Bayesian Interim Report

[Bouba]

I’m not qualified to comment on this thread so I won’t! I’d like to ask though, when there’s a mention of a boat at anchor “weather vaning” to the wind - would that expression be the same as “weather cocking” which is the expression I’ve grown up with. I curious and not intentionally being pedantic!

I’ve always called it weather vaning......and probably introduced it in this thread. But obviously the spinning thing on your roof is the description

 

[penberth3]

I’m not qualified to comment on this thread so I won’t! I’d like to ask though, when there’s a mention of a boat at anchor “weather vaning” to the wind - would that expression be the same as “weather cocking” which is the expression I’ve grown up with. I curious and not intentionally being pedantic!

I'll be pedantic. Not all weather vanes have the traditional silhouette of a cockerel. A lot have no decoration at all. So "weather-vaning" covers all bases.

 

[Frank Holden]

No mention in this thread of the angle at which downflooding would commence? By my reckoning that was about 40º so by the time she was knocked down beyond her AVS she was already filling and filling fast. No comparison with a yacht where in a knockdown a bit of water may come down the lee dorades.

Edit - a bit from the report
' There was no indication of flooding inside Bayesian until water came in over the starboard rails and, within seconds, entered the internal spaces down the stairwells.'
So started flooding within seconds of lee 'rails' submerging.

 

[Mark-1]

No mention in this thread of the angle at which downflooding would commence?

 

[doug748]

I think there was another thread where all sorts of points were made Frank, including stuff about basic stability, here is film of Maltese Falcon racing:

Bayesian was a different boat, however from the same yard and with the addition of two midships, sunken wells in the sidedecks, - surely nothing could go wrong at all.

.

 

[lustyd]

Can you provide any sources for these suggestions?

Glen Shepard, the skipper of the sister ship, has stated in an interview that there’s too much waterline length for downwind sailing so on ocean passages they motor because the wind is never fast enough to keep up. Aside from that he seemed to think it sails just fine.

 

[Mark-1]

there’s too much waterline length for downwind sailing

 

[Bouba]

Glen Shepard, the skipper of the sister ship, has stated in an interview that there’s too much waterline length for downwind sailing so on ocean passages they motor because the wind is never fast enough to keep up. Aside from that he seemed to think it sails just fine.

It does seem strange....but the life of a superyacht is different....nobody paying a quarter million a week is going to be happy waiting for a boat to sail to them

 

[mjcoon]

Must be true, then.

Doesn't it have to be said three times to be incontrovertible?

 

[boomerangben]

The CAs do assess the stability requirements and stability data of large vessels and small vessels, and are required to note the availability of the stability data on the vessel. That can be in the marine operations manual, or the stability book, where that format is allowed. What the CAs don’t do, is verify if the stability data is being used by the crew, or understood. However, stability is a key element of CA work at assessment time, initial or periodic, and will also validate the stability design data calculations and measurements, pre approval. If they don’t, they won’t class the vessel. Periodic assessments will be less robust, verifying presence of stability data for the management of the vessel, and validating no material changes have been made which could impact stability.

My experience comes from recent coding and recoding, yachts in the UK and assessing aspects of large vessels in conjunction with other colleagues who perform the marine assessment. I would think that the “stability book” and marine operations manual would be in place and verified on the Bayesian, which I do not think anyone is disputing.

On ships, at anchor, water tight, and weather doors have to remain closed, on leisure yachts, I am not aware of the requirements. They already have issues with lifeboat, abandon ship drills, which they are obliged to do, but may not because their guests are perceived to be too far up their own egos to do pleb stuff.

The Bayesian incident reminds me of the Marques incident where there was lots of speculation around stability, however, she was hit by a sudden squall and significant wave that rolled her under.

Roman poet and philosopher, Titus Luceretius Cams

If I’ve read the report correctly, the stability book didn’t contain keel up load conditions, so I wondered if a recommendation would require stability books to contain keel up and keel down data.

I doubt it would have made any significant difference to the outcome here though.

 

[shanemax]

It now seems the crew did everything by the book and correctly, but when the wind goes from 30 knots to 70 plus knots (some say perhaps 100 knots) in a matter of a few minutes tumbling off a mountain and changing direction you do not stand a chance.

 

[[194497]]

Jumping in a bit late to the topic of weather-vaning, but I've experienced a situation with strong winds while at anchor in a small boat (24') whereby the boat got caught by a side-wind and began to heel, just from the windage of mast and rig; once the mast was leaning out downwind it became the weather-vane, preventing the boat from rounding up. It was much like a classic broach but with no sail.up. In that situation the gust backed off quickly and the boat popped up, but it's easy to envisage that same dynamic operating on a much larger scale in this case.

