Did the Titanic have to sink?

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

  1. kapnD
    Joined: Jan 2003
    Posts: 1,304
    Likes: 414, Points: 83, 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: 2, 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: 2, 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
     
    Will Gilmore likes this.
  4. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,386
    Likes: 1,045, Points: 113, 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: 223
    Likes: 42, Points: 28, 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: 2, 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: 380
    Likes: 131, Points: 53, 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: 2,716
    Likes: 986, Points: 113
    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    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: 2, 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: 2, 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: 2,716
    Likes: 986, Points: 113
    Location: Victoria BC Canada

    BlueBell . . . _ _ _ . . . _ _ _

    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: 402
    Likes: 51, 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.
     
  13. Mando.Reforger
    Joined: Feb 2021
    Posts: 2
    Likes: 1, Points: 3
    Location: Kansas City

    Mando.Reforger New Member

    JohnBen,
    I have wondered the very same, and the vast majority of responses here have completely missed out on the physics involved in this theory, and they have missed several key details which support the reality that this strategy would have almost certainly worked.

    1. Titanic could almost certainly make 10-12 knots in reverse, and possibly more. Yes, only 2 of 3 propellers could spin, but they were by far the larger 2 props and had more powerful engines and all available power could be diverted to those engines.

    2. Any object at rest wants to stay at rest. Because of this, as soon as the boat starts to push (backward), the mass of all of that flooded water is going to push against the bow end of the hull and the pressure of all of that water will be directed at the point of least resistance, which will be those holes in the hull. This effectively turns the engines into an inertial water pump.

    3. Likewise, water has tremendous surface tension. This means that water, moving past other water will drag it along. The water moving along the hull as the ship moves forward will suction the water through the holes in the hull. This will amplify the inertial effect. Hasn’t anyone here ever pulled the drain plug in a moving boat to suck the water out? It is the same effect. Yes, the speeds are slower and the weight is greater, but the physical property remains. It will not fully reverse the flooding, but it will slow it and potentially stabilize it at a point where the pumps can keep up.

    4. These two forces (inertia and suction) only have to fight against the weight of the flooded compartments only, not the weight of the whole ship. The buoyancy of the remaining watertight ship supports that part of the ship.

    5. Next we add in the low pressure zone created by the shape of the hull and the Venturi Effect and this further reduces the inward pressure at those holes (because that pressure is distributed elsewhere).

    6. Now, we have the modest “planing effect”. The numbers presented by another post were contradictory. Every action has an equal and opposite reaction. If the angle of the boat only produces 3.9 tonnes pushing up, then the downward resistance to forward movement is only 3.9 tonnes. You cannot claim that there is no upward thrust and then claim that the additional resistance is enough to prevent forward motion. These are wildly contradictory claims. Only one can be true. The weight of the extra water displaced in the volume over that surface area of that angular differential (think of a 3d triangular wedge of water) is large. That is 1,900 tonnes (93ft beam x 600 flat bottom foot length x 20 feet down angle)/2 = 558K cubic feet of water = 4.16 million lbs of water / 2200 = 1,902 tonnes of water pushed down which is exactly the amount of boat pushed up! By moving the boat at that angle you have to move an extra 1,902 lbs of water, so it will push up on the hull by the exact same amount. This amounts to about 4% of gross tonnage so a 4% drag penalty gets you 1,902 tonnes of upward thrust. This is physics 101.

    So, the planing effect would be much, much higher because the hull acts as a lever. The fulcrum lies between the props and the CG of the flooding compartments. The effect would be at least 1,900 tonnes.

    7. Boiler room 5 was breached, but the water was as contained in the coal bunker until it burst. That took over an hour! This suggests that any modest reduction in pressure likely could have allowed the coal bunker to maintain integrity at least until it was shored up with equipment.

