According to MAN Diesel Fredrikshavn, Denmark, changing the propulsion equipment of a vessel can make a substantial difference in bollard pull, speed and overall efficiency. In a conversion they carried out toward the end of last year on a Danish trawler, bollard pull was increased by a huge 23.5 per cent and fuel consumption reduced by around 12 per cent. Pointing out that propeller and nozzle designs have improved considerably over the years, they suggest that propellers and nozzles more than ten years old can benefit from an upgrade.
In the vessel tested, the 1986 Danish launched F/V Jette Kristine is powered by an eight cylinder four stroke MAN 8L23/30-D diesel engine rated at 1080 kW (1470 hp) at 825 rpm and drives a 2650 mm (104 in) diameter propeller via a reduction gear ratio of 3.8:1. In the test only the propeller and nozzle were changed: the nozzle is a double-curved type on both inner and outer diameter. The engine, reduction gear and test conditions were identical for the before and after harbor measurements. Later, after two sea trials, including actual trawling even better results were reported, according to the skipper of the vessel, he recorded a 0.5 kt speed increase and 15 per cent reduction in fuel consumption. Furthermore noise levels in the saloon and cabins were noticeably quieter adding to the comfort of the crew.
Posted by: Keith Henderson, Editor – Maritime Professional