ENGINEERING FEATS

Greymouth Evening Star, 19 September 1938, Page 12

ENGINEERING FEATS

SALVAGE WORK AT SCAPA FLOW Sea pa Flow, Base of the British Navy during the Great M ar. The Ease to which the German High Fleet sailed in surrender after the conclusion of hostilities. And the base where, one afternoon, six months hater, those mighty fighting ships I sank to the sandy shore 24 fathoms I below, alter their officers ■'had scu*U.lcd them sooner than turn them over to the enemy, writes Leonard O. Mosley in the 'National Home Monthly,’ Winnipeg. We could see them as the plane banked towards the landing field at Stromness', smudgy patches, mottling the broad sweep of calm green seas. "Twenty-five thousand tons —some of those' battleships down there,’ shouted Bob Smith, pilot of the daily plane which links the Scottish mainland with the Orkney Isles. “You wodldn’t think it'd be possible to raise hulks as big as that, would you? The Germans certainly didn’t when thev sent them down.” “ But a British firm with headquarters on the little island of Hoy, lias already rescued a dozen of those huge ironclad monsters from their watery graves, even though they lay 140 ft below the surface of Scapa Flow, upside down. And upside down it has towed them 400 miles south to be broken up at Roslyth, in the Firth of Forth, to provide steel for Britain’s rearmament programme.

It takes Bob Smith’s plane an hour and a half to cover the 150 miles from Aberdeen to Stromness. It took longer than that to travel 15 miles up Scapa Flow to Lyness, the company’s headquarters' on Hoy, in the launch they had sent for me.

Hoy has a normal population of 150 —farmers and fishermen, most of them. Since the salvage firm set up headquarters on the island the population has trebled. Two hundred and fifty engineers, welders and metal experts have- set up house in the tin huts which were used by naval officers as messes' during the Great War. Winter and summer for the past [five years those 250 men have been achieving some of the. most miracuI tons feats of salvage known in modern engineering history. The story of how the Friedrich der Groose was “blown” to the surface and prepared for her journey to the south is worth Helling, I think. John Mackenzie, Glasgow '.salvage engineer in charge of operations at Scapa Flow, has been engaged most of his life in the business of rescuing ships from the clutches of the deep. During the war he was in command of a salvage ship stationed at Portsmouth, which shot out into the Channel as soon as an enemy submarine was reported. His job was to throw a tow' line over any merchant or cruiser unfortunate enough to be torpedoed, and to get her on to the beach before the waves engulfed her. He did it so successfully that “Mackenzie’s coming!” became a message of salvation in the Channel during the war.

At Scapa his job is no less dangerous than the one he had in 1917. He goes' down in a diving suit to examine the hulk of each wreck he raises, and, from his own observations works but a plan of campaign. The Friedrich der Grosse, like most of the scuttled battleships, .turned turtle as she sank. She was located four miles out from Lyness upside down with a slight list. Mackenzie’s method oj.' raising her was similar to one he had used bn eight of the other battleships. He was going to seal up every hole and aperture in the wrecked ship, and then, through pipes welded to the Friedrich’s keel, he was going t< pump compressed air into her so that, just like a balloon, she would burst clear of the mud and rush to the surface.

In his workshops on the quay at Lyness men had been working for months to manufacture the lohg pieces of piping that would be necessary. One hundred feet long, 4ft in diameter, these thick iron tubes tire known as “airlocks.’’ HARRIED BY STORMS. Though the divers and engineers were harried many times by storms, the’giant airlocks were lowered one by one until they touched the keel of the wrecked ship. Then divers', waiting below, welded them to the armour pitting. After this, the first process iwith the compressed air began. A giant machine aboard the tender began to whine. Thousands .of cubic feet of air were pushed into the interior of the Friedrich, and it drove the sea water out.

