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Flexi Steel

Discussion in 'YachtForums Yacht Club' started by K1W1, Jun 26, 2014.

  1. K1W1

    K1W1 Senior Member

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  2. chesapeake46

    chesapeake46 Senior Member

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    From the comments below the video...

    "Since it sister ship recently broke apart at sea and sank I think if I was a crew member of this ship I would be looking for a new ship to work on but that is just me"

    originally posted in 2012 and the comments around about December 2013.
    Is the comment above B.S. or id her sister ship really sink ?

    Either way the video makes the point. If it don't bend, it breaks.
  3. K1W1

    K1W1 Senior Member

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  4. chesapeake46

    chesapeake46 Senior Member

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    That is a pretty sad story. Like the ship was cursed to go down. No loss of life is good but still.

    If the salvage company lost the entire ship and contents, do they still get paid by someone, or is it just the risk they take ?
  5. K1W1

    K1W1 Senior Member

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    Hi,

    I have no idea, Salvage contracts can vary as much as Crew Contracts even with the advent of MLC 2006
  6. Capt J

    Capt J Senior Member

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    If you bend metal enough times in the same place, it's going to break. I have a feeling those ships are going to eventually meet their sisterships fate and go the way of ferro-cement ships.......I wouldn't want to set sail on that thing.
  7. K1W1

    K1W1 Senior Member

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    Hi,

    Would you care to expand upon this point?

    I am not aware of any ferro cement container or other cargo vessels that have all fallen apart enmasse so look forward to learning something new today.
  8. Capt J

    Capt J Senior Member

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    There is not one surviving concrete ship in use today. Look up the Sapona. It is a ferro-cement freighter that is sunk off of Bimini in shallow water that every snorkels. The reason is the steel and rebar used in their construction rots inside the concrete over a few decades severely weakening the concrete structure, and then it all crumbles and falls apart the moment it impacts something or runs aground. Much like the 80' Ferro Cement sailboat Norseman was involved in a few years back, after sitting behind a house for 2 decades it sold, and on it's maiden voyage bumped a channel marker in Bimini and immediately crumbled apart and sunk instantly.
  9. K1W1

    K1W1 Senior Member

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    Hi,

    From the article I found: SS Sapona was a concrete-hulled cargo steamer that ran aground near Bimini during a hurricane in 1926.

    There is a lot of difference between sinking due to Structural Failure mid voyage and being lost due to a grounding during a hurricane and subsequently breaking up.

    It may surprise you to know that there have been literally thousands of ferro cement or floating footpaths built by folks all over the world and sailed all over the world. If built properly and looked after they are a good cheap boat that enables many to get out and about who otherwise wouldn't.
  10. Capt J

    Capt J Senior Member

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    The Sapona ran aground and broke in half midships. Much like the sistership to the flexi-steel freighter featured in the video, broke in half midships in a rough sea without hitting anything or running aground. Had the Sapona been a normal steel ship, they most likely could've hauled it off of the reef and been on their way. There is a reason why there are no Concrete ships in use today. They made a lot of barges used in Europe and ships out of concrete and not a single one of them is still being used, for good reason they don't stand the test of time. How do you inspect the rebar inside of the concrete to look after it? How do you structurally fix a crack in the concrete? Yeah, there was a craze where a lot of people built these ferro cement boats with a realistic safe life of 20 years, but I haven't seen a single one of them in use today.

    There is a steel freighter the Carnarvon about 7 miles West of Chub Cay, aground on the same shelf the Sapona is and ran aground during the same Hurricane in 1916. It's been through several hurricanes also, and it's hull is still intact and it hasn't broken apart or anything to this day.
  11. Pascal

    Pascal Senior Member

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    The sapona didn't break in half amidship... Did she crack? Maybe, hard to tell after all these years but for the most part the hull is in one piece. The only part which broke off much later from what I understand, is the stern section.

    Considering she s been on the bank for almost 100 years and beat up by numerous hurricanes incl. cat 5 Andrew, I'd say the Sapona is pret good shape.

    Not sure about that wreck you mention west of Chub. Never seen it (the sapona is visible 10 miles out) never heard of it either. The only reference to a Carnarvon wreck is actually off the devils back bone in Eleuthera and indeed sunk in 1916. But it is an underwater wreck, not subject to the same beating from storms.
  12. Marmot

    Marmot Senior Member

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    Having spent a few years on boxboats and tankers crossing the Pacific via the Bering Sea I don't have any qualms about sailing on them.

