 microRa.