Breaking strength of a knot of fishing net as affected by the angle between legs of mesh.

引張り方向が網糸の結節強度に及ぼす影響

Kakuda Shunpei

広島大学水畜産学部紀要

Journal of the Faculty of Fisheries and Animal Husbandry, Hiroshima University

In order to clarify the effect of the spreading of the mesh to the breaking strength of the netting cord, two pieces of the cotton or cremona netting cord were linked by a "plain link" or tied into a flat knot or a trawler knot, and the breaking strength of the cord was investigated by changing the angle between the neighboring legs of the knot and applying static loads to the legs. The cord was broken almost always at the knot or crossing point, and only the breaking strengths of such cases were treated with. Following results were obtained:
1) In the plain link, the breaking strength of the netting cord is affected by the angle between the neighboring cords. The relation between the breaking strength and this angle is linear; the breaking strength increases as the angle a (i.e., the angle between a pair of legs representing a single piece of cord) increases. The effect of this angle to the breaking strength is greater in the cremona cords than in the cotton cords.
2) The breakinng strength of the netting cord tied into the trawler knot is hardly affected by the angle a throughout the range of a from 23° to 128°, and the value is closer to the breaking strength of the mesh stretched longitudinally (i.e., in the ordinary direction) than to that of the mesh stretched transversely (laterally). This holds in cotton cords as well as in cremona cords.
3) The breaking strength of the cotton cord tied into the flat knot is almost constant when the angle a is between 23° and about 90° and this value falls between the breaking strength of the mesh stretched longitudinally and that of the mesh stretched transversely.
4) The breaking strength of the cremona cord tied into the flat knot varies with the angle a. When this angle is between ca. 70° and ca. 90°, the breaking strength1 is at the maximum and is greater than in the mesh fully stretched either longitudinally or transversely. When the angle is between 23° and about 50°, the breaking strength is comparatively small and nearly constant, and falls between the breaking strength of the mesh stretched longitudinally and that of the mesh stretched transversely.

Fishing industry. Fisheries [ 660 ]

eng

広島大学水畜産学部

[ISSN] 0440-8756

[NCID] AN00213563