Tadanobu Machii

Determination of mechanical properties of a Peruvian purse winch

The study was undertaken utilizing only an engine tachometer and an oil pressure gauge of a prototype Peruvian small purse seiner. The empirical relationships between a velocity of a winch (Vw; m/s) and an enging revolution (Ne; rpm), and between an effective force of a winch (Fw; kgw) and an effective output pressure of an oil pump (P-Po; kgw/cm2) were determined based on the equations obtained by the previous study. Assuming the loaded pressure (P; kgw/cm2) and the non-loaded pressure (Po; kgw/cm2) of the pump, since Po=19.7kg/cm2, then Vw=0.000415Ne and Fw=24.5 (P-19.7) Moreover, in standard fishing operations of Peruvian small purse seiners, Vw=0.52m/s and Fw=367kgw could be practically determined. These values could be used to examine the mechanical properties of a fishing gear during fishing operation.

Size of Peruvian small purse seines.

The size of Peruvian small purse seines was examined applying the size of anchovy purse seine. Also, a comparison between Peruvian and Japanese purse seines was undertaken. The size adopted was the overall length (Loa; ft) and gross tonnage (GT; t) of the fishing boat, and float line length (Lf; fm), net height (He; fm) and net area (A; fm2) for the fishing net, where the units were fathoms. Analysis was based on the data for 1967, when it was considered that the fishing net in relation to fishing boat had reached a maximum size. The results were expressed for the size of fishing boat as, Lf/Loa=3.24, He/Loa=0.484, A/Loa2=1.57, or Lf/GT1/3=49.2, He/GT1/3=7.35, A/GT2/3=362.The Lf of Peruvian fishing net was designed shorter than the Japanese one for the same GT.

Comparisons of the equations to estimate the weight in air of nylon netting

We compared the results obtained in our previous studies (one strip of netting and a single mesh) with the results of other authors on the same subjects. We dealt with English knot nylon netting. The comparisons were made with the work of litaka for one strip of netting and with the works of Tauchi, Miyoshi and Iitaka for a single mesh. For the weight of one strip of netting (100 fathoms long and 100 meshes deep), our results fitted very well with the Netting Weight Table values, but Iitakas equation yielded values generally higher. For the weight of a single mesh (ω: two legs and one knot) ω=(π/2)D2 •L •{A+B(D/L)} •ρ, the constants A and B were obtained 1, 4 in Tauchi, 1, 6 in Miyoshi, 0.65, 6.5 in Iitaka, and 0.50, 4.5 in the authors respectively, where D is the diameter of twine, L is the length of one leg, and ρ is the density of twine. The assump-tions for leg and knot length are included in both the works of Tauchi and Miyoshi. litakas equation was derived from the weight of netting in water. Our results were obtained from the measurements of netting based on the theoretical relationships of the weight in air.