GREY BAR

Grey River Argus, 12 February 1936, Page 2

GREY BAR

Sounding Equipment FOR TUG WESTLAND. Tho Greymouth Harbour, Board lust evening received! the |follawing report from the engineer, Mr D, U Milne, recommending the acceptance of a lender for the supply of an A«miralty Echo Sounder for the tug:— The question of installing an echo sounding equipment on the tug Westland fun the purpose of bar soundings has been under consideration for the past three years. In June, 1932, the board was offered a maehiue mauufactored by Henry Hughes and Son, Ltd., England, and. although this ap paratus w,as capable of sounding in very shallow water, it did not, in my view, provide the degree of accuracy which is necessary to meet the conditions obtaining a-f Groymouth. From tjiine to |tlme advice was received from the manufacturers of various improvements which had been mail-, to the machine, but it was not until the end of last year that it had reamed that stage in its evolution when its installation cou d be safely considered by the board. The apparatus uow offered can be operated on two ranges—from 0-40 feet, or from 0-40 fathoms. The lower range has ti chan scale of l-Bin -lb one foot, and therefore capable of recording accurately the depths of water on the bar and entrance channel. The higher range will enable the machine to be used for off-shore soundings .which are taken periodically. The apparatus will therefore -meet all the board's requirements with relation to marine surveys. The equipment includes a recorder, transmitting and receiving oscillators and a 36 volt battery complete with a charge dynamo driven by a petrol engine. The oscillators are attached to the inside oi the hull, one on either side of the keel and about' 3 feet apart. It will not bo necessary to pace the tug on tho slip and the entire installation can be carried out without putting the vessel out of commission. The board is fully aware that accurate and reliable data relative io -the bar and entrance channel is a matter oi first importance in the operation or the port and within the limits set by the equipment at its disposal the board lias endeavoured to provide the necessary information. Although the existing system of bar sounding tn which two leadsmen are employed and soundings are accurately located by means of shore beacons and sextant fixes represents a definite improvement On tho method which was pievinusly in operation, it still possesses two defects inherent in this system of sounding. Firstly, the distance between successive soundings which may result in local shoaling not' being recorded on the lead lines. In order to maintain steerage way on the tug a speed ’of approximately 4 knots must be steamed, and even with two expert leadsmen it is not possible to obtain soundings closer than 50 feet apart, which represents an average rate of four soundings per leadsman per minute. Secondly, the personal equation—however expert a leadsman may bo there is always the possibility of error in reading the lead line, particular y when working in a swell. With the proposed apparatus, both these defects will disappear. The action of the machine is purely mechanical. and the human element is therefore completely eliminated. So long as the apparatus is kept iworking order, it will continue to function accurately. Soundings are taken o t 'the rate of approximately 350 per minute, and -a chart of the sea bottom is automatically recorded ns the vessel passes over it. By the installation of this modern echo sounding equipment, the board will place itself in an unassailable position with regard to the accuracy of bar surveys, anil it wi 1 make available t'or shipmasters -the information which is so cssent nl in the sate navigation of tho harbour entrance. I recommend accept-,anee of 'the tender by llenr v Hughes and Son, Ltd., for the supply and delivery of the following equipment: One Echo Sounding GearRevolving I’en Type Recorder Al-S.X. £330; 30 v<-lt' Battery 'with 57 amp. capacity £l5; Pygmy lyte Charge Dynamo set, complete with charging number £35; freight and packing £l5; total £395. The above total in pounds sterling for delivery at Greymou’h, and is subject’ to i>v<hange, primage and duty, and sa.**s tax, "find is cxc'usive of the cost of installation. These "charges I e'G mate as follows; Tender price sibling £395; exchange, primage, sales Hix £127; installation -and alteration.to tug £75; total £597. II was deeded to defer a decision on the matter until next meeting, and m the meantime further information is to be, obtained on the matter l>nn> tho Marine Department-