Cleaning Ship's Bottoms.

Progress, Volume IV, Issue 4, 1 February 1909, Page 139

Cleaning Ship's Bottoms.

The necessity of removing growth from the bottoms of ships entails a very large expenditure, as it is nearly always necessary to dock the vessel Ship-owners in New Zealand will do "well 1o inquire into an ingenious invention which, has been devised for this purpose, and which the inventor — an Englishman — lerms "The Electrical Scrubber." and by which ships ' bottoms may be cleaned without dry-docking. The principle of the invention i* \er\ simple. Tt is in effeel a huge flexible

scrubbing brush which is dragged up and down under the hull of the ship by ropes. By the use of electricity the brush is made to' cling to the ship's side like a magnet. The "mat." as the group of brushes is called, comprises a scries of battens carrying the brushes and magnets. These are threaded at either end on chains and separated from one another by cork discs, also threaded on the chain, to assist m giving the necessary buoyancy to the apparatus, and. to avoid injury to the battens from short-circuiting, uhich -would result if I\\o battens came into contact. When the mat is hung o\er the -vessel's side and lowered into position, the electric current is switched on. In this position the apex of the curve of each magnet comes into contact with the ship's side and secures a grip theron, but the brushes are not touching. As soon as hauling commences, however, the battens cant, thus bringing the Tore edge of each brush into touch with the hull of the ship. As it is dragged over the fouled surface the accumulated matter is nicked off. The electric current is furnished from the ship itself or from a special lender equipped witli the apparatus lying alongside. From aciu.il experience ii is found that the total gi"p of the whole mat is considerably over a ton The scrubber requires onl\ two men to work it. and an 18.000 ton battleship was completely scrubbed in twelve hours Vessels dr\ docked for examination after being cleaned by this method, have been found entirely free from any marine growth The cost of cleaning a vessel by this method is very small. A 12.000 ton ship can be cleaned, inclusive of the cost of labour, electrical curient, and all gear, for £'20 and the time occupied is only about 8 hours.