INSTALLATION, AND REPAIR

Press, Volume XCIX, Issue 29170, 2 April 1960, Page 7

INSTALLATION, AND REPAIR

Cook Strait’s Problems

(New Zealand Press Association) WELLINGTON, April 1. Tidal streams in Cook Strait were far worse than either the Saint Lawrence river, Canada, or Georgia Strait, Vancouver, places where submarine power cables have already been laid, said Captain O. R. Bates, of the 1 British Post Office, in his report to the consultants on the problems of cable installation and repair work across Cook Strait. Captain Bates spent a month last May making an independent appraisal of local conditions. He said that the approaches to some of the cable landings must be classed as dangerous from the point of view of big ship handling. Hardly any of the features which applied to the' St. Lawrence and Georgia operations on which he had worked applied to Cook Strait.

Discussing North Island landings, Captain Bates said that while the history of the telegraph cables at Oteranga Bay showed that they did not give much trouble, once laid, the strong tidal streams made it a dangerous place to work a heavy cable ship. There had been a total of 32 faults in three telegraph cables there over a period of 38 years. Three experienced seagoing captains who had worked cable and New Zealand Government ships in Cook Strait were, said Captain Bates “at one in saying that Oteranga and its environs is a bad place to work a cable ship and carry out repairs. They were speaking in terms of repairing plastic insulated and relatively light cable. The problem would undoubtedly be worse with a lead-sheathed cable.

"Three consecutive days of settled weather are rare in Cook Strait, and it would require that amount of time to start and finish a repair,” he continued. “On the score of cable maintenance, there seem to be good reasons for choosing a laying ground further to the north or south, where Post and Telegraph experience shows that faults are less frequent and ships are easier to handle.” Laying Feasible

Outlining his conclusions, Captain Bates said that given a route where tidal streams were moderate and not much in excess of two knots at half tide, the laying of a cable across Cook Strait by an experienced commander with a properly-equipped cable ship was feasible. The shore-end landing operation presented a severe problem and, to reduce the risks, the route should be chosen so that the first end was reasonably short and not in excess or 1000 yards, with the cable track running straight from the beach without large alterations of course. That would allow a closely-timed start so that the ship could enter the worst of the tidal stream area at a particular time. The far-end landing operation should preferably be done by an auxiliary craft so that the whole lay could extend over more than one day and yet not involve the principal ship being moored overnight off a beach. The operation, however, planned, should not involve the principal ship working close to the shore in the darkness or lying at buoys and to cable overnight. The chosen route should, as far as possible, be over “soft” bottom so that the cable would not be in suspension over pinnacles or in “hard” ground and thus liable to chafe by tidal-flow vibrations. The minimum spacing should be 1000 yards to enable a faulty cable to be picked out reliably. Cable Repair Ship After discussing technical and other aspects of cable-laying, Captain Bates urged that consideration should be given to the acquisition of a cable repair ship based in New Zealand. He said that the British Admiralty had surplus ships for disposal some time ago and it might be possible to refit one to make it suitable for power-cable repairs. Alternatively, a surplus British collier would provide a sound basis for modification.