Bayesian.

[capnsensible]

The downburst has literally been described by weather experts as unpredictable. The boat was designed for reasonable conditions and to be tucked up somewhere safe otherwise. Not everything needs to be a frigate.
50 knot gusts is different than 200kt downburst with significant rainfall

Not sure about the tucked up safe bit. These yachts and motorboats spend sunny season in places like Med and Caribbean then move to the other across oceans as required by the owner. Lost count of how many of these ocean going vessels we've seen on our travels.

 

[lustyd]

Not sure about the tucked up safe bit. These yachts and motorboats spend sunny season in places like Med and Caribbean then move to the other across oceans as required by the owner. Lost count of how many of these ocean going vessels we've seen on our travels.

What I meant was they’re not designed for particularly bad weather. Something like a Kraken has safety in the design brief. These will be more like regular yachts and will run for cover if anything big approaches just as the rest of us do. There’s nothing wrong with that at all, different boats for different folks.
Compromising on performance in a F10 in exchange for water sports garage and a hot tub doesn’t seem an unreasonable trade off in a boat that doesn’t expect to see a F10.

 

[Sea Change]

Well it would of had lateral force would you not think, I know nothing about sailing , but I do about counterbalance. So if the yacht was designed to have a shallow keel when there is a force against the yacht above the water, it would have a heavier keel.

The keel does two different jobs.
It slightly lowers centre of gravity, but not by as much as you might imagine. Swing keels often pivot part way down, to make the loads more manageable (my old boat did anyway). So the weight moves up but only a little bit. A ballasted daggerboard will have a more pronounced effect, but in most designs the vast majority of the ballast is actually within the hull.

The second thing the keel does is to provide resistance to leeway. The boat has to be moving forwards through the water for this to work. So there's generally no reason to have the keel down at anchor. It's just going to make noise and grow barnacles.

Having the keel down in squally conditions can actually make a boat *more* likely to capsize, by resisting a sudden sideways wind load and making the boat dip a gunwhale. There was a dinghy race where the only boat which didn't capsize was one who lifted his board as he saw the squall approaching.

 

[boomerangben]

no doubt the vessel will have been designed and constructed to well reputed standards by either a CS or other rigorous standards organisation.

If the vessel was knocked down by a freak weather event, then it enters the realms of other vessels sunken by freak events like unusually high waves or strong winds. In other words luck or rather lack thereof.

 

[doug748]

Ridiculous argument. There is no such thing as unexpected and unpredicted conditions at sea, especially nowadays in increasingly unstable weather. Two weeks ago we were anchored in zero wind. Within a few minutes we were seeing 50 knot gusts.

Indeed.

We get taught nasty lessons every few years and folk say "unprecedented..200 miles per hour winds" and the rest of it. Must admit though - never in a million years did I think that a yacht like that was so vulnerable. Ironically they would have been better off in a Nicholson 32.

The MCA produce guidelines for big boats, with graphs and lots of fancy sums, however this simple extract is worth noting:

"11.2.2.1 Monohulls …………………...The GZ curves required by .1 should have a positive range of not less than 90º.For vessels of more than 45m, a range of less than 90º may be considered but may be subject to agreed operational criteria."

Looks like it could have sneaked in as a boat with a restricted operating envelope. The poor downflooding angle is another matter, an abomination; this is true whatever the eventual cause of the accident is found to be.

.

 

[boomerangben]

Indeed.

We get taught nasty lessons every few years and folk say "unprecedented..200 miles per hour winds" and the rest of it. Must admit though - never in a million years did I think that a yacht like that was so vulnerable. Ironically they would have been better off in a Nicholson 32.

The MCA produce guidelines for big boats, with graphs and lots of fancy sums, however this simple extract is worth noting:

"11.2.2.1 Monohulls …………………...The GZ curves required by .1 should have a positive range of not less than 90º.For vessels of more than 45m, a range of less than 90º may be considered but may be subject to agreed operational criteria."

Looks like it could have sneaked in as a boat with a restricted operating envelope. The AVS is another matter, an abomination; this is true whatever the eventual cause of the accident is found to be.

.

AVS and GZ are the same thing, not another matter at all. Downflooding angles can be quite small on some vessels. Some quite big vessels like semi submersibles in fact, although not relevant here.

 

[doug748]

AVS and GZ are the same thing, not another matter at all. Downflooding angles can be quite small on some vessels. Some quite big vessels like semi submersibles in fact, although not relevant here.

#85 now edited to read properly.

 

[DreadShips]

AVS and GZ are the same thing, not another matter at all. Downflooding angles can be quite small on some vessels. Some quite big vessels like semi submersibles in fact, although not relevant here.

To be pedantic one is part of the other (you know this, but it might help somebody else to state directly that the angle of vanishing stability is the point on the GZ curve where the righting moment crosses the x axis and the boat is now happier being upside down. A dim prospect for anybody who preferred it the way it was...)

Due to the sheer size of Bayesian and the distribution of ballast, I'd be surprised if the keel position was important either way though. It's a lot of mass to either quickly pivot to lie head to wind or to reduce the forces by moving sideways. That's not to say a discussion of these factors isn't useful for those of us of more modest means (and commensurately smaller boats!).

 

[Pye_End]

Compromising on performance in a F10 in exchange for water sports garage and a hot tub doesn’t seem an unreasonable trade off in a boat that doesn’t expect to see a F10.

What makes you think the toys and toy design contributed to the accident?

 

[Forum Admin Team]

Please refrain from raising this issue on the YBW forum until the investigation is complete and the report published.

Thank you.

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Thread closed pending review.

"Bayesian" s/y sinks in Palermo