Flexibility in Ship Design: Off-Seasonal Utilization of Purse Seiner/Trawlers
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- Institutt for marin teknikk 
Due to overcapacity in the Norwegian purse seiner/trawler fleet, statistics show that the vessels have been idle for an average of 192 days each, the period 2006-2012. As the vessels and crew are highly regarded in shipping for their qualities and skills, there has been a increasing trend of the use of purse seiner/trawlers in unconventional operations. Despite the increasing trend, the vessel design has not been radically changed to fit the purpose. In this thesis, this trend was studied with the purpose of developing a design optimized for utilizing the vessels in off-season. The thesis investigates four additional markets, for which the requirements and challenges by hiring a purse seiner/trawler have been evaluated. The method used to compare the alternatives is by weighted grading with parameters such as profitability, regulations and technical implementation complexity. The four market segments were PSV, oil recovery, survey, research and live fish carriers.The evaluation of the markets showed that a purse seiner/trawler was most feasible to be combined with survey operations, and secondly research. The two scored satisfactorily in terms of technical implementation as well as regulation requirements, while survey surpassed research in terms of profitability. Due to the similarities in the research and survey vessel segments, the segments were merged into one for the development of a concept design to increase the size of the potential market, and thus increase the opportunities for charters. Further on, a concept design was developed for a purse seiner/trawler to be utilized in research and survey operations during off-season. This included establishing design criteria, by the basis of the state of the art as well as regulatory requirements and interviews from relevant market players. The concept vessel was designed with an increased cabin capacity, deck area and multi-purpose spaces dedicated for research/survey use. Additionally, a false keel was installed as well as transverse thrusters to increase the dynamic positioning capability and attain the DP1 certification. The vessel will also need to obtain certification as a cargo vessel, including load line certification. An evaluation of the concept design versus the state of the art indicates that it will not enable all functionality of the research and survey vessels, although it will increase the functionality compared to the existing purse seiner/trawlers engaged in such operations. This is enabled through a more flexible deck arrangement, increased cabin capacity and larger dynamic positioning capabilities. Still, it is recommended that an investment study is done to incorporate the capital expenditure and operating cost in the decision making analysis, caused by the additional steel and equipment due to the off-seasonal utilization.