TITANIC SINKING -Crucial Steering Error

[TamarMike]

I suspect that Titanic's bulkheads were as high as those of liners of earlier decades but as liners became more luxurious the topsides got higher. I expect it was thought higher bulkheads would make the first class accomodation claustrophobic.

 

[Andrew_Fanner]

As naval experience of the time showed, watertight bulkheads do not make for quick movement of people from one area of the ship to another. Warships accepted this issue because of enhanced battle survivability. Passenger craft were more concerned with comfort, especially the comfort of First Class passengers.

It is probably fair to add that the Titanic disaster was a relatively freak set of circumstances. Andrews was a highly regarded architect, H&W equally highly regarded for the quality of their construction and a four compartment standard is one of the issues behind the media concept of unsinkable.

Speculation runs now and again as to whether or not structural design issues in the region of the hold/BR6 bulkhead with the firemens tunnel caused the opening to the sea of BR6 and thus the sinking, Cameron's attempts to get an ROV in there being inconclusive, ditto attempts to view the area on board Britannic.

 

[Fascadale]

What an excellent and informative thread

It remains open to speculation what difference reaming punched rivet holes might have made, or better steel in the rivets, but some of that was a product of her time. Queen Mary, 20 years later, was specified with reamed rivet holes from the start, which is a major exercise and adds substantially to the cost and time of construction. The steel of the time, in the ambient temperature at the time, was below the brittle transition temperature and nobody really knew about designing out notches to stop crack propagation and catastrophic failure..

For the benefit of the ignorant (me) could somebody explain what are "reamed rivet holes"
and what are their advantages. I'm also a bit puzzled by "designing out notches to stop crack propagation and catastrophic failure"

Thanks

 

[snowleopard]

I'm also a bit puzzled by "designing out notches to stop crack propagation and catastrophic failure"

Take a sheet of paper and try to tear it by pulling along one of the edges. Now cut a small notch in that side and try again. It is all about stress concentration.

 

[Andrew_Fanner]

Rivet holes were usually punched in both shell plating and structiral framing in normal civillian ship construction. It was quick, inexpensive and "good enough" for normal use in the ships of the time. The process work hardens the metal around the hole and causes microscopic cracking which could propagate and cause localised failure around a rivet. In more extreme cases cracks could propagate between rivets and cause additional stress on the rest of the join, causing the possibility of failure by progressive overload. Rivet spacing was specified to try and mitigate this problem, but stronger joins would require more rows of rivets, which weakened the steel, requiring more rivets and so forth. If the rivet hole was drilled undersized and then reamed out very accurately the surrounding metal would not be work hardened and would be significantly more resistant to cracking. If you are unsure what a reamer is think of it as a very coarse file used to adjust a hole's diameter to a precise size, and percentage size change. It is used in a drilling machine on a slow speed, or turned by hand.

A notch is a sharp indentation in a given structural element. The important factors are the tip radius and depth as a proportion of the size of the base material, depending on the toughness of the material. A 15mm steel frame member with a 1mm deep radiused hole 45mm across is not significantly weakened. A hatchway 10m across with perfectly right angled corners may be a significant hole in the surrounding deck plating. It acts as a stress concentration. Think of a metal strip, say 25mm by 4mm. if you file a V cut 0.5mm deep along the 25mm flat side and then attempt to bend the strip it is most likely to fail where the V has been filed. Bend several times and suddenly the strip will break. Feel the break, the metal will be hot. Now scale that up to a square opening in a ship's structure, such as an accomodation doorway or a hatch. The sharp corners act as a stress concentration. If the corner is in an area that flexes the stress concentration will cause localised work hardening of the material and eventually a crack will develop. A crack can be viewed as a notch with an infitintesimal end radius which allows for rapid work hadening at the end and thus crack propagation. Ease of hardening and cracking is dependant, among other things, on the ductility of the material. 1912 mild steel was not ductile at the sort of temperatures seen in service in the North Atlantic and on a microscale was actually quite brittle.

