Assessing fishing vessel operability under changing loads: a case study in the Java Sea

In this study, an operability assessment was conducted on three different sizes of the same fishing boat's hull form. The fishing boat initially had a length of 5 metres, which was then doubled to 10 metres and subsequently scaled up again to 20 metres. The investigation aimed to determine the extent to which changes in size influenced the percentage of operability in the Java Sea, the same region of operation. The assessment involved various loading conditions, a characteristic feature of fishing boats where displacements and centre of gravity constantly change during operations. The boat speed for each load case was adjusted to three conditions: departure, fishing activity, and arrival. After determining the percentage operability for each load case, a weighting factor based on the time spent in each loading condition was implemented to calculate a single percentage operability for a fishing boat. The results demonstrate that the initial size (L = 5 m) achieved a low percentage operability of 58.04%. The value increased to 67.75% when the boat size was doubled (L = 10 m), and the highest length (L = 20 m) achieved the highest value of 84.03%. Considering the frequent occurrence of high waves in the Java Sea during low peak periods, a length of 20 metres or more is considered ideal for fishing vessels operating in this region. This paper showcases the influence of boat size on percentage operability and presents a methodology that can be utilised to select the best vessels with optimal seakeeping performance from a range of options, using the single percentage operability metric.