Did the Titanic have to sink?

Discussion in 'Stability' started by johnben, Apr 13, 2012.

  1. kapnD
    Joined: Jan 2003
    Posts: 546
    Likes: 50, Points: 28, Legacy Rep: 40
    Location: hawaii, usa

    kapnD Senior Member

    Hauling *** backwards with limited control in darkness, and in an area where there was known to be icebergs doesn’t initially sound like a great idea.
    The iceberg that they struck was lurking somewhere behind them.
     
  2. Bengo
    Joined: Feb 2019
    Posts: 6
    Likes: 0, Points: 1
    Location: UK

    Bengo Junior Member

    Well, thanks for that, and your figures seem to hang together. The vertical component is not really in dispute, save to say that it would exist and presumably be beneficial. That, however, is not the main thrust of our enquiry, which mainly concerns the flat bottom, of which I had seen little or no mention here, and any possible planing effect. It's a shame that all you have is what looks like forward thrust figures for 20 knots, because clearly the drag on the ship at that speed would be enormous, and if, say, an uplift were produced at 5 knots, then the calculation would be way out. Having seen the way large ships accumulate speed, i.e. very, very slowly, I am more than prepared to believe that the angle in the water alone might have defeated any acceleration altogether, and the ship might have been "dead in the water" in reverse, but still able to make speed forwards. Till we know the physics, these figures are interesting to chew on but still moot. One other factor in all of this is that presumably the rear of the ship would be where most of the weight was, though, once again, how much lighter would it have to be to make a difference. I'll have to try to link to the documentary where it got mentioned by James Cameron. I really can't remember their conclusions. I don't think anyone here is arguing that it should have been thought of, even if it would have worked. It would, nevertheless be good to know one way or the other without guessing, which is pretty much all I can see here so far. I'm here because I don't know. Most folks here seem to think they know, but without better figures and physics than this I'm not convinced - yet.
     
  3. Bengo
    Joined: Feb 2019
    Posts: 6
    Likes: 0, Points: 1
    Location: UK

    Bengo Junior Member

    PS. Thanks for the advice kapn, but I think I would have taken my chances on board the ship with the icebergs. Remember, of all that went into the water, only a handful lived, so just stick that baby in reverse before you jump kapn Birds Eye. I'll hang onto the mast in if we hit something. :D
     
  4. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,023
    Likes: 360, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    There is no "planing effect" with ships of this size, the bottom area, with which planing effects are closely related, grows with the square of the length, the weight however, grows with the cube of the length, and in these monsters, all but negates dynamic lift. Get the speed up to 200 knots, maybe different. :D
     
  5. The Q
    Joined: Feb 2014
    Posts: 146
    Likes: 8, Points: 18, Legacy Rep: 21
    Location: Norfolk, UK

    The Q Senior Member

    Why did they not climb on the iceberg?... Because it was several miles behind them. It was only a glancing blow that hit the berg, they would have coasted several miles before stopping or even going full astern 1 or two miles.. They actually must have been very close to missing the berg, maybe by as little as 20ft
     
  6. Bengo
    Joined: Feb 2019
    Posts: 6
    Likes: 0, Points: 1
    Location: UK

    Bengo Junior Member

    We are not talking about taking the passengers water skiing, for God's sake :D.

    Remember, we even don't even need to keep the ship on the surface. We only have to delay the sinking - which already took the best part of three hours - by minutes to save lives. The rescue ships are already speeding to the area, set to arrive only an hour or so too late. What would you have given for even another five minutes?

    Surely, you maritime experts are not trying to tell us that with the Titanic's engines you only have enough power to keep a couple of cars afloat :rolleyes:.

    In general terms: the sinking was already substantially delayed by the efforts of the puny human crew- forces nowhere near as powerful as the two Herculean props.

    So "planing" might be the wrong word. Then let's talk upward thrust - if we must. This is not about semantics; and it's not even just about getting calculations correct. It's about doing the right calculations in the first place - whatever those might be - again, who knows?. For instance, I doubt the above(?) forward/backward thrust at any given speed - say 20 knots gives us anything conclusive - though that might enter the calculation at some point. We need something more like upthrust as a proportion of the ship's effective weight. Any possible upthrust created by water thrust toward the stern and the flat, inclined hull by the propellers and/or the movement of the ship over/through the water. Moving at sample speeds of, say, 0, 1, 5 and 10 knots.

