In recent years, there has been a tendency, in some sectors of the fishing industry, towards the use of thicker and stiffer twines in the manufacture of netting materials. The use of such netting increases the mesh resistance to opening and consequently reduces the selective performance of fishing gears. The main twine characteristic that contributes to mesh resistance to opening is the flexural rigidity of the netting twine. This paper presents a methodology for quantifying mesh resistance to opening. A prototype equipment, named Resistance to Opening and Deflection meter (ROD-m), is developed. This instrumentation incorporates 4 load cells and 4 stepping motors, which are driven by 4 ministep bipolar chopper drives. Small panels of netting (3x3 meshes) can be mounted on ROD-m and the forces acting and position of the knots measured. Estimates of the flexural rigidity of the netting twine can be made from these data. The results of this analysis for some polyamide (PA) netting from Mediterranean, standard and brezline polyethylene (PE) netting from the North Sea are presented. For the netting of each material, there is an increase of EI with increasing linear density. Furthermore, it is also shown that brezline is much stiffer than the standard green PE although they are of equal thickness.
Experimental method for quantifying the resistance to opening of netting panels
Sala A;Buglioni G;Lucchetti A;Palumbo V;
2006
Abstract
In recent years, there has been a tendency, in some sectors of the fishing industry, towards the use of thicker and stiffer twines in the manufacture of netting materials. The use of such netting increases the mesh resistance to opening and consequently reduces the selective performance of fishing gears. The main twine characteristic that contributes to mesh resistance to opening is the flexural rigidity of the netting twine. This paper presents a methodology for quantifying mesh resistance to opening. A prototype equipment, named Resistance to Opening and Deflection meter (ROD-m), is developed. This instrumentation incorporates 4 load cells and 4 stepping motors, which are driven by 4 ministep bipolar chopper drives. Small panels of netting (3x3 meshes) can be mounted on ROD-m and the forces acting and position of the knots measured. Estimates of the flexural rigidity of the netting twine can be made from these data. The results of this analysis for some polyamide (PA) netting from Mediterranean, standard and brezline polyethylene (PE) netting from the North Sea are presented. For the netting of each material, there is an increase of EI with increasing linear density. Furthermore, it is also shown that brezline is much stiffer than the standard green PE although they are of equal thickness.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
