Super Yacht sank in the med 3

[Alistair_Heaton]

https://www.bbc.com/news/articles/cvg343vjwklo

This is hot news at the moment mainly due to who was killed.

Seemed to go down very quickly.

 

[3DDave]

A buddy of mine worked at a river barge fabricator. His boss noted that the majority of the welding on the hulls was overhead, which means you need experienced welders and they cost more. So the boss had this plan. Build them inverted and flip them. I guess for anything with size there is something bigger, but barges still rank as huge compared to many land based items and flipping one seems daunting.

Anyway, they do this - frame it up and then weld on the hull plates; goes exactly as the boss imagined.

And then it went sooooo wrong.

They figured up some kind of poles to rig winches to, more than sturdy enough for the job. Attached the cables to the hull on the uphill side, and began pulling. Instead of completely flipping, at some angle the downhill/riverbank side slipped and it went into the river topside down.

My buddy suggested that the cost of recovery and properly flipping it over was so high (I think they actually did that part) that the boss never mentioned it again.

Now I am replaying parts of the Poseidon Adventure in my head. RIP Shelly Winters. Also, the gas burner supply really needed a heel shutoff switch, one that stayed off until someone reset it. That scene was gruesome.

 

[waross]

True story.
Working on an island in Central America, we road to work in a crew boat each morning.
It was only about 1200 feet point dock to dock.
As we pulled into our slip one morning, there in the next property over was a lobster boat.
It was about 100 feet long and was lying on its side.
As we pulled up to our dock, a VHF radio emerged from the water beside the wheelhouse, followed by the arm of the diver.
It was the off season and the owners of the boat were planning some construction work.
They had sent the boat into the mainland to pickup some Portland Cement and some lobster traps.
With a freight boat the cement would have been stowed in the holds.
This was a lobster boat and the access to the holds may have been more restricted than on a freight boat.
Besides, these were fishermen, not freight handlers.
They piled the cement on the deck, a lot of cement.
A feature of the fish boats and lobster boats in this area was bulkheads in the engine room inset about 2 feet from the hull.
The voids thus formed on each side are used for fuel tanks.
A small equalizer line connects them.
Whether the list developed on the voyage or whether they had unloaded some cement the evening before, in the morning the ship had a bad list.
Of course with a sustained list, the fuel slowly transfers from the high side to the low side and the list gets worse.
Early in the morning the boat wa listing badly and they called in a crew.
The crew went to work and started to unloadtraps and cement just s fast as they could.
FROM THE HIGH SIDE.
It didn't take long for the boat to finish unloading itself. grin

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[Alistair_Heaton]

Seems it was a down burst which I presume is a microburst not a water spout.

 

[3DDave]

Road, rode, rowed your boat...

English is hoot. Too many words, not enough sounds to go around.

 

[Alistair_Heaton]

I have learned over the years especially with met not to presume a linkage with terms.

It can seriously bite you in my game. There is a load of french in the mix especially about forms of ice.

Btw if it's french sounding it's usually horrible and dangerous for aircraft.

I know you get wet and dry microbursts thanks to a thread about a roof failure.

The wet ones I hadn't been educated about. We are more concerned about the wind direction and speed.

I was actually hoping the nautical types would further my education on the subject in the forum.

 

[3DDave]

From the Express, apparently repeating from Italian investigators:

The black box showed the Bayesian began to shake "dangerously" at approximately 3.50 am on Monday morning, according to Italian newspaper Corriere della Sera.

Within minutes, the yacht's anchor gave way. A source close to the investigation said the data had shown there was "no anchor left to hold," by 3.59 am.

After a storm ripped the Bayesian's mooring, the yacht was dragged through the water for some 358 metres and started taking in water at 4 am.

By 4.05 am, the superyacht had completely disappeared under the water with six passengers and one crew still inside.

A distress signal was finally emitted a minute later alerting the Coast Guard station nearest to Ponticello, the closest coastal town to where the ship vanished.

What it occurs to me is missing is mention of any doppler weather radar recordings from the shore over this area. Understanding the sort of weather event is a critical part of completely understanding the situation. Perhaps there isn't coverage?

Also, in other coverage, the yacht designer uses the word "unsinkable" a lot, though maybe he said it once and there are just a bunch of copies in various coverage. I think the number of times it should be used following a sinking is zero.

