1National Research Institute of Fisheries Engineering, Fisheries Research Agency, Kamisu, Ibaraki 314-0408, 2Aichi Fisheries Research Institute, Minamichita, Aichi, 470-3412, 3Shimonoseki Research Institute, Nichimo Co., Ltd., Shimonoseki, Yamaguchi 750-1136, Japan
To improve the otter board used with a semi-pelagic trawl net, we evaluated the conventional otter board used in Ise-wan Bay and compared the lift and drag characteristics with the following experimental otter board. The experimental otter board was designed to enable both semi-pelagic and bottom trawl operations along with a high lift-drag ratio. Results of model experiments indicated that the drag coefficient of the experimental otter board was smaller, and the lift-drag ratio of the experimental otter board was 1.41 times higher than those of the conventional otter board respectively at intended attack angles. In an experimental operation using a semi-pelagic trawl net, the otter board distance was 1.1-1.2 times wider than that of the conventional otter board.