    That clip shows a normal occurence in rough weather, the ship is nearly a thousand feet long, of course it is going to bend. In bad weather that door at the end of the tunnel would be moving out of view regularly. On tankers you can see the motion moving down the deck as a wave.

    The only ships I have been on that had problems related to that motion were a class of supertankers that were made of high tensile steel in order to reduce weight and increase cargo capacity. They developed cracks on the main deck nearly every trip, especially in the Winter when temperatures dropped and waves rose higher. You could find the cracks by the bubbles of inerting gas that fizzed when a wave washed over. The last few years they were operated we had strain gauges mounted on deck and immersion gauges fitted under the waterline at several points and connected to a computer that warned if hull strains were reaching the danger point. That class of ships were all scrapped long before they should have been.

    In the case of the MOL boxboat that broke in half, we will probably never know the real reason but it is very common for shippers to mis-state container weights and if the load is wrong it can create strain in the wrong places.

    Even tall buildings move more than many people would like to know. Ever watch an airplane wing in rough air?
  13. Capt J

    Capt J Senior Member

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    If you look at the video, it is the class of the freighters made with high tensile steel with thinner main decks and so forth for increased cargo capacity that we are talking about.
  14. Capt J

    Capt J Senior Member

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    There are numerous articles on the Sapona breaking in 2 midships:

    The Sapona was run aground in 1926 and broken in two by the great storm of that same year.

    Bimini Bahamas History
    This Post is for Wreck Nuts Only! | National Underwater and Marine Agency

    Such was the case when I explored my first wreck, the Sapona, a freighter cast in concrete. A ship made of concrete! Sounds crazy doesn’t it? That’s what intrigued me. Built in 1919, the 181-foot freighter was one of a fleet of twelve tankers and freighters whose hulls were poured concrete—a means of saving steel during the WW I. But the concrete prematurely cracked and the ship sailed for only three years. - See more at: This Post is for Wreck Nuts Only! | National Underwater and Marine Agency

    Bruce Bethell, a one-armed gangster from Miami, bought it with plans to convert it into an international gambling casino. Unfortunately, the vessel ran aground while being towed to Bimini in the Bahama Islands. That’s were it sits today, about two miles offshore, broken in two at midship with half of the hull above the water. - See more at: This Post is for Wreck Nuts Only! | National Underwater and Marine Agency
  15. K1W1

    K1W1 Senior Member

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    I think he might have seen it, maybe you should have read what he wrote before hitting the quote button.

  16. Marmot

    Marmot Senior Member

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    When I look at the video I see what is seen on every large ship every day.

    The main deck was the last part of the ship to break. The fracture started in the bottom plating.

    Read this: www.tradewindsnews.com/weekly/329515/probe-finds-mol-comfort-hull-was-not-overstressed

    http://www.mlit.go.jp/common/001029660.pdf
  17. K1W1

    K1W1 Senior Member

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  18. Capt J

    Capt J Senior Member

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    The last few years they were operated we had strain gauges mounted on deck and immersion gauges fitted under the waterline at several points and connected to a computer that warned if hull strains were reaching the danger point. -Marmot


    Ok, so if the ship got into a rough sea and the hull strains were reaching the danger point, does the crew just shut off the engine and put the anchor out or do they pull into the nearest port which might be 1,000 or more miles away, or just pray that the ship doesn't break in half like the last one did?
  19. K1W1

    K1W1 Senior Member

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    Hi,

    Deep Sea you don't have the option of pulling into port or anchoring.

    You modify how the vessel is operated, reduce speed, alter course whatever it needs to reduce the problem.
  20. Capt J

    Capt J Senior Member

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    Ok, so you reduce speed and alter course and then PRAY the ship doesn't break in half like the previous one.

    High Tensile steel is a double edged sword.....The Titanic sank because of the same fate and similar steel production just a lot earlier (heat treatment). When you heat treat steel it does indeed make it stronger, however it also makes it more brittle to bending forces than mild steel. So in a ship that see's forces from various directions and bends by nature it is not a good material to use. High Tensile steel has it's place, but shipbuilding in my opinion for the entire ship is not one of those places.

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