It's Italy. Someone is going to prison.

 

[1503-44]

Passed the rewind limit now.

https://www.weatherworld.com/radar-loop-int/it/sicily.html

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Alistair_Heaton]

There is a Doppler network round major airports.

But I don't think they need them in maritime.

To be honest Italy isn't really a first world nation for aviation. The northern airports such as Milan and Rome might have them. Down in the south they don't even have digital atis to get weather

 

[zeusfaber]

Stability is a matter of keeping the center of buoyancy above the center of gravity in all conditions

That's not actually right. Picture for a moment a stand-up paddleboarder.

If the centre of buoyancy is above the centre of gravity then the system will be stable - that much is true.

If the centre of buoyancy is lower than the centre of gravity then - as long as you can arrange matters so that, when the system is disturbed, the centre of buoyancy moves into the list faster than the centre of gravity does - the system will still be stable. That's how most ships stay upright (and why most of them won't self-right once you do capsize them).

Naval Archs will tell you that the thing that really matters is for the Metacentre to lie higher than than the centre of gravity.

A.

 

[FacEngrPE]

A paddle boarder is a bad example of ship stability, and a very good example of active balance control,

I stand corrected for incorrectly simplifying the ship stability diagram.

Marine insight has a better explanation.

https://www.marineinsight.com/naval-architecture/ship-stability-makes-ship-unstable/

A typical stability curve

In this example, maximum righting moment occurs at a heel of 45 degrees. If the boat heels to the point where righting moment goes negative it's going upside down.

 

[TugboatEng]

Is a ship rolls point the axis about which it rolls is the metacenter. The distance between the metacenter and the center of gravity determines the righting moment. A greater distance between the two means a more stable ship. Too much stability is not a good thing because it produces a snap roll. Cruise ships and yachts tend to run with lower metacentric heights in order to create a softer rolling action.

 

[Alistair_Heaton]

How big a hole would be required though to cause it to sink in under 5mins?

Even if it's the lower deck public areas that got flooded there would still be the engine room and other water tight areas surely.

Can't seem to find it's displacement.

I don't see any indication it was a capsize. More of a bow first trip to the bottom

 

[Alistair_Heaton]

https://www.1news.co.nz/2024/08/24/...waterspouts-can-be-as-dangerous-as-tornadoes/

Just a link to an article about waterspouts

 

[FacEngrPE]

Sal provided some information I had not previously seen.

https://youtu.be/empty_video

IE Mast Height = 230 ft.
Some protection from extreme wind events is usually provided by dismasting, however in this case the mast and rigging are reported to have survived.
This leads to a question that hopefully the inquest will consider -
[ul]
[li]Was the windage force on the mast and rigging enough to tip the boat beyond the point of no return without crew "mistakes". The tipping force could have been pointed toward the bow or in any direction.[/li]
[li]Did the builder perform a tipping experiment to confirm the as built stability characteristic?[/li]
[/ul]
I am using the term "Mistake" loosely, there are perceived mistakes, but no indication at this time if these are real or material.

 

[XR250]

Apparently according to the user manual for the yacht, the keel was not required to be down in the event of a storm.
Also, on this particular yacht, when it heels more than 40° or so the vents for the mechanicals will start filling up with water and flooding the boat.
Not sure how the manufacturer calls this "unsinkable"
Check out eSysman's videos

According to Captain Stephen Edwards, who posted his analysis on LinkedIn.

“The Downflooding Angle is much more important though in the scenario we are talking about.”

“This is the angle of heel at which water will start to enter the vessel (usually through engine room or accommodation ventilation ducts)... once this starts the vessels is in serious trouble as stability is quickly reduced or lost due to the flooding.”

“The downflooding angle for Bayesian was around 40-45 degrees... much less than the AVS. So, unless the vent dampers are closed (which with HVAC systems and generator running they would NOT be as they need to be open for that), the vessel will start to flood rapidly if heeled more than the downflooding angle.”

“The vessel Bayesian was sound and seaworthy by design, and to my knowledge well maintained as such. However heeling her to more than around 45 degrees while in normal operational state could result in flooding and subsequent loss if the flooding could not be controlled.”