Initial Immersion Rate and damage area

Martin Owen Cahill

Martin Owen Cahill

Member
Here is one for the mathematicians and enineers among you.

It took 4 minutes for the Lusitania's stem to completely submerge. This means it sank at a speed of 12.5 feet per minute and 2.5 inches per second. This would be before loose forward hatches or open D deck portholes could factor into the scheme of things.

The question would be what kind of damage would do this and would that include the hull area around the hole where rivets popped and plate seams split?
I look forward to your answers as this is way beyond my limited math skills.
Thanks

Martin
 
Martin:

Every 130 tons added weight causes Lusitania to settle in the water an inch deeper. A porthole just submerged under the surface will admit 2.5 tons of water per minute.

Neither of these figures can be used reliably to work out a sinking scenario for Lusitania (because of complicating factors ignored in the examples) but you can see that frankly, it doesn't take a very large hole to get a ship to sink quickly if the flooding can't be contained.

By the way, where did you get the 4 minutes for the stem to submerge figure?

Bill Sauder
 
Bill:

Thanks for the analysis. I can't recall the source of 4 minutes and have checked from Hoehling to Hickey & Smith as It has something I have known of for a long time. There are no direct refs in the literature.

That said it seems that events unfolded with frightening rapidity when I read the accounts.
Capt. Turner is reluctant to launch the boats at first but after 10 minutes changes his mind despite the ship still being under way. What changed his mind? Did he see the foreward deck start to disappear in front of him?

Given your collective knowledge I would be most keen to know what you and Eric think/know. The sinking is 18 minutes of history that I have many unanswered questions about.

cheers

Martin
 
Martin,

Thanks for your kind comments. I have been called out of town on business but look forward to resuming the coverstation in July.

Bill Sauder
 
I've often wondered if the fact that the ship was moving at a pretty fair speed may have contributed to this, inasmuch as it may have induced a 'ram effect' into the ingress of water into the hull. My engineering expertise doesn't include a heck of a lot of hydrodynamics - so I'm sorry if this is a completely stupid question...but, I'm interested...

John M
 
I have just finished reading David Brown's Last Log of the TITANIC which has as part of its central arguements that the ship was run at half ahead for 10min after the ship struck the iceberg. This is cited as cause of the bulkhead failure between boiler rooms 6 and 5.

Given the inability to stop the Lusitania, the damage to already weakened bulkheads must have caused some to collapse. This combined with 18knots of forward momentum would contribute to rapid. immersion. any thoughts

Martin
 
Some explanation as to effect of movement under damaged conditions on increased flooding rate can be found at

It's somewhat technical, but does explain how this effect can be estimated. It all depends on where the damage is and the size of the damage. Regarding the Titanic situation, I concluded:

"The bottom line is that a moving ship will cause an increase in flooding rate as well as an increase in pressure against the hull. However, as the numbers indicate, it may not be as severe as one might assume, with the flooding rate being only 6% greater than that of a ship not moving. If you have a reasonable chance to reach shallow water, it seams a good idea to go for it."
 
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