An experiment on the moving performance of trolling depressor

Abstract

The moving performance of commercially used trolling depressor was investigated in a flume tank. The ratio of distance between the snout of trolling depressor and the connecting point of leader was changed 3 to 43%. Flow speeds were varied from 0.75 to 1.05m/s. Three components of tension of leader were measured by three components load cell. Positions of connecting point were expressed in a space co-ordinate system located on attaching equipment of load cell. Moving trace of connecting point was estimated basing on the equilibrium of three components of tension. Moving performance of trolling depressor were recorded and analyzed at various conditions. Mean resultant tension increased in square of flow speed at any connecting points. Trolling depressor glided from side to side and turned at short period in any flow speed and the calculated moving trace of connecting point showed an eight figured shape. Theoretically estimated trace agreed with measured one within connected points less than 35% of ratio. Trolling depressor swung uniquely at 43% of the ratio. These results suggested that the distance between the snout and the connecting point affected moving performance of trolling depressor.