Blue Water Concepts
Interactions between vertical lines under increased tension with a physical model of a North Atlantic right whale flipper was investigated. This was an updated experiment. The original flipper model was based on data (flipper outlines and bone measurements) collected from three different whales. The physical flipper was computer generated from these data and covered with 1/2 in neoprene rubber, which was overlayed with 1/8 in thick vinyl rubber sheeting. The flipper was made from fiberglass, was free flooding and covered with 1/2 in neoprene and then with 1/8 in vinyl-rubber. The flipper angle was adjustable forward and aft, relative to the 'whale body'. The flipper and frame was attached to a fishing boat, and deployed 12 feet below the surface. A taut vertical line was created using a large mooring block, which was fitted with a pulley and a swivel. A 5/8 in line was attached to a 28 in float and attached to a sinking line that ran across the bottom. Cameras were used to observe the flipper-line interactions. Scenarios were run using both forward and aft flipper positions, and at different contact points along the flipper's leading edge. There were three zones (relative to the whale body panel) on the leading edge: A) acute, N) normal and O) oblique. During the first 11 trials, six events were glancing interactions in zone C (outer edge) and five interactions occurred at zones A and B. The flipper moved vertically down, with a slight angle towards the back edge of the flipper, in the water column during these interactions. The second 11 trials occurred in zones A and B with one glancing event in zone C. The interactions (except for the glancing) resulted in the float moving downward. Interactions that occurred in zone A and B lead to significant damage to the leading edge of the flipper. The results from these trials suggest that for entanglements involving a whale flipper as the initial point of contact with vertical fishing ropes, increased line tension will likely produce more severe lacerations than ropes under lower tension. Any potential benefit of using ropes with increased tension may be offset by the potential for more severe injury.