Thanks to the genius of modern engineering which had evolved this method of pumping out the water, the men could work down there in the depths clad only in their ordinary clothes. They made l their way into the twisted interior of the ship, closing up bulkheads, sealing doors', and striving in every way to make the boat airtight. That is no easy job. that labour in the depths, for the pressure under which it was being done down there was between 55 and 65 pounds to the square inch. After one and one-half hours inside the Friedrich over two hours had to be spent in a decompressing chamber, fitted into the airlocks, to avoid risk of compressed-air illness. Despite this precaution, cases of “bubbles" or “bends" as the illness is called, had been frequent on all the jobs. Fortunately, though all were severely painful, none of the cases have been serious. Finally, the last, workers' ctimc out of the interior of the ship and climbed up the long airlocks to the surface of the sea. The pressure of air was gradually increased, and the Friedrich der Grosse began to stir in the mud at the bottom of Scapa Flow. To watch 26.0(1(1 tons of iron and steel bui'st to the surface amid clouds of water, oil and mud is a sight well worth a journey of 800 miles to see First the bows of the Friedrich burst into view, and then after the ptim]>ing of more air the stern camo up and the Friedrich, though shb was seeing it bottomside up. was looking once more on the outside world which she had loft on that dramatic afternoon in l!)l!i.

rugs came fussily forward after the cascade of mud had settled: lines were thrown out: and the following da.y the battleship was grounded in shallower water. The divers went down, placed charges of dvnamile and blew off the funnels and super's 11 net u re. I heli the ship was towed to Lyness. The airlocks were shortened. and Ute Friedrich, still upside down, wallowing in the water like a. great sea monster, was kept afloat by

the continual pumping of air into her interior.. The Zwarte Zee, from Holland, the most powerful tug in the world, was; with the aid of two smaller craft, going to undertake the hazardous job op towing her 400 miles down the North Sea to Rosyth. Tin huts had been strapped to the keel in which 14 of us were to live during the four days , which the journey would take. Carefully the tugs edged out beyond the protection of land, dragging the Friedrich after them. All went well while we were still between the islands, but no sooner had we ventured out than the “race” caught us. We- could see the Zwarte Zee, which is capable of nearly 20 knots and develops 4,000 horse-power, heeling over like a racing motor boat as her speed increased. Brit, though they tried so hard, the tugs could not hold vs. Back the Friedrich swept, drawn by the ebb, pulling the tugs after her; she swung round slowly and edged, broadside on. towards' the rocks under John o’ Groats.

To my mind it lotiked like disaster. For the next half-hour we were swept backwards and shorewards. We were supposed to be going east, but until 1.30 that day we travelled west, while the tugs grunted and strained to hold us. The battle was fought until the tide turned and the sea began to surge from the Atlantic. •» Almost abruptly, the Friedrich stopped her westward career and started moving towards the North Sea; and so powerful was the tide that she moved of her own accord, without any help from the tugs, which for a. time did little more than keep her headed through the passage. • Then a stiff breeze began to blow across the North Sea, making the heavy bulk sway as the waves washed over it. Hurried consultations were- hold. Each time we slobbed into the trough of a wave and began to roll the battleship lost some of the air inside it. We had to pump for hours to keep her afloat. Divers hurried below to seal up the holes inside her.

By noon that day we had sighted Fife Ness. Slowly, as the tugs pulled us forward, we rounded the bend and came into the mouth of the Firth of Forth. Ahead, we could see the huge span of the Forth Bridge sprawling like the skeleton of‘a giant from Midlothian's shore to Fife.

The spaces' under that bridge looked alarmingly small from that distance. There was some tricky work ahead. We were 600 ft long, 100 ft wide—26,ooo tons, with no power of our own. which had to be edged along a narrow' channel, under one of those spans, and then swung into the naval yards at Rosyth. It. took us six hours to shoot the bridge. Once we scraped the stonework and might, have crumbled it if the Zwarte Zee hadn’t surged forward and pushed us off just in time. But at last we made it. The tugsstraightened us up, and pushed us through, and then pointed the nose of the Friedrich toward the sea-lock. The last voyage of another great ship was over. The Friedrich der Grosse, raised from, her grave bj’ superb engineering skill, was in the breaking-’ up yards al last. She was meeting the fate already met. by 11 others —a fate which the other battleships on the bed of Scapa Flow' will encounter in the next few j months. Each one of those German ships means £1,50,000 worth of iron 1 and steel to the British Government. |