TO DEFY THE WAVES

Nelson Evening Mail, Volume LXIV, 4 July 1931, Page 3

TO DEFY THE WAVES

NEW ITALIAN LINER

COMFORT FOR SEA TRAVELLERS HUGE GYRO-STABILISERS OVERCOME PITCHING AND ROLLINGWho. believes that a thing no larger than an apple can steady a barrel? If a barrel were floating on rough water, and the apple made to spin within, it would have a steadying effect in the barrel. Thus you have stabilised a barrel with an apple. The principle is ancient, and was first demonstrated in 1851 by a French genius, Foucault, who built the gyro-compass. . Forty gyro-stabilised ships sail the high seas, the largest a 10,000-ton man of war. While others pitch and dance, these vessels brush aside \the rollers as if they were fleas. What prevents most people from taking voyages is, of course, the dread of sea sj.ckness. No matter how palatial and comfortable your floating, home, this nausea damages happiness and health. Now the Italians have come to the aid of travellers with a sample of adventurous enterprise. They have contracted with the Sperry Gyroscope company for three stabilisers, the largest ever built, to steady the new 45,000-ton Conte di Savoia, now under construction at Trieste. Thus the Lloyd Sabaudo line plans to invest a cool £200,000 to minimise illness and maximise passenger comfort, states Don Glassman in “Popular Mechanics.” The ship in which the stabilisers are being fitted is exceeded in size by only seven others in the world. The gyro units, weighing 900 tons together, will be expected to stabilise a 45,000-ton mass. Thus we strike this equation: Nine hundred tons of stabilising machinery equals two per cent, of the ship’s displacement. News of the installation threw a bomb into the shipping industry, continues Mr Glassman. So long ■ as all companies steer clear of special innovations, the merchant marines remain on a basis of equality. But let one seize an improvement and proceed to place it in operation, and the others begin to take notice. Thus it was when the Bremen flashed across the headlines with her blunt bow. Every greyhound now planned or under construction has a similar bulbous bow. But the miracle of a stabilised passenger vess.el surpassed that of a bulbous bow. Heretofore gyro-sta-bilisers have been employed only on private yachts, on aircraft carriers and destroyers. All merchant mariners await the trials of the Conte di Savoia. To make a prediction, which is hardly bold, if this great ship overcomes pitching and rolling even moderately, the next five years will witness the adoption of stabilisers as standard equipment for all merchant mariners. No man who anticipates the ghastly horror of sea. sickness will board a non-stabilised vessel if he can help it. To build a single stabiliser for the Savoia would be impracticable. Single units are all right for yachts or 10,000ton warships. But it requires three “apples” to stabilise a 45,000-ton ship. No ship afloat carries more than one of theso “apples/’ The Savoia’s three units will operato singly or. together. For the moderate ocean swell, only one unit will be necessary; for fairly bad weather,

