Untitled - CNR

Marine research at CNR(a)(b)Figure 1: Button load cells in place of existing shoe (a) and (b) particular of the leverplates and ridge bars acting on the load cell.ParameterLHA pW TARClarck-YST FT ST FT1.800 0.710 1.800 0.7101.050 0.480 1.060 0.4801.764 0.338 1.709 0.332310 16.67 275 18.05L[m]: Length of otterboard; H[m]: Height of otterboard; A p[m 2 ]: projected area of otterboard; W T[kg]: weight of otterboard in water.Table 1: Characteristics of the traditional Cambered Vee otterboard (AR), which is commonlyused in the commercial Italian demersal trawl fisheries and of the experimentalotterboard (Clarck-Y). ST: full-scale, FT: scaled door.case the door under test pitched the nose upor down and lifted one off the bottom. Buttonload cells were used to satisfy the needfor a compact low profile shape Figure 1.Both the full-scale AR and Clarck-Y otterboardsFigure 2 were tested in the AdriaticSea, using the Italian Research Vessel“G. Dallaporta”. All rigging componentsof the gear were identical with thosecommonly adopted in commercial practicein Mediterranean demersal trawl fisheriesFigure 3. Sea trials were conducted in thecourse of three sea cruises on two differentfishing grounds with depth ranges of 25-30 m and 60-70 m. The first and the thirdcruises (termed ST3.8[1] and ST3.8[3] respectively)took place from 31/05/07 to05/06/07 and from 03/03/08 to 13/03/08respectively at about 27 m of depth witha towing speed of 3.8 knots. The secondcruise (termed ST3.2[2]) was conductedfrom 16/10/07 to 18/10/07 at a depth ofabout 66 m with a towing speed of 3.2knots. Overall, 12 valid hauls of the firstcruise, 9 of the second and 8 of the thirdwere analysed. In order to determine theeffects of the sea current, at least two towson reciprocal courses were made for eachgear arrangement tested. After the firsttwo cruises we realized that the Clarck-Ydoor had poor spreading and shooting behaviourand hence instability might haveoccurred. Therefore, in the third cruise theattachment of the chain backstrop bracketswas moved 23 cm forward to try gettinglarger spreading. The otterboard tobe used first was chosen randomly at thebeginning of each trip, then the two otterboardswere alternated on the same trawl.Adverse weather conditions prevented the1877