    8. Recall, that this is ultimately a geometry problem. All we need to do is shift the angle of the bow by a few degrees and water cannot spill over the bulkheads. To tilt Titanic by a few degrees does not take 10,000 tonnes, it takes maybe 2 thousand tonnes . Moving the passengers to the stern is 120 tonnes of weight, but remember, the hull is a lever, so that gets multiplied 2-3x. It only matters if you can get close, but this idea gets us close. We have at least 1,900 tonnes of upthrust relative to the mass of the ship. We have a somewhat reduced rate of flooding due to inertial pumping action and the suction created by surface tension along with the low pressure zone created by the hull.

    At that point is a game of inches...moving bodies around could be just enough to prevent water spilling over the bulkheads.

    9. The D-deck gangway door...most people do not know about this. The D-deck gangway door was left open, and the wrecksite confirmed this. Once submerged, this would have accelerated the sinking of the ship. The size of the door was several times greater than the surface area of the damage to Titanic’s hull (which is as about 12 square feet). It is hypothesized that the D-deck door being open caused the slight starboard list to reverse and a pronounced port list ensued. This likely shortened Titanic’s lifespan by 30 minutes or more.

    Key takeaway: if the ship is underway in reverse, the D-deck door is never opened. This alone adds roughly at least 30 minutes to her survival.

    10. Here is the Coup de Grace. If you steam backwards...where do you steam?

    IN THE DIRECTION OF CARPATHIA!!!!

    Carpathia arrived 90 minutes after Titanic sank. You only need to make up 90 minutes. Carpathia was 58 miles away. It covered that distance in 4 hours. Titanic, even at 10 knots for one hour would cover almost 12 miles. Now, if you can extend the life of the ship (and we already did by 30 minutes at least) you can steam for 2 hours in reverse at 10 knots you will meet Carpathia with time to spare. Titanic lasted nearly 3 hours as it was, and 4 hours is likely given the dynamics we described. Preparations could be made en route, Lifeboats then could be lowered immediately, or Titanic could continue west with Carpathia in escort if flooding had stabilized (probably to beach herself at the nearest available sandy bottom off Cape Cod)...

    THAT is how this idea is genius, and there is a 50/50 chance that flooding would have stabilized and a 100% chance of survival the coal bunker in boiler room #5 could have been reinforced with carpentry...that last compartment was key.
     
    Last edited: Feb 9, 2021
    Will Gilmore likes this.
  14. Mando.Reforger
    Joined: Feb 2021
    Posts: 2
    Likes: 1, Points: 3
    Location: Kansas City

    Mando.Reforger New Member

    It is 1902 tonnes give or take. Speed really does not matter in this equation.

    What matters is the extra amount of water you have to displace in order to move the ship, relative to a normal angle in the water.

    Imagine a triangular wedge of water that exists from beam to beam under that tilted flat bottom. If the ship is down 20 feet by the head and there is about 600 feet of hull length to consider, you have a wedge that is 93” by 600” by 20” and divided by 2 (the volume of the rectangle, then cut in half).

    This is 558K cubic feet of water, which weighs 4.163 million pounds of water. You have to move that much extra water to move the ship forward by one boat length.

    Since every action has an equal and opposite reaction, that is exactly the same amount of water that will push up against the hull...you get ~1,900 tonnes of upthrust.

    Speed does not really weigh in much to the equation.

    Bear in mind that this is the amount of upthrust you get at a 20 foot down angle. If the hull starts to lift up, you get less. If it lowers more, you get more.

    At some point it stabilizes.
    Bottom line, the amount of extra displaced water required is exactly the amount that will push up against the hull.

    It is likely several thousand tonnes of water.
     

  15. fallguy
    Joined: Dec 2016
    Posts: 7,695
    Likes: 1,707, Points: 123, Legacy Rep: 10
    Location: usa

    fallguy Senior Member

    Doesn't all of the presume the guys shoveling coal were chained to the furnaces?

    I can't, as a captain, fathom asking the guys in a room filling with water to stay far below decks.
     
    Will Gilmore likes this.
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.