• Quick note - the problem with Youtube videos not embedding on the forum appears to have been fixed, thanks to ZiprHead. If you do still see problems let me know.

The Sinking of MS Estonia: Case Re-opened Part II

Status
Not open for further replies.
JayUtah said:
Capsizing requires a roll moment. This source does not discuss that. Show us, preferably with a vector diagram relating the center of gravity to the center of buoyancy, how a ship that fills with water will inevitably capsize. Show us the roll moment.
Click to expand...


Did I miss the part where Vixen addresses this matter?
 
Vixen said:
We were talking about capsizing right, when the trim (centre of gravity) is displaced (listing). When a vessel lists at 90° it capsizes belly up.
Click to expand...

What is your evidence for this?

ship's turning right over and staying afloat are very rare. If a ship goes to 90° it usually goes under.

It is difficult (but not impossible) to find examples of ships floating upside down for any time at all.
 
Vixen said:
We were talking about capsizing right, when the trim (centre of gravity) is displaced (listing). When a vessel lists at 90° it capsizes belly up.
Click to expand...

What is your evidence for this?

ship's turning right over and staying afloat are very rare. If a ship goes to 90° it usually goes under.

It is difficult (but not impossible) to find examples of ships floating upside down for any time at all.


It is a lot more common for small fishing boats and dinghies with built in buoyancy or sailing boats with tall masts and rigging.
 
Vixen said:
Do look up how bulkheads in the hull add to the buoyancy of a ship. Stop harping on about overloading the wretched thing and thereby claiming that elementary laws of physics do not apply. (Short answer: they do.)

Look up Vasa to find out why it sank.
Click to expand...

What does Vasa have to do with anything?

Bulkheads will limit flooding but only if they are sealed. If there are openings then water will flood through.
If machinery spaces flood then there very well may not be enough buoyancy in other compartments to keep a ship afloat.

If water is flooding down from higher decks in to compartments then bulkheads will not help.

In the case of Estonia the thousands of tons of water on the car deck heeled the ship over submerging openings that allowed flooding of lower compartments and water gained entry from above through open stairwells and ventilators in to machinery spaces and accommodation.
 
Vixen said:
Longboats had sails, did they not?
Click to expand...

Yes but they were mainly rowing vessels, the sail was an auxiliary only used when conditions were right. It still applies to them though, an inexperienced skipper or a sudden blow up could capsize them like any other sailing ship.
 
Vixen said:
May I politely suggest you look up the priniciples of displacement of air so that you have a better understanding of what happens when you carefully load up your boat with the aim of making it sink?

Anyone can deliberately crash a car or an aeroplane but it doesn't mean you've outwitted the designers.
Click to expand...

All you need to do to sink a boat is let water in. You don't need to overload it. In a dinghy the easiest way is to tip it over.

I remember when I learned to sail many decades ago with the Sea Cadets, it was quite difficult to make a dinghy turn right over to do recovery drill on a capsized boat.
It was easy to get it on it's side but more difficult to force it further over.
 
Captain_Swoop said:
And still, by far the vast majority of boats and ships do not turn over when they sink and even those that do sink very quickly.

[qimg]https://i.imgur.com/bYZPKDnl.jpg[/qimg]

[qimg]https://i.imgur.com/Iqz1pz2l.jpg[/qimg]
Click to expand...


Actually, that photo of a rowing eight sinking is an excellent example to take.

It's a great example for this reason: these sorts of rowing boats don't typically sink because they collide with something, or because they develop leaks. They sink because they have very little free board (in order to facilitate fast and efficient rowing strokes) - which means it's relatively easy for water from the lake/river to splash above that free board and into the boat. The boat is buoyant when its cargo is merely the rowers and the cox. But if/when more water gets over the side and into the boat than can be auto-bilged out, there comes a point when the additional mass of this water pushes the boat past its buoyancy limit. And it starts to sink.

Furthermore, there's ample empirical evidence (not least from the televised annual Boat Race in the UK) that when these sorts of rowing boats start to sink in this way, they simply sink straight downwards, without capsizing. As your photo elegantly shows.....
 
Last edited:
Captain_Swoop said:
What is your evidence for this?

ship's turning right over and staying afloat are very rare. If a ship goes to 90° it usually goes under.
Click to expand...


Yes. And when it reaches that 90° inclination, it usually sinks in that inclination. It doesn't continue rolling until it's completely upside down, as Vixen would (for some reason) like to believe.
 
Captain_Swoop said:
Uranium is used in the bulb keel on a racing yacht to add ballast. It is very dense so weight can be added while keeping the bulb streamlined.
Click to expand...


Indeed. And if too much of it was used, it would sink the yacht - while still barely making a dent in this "displacement of air" nonsense that Vixen seems to think of as all-important.
 
On a kind-of-related topic, I remember an episode of Mythbusters (in its original incarnation) where they were testing the effects of inflation pressure on the throwing/placekicking distances of a (American) football. They tried the test using either regular air or helium to inflate the footballs, at varying inflation pressures.

Before each test, they weighed the football. And it temporarily bamboozled even the great Adam and Jamie when the football inflated with helium to (say) 16psi was heavier than the same football inflated with helium to (say) 11psi. Instinctively, one would be tempted to think that "more helium" equals "lighter". But, of course, if that "more helium" is contained/constrained within the same volume (here, the internal volume of the football), it is indeed heavier.


