Department of Marine Science and Technology, Tokyo University of Fisheries, Tokyo 108-8477, Japan
Flume tank experiments were conducted to clarify the relationship among tied-eye position, line tension and diving behavior of crank bait lures with different shapes of lip. Experimental lure-lips having the same area and different aspect ratio (λ=0.3, 0.5, 1.0, 1.5, 2.0) in the plane view were made. Trial lures with the same body were used in the experiments at velocities of 40, 60 and 80cm/s in the flow. Attack angle of the lures and tension on the towing line were measured in the tank test. The lure behavior was also recorded by video cameras from the top and the side of the observation area. We used an index Cs(=SF/S) that indicates the areal ratio of the forepart of the tied-eye (SF) to the whole area (S) of the lure in the plane view. It was confirmed that there was a constant relationship respectively between the areal ratio (Cs) and line tension on a towing line, Cs and attack angle of the line, even for different shapes of lip attached. In the case of different lips, the tested lures showed steady diving behavior within the range of Cs=0.2 to 0.3.