“Good. The steam salvage-dock Vulcan has been sent for and will be here before then, Herr Kapitan.”
But before the Vulcan arrived, it occurred to some one in authority to attempt to raise the U-3 with a large floating crane then available. The strong steel chain ready coiled at the lower end of the buoy-line was drawn up and made fast to the crane, which could not lift the 300-ton submarine bodily, but succeeded in hauling up its bow sufficiently for the twenty-seven petty officers and seamen on board the U-3 to be shot up through the torpedo tube to the surface. The captain and his two lieutenants chose to remain. Shortly afterwards the chain slipped and broke off one of the boat’s ventilators, letting water into the hull and drowning all three officers.
Then the sea-going, steam salvage-dock Vulcan reached the scene and brought the U-3 to the surface in three hours.
“The Vulcan is a double-hulled vessel, 230 feet in length with a lifting capacity of 500 tons. The width between the two hulls is sufficient to admit with good clearance the largest submarines. At a suitable height a shelf is formed along each wall of the interior opening, and upon this rests the removable floor of the dock. The two hulls of the ship are each built with water-tight compartments of large capacity, similar to those which are found in the side walls of the ordinary floating dock. When a sunken submarine is to be raised, the Vulcan steams to the wreck and is moored securely in position above it. Spanning the well between the two hulls are two massive gantry cranes, each provided with heavy lifting tackle driven by electric motors. The first operation is to fill the compartments until the vessel has sunk to the required depth. The floor of the dock is then moved clear of the well. The lifting tackles are now lowered and made fast, either to chains which have been slung around the body of the submarine, or to two massive eyebolts which are permanently riveted into the submarine’s hull. At the order to hoist away, the submarine is lifted free from the mud and drawn up within the well, until its bottom is clear of the supporting shelves on the inner faces of the two hulls, above referred to. The dock floor is then placed in position on the shelves, the water is pumped out of the two hulls, and the Vulcan rises, lifting the submarine and the dock floor clear of the water.”[18]
Courtesy of the Scientific American.
The Vulcan salvaging the U-3.
A similar vessel was built by the French government as a result of public indignation over the delay in raising the sunken Pluviôse. Great Britain has a salvage dock with a lifting capacity of 1000 tons. But the most remarkable craft of this kind belongs to Italy and was designed by the famous engineer Major Cesare Laurenti, technical director of the Fiat-San Giorgio works, builders of some of the world’s best submarines. She is a twin-hulled vessel, fitted not only to pick a sunken submarine from the sea bottom, but to care for it in every way, for she is also a floating dry-dock, capable of repairing two of the largest submarines, besides being a fully equipped mother-ship for a flotilla of six. With the ends of her central tunnel closed by a false stem and stern, and propelled by twin screws driven by powerful Diesel engines, she is a fast and seaworthy vessel, capable of keeping company with her flotilla on a surface cruise. She carries a sufficient armament of quick-firing guns to beat off a hostile destroyer. But the most noteworthy feature of the Laurenti dock is a long steel cylinder, capable of enduring great pressure from within, that is used to test the resisting strength of new submarines. A new boat, or a section of a proposed new type, is placed in this tube, which is filled with water that is then compressed by pumps, reproducing the effect of submergence to any desired depth.
The United States navy tests each new submarine built for it by actually lowering the boat, with no one in it, to a depth of 200 feet. We have no Laurenti dock, no Vulcan, no sea-going salvage dock of any kind. The tender Fulton has a powerful crane, but she cannot be on the Atlantic and Pacific coasts and in the Far East, simultaneously.
“The difficulties encountered in raising the sunken British submarine A-3,” wrote Mr. R. G. Skerrett in the “Scientific American” some years ago, “have in them a note of warning for us. We are steadily adding to our flotilla of under-water boats, and yet we have no proper facilities in the government service for the prompt salvage of any of these boats should they be carried suddenly to the bottom. We have been fortunate so far in escaping serious accidents, but that is no reason for assuming that we are any more likely to be immune from disaster than any other naval service. We should profit by the catastrophes which have befallen England, Russia, France, Germany, and Japan, and no longer continue unprepared for kindred mishaps.”[19]