Friday, 18 March 2016

CATASTROPHIC STRUCTURAL FAILURE

Wikipedia
USS Cyclops (AC-4) was one of four Proteus-class colliers built for the United States Navy several years before World War I. Named for the Cyclops, a primordial race of giants from Greek mythology, she was the second U.S. Naval vessel to bear the name. The loss of the ship and 306 crew and passengers without a trace within the area known as the Bermuda Triangle[1]some time after 4 March 1918 remains the single largest loss of life in U.S. Naval history not directly involving combat. As it was wartime, there was speculation she was captured or sunk by a German raider or submarine, because she was carrying 10,800 long tons (11,000 t) of manganese ore used to produce munitions, but German authorities at the time, and subsequently, denied any knowledge of the vessel.[2] The Naval History & Heritage Command has stated she "probably sank in an unexpected storm"[1] but the ultimate cause of the ship's fate is unknown.


Class and type:Proteus-class collier
Displacement:19,360 long tons (19,670 t) full
Length:542 ft (165 m)
Beam:65 ft (20 m)
Draft:27 ft 8 in (8.43 m)
Speed:15 kn (28 km/h; 17 mph)
Complement:236 officers and enlisted

She put to sea from Rio de Janeiro on 16 February 1918 and entered Salvador on 20 February. Two days later, she departed for Baltimore, Maryland, with no stops scheduled, carrying the manganese ore. The ship was thought to be overloaded when she left Brazil, as her maximum capacity was 8,000 long tons (8,100 t).[vague] Before leaving port, Commander Worley had submitted a report that the starboard engine had a cracked cylinder and was not operative. This report was confirmed by a survey board, which recommended, however, that the ship be returned to the U.S. She made an unscheduled stop in Barbados because the water level was over the Plimsoll line, indicating an overloaded condition;[2] however investigations in Rio proved the ship had been loaded and secured properly. Cyclops never made it to Baltimore, and no wreckage of her has ever been found

 "Many theories have been advanced, but none that satisfactorily accounts for her disappearance."[5] This summation was written, however, before two of Cyclops'sister shipsProteus and Nereus, vanished in the North Atlantic during World War II. Both ships were transporting heavy loads of metallic ore similar to that which was loaded on Cyclops during her fatal voyage. In both cases, it was theorized that their loss was the result of catastrophic structural failure,

Rear Admiral George van Deurs suggested that the loss of Cyclops could be owing to structural failure, as her sister ships suffered from issues where the I-beams that ran the length of the ship had eroded owing to the corrosive nature of some of the cargo carried. This was observed definitively on the USS Jason, and is believed to have contributed to the sinking of another similar freighter, Chuky, which snapped in two in calm seas. Moreover, Cyclops may have hit a storm with 30–40 kn (56–74 km/h; 35–46 mph) winds. These would have resulted in waves just far enough apart to leave the bow and stern supported on the peaks of successive waves, but with the middle unsupported, resulting in extra strain on the already weakened middle.

One of the navy officers, Nervig was on board the Cyclops to Rio. He wrote a report that he often found the deck of the ship swaying when large waves struck the ship, suggesting the ship was showing signs of weakening.

There were reports that the Cyclops had suffered hull damage due to a coal fire which contributed to hull failure. Another theory suggests that cargo shifted allowing water to enter the hull, affecting stability and buoyancy - free surface effect causing progressive flooding, unperceived to the bridge watch, particularly at night and rough seas. The overloaded ship would also have driven her bow into oncoming swells, further exacerbating the problem.

In my opinion the above hull failure theory could apply to Waratah. I have devoted a number of posts to Waratah's inadequate hull integrity - dual purpose spar deck and plated bridge deck which spanned considerably less than 50% of hull length. Further to this I believe Waratah was functionally overloaded (9000 tons cargo) which placed considerable strain on her hull. There had to be a reason for her plowing into oncoming swells rather than riding them and some observers referring to her as 'dead in the water'. 

Waratah disappeared very quickly astern of the Harlow, 8 pm, 27 July, and the above theory and rationale could easily explain the cause, rather than striking an object. According to Captain Bruce there was a fire on board and this could have been the last straw in terms of hull weakening. All things considered there is a possibility that Waratah disappeared due to the same reason Cyclops vanished without a trace. However, longer wave lengths are generally found much further out to sea which does not favour such an event occurring just off Port St Johns. 

Note that the Cyclops had a draught of 27 ft. 8 in. which was within the general ball park of steamers from the era - certainly not 30.375 ft. as in the case of Waratah!

See:

http://waratahrevisited.blogspot.co.za/2016/04/needed-12000-tons-cargo-for-stability.html







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