    There's plenty of coal, so if by some miracle the props could only achieve stasis with the ship stationary in the water, we could tell the orchestra to drop the hymns and play something a bit more cheerful :). The posh drunks all can go back into the bar, and all the stowaways get to live. They can't go water skiing, of course, but the upside of that is that they won't be molesting any more poor defenceless icebergs either.

    As I said, I'm not even convinced you could get the ship moving when the pointy bit at the front :D even slightly down in the water, but it would be nice to know one way or the other. However, even at zero knots, the props would still be forcing water under the hull and presumably, creating at least some upward thrust as the considerable flat base forced the moving water downwards and outwards. And even if the ship could not move, the backward traction might still help prevent the ship from sliding freely forward and deeper - where the water pressure would be greater, and more water would be forced sooner into the bows of the ship, where the crew are working against time to shore up the bulkheads.

    One horse power, for instance will apparently lift 15 tons one foot (300mm) in one minute, so at a slower speed with minimal drag on the hull, say at a glorious, fearful, one knot, the upward thrust could still, for all we know, be thousands of tons, and at the said tiny initial incline the ship would still plane :) over and out of the water - rising however slightly, or sinking more slowly - however slightly - at the bow.

    Such might be the sheer thrill of speed - for the otherwise condemned passengers and crew.

    But maybe not. Either way the calculations alone would be interesting. You need someone unbiased and clever enough to work it all out but dumb enough - like us - to waste time on this. Could be tough.
     
    Last edited: Dec 18, 2019
  7. alan craig
    Joined: Jul 2012
    Posts: 231
    Likes: 33, Points: 38, Legacy Rep: 14
    Location: s.e. england

    alan craig Senior Member

    I don't think the iceberg was one of those icebergs with steps up from the waterline to a flat holding area with made-of-ice bollards to moor the ship or lifeboats to.
     
  8. BlueBell
    Joined: May 2017
    Posts: 985
    Likes: 137, Points: 43
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Bengo,

    John hasn't visited, let alone posted here on the forum, for over seven years...

    In regard to your speeding up to reduce water ingress through the TITANIC's hull:
    No, in fact it would flow in even faster if anything.

    Now, if you could move enough people to the port side to roll the holes clear of the water's
    surface, without rolling all the way over, then maybe more time could have been bought.
    Maybe.
     
  9. Bengo
    Joined: Feb 2019
    Posts: 6
    Likes: 0, Points: 1
    Location: UK

    Bengo Junior Member

    Heh. Heh. They had iceberg ladders crampons and landing craft. Just no binoculars :).
     
    Last edited: Dec 18, 2019
  10. Bengo
    Joined: Feb 2019
    Posts: 6
    Likes: 0, Points: 1
    Location: UK

    Bengo Junior Member

    Love it. Thanks for the inside info. It's not about John. If you look, I haven't been here myself for long enough either :).

    And it's not about the or the amount of water forced through the hole - or not. I don't believe that was my point. I just don't think any increased flow through the hole would matter if other things were keeping the ship buoyant.

    For whatever it's worth to you, probably nothing, it's about upthrust of the moving water on the ship's stern and flat bottom caused by the turning propellers and any possible backward movement of the ship.

    If the ship can't sink, or can just sink more slowly, then speed of water past the "hole" would logically be beside the point, as the water pressure inside and outside the hole would have to equalise for any given speed angle of the ship and depth of the "hole" - if, indeed it was a hole, of course.

    That is what I was suggesting in my first post here. I'm surprised that anyone has even responded.

    So thanks.
     
    Last edited: Dec 18, 2019
  11. BlueBell
    Joined: May 2017
    Posts: 985
    Likes: 137, Points: 43
    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Bengo,

    Sorry for the confusion.
    I'm really confused now.
    Wrapping/stringing bed sheets/tarps around the open gaps may have slowed ingress.
    Works a lot better on smaller boats!
    Plugging from the inside may have helped, I don't know, I wasn't there.
    It was a sign of the times however.
    Tragic loss of life.
     

  12. latestarter
    Joined: Jul 2010
    Posts: 341
    Likes: 29, Points: 28, Legacy Rep: 233
    Location: N.W. England

    latestarter Senior Member

    Bengo
    One of the points you are missing is, water is free to flow sideways, your idea of increased pressure on the inclined flat bottom due to movement assumes the water beneath the hull is prevented from moving.
    Any theoretical rise in pressure will be dissipated by the water being squeezed out the sides.
     
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.