Analysis The Effect of Outrigger (Cadik) Variations on Motion Response of Fishing Boat Using CFD Method

Abstract

Jukung is a type of traditional fishing boat used as transportation for fishing activities in Muncar, Banyuwangi, which has a wave as high as 2 m with a period of 4.6 s which is classified as 2nd sea state. One of the boats used has a length of 7.2 m, width 0.75 m, and height of 0.8 m. The characteristics of the hull which with an L/B ratio of 9.6 require outriggers to help balance while sailing. The outrigger itself is a cylindrical component that is placed at a certain distance on both sides of the boat. Since ancient times, the construction of outrigger boats has been carried out by local artisans by relying on experience. This is certainly very risky because it is not known for certain whether the construction, in this case, the outrigger can keep the boat stable. For this reason, we researched the boat’s motion using the CFD method to provide a reference for the construction of the outrigger design. Using one of the existing boats with LOA 7.2 m, B 0.671 m, and H 0.8 m, and Vs 4.385 kt as a simulation model, we varied the outrigger-centerline distance by 2.5 m and 2.8 m; diameters of 90 mm, 120 mm, and 150 mm; which tested under conditions of full load and light load with the wave directions of headsea (180°), headquarter (135°), and beamsea (90°), resulting in Response Amplitude Operator (RAO) as follows. The model with an outrigger-CL distance of 2.8 m and diameter of 150 mm has the lowest heaving value of 0.02 m/m at a frequency of 4.1 rad/s from the headsea direction, 0.44 m/m at a frequency of 3.7 rad/s from the headquarter direction, and 0.4 m/m at a frequency of 6.2 rad/s from the beamsea direction. This model also has the lowest value in pitching and rolling responses from all directions with each value of 0.4 rad/m to 0.15 rad/m in pitching and relatively 0 rad/m in rolling responses.