Bayesian Interim Report

westernman said:
In strong winds with the anchor starting to drag, I would run the engine to reduce the load and stop it dragging. I would not expect to need more than about 1/3 throttle.
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How often have you tried that technique in hurricane force winds? And must have an enormously powerful engine if 1/3 throttle would power the bows up in 70+ knots. I need a lot more than 1/3 throttle to get the bows up even in a F8, which I have tried.
 
dunedin said:
How often have you tried that technique in hurricane force winds? And must have an enormously powerful engine if 1/3 throttle would power the bows up in 70+ knots. I need a lot more than 1/3 throttle to get the bows up even in a F8, which I have tried.
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I can make progress at full throttle into a F8.

I would not expect to be making headway into a hurricane - but just reducing the load on the anchor to what it would be in a F8 or less.
My anchor will and has held in a F8.

I would not be expecting to power the bows up - the anchor should be holding the bows into the wind.
 
Poignard said:
For the record.

Bouba wanted to know why an anchored yacht’s head could not be kept pointing into the wind if she was at anchor.

I explained the effect of windage on the bow.

I then went on to say that if, repeat if, the sunken yacht had been a yawl or mizzen then a mizzen sail set might, repeat might, have helped.

Next minute, I have some clown telling me that what I said is ‘stupid’.

A bit irritating, to say the least.
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Thank you for clarifying.

For the record

Talk of setting a mizzen as a riding sail, reefed or not, in 70 knots of wind is stupid.

Have you, in all your days, ever heard of anyone preparing for hurricane force winds by setting a riding sail? Ever?
 
Laser310 said:
maybe not so poor for a motor boat

that figure is for the boat in its motoring state.

what is a typical AVS for a motor powered superyacht? I have no idea...
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IIRC it lets in water in a substantial way at only 40°. So the 70 degs might be a bit academic.
 
billskip said:
Something a bit fishy about that....
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Which bit is fishy? I wouldn't hesitate to spend the night at anchor with family with that kind of forecast.

If the forecast was for a supercell derived tornado briefly wrecking havoc exactly where I had planned to anchor, I may have reconsidered and moved to the next bay.
 
Rappey said:
"Parsifal 3" featured in "below decks". She looks very similar to Bayesian.
Parsifal 3 has a 60-63m main mast and 46m mizzen with a fixed keel. It never appeared to be happy when heeled more than 15 degrees under sail.

With possible downdraughts and water spouts affecting small areas of 50 to 100 metres could the Bayesian ever point into the wind ?
Keel down might have made no difference in what seem like extreme and rare circumstances.
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If it was a heavy keel rather than a centreboard. (I may have missed that being established for definite.)

I remember, decades ago, trying to correct my mother's assumption that lowering my sailing dinghy's wooden centreboard would enhance the boat's stability...
 
westernman said:
I would not be expecting to power the bows up - the anchor should be holding the bows into the wind.
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The interim report suggests that it was never fully head to wind (hence the discussion earlier). Funnily a stern anchor might have been a safer situation - it's more stable with wind over the stern quarter than the bow.

Lots of possible things they could have done, but right now I can't see how the crew could have, or would have, thought of them in advance. It rather feels like they were sitting ducks.
 
flaming said:
Thank you for clarifying.

For the record

Talk of setting a mizzen as a riding sail, reefed or not, in 70 knots of wind is stupid.

Have you, in all your days, ever heard of anyone preparing for hurricane force winds by setting a riding sail? Ever?
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The skipper was woken at 0400 and by then the wind had increased to 70kts, and of course it was too late to do anything

But the approaching storm had been observed by the watchkeeper at 0300, when the wind was still light (8kts). It did not suddenly increase (to 30kts) until 0355.

Had there been a mizzen to set, it seems reasonable to assume that the 55 minutes between the watchkeeper observing the storm, and its arrival, would have been sufficient time in which to set and reef it, in anticipation of the possibility of severe weather coming.

But, according to the MAIB Interim Report, the watchkeeper's orders were to wake the skipper if the windspeed increased to more than 20kts, or if there were signs of the anchor dragging. There is no mention of his being ordered to wake the skipper if a storm approached.

The storm continued to approach, and at 0355 the watchkeeper actually started videoing it to post on social media! Obviously, he did not appreciate that the approaching storm posed any threat and, since he had not been ordered to wake the skipper if a storm did approach, he didn't.


At 2100 the evening before, Italian forecasters had issued a warning of north westerly gale force 8 winds for Sardinia and Corsica with associated isolated thunderstorms with local gusts for Sicily. This was repeated at 0000. Conditions were far from benign.

So, had the stricken yacht been a yawl or ketch, and had the skipper been woken when the storm was first observed to be approaching, there would have been time to set a mizzen sail, and to reef it. And time to take any other necessary precautions.


"What caused the extreme weather?

The type of storm that struck Monday is fuelled by warm water and the Mediterranean is warmer than ever, said Boxall [an oceanographer and senior lecturer at the University of Southampton] noting there's been about a three and a half degree increase in the 20-year average temperature.

Climatologists say global warming is making such violent and unexpected tempests more frequent.

Luca Mercalli, president of Italy's meteorological society, said the sea surface temperature around Sicily in the days leading up to the shipwreck was about 30 C.

"This creates an enormous source of energy that contributes to these storms," he told Reuters."

https://www.cbc.ca/news/world/how-did-bayesian-sink-1.7299720
 
I would have little confidence in the Italian investigation. This MAIB report is just the sort of factual examination needed and typical of the quality detail work done by the MAIB.

However, I worry that the Italian criminal investigation maybe tempted to downplay any Italian design shortcomings. I hope I am wrong.
 
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I would also suggest that if the crew knew that the angle of vanishing stability was as low as it was then they might have reacted differently.
It is quite amazing that a sailing yacht can have such a low stability curve.
 
Poignard said:
Perhaps, in your excitement at the possibility of making yourself look good by having a pop at someone, you had not noticed that I was replying to a particular point in a post by Bouba, who was wondering why a yacht's bow might not be held into the wind in a gust by its anchor chain

So may I , with all possible respect, suggest that you back off; as they say.
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On the other hand you could engage brain before typing.
 
billskip said:
It couldn't invert, the water wasn't deep enough...so AVS is not relevant anyway.
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At seventy degrees it's going over permanently whether it wants to or not. That it couldn't fully invert is neither here nor there - the AVS absolutely is relevant.

And likely getting worse with every second due to downflooding, to boot.
 
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