New Statistical Regression Analysis for Fishing Boat Hull Resistance

Abstract

There are many kinds of fishing boats in Japan, and fairly amount of them have bad resistance characteristics. The tendency is getting hard especially in these few years.To improve the circumstances, simple estimation methods of EHP values for any fishing boat at any speed in the initial design step are necessary. FAO has published a equation to estimate the total resistance coefficient CR16 of fishing boats by statistical regression analysis of tank tests in 1969. But, as it is not convenient enough when the displacement and speed are given but the water line length is varied, new analysis is tried for the same samples after the re-arrangement of them, which are as follows : (1) Total resistance coefficient r=Rt/ (1/2ρ·∇2/3·V2) is used.(2) The r values of each model test are corrected by the ITTC 1957 model ship correlation line to those of Δ=300t.(3) Froude number Fn∇=V/√∇1/3·g is used.(4) Hull form parameter L/∇1/3 is used instead of L/B.(5) The values of hull form parameters are normalized by using modification factor to reduce the estimation error for those which exist at fewer samples' zones.(6) Samples having quite different hull forms are excluded.After the analysis, new regression equation is introduced which has almost enough accuracy for practical use, and is put into the computer program for the initial design of fishing boats. By the program, a improvement of traditional tuna long liner is tried, and after the tank tests, about 40 % of EHP reduction is confirmed. This method will be used for improving the other kinds of fishing boats in Japan.