Bayesian

[Gardenshed]

Letter to the editor of Seahorse magazine from Butch Dalrymple Smith, Butchdesign SAS:
(Worked for Ron Holland yacht design for many years. RH designed the Bayesian)

The sinking of the Bayesian was a shocking tragedy.

Yachts have to meet strict standards of stability and watertight integrity as well as a litany of other safety features (fire safety, rescue equipment, etc.) Stability, for example, must not only be proven theoretically, but regular physical tests are made every five years to all yachts to verify that they meet the required standard. It is almost inconceivable that a yacht could capsize in sheltered water when meeting MCA standards.

It is sometimes challenging to design a sailing yacht that meets the standards, but the moment a yacht loses its mast (as apparently happened before the Bayesian foundered) the stability goes up to ridiculous levels. The phrase the BBC used, that the yacht "lost its balance and sank" is meaningless and absurd.

It is imperative that the causes of the accident become known and are broadcast as widely and as early as possible to designers, surveyors, boatyards and operators of similar vessels.

Unfortunately, those in the know tend to hide their conclusions due to concerns about liability and potential litigation. This must stop. We must follow the example of aviation in quickly letting everyone know why it happened. There will be lessons to be learned regarding the current safety regulations, the methods of testing stability, the way large yachts are operated, etc. and we need to know this as soon as possible, without waiting for the conclusions of an official enquiry.

[BlowingOldBoots]

Mast or not mast damage, I have watched yachts at Craobh heal over where the gunwale was very close to the pontoon and a lot of underwater hull exposed. This in 60kt gusts. As windage, water drag responds to a power law, then in exceptionally strong winds, maybe even large volume, high velocity, flow rate water from a water spout, tipping a yacht to the down flooding angle is not difficult to imagine, nor are open doors and large spaces, or even panned in windows, such that rapid flooding dooms the yacht.

It is a horrendous thought, but all our vessels are capable of being lost like this. I bet most on here have experienced being slammed in calm anchorages, sheltering from a gale, or even a big broach and well dug in side decks in strong winds. A bit more force and down flooding happens.

Until the MCA or other investigation is completed, it is all speculation, even Smith’s letter is shabby, with its hidden meanings that we know, you don’t bollocks. Still it’s good to speculate and debate as it makes on think.

[Bodach na mara]

I agree with BOB that the letter from Butch Smith is ill-advised and contains unfounded speculation. He is right however to point out the nonsense of the BBC statement about the loss of stability if the mast broke. Within the thread in TOP Scuttlebum (I think) there is a link in a post on the first page to a video on YouTube from a webcam in Auckland of a storm. The main point of the video is to show a large catamaran being flipped arse over tit at it's pontoon berth. However, in the background on the right hand side, you can see a very large yacht not dissimilar to Bayesian with a very tall mast with at least 5 spreaders. (Bayesian has 6.) As the video continues, this yacht is blown almost flat in water, the mast rotating at least 80 degrees and then recovering. The video continues to show both incidents in closer focus although the rain hitting the lens makes it hard to see clearly.

The BBC also boobed on the first day with an "expert" declaring that "water spouts are seldom seen except in tropical waters") whereas yesterday a different expert said that there have been many reported in the Med recently. I have seen one myself several years ago from a cruise ship approaching the Straits of Gibraltar. It was about 1/2 a mile from us and right in the path of a small cargo vessel on a parallel course with us. It steamed right into the spout, which immediately collapsed and disappeared. God knows what the physics behind that tells us.

[Burst Boiler]

That video of the yacht heeling is good because it shuts up folk that say it cant happen. I do wonder how relevant it is to this case though - there's a difference between a yacht made fast to a pontoon beam-on to the wind vs one at anchor that you imagine would head up to the wind. Or would the spout appear so quickly before the yacht could head-up to it?

[Bodach na mara]

My thoughts entirely BB. I have wondered all along how a boat at anchor was not head to wind. Then I remembered that when I used to keep my boat on a mooring at Cardwell Bay it used to veer about and occasionally got caught side-on to a gust that came from a direction different from the main wind.

However the latest information that I have seen is that Bayesian was not anchored. Data from an AIS tracking website suggests that it had moved away from its anchored position at 4am and that its signal ceased at 4.05 The evidence about a waterspout seems to have come from the Danish skipper who was pretty fully occupied with looking after his own vessel and he also said that visibility was poor. I wonder if the waterspout is a red herring. There is also a statement attributed to the spokesman for the diving team that Bayesian is lying at an angle on the seabed intact. I wonder if the last word applies to the mast as well.

Finally a random thought about the size of the vessel. If they could get it vertical again while standing on the seabed there would be over 30 metres of mast sticking out of the water!

[Gardenshed]

the letter that I posted is by Butch Dalrymple Smith, who was one of the Ron Holland Design team, Ron Holland who designed (Naval Architecture, not interior and cosmetics) the boat.

Given the size of the boat, it's likely that with the changing direction of the wind, whether anchored or not, it couldn't be turned into the wind quickly enough to avoid being blown flat. No-one would expect a large yacht like that to heeled over so far, and even when sailing. Super yachts like that have heeling limits (typically backed up by load cells on the rigging) which are conditions of their insurance. At anchor, you'd not expect to heel over, so who knows what the condition of doors/vents/openings would have been.

It's an awful event and like many accidents, a sequence of unfortunate events and circumstances creating a scenario that could not be foreseen.