Abstract
The samples of net and rope disused after their usage in set fishings were obtained from various fiishing grounds (Tables 2, 4, 5, 6) and examined of their properties in order to formulate the knowledges about the safty limit of their utility taking into account of the peculiarities in the disposition of the net as well as the circumstances in which the net is used.
The mesh size of the nets being already out of use are shown in Table 3.
The knot strength was adopted on this occain as the measure of net-fablic strength. To determine the knot strength each two of the four arms around a knot were gathered and stretched by a tensile tester.
Now, if minimum strengths allowable for net-fabrics of “bag”, “funnel”, “heart” and “sand bag” (anchor) rope are denoted by Tu, Tv, Tw and Tx, respectively, we get the following equations:
for “bag”, Tu=K4D(H+B/2)2 (Fig. 3)
for “funnel”, Tv=K5D1(H1+B1/2)2 (Fig. 4)
for “heart”, Tw=K6D2H22 (Fig. 5)
for “sand bag” (anchor) rope, Tx=K10D3/L3(H3+B3/2)2 (Fig. 6)
Where the various letters have the following meanings, respectively:
K4, K5, K6, and K10, constant number; D, D1, D2, and D3, diameter of netting thread; L3, mesh size; H, H1, H2, and H3, depth of water; B, B1, B2, and B3, greatest width of net.
