Inside Angle: Bayesian Sinking

Editor Dan Harding sat me down for a video/podcast interview not long ago. After we finished making jokes at one another’s expense, we squared up to a more serious topic: the tragic and unforeseen sinking of a 184-foot yacht at anchor. The story of the sinking of the yacht Bayesian has all the ingredients of pop-culture clickbait: a billionaire and his wife, a superyacht, the chairman of Morgan Stanley International, conspiracy theories surrounding a high-finance criminal case, even a coincidental death occurring only two days before.

This event, unique in the modern history of superyachts, cost the lives of seven people. There has been no shortage of speculation globally. What follows is an independent yacht designer’s take on the facts as we know them as of this writing, with knowledge of the regulatory design, engineering and construction hurdles that must be overcome in order for a vessel of this size to achieve classification society approval.

A casual notion among some onlookers is that superyachts must be haphazardly engineered and constructed. The level of engineering that goes into the design of a vessel that weighs over a million pounds, which must be certified by international governing bodies in order to even be insured, proves otherwise. These are among the safest and most thoroughly engineered structures on earth. Bayesian is not the S.S. Minnow, which makes this a story.

Much will be said about the actions of the crew on that early morning. Investigations will determine who did what and when, and whether some watertight doors were open when they should have been closed.

“Downflooding” is the entry of seawater through any opening due to heel, trim or submergence. It is almost certainly the ultimate cause of Bayesian’s sinking. Some have pointed to the port-side lazarette door—the lowest hull opening on Bayesian—being open. But even if this was open, it would have risen higher above the water as the yacht heeled to starboard when blasted by winds of the storm. So if it wasn’t that port side door, where did the downflooding begin? A large sailing yacht like this is not “a sailor’s sailboat.” With twin diesels and multiple generators, Bayesian’s engine room looks much like one in any traditional long-range motoryacht. Engine rooms need ventilation so, much like a powerboat, Bayesian would have air inlets and outlets on her hullsides below the weather deck. A massive downburst, or a waterspout could heel the yacht over such that water might rapidly enter these vents and begin to flood the engine room.

Bayesian, like most modern yachts of this size, has six separate watertight compartments. These yachts are designed to withstand the flooding of any two of the six compartments and remain afloat. It follows that more than two compartments flooded in short order for this tragedy to unfold. The yacht’s air-conditioning systems need hullside vents too, so downflooding at an extreme angle of heel could have occurred in the master stateroom and guest cabins, these being two more of the six watertight compartments. Then there’s the main salon, whose door could have slid itself open as the yacht heeled sharply, via the starboard deck recess. So there are three flooded compartments. And if the watertight door from the engine room to the lazarette was open, that makes four.

How did such a massive yacht heel so wildly at anchor? Obviously the downburst or waterspout would be nearly impossible to predict in the darkness of that wee hour. Some of this yacht’s ballast was in a retractable keel, which was almost certainly in its “up” position at anchor, because reportedly it would make noises at anchor when down. Those noises would disrupt the evening’s peace. A normal evening’s peace.

More than motoryachts, sailboats can heel steeply and safely return upright. The angle of heel at which any vessel will no longer return upright is called the angle of vanishing stability (AVS). A large sailing yacht will have an AVS much greater than the downflooding angle through engine room vents. Uncontrolled downflooding would lead a vessel to reach and exceed her AVS, causing a capsize.

At five o’clock in the morning, with likely no electricity once the flooding began, guests unfamiliar with their surroundings would be sitting ducks as their cabins below deck tragically filled with water.

Hear Bill and Dan’s viral, full-length discussion in the players below:

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This article originally appeared in the November 2024 issue of Power & Motoryacht magazine.

View the original article to see embedded media.

Source: https://www.powerandmotoryacht.com/column/inside-angle-bayesian-sinking