The Relation between the Mouth Height of the Square Part of Small Trawl Net and its Pulling Velocity

The experiments on the relations between the mouth height of the square part of the net and tension on the rope in proportion to the differences of pulling directions and current directions under various pulling velocities, have been carried out by using small trawl nets (8 HP) in Ise Bay. From these experimen's, the following results were obtained. 1. In spite of the equal pulling velocities related to the sea-bottom, the mouth height of the square part, be pulled in the same direction as the current flows, is higher than in the opposite direction (Fig. 3, Fig. 5). 2. The tension on the rope pulled in the same direction as the current flows, is weaker than against the current while the pulling velocities related to the sea-bottom are equal (Fig. 4). 3. In the cases of the equal pulling velocities related to water, the mouth height of the square part, be pulled in the same direction as the current flows, is equal against the current (Fig.8, F ig. 10). 4. Let the mouth height of the square part and the pulling velocity related to water express by h and v respectively, when the pulling velocity is related to water, the results are following: h∞V-1•3 …… (indicated in Fig. 9) h∞V-1•3 …… (indicated in Fig. 11)