A wire-angle indicator for use when towing plankton nets

Extract

The old type of wire-angle indicator, which consisted of a pendulum swinging across an arc of a circle graduated in degrees, and which had to be applied by hand to the wire, was clumsy to use, especially in bad weather, and when the wire led out over the stern of the ship. It needed someone to attend to it, which often resulted in the wire angle not being checked more than once every five or ten minutes when the crew were busy. This instrument was therefore designed to remain in place throughout the tow, and to give a large dial reading which could be easily seen from a distance. On the research ketch Culver there is an engine throttle control mounted close to the wheel, and all the man there has to do is to adjust the engine speed so that the large indicator in the instrument remains on the red line. In practice it was found that the wire angle rarely varied more than about ±2°, except in very bad weather, and so the depth of the nets could be regulated very closely. The instrument is oil damped, so that the pitching of the ship and the vibration of the wire during hauling do not affect it. It has been used for about two years on the Culver at Bermuda; it has needed no attention in that time, and, which is a good point, the crew like using it.