 

[Bouba]

Jumping in a bit late to the topic of weather-vaning, but I've experienced a situation with strong winds while at anchor in a small boat (24') whereby the boat got caught by a side-wind and began to heel, just from the windage of mast and rig; once the mast was leaning out downwind it became the weather-vane, preventing the boat from rounding up. It was much like a classic broach but with no sail.up. In that situation the gust backed off quickly and the boat popped up, but it's easy to envisage that same dynamic operating on a much larger scale in this case.

From your experience it could mean the Bayesian mask was too tall

 

[boomerangben]

From your experience it could mean the Bayesian mask was too tall

Sounds like any mast in supercells is too tall

 

[boomerangben]

Jumping in a bit late to the topic of weather-vaning, but I've experienced a situation with strong winds while at anchor in a small boat (24') whereby the boat got caught by a side-wind and began to heel, just from the windage of mast and rig; once the mast was leaning out downwind it became the weather-vane, preventing the boat from rounding up. It was much like a classic broach but with no sail.up. In that situation the gust backed off quickly and the boat popped up, but it's easy to envisage that same dynamic operating on a much larger scale in this case.

Thank you sharing. An interesting experience and I’m sure one you wouldn’t want to repeat. Goes to show how dynamic these situations are and how hard it would be to consider and design for.

 

[potentillaCO32]

It now seems the crew did everything by the book and correctly, but when the wind goes from 30 knots to 70 plus knots (some say perhaps 100 knots) in a matter of a few minutes tumbling off a mountain and changing direction you do not stand a chance.

The report seems to indicate that the crew did everything that you could have reasonably expected.

however, the boat anchored next to it survived.

Reading the report several times it is clear that the design of the ship meant it was not able to resist extreme high winds, when at anchor. It had a low angle of vanishing stability and a downflooding angle of just beyond where the guardrails go into the sea.

 

[dunedin]

Glen Shepard, the skipper of the sister ship, has stated in an interview that there’s too much waterline length for downwind sailing so on ocean passages they motor because the wind is never fast enough to keep up. Aside from that he seemed to think it sails just fine.

You must have got something very confused there - long waterline length does NOT cause any issue sailing downwind (witness Cutty Sark etc), not does it make sense that “the wind is never fast enough to keep up”, as loads of modern very fast or foiling craft sail downwind faster than the wind speed (watch SailGP for an example). So that is Gobble de Gook.

There are plenty of videos of the boat sailing under its original name Salute.

And as noted previously, the reason for motoring on deliveries is often to reduce wear and tear on very expensive sails (diesel is much cheaper) and also may be short crewed.

 

[westernman]

The report seems to indicate that the crew did everything that you could have reasonably expected.

however, the boat anchored next to it survived.

Reading the report several times it is clear that the design of the ship meant it was not able to resist extreme high winds, when at anchor. It had a low angle of vanishing stability and a downflooding angle of just beyond where the guardrails go into the sea.

Were they anchored in a place susceptible to such violent wind shears and should have known better?
Or were they just very very unlucky?

 

[Mark-1]

Were they anchored in a place susceptible to such violent wind shears and should have known better?
Or were they just very very unlucky?

I've not seen any comment that the location was especially susceptible. Seems like this kind of weather occurs over the entire region. Pretty sure there's a marina or harbour nearby and another boat chose to anchor nearby. So it wasn't as though boats avoided the area, quite the opposite.

 

[lustyd]

You must have got something very confused there - long waterline length does NOT cause any issue sailing downwind (witness Cutty Sark etc), not does it make sense that “the wind is never fast enough to keep up”, as loads of modern very fast or foiling craft sail downwind faster than the wind speed (watch SailGP for an example). So that is Gobble de Gook.

There are plenty of videos of the boat sailing under its original name Salute.

And as noted previously, the reason for motoring on deliveries is often to reduce wear and tear on very expensive sails (diesel is much cheaper) and also may be short crewed.

When sailing downwind, unless you do something clever, your apparent wind speed effectively becomes the wind speed minus your hull speed or zero, if the hull speed is greater than the wind speed.
Obviously any boat can sail downwind and make it work, but if the boat gets up to the actual wind speed then there’s no pressure on the sails so everything flaps and then bangs when the boat speed drops again. Lightweight sails mitigate this by being light and hopefully not dropping quite enough to bang, but it’s still frustrating.
On a standard boat that’s fine because your hull speed is maybe 6-7 knots so you usually have sufficient wind to make it work. I don’t know what the hull speed is on Parsifal 3 but it’s certainly more than 7 knots!

Edit: it’s around 18-19 knots, so I think he had a good point.