Comparison between model testing and full-scale trials of new trawl design for Italian bottom fisheries

Two large trawl models, at a one-quarter scale, were designed, produced and tested in a flume tank in Hirtshals (Denmark). A traditional trawl, typical for the commercially bottom fisheries in Italy, was selected as a basic design for the development of a new trawl. Characteristics of the new design should include larger meshes in the net areas, where no negative effect on catching power is foreseen, high bosom height, good bottom contact and low towing resistance. The geometry and towing resistance of both the traditional and the experimental trawl models were initially measured in the flume tank for different riggings. Based on the results from detailed flume tank tests, two full-scale trawls were designed and produced. Engineering sea trials have been made on a research vessel to measure the performance of the full-scale trawls and to verify the findings from the flume tank tests. The comparison between sea trials and flume tank tests shows that it is very difficult to accurately model, in the flume tank, trawl sections where the highly elastic Rachel netting made from polyamide is used.