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The sinking of MS Estonia: Case Reopened Part VII

JayUtah said:
Since Vixen seems to be applying all three nines to the remedial study of the mechanics of materials (or maybe the sauna door is stuck), anyone else who wants to take a crack at this is welcome to do so. The equations are scattered a few pages back in the thread—fluid drag loading and hydrostatic pressure at depth. I didn't ask for wave impact force because that's a more advanced topic for which I haven't supplied the math. If you're interested, you can adapt the ASCE wave loading model by removing the hydrostatic pressure part, for the case when the window on a ship is above the stillwater level. But you'll have to guess at the remaining parameters.

It's not important to get the very accurate right answer. In fact, you'll want to apply some simplifying approximations in order not to have to do calculus. What's important is to look at the ballparks of the numbers you get so that you can compare the loading from "gale force winds" (i.e., 44 m/s) to the simple static loading of having the ship roll or settle slightly until the window is just a bit submerged. There's an "Oh, wow!" moment at the end of the exercise that amply illustrates why we do science instead of vibes.
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I could do you Porter's Five Forces...? Er, I just need to go and check the the drainage in the lower field.
 
JayUtah said:
You would just do it wrong anyway.
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Look. No-one is disputing that the windows of a ship cannot break against wind or waves. Of course they can. The point being made is that the JAIC simply hypothesized that this is what happened based on the volume of water that would be required to put the vessel into negative stability to tip it over, ceteris paribus, i.e., no puncture in the hull.
 
Vixen said:
No-one is disputing that the windows of a ship cannot break against wind or waves.
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You were. You were skeptical that windows that could withstand gale force winds would be susceptible to breakage from water and waves.

You are wrong.

The only reason I said you would do whatever it is you mentioned wrong was to point out how silly it seems for people to set themselves up as judges of others' performance in a field they know nothing about.

Vixen said:
The point being made is that the JAIC simply hypothesized that this is what happened based on the volume of water that would be required to put the vessel into negative stability to tip it over, ceteris paribus, i.e., no puncture in the hull.
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And it's a perfectly sound hypothesis supported by history and engineering fact. The only reason it seems suspicious to you is that you wrongly believed it was an improbable thing to imagine. Ordinary downflooding is far more likely than punctures in the hull from some unknown, unevidenced source.

How are you coming on the Southwest Research Institute report?
 
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Ok, I took a crack at calculating the load on the window underwater and came up with 54,180 pounds.

Goods lord that seems high. Am I even in the ballpark? What have I messed up?
 
JayUtah said:
You were. You were skeptical that windows that could withstand gale force winds would be susceptible to breakage from water and waves.

You are wrong.

The only reason I said you would do whatever it is you mentioned wrong was to point out how silly it seems for people to set themselves up as judges of others' performance in a field they know nothing about.


And it's a perfectly sound hypothesis supported by history and engineering fact. The only reason it seems suspicious to you is that you wrongly believed it was an improbable thing to imagine. Ordinary downflooding is far more likely than punctures in the hull from some unknown, unevidenced source.

How are you coming on the Southwest Research Institute report?
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No, the objection put forward was is that it was never reconstructed in a laboratory based on the specifications of the windows installed in the passenger decks four and five of the M/V Estonia. The extra 4,000 tonnes of water was simply assumed by calculating backwards from a figure of 6,000 tonnes needed to capsize the vessel, based on the maximum free surface capacity of the car ramp of 2,000 tonnes.
 
JayUtah said:
I put it at 181,000 N or about 40,700 lbf. You're in the ball park. Use the middle of the pane, not the bottom edge.
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Ok, thanks! I thought I did use the middle, but obviously mucked it up. Got to run out now, but I'll do it again when I get back and see if I can find my error.
 
JimOfAllTrades said:
Ok, thanks! I thought I did use the middle, but obviously mucked it up. Got to run out now, but I'll do it again when I get back and see if I can find my error.
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I'll post my solution after a polite interval and you can see if I'm the one who mucked up. Since we have contributors from all over, I want to let the planet spin a couple of times so everyone has a chance.
 
Vixen said:
The extra 4,000 tonnes of water was simply assumed by calculating backwards from a figure of 6,000 tonnes needed to capsize the vessel, based on the maximum free surface capacity of the car ramp of 2,000 tonnes.
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No, they didn't simply work backwards and call it finished. They looked at whether the available downflooding paths could accommodate the implied flood rate. They can, and we can know this using math. Your insistence that it has to be physically demonstrated seems to presume that science doesn't exist.

Remember this?
Here_to_learn said:
You mean like chapter 13.6? Here is an extract from it:
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This is what I mean when I say you're not simply "interested" or "curious." You're directly challenging the JAIC methods and findings on no better authority than that they didn't do the analysis you think they should have done, or in the way you think they should have done it. It doesn't even cross your mind that your uninformed expectations are what's wrong. That lack of introspection is why you don't get to be a real investigator.

Initially we used empirical methods to develop an engineering model for water flooding through an opening. And by "we" I mean first Leonardo da Vinci and later Sir Isaac Newton. We validated those models hundreds of years ago, and now we get to use math. Just because you don't get how math works doesn't mean everyone else has to dumb down their findings for you.
 
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Vixen said:
No, the objection put forward was is that it was never reconstructed in a laboratory based on the specifications of the windows installed in the passenger decks four and five of the M/V Estonia. The extra 4,000 tonnes of water was simply assumed by calculating backwards from a figure of 6,000 tonnes needed to capsize the vessel, based on the maximum free surface capacity of the car ramp of 2,000 tonnes.
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Why would anyone do that in this case?

The cause of the sinking was the loss of the bow visor and the open car ramp. Sinking a ship is a process, there is a primary cause, and a series of follow-on factors which contribute to the end result. The USS Indianapolis was struck by two torpedoes and sank in 12 minutes. The ship's water-tight compartments were compromised by the fact that the captain allowed portholes and hatches to be left open for ventilation in the crippling heat (fleet HQ had not forwarded a report of a submarine in the area). But while the open portholes and hatches were a factor in the sinking the main cause was the torpedoes.

Your other failure is the assumption that the water in the car deck somehow magically staid there, and didn't flow into ventilation shafts, stairwells, and access panels. This certainly did happen, and I don't need to test or model it for you.
 
Ok, I tried to do this with just my high school physics class, what I could remember from when I sold pressure gauges and instrumentation, and my calculator. I also did everything in pounds and inches since that's what I learned way back when.

So, first I converted everything to inches. The window is 3 meters tall and at a depth of 2.5 to 5.5 meters. This makes the window at about 118” high and puts the middle of the window at 4 meters depth or about 157.5”. The window is 1.5 meters wide, or about 59”.

Since the pressure of the water is linear with respect to depth I assumed that taking the pressure at the depth of the middle of the window and using that for the entire area of the window would be close enough.

So, my memory is that every 28” of pure water gets you about 1 psi. That makes the pressure at 157.5” about 5.6 psi. The area of the window is 118” x 59” or 6962 square inches. 5.6 psi on an area of 6962 sq. inches gets me 38987.2 pounds. (And now I know where I screwed up. I typoed 6962 when I entered it into the calculator. Where’s that head smack emoji?) I ignored the atmospheric pressure above the water since the window has that pressure on both sides so it cancels out. Seawater is a little heavier than pure water by something like 3%, so the final pressure on the window should be about 40156 pounds.

That’s still an enormous pressure, but at least I got (close to) the right answer this time. :)
 
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