I recently saw a History Channel presentation saying that the Titanic's max angle out of water was only about 18 degrees and that when it broke in two the bow of the ship rose out of the water because of the sterns weight. So you think this is true?
I think it's open to debate and has been debated for quite some time now. I think it was Answers From The Abyss which asserted that the angle was probably no more then 32° but then I may have my documentaries mixed up. What I do know is that opinions vary by quite a substantial degree on this. The nature of historical research and forensics being what it is, this is not something that will be known with absolute discussion stopping certainty.
The best we can do with the evidence and knowledge we have is be open to the possibility of what most probably happened as well as rule out that which could not possibly have happened at all.
Based on testimony from Lightoller, the bridge was just going under as the crow's nest was at the water. Depending upon how you choose to draw that line, it measures 11 to 15 degrees. The events surrounding Lightoller's observation dovetail nicely with a rather sudden change in the condition of the ship which is nicely explained by the beginning of the breakup. That's how the shallow angle break comes to be explained.
I subscribe to this theory presently. Using virtually the same documentation, my good friend Parks Stephenson has come to the conclusion the angle was somewhat steeper at breakup.
Both the shallow and steep angle at breakup have very strong arguments in their favor. Choose the one you prefer, of sit it out until more data becomes available.
I'm with David B on the whole. When you think about it, the weight of the stern exerted its greatest leverage when the hull was at quite a low angle. Think of it as a see-saw. When is the bending load on the mid-point of the board greatest?
I have testimony that the hull was failing quite early, maybe even before the props broke the surface.
I wonder whether the 'plunge' and the 'wave' noticed by Lightoller and Gracie mark the moment when the hull failed. Was the air that forced Lightoller away from the ventilator driven into the fore part of the hull by water rapidly flooding in from the break aft?
Not too sure about the max angle that was reached but i remember reading somewheres in the testomony about a passenger seeing the props and the keel of the ship as the first funnel was falling or already fell. to see the actuall keel it would have to be maxed at the max angle most likely at the time. I used a photo software i have and used a profile blueprint and i angled her at a 11 deg sinking at the bow well if i put it where the props are just breaking the water that puts water halfways up the No 1 funnel and is about to pour over the top of the weather cover for the first class staircase dome. Also the weather cover for the A deck sides are fully underwater at that angle just one window can be partialy seen. At 15 degs if the program is correctly angling the diagram right if i dont adjust the diagram any and leave it where it is for a 11 deg sinking it puts her keel visable out of the water up to where the wings for the propellers are visable fully.
Be careful about coming to conclusions based on analogies with such things as a see-saw. The see-saw has a single point of upward force at the midpoint. The ship had its buoyant force distributed horizontally. As the stern got higher there would be less buoyant force contributed by the after end thus increasing the stress moment as the stern increased in angle. Try lifting a child out of water and what you feel is that they seem the get heavier the higher out of the water they are lifted. There will be a point where a maximum is reached.
As far as the props being out of the water, it was noted that the props were half-way out about 1:30 after lifeboat #15 was launched. By 2 AM the props were already above the water as noted by Boxhall as he went around the stern toward the starboard side in boat #2. Just before Lightoller left, the crow's nest was level with the water just as the forebridge went under. That puts a 10 degree down angle on bow based on the ship's dimensions. If you try to angle a profile view of the ship to see what this looks like you have to use the correct center of flotation under the flooding conditions at the time. That point was well aft of amidships all night and moved a bit further aft before the break took place.
Going out on a limb, I believe that Wilding was telling the truth when he said that the ship should not have broken at the 11 to 15 degree angle--or, maybe even the higher one proposed by Parks.
The physical evidence from those two pieces of double bottom is that the cellular bottom was holding the stress without deformation. There is really no evidence of the wrinkles associated with failure in compression.
Naval architect Roger Long of the History Channel team noted the lack of compression damage coupled with the obvious signs that the pieces came out of the ship in tension. The simplest reason for this is that the girder was not failing at the level of the keel when the ship broke. Most likely, the stress was within the "design envelope" to use a modern term.
What happened? Well, the transverse location where the two pieces of double bottom came apart was directly beneath the after expansion joint. And, the design of this joint was such that it was not contained entirely within the lightweight superstructure, which it was intended to protect against flexing of the hull. Rather, the joint was extended into the bulwark formed by extending the shell plating above the strength deck (B deck in Titanic). This joint also extended below the strength deck by about 8 inches if my memory serves.
I support Roger's contention that the joint was effectively a notch in the hull girder which acted as a stress riser. It had the effect of concentrating the stress of lifting the stern onto a small area of steel. It was that small area that failed, causing cracks to migrate down both sides from B deck to the tank top.