(Not to mention the fact that more helium - whatever volume it's contained within - always has a greater mass than less helium. It's just that one would have to assess the helium in a vacuum to make that determination, owing to the fundamental difficulty of "weighing" helium when it's surrounded by air)
 
Last edited:
junkshop said:
I disagree. Creating watertight compartments may help maintain buoyancy in case of a hull breach, but it cannot add to the buoyancy, which was Vixen's claim.
Click to expand...


I suppose so. I’m still not convinced of the relevance of bulkheads to water flooding the car deck of a ferry, in any case.
 
Mojo said:
I suppose so. I’m still not convinced of the relevance of bulkheads to water flooding the car deck of a ferry, in any case.
Click to expand...

Well, they're not relevant, are they? :)

I suspect this may have been intended as a set-up for Vixen to revisit some of her earlier theories about passanger cabins being watertight, and 'therefore there must have been a breach in the starboard side of the hull'. There was something about swimming pools in there, too. Maybe l'm just a cynic.

I hope we get the one with the mini-sub, that was a favourite of mine. :D
 
Last edited:
junkshop said:
Well, they're not relevant, are they? :)

I suspect this may have been intended as a set-up for Vixen to revisit some of her earlier theories about passanger cabins being watertight, and 'therefore there must have been a breach in the starboard side of the hull'. There was something about swimming pools in there, too. Maybe l'm just a cynic.

I hope we get the one with the mini-sub, that was a favourite of mine. :D
Click to expand...

I think her trump card at the moment is the report she told us about saying that two out of six doors leading from the car deck were found to be intact.

It's not clear which side of the ship those doors are on, which would obviously matter since if they were on the port side they'd not be involved in the flooding.
 
Vixen said:
May I politely suggest you look up the priniciples of displacement of air so that you have a better understanding of what happens when you carefully load up your boat with the aim of making it sink?
Click to expand...


No. I'd rather not argue about predictions based on "principles" when I have everything I need to try it out for myself.

Awaiting your instructions for how to introduce the water in an appropriately unbalanced way, for your clearly stated prediction of the results based on the principles you describe, and of course your wager.
 
Jack by the hedge said:
I think her trump card at the moment is the report she told us about saying that two out of six doors leading from the car deck were found to be intact.

It's not clear which side of the ship those doors are on, which would obviously matter since if they were on the port side they'd not be involved in the flooding.
Click to expand...

They make no difference as there are lots of other openings to the hull.
 
Myriad said:
No. I'd rather not argue about predictions based on "principles" when I have everything I need to try it out for myself.

Awaiting your instructions for how to introduce the water in an appropriately unbalanced way, for your clearly stated prediction of the results based on the principles you describe, and of course your wager.
Click to expand...

You need to blow a hole in the side
 
Vixen said:
We were talking about capsizing right...
Click to expand...

We're talking about two things. You've conflated them incorrectly because you're letting Anders Björkmann teach you his special brand of physics. Capsizing has to do with the balance of roll moments and righting moments and has nothing to do with a change in buoyancy. Sinking has to do with a change in buoyancy, which has nothing to do with roll. In your haste to appear smart, you've cited factors for one as if they were factors for the other, and are frantically trying to suggest that your critics don't understand "simple" physics. And now you're waffling your way out of a practical experiment to demonstrate that "simple physics" doesn't do what you say it does.

...when the trim (centre of gravity) is displaced (listing).
Click to expand...

Displaced with respect to what? What are the forces involved? Upon what centers do they act? What physical phenomena define these centers? In what directions must each force act? What are the force vectors involved, and how do they sum? Draw us a diagram that shows that a mere change in the magnitude of the buoyancy vector will also necessarily change the center where it acts and thus create a roll moment that inevitably capsizes the ship.

...When a vessel lists at 90° it capsizes belly up.
Click to expand...

No. When a vessel lists at 90° it lists at 90°. When a vessel lists at 180° it will have capsized belly-up because that's just a different way of saying that's what its roll angle is. This is a function of the vector sum of forces and the dynamics of it are driven by factors that are only partly related to the magnitudes of these vectors. You present a source that deals only in the magnitude of vectors (in fact eliminating the vector reality altogether) and cite it as proof that the directions of these vectors and where they act upon the structure of the ship makes capsizing inevitable.

In practical shipbuilding, once a vessel has rolled to particularly degree and after the righting moment is no longer strong enough to restore trim, openings in the vessel become vulnerable to shipping water into the hull that a were intended to remain above water. The notion that any ship whose "hull is not breached" will float upside down for hours in any roll attitude is naive.

If it has a superstructure such as a liner or cruiser, then the amount of time it takes water to displace the air guides you as to how long before it sinks.
Click to expand...

A superstructure changes the vector sum, to be sure. But in ways your model of the dynamics doesn't properly consider. Draw us vector diagrams of a ships with and without a superstructure and show how the sums change as buoyancy increases or decreases.

Of course, if you cynically believe that artificially pouring water into it to the brim or adding 40K or iron ore, as someone claiming to be an expert suggested, you are merely cheating instead of truthfully acknowledging the case.
Click to expand...

Ah, we're to the, "You may be an expert, but I say you're lying," stage of the conspiracy-theorist's pattern argument.
 
Status
Not open for further replies.

Back
Top Bottom