A study on the design of nozzle propeller for trawler

Trawlers have to a sufficient towing force due to its characteristics of the high performance. The newlyconstructed trawler with the conventional propellers shows the sufficient towing force, so that the propellerand engine are optimized. In the 1970s, many trawlers were imported from overseas by Korean fisheriesindustries. But the engine output degradation with year by year caused the trawlers to decrease the towingspeed of the vessels. On the previous studies, the nozzle propeller had not so good efficiency with increasingof resistance in high-speed cruising operation over 15knots. But the trawling operation is just required thehigher thrust and towing force, so that the nozzle propeller is very profitable for the its effectiveness. A newnozzle propeller was designed for the 4,462G/T trawler, Dong-San, operated by Dongwon Industries Co.,Ltd. to improve the towing speed, and the model tests were performed. The model ship and model propellerare preciously manufactured and used model tests in basin. The resistance test and propeller open water testwere performed for the cases of the half and full loads. The required engine horse power and RPM wereevaluated analytically by the speed-power curve, when the trawler was equipped with the nozzle propeller.The results of tests showed that the towing speed 4.85knots on the design load waterline requires the 200engine RPM and 2,567ps in the delivered horsepower.Key words : Trawler, Ducted propeller(Kort nozzle propeller), Design