Think of a traditional glass cutter, same principle but you want the crack to propagate catastrophically.

So, round the edges to doors and hatches!

The ductile/brittle transition temperature and stress notches issue was not fully understood until post WW2, it was also a problem with the Liberty Ships.

We avoid cracking being a major issue with boats made from composite materials. The brittle but nice to look at resin can crack, but the crack tip hits the glass strands and is irretrieveably blunted.

I can go on about this for ages, but much more and its back to some of my text and reference books. SWMBO sometimes gets this sort of thing at work, as you may be able to guess, some of our meal table conversations are far more interesting than debating a new set of curtains!

 

[Fascadale]

Many thanks for the explanations

Its all very interesting: what a great forum this can be

 

[Deleted member 36384]

Dinner At The Fanner's

..... SWMBO sometimes gets this sort of thing at work, as you may be able to guess, some of our meal table conversations are far more interesting than debating a new set of curtains!

Mr Fanner, "Lovely peas."
Mrs Fanner, "Yes they are."
Mr Fanner, "Is that butter you put on the peas?"
Mrs Fanner, "No it's Just Like Butter."
Mr Fanner, "Tastes like butter."
Mrs Fanner, "That's probably why its called Just Like Butter."
Mr Fanner, "Oh, of course."
Mrs Fanner, "Those curtains are looking grubby."
Mr Fanner, "Cant say I noticed, but now that you mention it."
Mrs Fanner, "I never really liked the colour anyway."
Mr Fanner, "Well your mother did buy them, what do you expect."
Mrs Fanner, "What do you mean by that?"
Mr Fanner, "Well you know."
Mrs Fanner, "Know what?"
Mr Fanner, "She's a Plater, not exactly a member of the WRI."
Mrs Fanner, "Just because she's a Plater, doesn't mean she hasn't any decorum."
Mr Fanner, "I didn't say she had no decorum, it was you who said you didn't like the colour of the bloody curtains, I was agreeing with you."
Mrs Fanner, "You always blame her when things are wrong."
Mr Fanner (mumbles), "No I dont. The BOT didn't either."

A period of silence follows for a few minutes

Mrs Fanner, "I noticed that the molybdenum content has increased in tempered, foundry steel for flat pressing and rolling."
Mr Fanner, "Yes its in response to the phase shift on the Eutectic diagram caused by the drop in carbon,"
Mrs Fanner, "I thought so."
Mr Fanner, "I was thinking that it may increase the permissible stress range, what do think?"
Mrs Fanner, "Mmm, not sure that will work as it will reduce the vibration damping factor."
Mr Fanner, "Ah! Of course it will, because the Stress Intensity factor will increase."
Mrs Fanner, "It could be somewhat countered in the quenched state and by specifying a corner radius not less than 5/8' R, what do think?"
Mr Fanner, "That would maintain the Photo-elasticity factor around 1.21."
Mrs Fanner (excitedly), "Yes and keep the Stress Concentration Factor around 1.77!"
Both the Fanners (simultaneously), "Wonderful!"
Mrs Fanner, "More peas darling?"
Mr Fanner, "Rather!"

 

[Major Catastrophe]

Rivet holes were usually punched in both shell plating and structiral framing in normal civillian ship construction. It was quick, inexpensive and "good enough" for normal use in the ships of the time. The process work hardens the metal around the hole and causes microscopic cracking which could propagate and cause localised failure around a rivet. In more extreme cases cracks could propagate between rivets and cause additional stress on the rest of the join, causing the possibility of failure by progressive overload. Rivet spacing was specified to try and mitigate this problem, but stronger joins would require more rows of rivets, which weakened the steel, requiring more rivets and so forth. If the rivet hole was drilled undersized and then reamed out very accurately the surrounding metal would not be work hardened and would be significantly more resistant to cracking. If you are unsure what a reamer is think of it as a very coarse file used to adjust a hole's diameter to a precise size, and percentage size change. It is used in a drilling machine on a slow speed, or turned by hand.

