Untitled - CNR

Fishery and Sea ResourcesFigure 2: Particular of the Cambered vee AR (on the left) and Clarck-Y (on the right)otterboards. Pictures on the top show the SCANMAR angle sensor mounted on the otterboardfor measuring heel- and pitch-angles of the door.same number of hauls from being performedwith both otterboards. During allthe hauls done, the SCANBAS SGM-15system (SCANMAR, Norway) was usedto measure the gear performance: doorspread, horizontal net opening, heel andpitch door angles. Moreover, two MICREL(France) underwater force sensors were insertedjust in front and in the backside ofthe port-door to measure the drags aheadand behind the otterboard. All the instrumentswere linked by RS232/485 serialports to a personal computer, whichautomatically control the data acquisitionand provide the correct functioning of thesystem in real time through an appropriatelydeveloped Microsoft Visual Basic 6.0program. In order to compare full- andscaled-otterboards, we balanced the forcesand then the spreading-, drag- and downforcesof full-scale otterboard have beenobtained. These forces in the case of scaleddoor are known as a function of attack- andheel-angle with zero pitch-angle, howeverattack-angle of the full-scale door was unknown,therefore we also propose a modelto calculate the attack-angle at sea trials. Amore detailed description of the analysis isgiven in [2].3 ResultsData from the flume-tank and the experimentalsea trials, together with the resultsobtained by the model, are summarized inTable 2. In the sea trials we have measuredthe door spread (HDS[m]), the horizontalnet opening (HNO[m]), the heel- (φ [deg.])and the pitch-angle (θ [deg.]) of the door,the warp attachment position to the otterboard(so named hole number HF on Table2) as well as the tensions exerted to the otterboardby the warp (W[kg]) and by thebridle (B[kg]). We also have reported theresults obtained with our analysis appliedto the sea trials data: drag-, spreading- anddown-force coefficients, efficiency and thecorresponding attack angles (α[deg.]). In1878