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0 pointsjabl1y ago0 comments

> Self-righting yachts exist.[2] But they look like rescue boats with nicer interiors.

> Many recreational sailboats have enough flotation to survive 90 degrees of roll, with the sails flat on the water. This is called a "knockdown". In small craft, it's usually embarrassing but not a disaster. Larger sailing craft are usually built to avoid rolling that far.

Offshore racing rules tend to specify things like minimum angle of vanishing stability (AVS), they tend to be around 130 degrees. Similarly yachts sold in the EU must fulfill ISO 12217-2 which, AFAIU, also requires a minimum AVS of 130 degrees.

Not sure if that applies to the Bayesian, it might be old or big enough to be exempt from these rules.

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Animats1y ago· 2 in thread

A former captain of the Bayesian wrote a 2-page note.[1] "The downflooding angle for Bayesian was around 40-45 degrees". The Angle of Vanishing Stability was, he says, in the 75 to 90 degree range, depending on whether the moveable keel was down. The movable keel, he writes, weighed 60 tons. It had to be down when sails were raised, but usually wouldn't be lowered in harbor. There were 200 tons of fixed keel ballast.

[1] https://www.linkedin.com/posts/stephen-edwards-78539147_some...

jablOP1y ago

Yes, I saw that writeup linked to in the discussion earlier. I'm no naval architect, but I'd imagine for such a big boat an AVS of 90 degrees sounds reasonable. But a downflooding angle of only 40-45 degrees, that's just bonkers.

Animats1y ago

The former captain says that's the angle at which the generator and HVAC air intakes flood. Those are closeable if the equipment is turned off. The US Coast Guard definition is "Downflooding angle means the static angle from the intersection of the vessel's centerline and the waterline in calm water to the first opening that cannot be closed weathertight and through which downflooding can occur."

So downflooding angle safety certification for bad weather apparently assumes the boat being in a buttoned-up condition. But, buttoned up, the yacht has no air conditioning or non-battery power. One article mentions that lowering the moveable keel for more stability results in a much noisier environment below decks. So, rigged fully for bad weather, it ceases to be a luxury yacht.

The ship was in harbor, at anchor. That's not usually a situation in which a ship is rigged for worst case conditions.

Here's a picture of the infamous mast.[1] It's not just a pole. There's a lot of structure with surface area. Nobody seems to have anticipated that wind on the bare mast system was enough to knock the boat down. But it was.

[1] https://www.msn.com/en-us/money/markets/how-the-defining-fea...

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