A notch is a sharp indentation in a given structural element. The important factors are the tip radius and depth as a proportion of the size of the base material, depending on the toughness of the material. A 15mm steel frame member with a 1mm deep radiused hole 45mm across is not significantly weakened. A hatchway 10m across with perfectly right angled corners may be a significant hole in the surrounding deck plating. It acts as a stress concentration. Think of a metal strip, say 25mm by 4mm. if you file a V cut 0.5mm deep along the 25mm flat side and then attempt to bend the strip it is most likely to fail where the V has been filed. Bend several times and suddenly the strip will break. Feel the break, the metal will be hot. Now scale that up to a square opening in a ship's structure, such as an accomodation doorway or a hatch. The sharp corners act as a stress concentration. If the corner is in an area that flexes the stress concentration will cause localised work hardening of the material and eventually a crack will develop. A crack can be viewed as a notch with an infitintesimal end radius which allows for rapid work hadening at the end and thus crack propagation. Ease of hardening and cracking is dependant, among other things, on the ductility of the material. 1912 mild steel was not ductile at the sort of temperatures seen in service in the North Atlantic and on a microscale was actually quite brittle.

Think of a traditional glass cutter, same principle but you want the crack to propagate catastrophically.

So, round the edges to doors and hatches!

The ductile/brittle transition temperature and stress notches issue was not fully understood until post WW2, it was also a problem with the Liberty Ships.

We avoid cracking being a major issue with boats made from composite materials. The brittle but nice to look at resin can crack, but the crack tip hits the glass strands and is irretrieveably blunted.

I can go on about this for ages, but much more and its back to some of my text and reference books. SWMBO sometimes gets this sort of thing at work, as you may be able to guess, some of our meal table conversations are far more interesting than debating a new set of curtains!

Very informative. I have learned something today.

Please do not use the word 'catastrophic' quite so much, please. It panics the family when I read threads aloud.

 

[Andrew_Fanner]

Mr Fanner, "Lovely peas."
Mrs Fanner, "Yes they are."
Mr Fanner, "Is that butter you put on the peas?"
Mrs Fanner, "No it's Just Like Butter."
Mr Fanner, "Tastes like butter."
Mrs Fanner, "That's probably why its called Just Like Butter."
Mr Fanner, "Oh, of course."
Mrs Fanner, "Those curtains are looking grubby."
Mr Fanner, "Cant say I noticed, but now that you mention it."
Mrs Fanner, "I never really liked the colour anyway."
Mr Fanner, "Well your mother did buy them, what do you expect."
Mrs Fanner, "What do you mean by that?"
Mr Fanner, "Well you know."
Mrs Fanner, "Know what?"
Mr Fanner, "She's a Plater, not exactly a member of the WRI."
Mrs Fanner, "Just because she's a Plater, doesn't mean she hasn't any decorum."
Mr Fanner, "I didn't say she had no decorum, it was you who said you didn't like the colour of the bloody curtains, I was agreeing with you."
Mrs Fanner, "You always blame her when things are wrong."
Mr Fanner (mumbles), "No I dont. The BOT didn't either."

A period of silence follows for a few minutes

Mrs Fanner, "I noticed that the molybdenum content has increased in tempered, foundry steel for flat pressing and rolling."
Mr Fanner, "Yes its in response to the phase shift on the Eutectic diagram caused by the drop in carbon,"
Mrs Fanner, "I thought so."
Mr Fanner, "I was thinking that it may increase the permissible stress range, what do think?"
Mrs Fanner, "Mmm, not sure that will work as it will reduce the vibration damping factor."
Mr Fanner, "Ah! Of course it will, because the Stress Intensity factor will increase."
Mrs Fanner, "It could be somewhat countered in the quenched state and by specifying a corner radius not less than 5/8' R, what do think?"
Mr Fanner, "That would maintain the Photo-elasticity factor around 1.21."
Mrs Fanner (excitedly), "Yes and keep the Stress Concentration Factor around 1.77!"
Both the Fanners (simultaneously), "Wonderful!"
Mrs Fanner, "More peas darling?"
Mr Fanner, "Rather!"

he he he!

