Cont: The Sinking of MS Estonia: Case Re-opened Part IV

[Andy_Ross]

Why would 0° usefully refer to a mast or funnel that sits perpendicular to the deck and when the ship is at rest on a calm surface?

Because that is the convention. It is a standard way of doing it so everyone knows what is being refered to. IF you look at the Clinometer on a ship that records the angles of heel and roll it will gave zero as the vertical.

No, in simple terms, it doesn't mean "capsizing 90° to either port or starboard would then see the mast parallel to the water's surface, while 180° would see the mast pointing straight down, i.e. a precise 'turtling'."

Yes it does. That is the convention used so that there is no confusion as to the term being used. If you look at the Clinomewter on a ship you will see that 90 degrees to port and starboard means the ship's mast will be parallel to the water.

Forget about listing for a moment.

Think of a number between say 10 and 260. Draw a circle. Draw a straight line which passes through the middle. Jot down your number at one end of your straight line. If the number you chose was less than 180, add this to 180 and jot down the total at the other end of your line. If your number was more than 180, subtract it from 360 and jot it down.

Now draw a line that bisects the other line at right angles. This will be 90°
away from the start and end of the other two lines, whatever the figure is you have.

So, 10°, 20°, 30°, etcetera, will always be 10°, 20°, 30° relative to that point, no matter what configuration you have of your circle, whether it is upside down or back to front.

Why the **** would anyone want to go through that whole mess of a thing you just made up when there is a standard convention that is adhered to?

So, the centre of gravity is not necessarily bang in the physical middle of an object. It lies at the average where all of the points of its average weight lies. So we call this point – where there is perfect balance, the centre of gravity.

So imagine you now have a boat floating in water, which is not flat, but has a rounded hull. Depending on how its cargo is loaded, the centre of gravity is not necessarily in the middle. If it floats, it means there is a centre of buoyancy, also not necessarily at the middle of the boat. (Albeit the crew will aim for trim so that it is.) There is gravity which is perpendicular to the boat (straight downwards, regardless of where it is) and buoyancy which pushes upwards, also perpendicular. The metacentre is the imaginary straight line that passes through the point where the centre of gravity line and the centre of buoyancy line meet and this will vary depending on the angle that the boat is listing in. It is not necessarily upright. As the vessel lists to one side (Z) , say to starboard, say by a movement of one unit downwards, the centre of gravity moves likewise as the weight average is now weighted to its right and the centre of buoyancy moves likewise, thus it carries on floating. This is because the rotational force, the righting arm, exerts a momentum pulling the list back into equilibrium. The more the boat lists, say by two units and then three, this righting force weakens. There comes a point where the boat capsizes owing to the angle of the list, and the side of the ship hitting the surface of the water and concomitant surge of water flooding into it, after which point it flips, Z becomes a rotational force in the opposite direction from the centre of gravity. We have negative stability at the point Z reverses with G. Once toppled over, the boat will continue to interplay gravity versus buoyancy, but this time, whilst upside down. Because there is lesser list whilst upside down, due to the hull shape limitation, one could say a boat is more stable in this position than when it is upright.

So, if we call the centre of gravity in its upright position 0°, the angle of list is relative to this centre of gravity not to an abstract right angle or where the mast stands upright.

Why would we take any notice of any of that **** when there are industry standard conventions that are universally used and have been for centuries?

 

[GlennB]

Assuming there is no breach in the hull or other circumstances. What do you think ceteris paribus means?

This renders your post meaningless.

 

[Jack by the hedge]

At 180° it would no longer be subject to the same list that capsized it.

"List that capsized it"? What does that mean (other than the trivial observation that when a ship is upside down it has finished turning upside down)?

 

[Andy_Ross]

My google lens identified that vessel as the following the MV Tricolor:


Marine Insight

That ship is not floating, old chap, it is sinking. It had an enormous breach in its hull which was letting in water (letting in water).

Yes we know, that's why it's under the surface

 

[Andy_Ross]

That's what happened two to Egyptian suspected terrorists in Sweden in 2002 IIRC. They were 'disappeared'.

The fact there is a Treaty 1988 (Criminal Law) that forbids the disappearance of suspects, must mean that it had been happening.

So that is where the captain of the Estonia is?

 

[JayUtah]

Once toppled over...

You're making the mistake of assuming negative stability prevails until a roll of 180 degrees has occurred. Let's assume a ship with a critical roll angle of 52 degrees. Your video shows you what the GZ curve looks like from 0 to 52 degrees. Compute for us what the graph will look like between 52 and 180 degrees.

 

[GlennB]

Why would 0° usefully refer to a mast or funnel that sits perpendicular to the deck and when the ship is at rest on a calm surface?

Because if we're going to consider the effect of, or amount of, rotation then we need a reference orientation that tells us where we started from.

So, if we call the centre of gravity in its upright position 0°, the angle of list is relative to this centre of gravity not to an abstract right angle or where the mast stands upright.

