The angle of attack of a cambered otter board in a bottom trawl was estimated using a three-dimensional semi-analytic treatment of a towing cable (warp) system that was applied to the field experiments of a bottom trawl obtained by the Scanmar system. The equilibrium condition of the horizontal component and vertical component of forces was used to the three forces acting on the otter board in the horizontal plane. Those forces were the force on the warp at the bracket, hydrodynamic lift and drag forces on the otter board and the force on the hand rope attached just behind the otter board. Also the equilibrium of moment about the front edge of the otter board was used to find out the angle of attack of the cambered otter board. When the warp length was 120m and 180m long and the towing speed was between 1.23 and 1.90 m/s, the estimated angle of attack of the cambered otter board was ranged between 26.1° and 29.6°, respectively, though the maximum lift force was at the angle of attack 22.6°. The angle of attack of the otter board was tended to increase weakly with the longer length of warp (180 m) at the same towing speed in the experiment.

본 연구는 실습선에서 사용 중인 6폭짜리 저층트롤 어구의 저항을 끌줄의 길이와 예망 속도별로 분석하기 위하여 그물의 저항과 전개판의 저항을 계측하고, 어구의 저항계수를 산정하였으며, 그 결과를 요약하면 다음과 같다. 1. 시험 어구의 저항은 끌줄의 길이가 길수록 증가하나, 저항 R§ubt-w/=3800v2으로 대표할 수 있다. 2. 그물 어구의 저항은 끌줄의 길이에 따라 다소 증가하나, 그물 어구의 저항 R§ubn/=10R§ubn/=10d/lλ§uba/λ§ubb/v1.3/의 식으로 대표할 수 있다. 3. 시험 어구의 전개판의 저항 R§ubb/=1810v0.8/으로 대표할 수 있다. 4. 끌줄의 길이별로 측정된 저항값과 Koyama의 저항식과 비교하면, 예망속도가 작을 때는 시험 어구의 저항이, 예망속도가 클 때는 Koyama의 저항식에 의한 저항값이 크게 나타났다.