Abstract
Various types of shearing devices which may be a substitute for the conventional beams in stow nets were considered, and then tentatively named "the zonal canvas type of stow net" having the shearing device made of zonal canvas was devised. A 1/3 model of the net was made and experimented at sea. Converted to the full scale, the measured water resistance R(kg) of the net was given by $R=5.6{\times}10^{3}V^{l.5}$ or $R=3.5\frac{d}{l}{\lambda}_b{\lambda}_l\;V^{1.5}$, where V is the water velocity (m/sec), d the diameter of netting bars, l the length of the bars, ${\lambda}_b$ the stretched circumference of net mouth (m), ${\lambda}_l$ the length of net stretched. The net height kept about $83\%$ of the side rope length regardless of the variation of V and the net breadth kept a value over $90\%$ of the head rope length until V reached 1 m/sec. These results were very successful according to expectation, but the conventional netting was requested a further improvement. Therefore, the netting was newly designed to have smaller size of meshes in the vicinity of net mouth and larger hanging ratio breadthwise. With the netting a full scale net was made and experimented by a stern trawler. The experiment gave a net breadth over $95\%$ of the head rope length until V reached 1m/sec and showed no faults in the net. But the net operation by the stern trawler was ascribed an inconvenience to its narrow breadth of stern slip way.
본연구에서는 전개장치를 띠모양의 소형 범포들로 구성하는 띠전개범식 안강망어구를 고안하여 재래의 그들을 이용한 1/3 모형어구 및 그물을 개량한 실물어구를 각각 제작하여 실험하였던 바, 다음과 같은 결과를 얻었다. 1. 재래의 안강망어구의 축척비 1/3인 모형어구의 총저항 R(kg)을 실물로 환산하면 $R=5.6{\times}10^{3}V^{l.5}$ 또는 $R=3.5\frac{d}{l}{\lambda}_b{\lambda}_l\;V^{1.5}$로 주어진다. 단, V 유속(m/sec), d는 그물실의 직경, l은 그물코 다리 한개의 길이, ${\lambda}_b$는 그물아궁이의 뻗친 둘레(m), ${\lambda}_l$은 그물의 뻗친 길이(m)이다. 2. 모형실험에서 망고는 유속에 따라 거의 일정하며 옆줄 길이의 $83\%$ 정도로 유지하였다. 3. 망폭은 유속의 증가에 따라 서서히 감소하여 유속 1m/sec 일 때 모형실험에서는 뜸줄길이의 $90\%$정도, 실물실험에서는 $95\%$정도 유지하였다. 4. 어구조작은 선미식 트롤어선으로 행한 결과 전개장치의 선미경사로 통과가 여의치 않았고 장망시 선미경사로상에서 뜸줄, 발줄 및 옆줄이 뒤로 쳐져 엉키는 현상이 일어났다.