two stabilisers; for stormy seas and battering waves, all three stabilisers will be turned on. Extreme flexibility is their great advantage. In ideal weather, such as may prevail on the South Atlantic, a ship requires no stabilisation; but ninetenths of the time passengers are discomforted by tipping decks. “Turn off the waves,” will be the captain’s order,' hereafter. And to execute the command, one of his subordinates will merely throw a switch. There is the story of an American yachtsman who wired a local pilot to steer his ship into a foreign port. While still in open water, the skipper ordered the “waves turned off.” The pilot suddenly found himself standing on a flood as stable as a sidewalk. He dropped the wheel, ordered the engines stopped and turned to the yachtsman, saying pathetically: “We’ve run aground!” When shown the “apple” spinning in the barrel, he shook his head. It looked fishy. The stabiliser can be turned on and off just like an elevator. When off it stands silent and rigid like a dumb robot. The three units for Savoia will stand on the ship’s double bottom, in the forward end, right below the bridge, in what corresponds to hold No. 3. The units will extend about F-deck and halfway up the wall of E-deck. The floor arrangement of the gyros will correspond to an isosceles triangle, the altitude of which will be 25 feet. At the base the gyros will be about seven feet apart. The switchboard will be at the heart of the triangle which will be flanked on the port side by three control gyro units, and on the starboard side by the generating machinery. The three small gyros will control the larger units by'electrical connections. The smaller mechanisms will naturally be more sensitive and respond quicker to rolling. The controls can be so adjusted that the slightest tipping of the ship will direct the gyros which way to apply force. The gyro is essentially a balanced flywheel inside a casing. This flywheel, called a rotor, makes 750 revolutions per minute, and measures 13 feet in diameter. It is balanced with high precision, so that a coin can stand up on its casing. Its weight is 100 tons. The casing is kept airtight in order that the rotor may spin with the least air friction. Spin these 100-ton rotors at 750 revolutions, and they acquire stupendous amounts of thrust and force energy. If the wheel axle is turned in one direction it resists and turns instead at right angles, applying the force on bearingears at the ends of the axle. The ship frame receives the thrust. A great ship does not take to rolling suddenly. It gains momentum like a swinging pendulum, the first swing having a longer amplitude than the preceding swings, until a maximum is reached. If the pounding of rollers grew stronger progressively the vessel would bo thrown over on her beam ends and capsized. The gyro goes into action at the very word “roll.” The first feel of a tipping foundation starts the rotor turning. By stifling the first roll and the second and so on the gyro never allows the waves to throw the ship out of control. For every thrust from the waves the gyro delivers a counter thrust. It is a blow-for-blow battle. Round in, round out, the gyro retaliates, never missing. By quenching rolling at its beginning a small gyro is thus able to control a mammoth ship!' The wave passes under the hull and the gyro is ready for the next one. In holding the vessel from listing the stabiliser does the same work as gradually lifting a weight from one side of a ship and gently placing it on the other side. In addition to giving comfort, the

stabiliser decreases stress on a ship’s hull. A stabilised vessel does not creak and groan. An ordinary vessel rolling in a seaway accumulates a great deal of strain oil the ship’s superstructure. There is a sympathetic bond between rolling and pitching. Although the gyro has no direct control over pitching, the reduction of rolling automatically minimises the forward plunge and dip. To accomplish all this on the new Savoia her generators will have to deliver only 1500 horse power to the three stabilisers. With these stabilisers a ship in perfectly calm water can be made to roll violently—experimentally, of course. In rough water a 20 to 30-degree roll can be reduced to one and a-half degree. Ships left to themselves plough and wallow through heavy seas. It is difficult to steer them on straight courses. Stabilised ships can be held to any point of the compass. Ships are said to roll because “they have nothing else to do.” The strains forced on ships by waves are stupendous. There is one instance of a large vessel having been broken in two by a terrific wave. The wrenching, twisting movements of choppy seas are estimated to exert as much as 2,400,000 foot tons on a vessel of lai'ge displacement. When wave crests are at both ends of the ship and the middle sags the strain is said to equal 1,050,000 foot tons. Hence the shipping world awaits the Conte di Savoia with more than ordinary suspense. Aside from her ultramodern stabilising equipment, this greyhound will embody the latest improvements, a number of which are made possible by her gvros. ITer top deck will be so steady that it will have a great swimming pool inclosed by glass, admitting ultraviolet rays from the sun. The pool will be aft of the twin funnels. and around it will be laid out a miniature golf course. This pool may be used in all kinds of weather because the stabilisers will maintain constant equilibrium. There will be another pool between lower docks for the use of sc cond and tourist classes The Savoia’s hull design will not only embody the bulbous bow but other refinements now being worked out in the test pool at Hamburg, Germany. Her outboard profile will extend 820 feet. The beam will be 96 feet. Her silhouette will appear rakish and jaunty. Short, stubby funnels will lean back to preserve the streamline effect. Another notable feature of this ship will be the absence of the third, or dummy funnel. Most passenger greyhounds have included it merely to balance the superstructure and to give the ship an appearance of greatness. But the Lloyd Saba udo architects believe that the dav when a passenger stops to count funnels is past, and they are aware that a modern electrically propelled ship might just as well do away with all her smokestacks.