Actually recently its been the theoretical purpose of battlecruisers and why Britain still argued for them at the Washington Naval Conference, we've been helping on a Phd thesis. Youngest won't eat peas so the Mrs wont do them as often as I'd like

 

[richardsn9]

The Titanic was a mobo?

Ah! I can begin to follow the logic here. A mobo is travelling at speed (possibly excessive for the conditions), and sees a large white object ahead? Could those be sails; a raggie without doubt! First Officer Murdoch, a true gentleman to the core, alters course to avoid. The rest is history.......

The lesson learned: never alter course to avoid a raggie or you will sink.... This is the origin of an ancient seafaring tradition followed on the south coast to this very day!

 

[Skysail]

Lady Patten's story is repeated at length in today's Guardian.

Is the wording in the Act (Irish version but I assume it would be the same):

29.—(1) It shall not be lawful for any person on any Saorstát Eireann ship, when such ship is going ahead, either to give a helm or steering order containing the word "starboard" or the word "right" or any equivalent of either of those words unless such person intends that the head of such ship shall move to the right, or to give a helm or steering order containing the word "port" or the word "left" or any equivalent of either of those words unless such person intends that the head of the ship shall move to the left.

[GA] (2) Every person who does any act which is a contravention of this section shall be guilty of an offence under this section and shall be liable on summary conviction thereof to a fine not exceeding fifty pounds. (sic)

 

[Seajet]

Is that right about the Titanic sinking the next day while under tow ?!

This tends to go against everything one has been brought up with, and the enthusiasm to get off the thing would appear to be a bit hasty if this were true.

 

[Little Rascal]

I dispute quite strongly that a deliberate head on would ever have been a viable, as opposed to theoretical, alternative prospect.

"So, Mr Murdoch, why did you cause the vessel to crash head on into the iceberg?"
"Well Sir, in my judgment it gave the ship the best chance of survival. In fact Titanic did not finally sink until a day after Carpathia arrived to take off the passengers and Olympic had arrived and taken her in tow.Only then was it obvious that her keel had cracked open near boiler room six and she was slowly flooding aft through the double bottoms..."

I think this was an imagined theoretical scenario from Mr Fanner regarding the consequences of an alternative head on collision...

Don't think he's disputing the facts!

 

[Alfie168]

Liberty ships got a reputation for inexplicably breaking in two, which did not endear them to seafarers. My mother told me my Grandad (Engineer White Star M.V. Brittanic) said they were grateful not to be on them.

Once they sorted out the crack progagation issue they were fine, but welded ships were still new technology and not fully understood.

Tim

 

[Andrew_Fanner]

I think this was an imagined theoretical scenario from Mr Fanner regarding the consequences of an alternative head on collision...

Don't think he's disputing the facts!

The theoretical scenario is actually drawn from RL when HMS Audacious, a brand spanking new battleship, was mined off the Irish coast in 1914 at the start of WW1. RMS Olympic was nearby and indeed attempted to take Audacious in tow but it proved impossible and Audacious subsequently sank, a mix of slightly dubious design and very poor damage control.

The Admiralty tried to hush the whole thing up and did not remove Audacious from the Navy List or report her sunk. As there were no caslalties from the crew any relative's enquiries could be answered with "is well and serving with the Fleet". The hushup wasa failure, despite even modifying a merchantman to look like Audacious, passengers on board Olympic took photographs!

 

[Seajet]

I doubt a liner could tow a waterlogged battleship but a good try...

The WWII Ark Royal also suffered from 'very poor damage control' and was lost as a result from what I've read; though I haven't seen the findings of the BBC dive on the wreck, a book I'm ordering.