Once the crack reached the tank top, the ship transitioned from a hogged situation to a sag. This caused the vertical sides to come away from the pieces of double bottom. In addition, the upper decks were crunched together.
Parks has an excellent interpretation of the high-angle breakup scenario on his marconigraph web site. Roger Long went with the shallow angle concept. I find that my research into the timeline of events favors Roger, but as I have said the jury is still out as far as the high/low question goes.
"High" and "low in this discussion are relative to each other. The high version is still at a very conservative angle compared to some suggestions in the past.
Tough nut. Let's start with the definition of a "girder." Dictionary says it is an "iron or steel beam...built up in plates, bars, latticework, etc., often of very large size (as in bridge construction) used for the same or similar purpose."
Think of a ship as a box without point or propeller. It would resemble a hollow tube. A ship is made of solid steel not only for strength, but also to keep the water out.
Now think of an old-style steel girder railroad bridge. Note that it has a top, sides, and bottom. The only difference is that the railroad bridge doesn't need to keep water out. So, the unnecessary steel has been pared away, leaving only the skeleton of steelwork.
Think now of an "I" beam. It is rigid because the two horizontal plates are separated by a vertical web. The plate on top must be stretched and the plate on the bottom compressed for the beam to bend in an inverted "U." As long as the web does not fail, the beam resists bending. But, if the web fails, the I-beam takes on the rigidity of spaghetti prepared for a man without teeth.
Slice a ship down the center along the keel and you effectively get two U-shaped channels. In effect, it is a mis-shapen "I" beam. Put together, the two halves once again form a full structure much like a box beam. It is the totality of the shape and placement of materials in the hull which give it rigidity, not just the qualities of the metal.
In the analysis of structural failure in a ship...like the breakup of Titanic...it helps to think of the hull as a "girder" much like that railroad bridge. The result of bending forces applied to the hull, or the loss of structural members within the hull, can be understood by thinking of the hull as a girder...in this case, a "hull girder."
So, the concept of "hull girder" is generally used as a way of examining the longitudinal (fore and aft along the keel) strength and flexibility of a vessel. To naval architects things are a lot more complex. My examples are deliberately over-simplified for clarity to non-techies like me who don't understand the finer points. However, for this discussion it is probably enough to know that if the hull girder holds intact, the ship does not break apart. On any ship, loss of the hull girder is always the start of a very bad day (or in Titanic's case, night).
well i remember the discovery channel special back in the 90`s where they used the computer generated ship to dertimine where stress would be the strongest not sure what angle they tried to put the ship at but it showed the I beam keel deforming and the keel compressing but from all the pictures of the stern ive seen it appears the double bottom didnt compress but broke into pieces. I think that the hull would be designed to support itself enough. Think about when she was launched she didnt go into water level but at about a 8 to 9 deg angle stern first if she broke at say 10 to 15 degs that means that even as a non completed ship she would have had stress fractures or cracks in the hull during the launch just my opinion from seeing pictures of the launch.
>>I think that the hull would be designed to support itself enough.<<
Not entirely acurate I'm afraid. A hull is designed to float...obviously...and get it's exterior support from being afloat in the water itself. A hull that's not afloat can be under a surprising amount of stress as there's nothing supporting the structure from the outside. That's why the placement of keel and hull blocks is as important, and the exact science that it is, when I ship is going to be in drydock.
>>but at about a 8 to 9 deg angle stern first if she broke at say 10 to 15 degs that means that even as a non completed ship she would have had stress fractures or cracks in the hull during the launch<<
Errrrr...probably not. I can't rule it out past the point of debate but a hull is designed with the launching in mind. In fact, that's about when it suffers through some of it's greatest stresses, and that's when it takes to the water for the first time. The reason for that is at some point, part of the hull is in the water and afloat, but the rest is still high and dry on the ways. Since it's going in at an angle, this imposes enormous bending loads on the keel.
Sam, I don't see what lifting a child from the water has to do with it. The increase in weight in that situation is due to the fact that the weight of the human body when immersed in water is about zero. As somebody is lifted out, their weight goes from zero to, in my case, about 100kg.
When we look at steel, it's another story. An Imperial ton of steel (2,240lb) still weighs some 1,947lb when immersed in seawater. When lifting an anchor, there's no large increase in weight as it clears the surface.
In the case of Titanic, we have a forward end that weighed almost as much when well immersed as it did when floating normally. We have a stern section full of heavy machinery. As you say, the centre of buoyancy moved aft during the sinking. With two huge weights opposing each other, something was likely to give.
