ii6 



THE TECHNIQ^UE OF TRAWLING 



Gauging the angle while paying out; and angle gauge in position while trawling. 



the following sections are nearly straight, and the greater the diameter 

 the steeper they become. On the basis of calculations made for wires 

 uniform in diameter we worked out diagrams showing the length of wire 

 to be paid out in order that the trawl should reach the bottom, taking 

 into account the depth and the desired speed, as well as the required 

 angle of the wire on leaving the ship. The diagrams on p. 115 refer (a) to 

 the otter trawl, and (b) to the sledge trawl. Two diagrams are neces- 

 sary because the two types of trawl have a different drag. 



As far as possible, the trawl is lowered while the vessel is travelling 

 against the current. While the wire is being unwound the ship must move 

 with sufficient speed to enable the trawl to go forward through the water; 

 but in order that it may quickly sink to the bottom the speed should not 

 be greater than necessary. It is not easy to tell for certain when the 



Pulling in the trawl. 



