الفهرس 
chapter 1Only 14 pages are availabe for public view
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Abstract
Tug boats are distinguished than other ships in shape and high power, their features, different propulsion systems besides the main dimensions as well as girting stability and sea-tug relation are dealt with. Different propulsion system was dealt with in details regarding its working theory, construction, performance, maintenance and merits. A special attention was paid to the ducted propeller other than propeller types for the advantages of the duct in protection and increasing the propeller thrust. For this reason the characteristics of airfoil sections used in these nozzles was studied. A proposed method was deduced and validated successfully according to NACA laboratorial work on airfoil sections through applying wing section and linear lifting line theories in the ideal flow, and then the method was applied on both MARIN standard and the other new nozzles to find the most efficient one and then was applied on two tug boat propellers by replacing the standard their MARIN standard nozzles with the new nozzles to get the increase in propeller thrust and bollard pull due to each nozzle.