On the subject of launching, H & W naturally knew of the risks. To minimise them, Titanic was launched without much of her heavy equipment. Her hull weighed only 24,360 tons when launched, as compared with 38,760 tons when completed, but without fuel, cargo, stores and so on.
Dave G., you said "The increase in weight in that situation is due to the fact that the weight of the human body when immersed in water is about zero." The weight of the stern section when immersed under normal conditions would also be zero because the amount of water it displaces would be equal to its entire weight, including all the machinery within. That is why any ship floats to begin with as you know. As the stern was pulled out of the water the displacement of water underneath it became less. The difference between its weight and the water that it still displaced was more or less the force that was lifting it out. The more it was pulled out, the less remaining displacement force and the greater the force trying to hold it up.
Your observation concerning the weight of steel in water Vs. out of water is correct. The difference between the two is the weight of water displaced by a solid lump of steel. If you can hollow out an anchor leaving only a thin watertight shell in the shape of that anchor in its place, you can get it to float.
Thanks Dave B., for your explanation of the term "hull girder." I see that the use of the term "girder" refers to the strengthening/stiffening characteristics built into the entire hull structure, including the keel, ribs, plating, bulkheads, etc. Please correct me if I'm wrong.
As far as Titanic's launch and the resulting stresses on her keel are concerned--I assume those stresses "moved" along the keel as the ship entered the water. At what point along the keel would the greatest stress have occurred (if anyone knows)?
>>At what point along the keel would the greatest stress have occurred (if anyone knows)?<<
As I understand it...and I could be mistaken...about half to about 2/3rds down the launching ways when you had part of the hull afloat in the water and the rest of it still angled up on dry land with all of the weight bearing down on the keel.
When i said that about the launch i was pointing out that even during the launch there would be stresses on the keel and the hull since it will try to sag under its own weight that isnt being supported by the slipway or the water. I doubt they would have built her not to handle stress cause if she was in heavy seas that would cause her folksel to be just about underwater as her props are starting to break the surface in normal high sea conditions im fairly sure in very calm sea`s lifting herself out of the water up to 20 degs possibly 25 degs seems possible considering theres no rocking up and down of waves to put mores stress on her hull. Be very simmilar to as if she was launched from the slipway.
>>When i said that about the launch i was pointing out that even during the launch there would be stresses on the keel and the hull since it will try to sag under its own weight that isnt being supported by the slipway or the water.<<
You're right. There are, and if I recall correctly, these are about the highest bending loads that will ever be imposed on the hull during the service life of the ship...even in some of the most savage storms. That's why launchings were always carefully planned out ahead of time. To just put it on a set of sliding ways and shove the beast in without giving due consideration to the weight of the ship, the declination of the ways, the stresses imposed on the hull girder, the stabilty of the ship (Actually quite tender at this point since it was essentially an empty shell with no ballast and a lot of topweight) was to invite disaster.
And sometimes it did.
I don't know of any ship that broke up on launching in this or the last century, but there have been some embarrassing incidents such as that of the Principessa Jolanda which went in, rolled over and sank on the spot in 1909. This happened in front of a crowd of 6000 people including some of the Italian nobility.
Steel framed ships can handle a lot of stress and for the reasons you pointed out, they have to be. Still, if you impose loads on the hull greater then it can survive it breaks. That's what happened to the Titanic.
It was a empty shell, they even had to lock the rudder in place since there was no steering gear installed yet, and she wouldnt have been that top heavy since all her steel decks were ribbed and plated atop but she did have more weight on top from deck house, then the engine casting, From the pictures ive seen looks to be about a 5 deg angle on launch, I figured about a 15 deg tilt max before she broke, taking into thinking of the COG moving back as more compartments filled, that would put the COG just aft of the compartment that is just flooding. At 15 degs it would give her about enough angle to enable the No 2 funnel about to have water pour in through the top when water was lapping at the No 3 funnel housing. I remember cant remember who said it but i remember a passenger i think it was stating that they saw passengers swimming in the water about to be sucked down the No 2 funnel. Thats the only angle i can get that would allow water to flow in the top of the funnel but not put the stern so high that in the break it would cause a large wave.
The empty hull would have been top heavy enough. The engines and boilers account for a substantial amount of weight and at the time any of the Olympics were launched, they just weren't there to ballast the thing down. Crunch the numbers right and there's no problem. Crunch them wrong and the yard manager can find it nesseccery to update his resume.
Obviously, I can't speak conclusively about what angle the Titanic's hull finally gave up he ghost. That's been a matter of debate among people much better versed in the forensics then I can ever hope to be.