The centre of gravity is a point. It cannot be 'upright' any more than the very centre of the Earth or a dot on a piece of paper can be 'upright'. However, a line drawn between the c-of-g and some other point can be upright, as long as we define what we mean by upright. A mast standing perpendicular to a flat deck on a ship that's at rest on calm water is a reasonable definition, and one that fits handily with daily use such as buildings standing upright, sitting upright in a chair (colloquial) etc etc.

 

[Jack by the hedge]

... According to JAIC, the vessel turned to 70° circ 01:30 and 90° shortly after...and then it floated on its superstructure before sinking stern first and then turning forward. Hull intact, no problems with fire or pipes or anything else.

Once again your obsessive, idiosyncratic and never-defined "float on its superstructure" mantra, which you once again attribute the the JAIC even though they obviously never said it because it's meaningless.

Either define the term or kindly stop using it.

 

[Andy_Ross]

JAIC never explained how it happened. It is noticeable that rather than saying anything that is not true, it simply just doesn't mention it.

For example, the communications interference, the crew habitually using bedding to plug the leak in the car ramp door. the mystery of the EPIRB's, etc.

Radio communication is covered in depth by the report

What mystery with the EPIRBs?

 

[Vixen]

Yes we know, that's why it's under the surface

...and why it hasn't turtled.

 

[MarkCorrigan]

So am I to take your silence as confirmation that you have retracted your claim to be a scientist, and further your acceptance that this was, at best, a knowing lie that you deeply regret now?

 

[Vixen]

Because that is the convention. It is a standard way of doing it so everyone knows what is being refered to. IF you look at the Clinometer on a ship that records the angles of heel and roll it will gave zero as the vertical.



Yes it does. That is the convention used so that there is no confusion as to the term being used. If you look at the Clinomewter on a ship you will see that 90 degrees to port and starboard means the ship's mast will be parallel to the water.



Why the **** would anyone want to go through that whole mess of a thing you just made up when there is a standard convention that is adhered to?




Why would we take any notice of any of that **** when there are industry standard conventions that are universally used and have been for centuries?

We were talking about calculating stability and that is based on centre of gravity, centre of buoyancy, metacentric height, GZ, load balance and weight, trim, etc., which does not necessarily agree with, 'where the mast is'.

 

[MarkCorrigan]

Do you believe yourself to be competent enough in nautical physics to correctly determine those things?

 

[Vixen]

So that is where the captain of the Estonia is?

We are not told where the captain of Estonia is and the JAIC does not inform us whether it knows or does not know. On that matter it is silent. The star witnesses are a couple of able seaman and three engineers, one a newbie. All four were on the same lifeboat just as Tammes was sending out his Mayday.

The senior officers, some of whom were adjacent to the same luxury cabins as the Voronin family somehow never managed to access rescue equipment, whilst the Voronins and the very elderly old sea captain did.

 

[carlitos]

The geometry discussion in this thread almost broke my brain.

 

[JayUtah]

We were talking about calculating stability and that is based on centre of gravity, centre of buoyancy, metacentric height, GZ, load balance and weight, trim, etc., which does not necessarily agree with, 'where the mast is'.

But you tried to establish a new kind of reference frame against which to reckon all those things. A standardized reference frame already exists. Maybe you should know the subject before you attempt to lecture others on it.

 

[Andy_Ross]

Interestingly, Mr. Justice Sheen in his inquiry into The Herald off Free Enterprise deemed that the maximum list allowable on such a ro-ro car ferry should not be greater than 20°. Beyond that, if your ballasts are already at full capacity and you are going too fast, then the chances of righting the vessel before it gets to the inevitable stage of capsize begin to lessen rapidly.

What is your evidence for this?

floated on its superstructure before sinking stern first and then turning forward. Hull intact, no problems with fire or pipes or anything else.

You made that up.

 

[JayUtah]

The geometry discussion in this thread almost broke my brain.

Indeed, I've seen students struggle with elementary concepts like points, vectors, and reference frames. However these students were 12 years old and meeting these concepts for the first time. I don't think Vixen has the slightest idea just how very incompetent and misinformed she sounds.

 

[Jack by the hedge]

We were talking about calculating stability and that is based on centre of gravity, centre of buoyancy, metacentric height, GZ, load balance and weight, trim, etc., which does not necessarily agree with, 'where the mast is'.

Throwing around terminology you have newly picked up does not help make sense of the gibberish you were talking earlier about list angles. There is no point in your attempting to talk about stability when you cannot yet express yourself understandably in describing something as straightforward as the angle a ship is sitting at.

 

[autumn1971]

Capsize = turn over.


A ship doesn't float on its side.

Imagine a flat board of wood say, ten feet long and five feet wide, one foot depth, floating on a calm stretch of water. You are standing at its centre of gravity and are perfectly buoyant. The force of gravity pulling downwards and the centre of buoyancy pushing upwards means you are superbly balanced. You then step to your right a couple of feet. You are now not at the centre of gravity. Being flat wood, there is no righting mechanism as one would have on a boat. The board tips over toppling you out in the process.

Question: Does the flat board of wood float on its twelve-inch side even for a minute?

One can conclude from the above argument that whoever posted it has never seen water or been near it. Nor has the poster ever seen anything floating in water.

I am amazed that the Atacama Desert has such a good internet connection