TRAWLING PUll EXERTED BY A TRAWLER .. A METHOD OF EST~MATION fROM PROPELLER ITS COtJIJPARISON WiTH SEA DIMENSIONS MEASUREMENTS

Abstract

The proper matching of the pull exerted by a trawler and the
size of trawl is important for maximising the catching efficiency. The
available pu]] is more dependant on the propeller and its working
conditions than the installed engine nower. The normal practice is
to directely connect net size to the installed power in the boat by
formulae without reference to the prooe1ler dimensions or the availahle
trr~wling pnll and this ic;; not A,d~quate to find out the ontimum
combination. By the method outlined in this paper, the accurate
calculation of trawling pull is possible by taking into account only
the propeller diameter, pitch and r. p, m. The predictions by the
method are compared for trawlers with powers between 30 and 60
H. P. and agreement is found to be within + 5%. The power
absorbed by the propeller in trawling condition can also be calculated
by this method for checking whether the engine is being overloaded.