Sinking of "Bayesian" Raises Question(s) About Watertight Compartments

HOW DID A 180-FOOT YACHT, REPORTED TO INCORPORATE SEVERAL WATERTIGHT COMPARTMENTS, GO DOWN SO QUICKLY?

180-foot Sloop Bayesian (Perrini Navi) - Photo courtesy of SuperYacht Times

In the morning hours of August 19, 2024, the 180’ yacht Bayesian, went down whilst anchored off the coast of Sicily. The sinking is believed to be the result of a waterspout (a waterborne tornado) running the vessel down as her passengers slept and her crew was on deck battening down against a storm that was moving in quickly and unexpectedly. Tragically, several lives were lost when the yacht foundered. Sincere condolences to the families and friends of those who perished. RIP.

The investigation to determine more precisely the contributing factors is ongoing and likely to be so for many months, if not a year or more. In the meantime, speculation about the cause or causes of the sinking is widespread among sailing enthusiasts, sailors, yacht designers and naval architects, and, of course, boating journalists. Although some might see such speculation as fruitless and morbid, I believe that, in these circumstances, such discussion is healthy and good for all — because it occasions a broad-based consideration of not only the specific occurrence at hand, but also of common practice in the yachtbuilding industry and the sport of sailing.

IMO, Catastrophic Down-Flooding Is Most Likely the Proximate Cause

My contact with just such a discussion began with a post published on Facebook by Tad Roberts, a well-known boatbuilder, yacht designer, and boating writer. That post is part of a pretty extensive (3-post) discussion. This was my initial contribution to that discussion:

Tad, it's pretty clear that, as you say, the proximate cause of the sinking is most likely a massive and rapid down-flooding that must have occurred as the yacht heeled over onto her beam ends. The fact she is on the bottom — and not floating on her side or upside down also argues for rapid down-flooding.

If the mast and rig are intact as reported, then that rules out a snapped mast driving a hole into her hull or tearing up her deck. Moreover, the swing keel or ballasted dagger board being in its raised position would not be that unusual on the hook because play in its mounting system would likely let it flap noisily a bit when in the down position and not sailing. In anticipation of "normal" weather, the raised board would not likely have been seen as presenting a danger overnight.

But here's a question: could a powerful waterspout with circular wind velocity of 300+ mph suck enough water away from one side of her hull rapidly enough to interfere sufficiently with her static/buoyant stability to cause her to lay right over. If so, it may have been a freak, once-in-a-lifetime tragic accident that could not have been reasonably anticipated. — Phil Friedman

There is little point in rehashing that discussion here. So, if you’re interested, I recommend you read Tad’s Facebook posts, starting with:

➡️[ More On the Sinking of Bayesian ].

And if you’re really interested in a solid discussion amongst a trio of experts, you can take a look at a piece that appeared recently in Peter Swanson’s Loose Cannon newsletter:

➡️ [Yacht Design Experts Dissect How an 'Act of God' Sank Bayesian]

The 800 lb Gorilla in the Room

However, that said, a question which I have yet to see raised is, how does a high-quality yacht from a major builder, reportedly fitted with several “watertight” compartments, sink so quickly, even in the face of massive down-flooding?

Is it the result of a semantic disconnect? That is, does the term ‘watertight compartment’ mean different things to different people? Maybe.

1. You can have a bow compartment forward of a watertight “collision partition”, designed to confine flooding to a non-catastrophic level in the event the bow is smashed in by a collision with flotsam (like a rogue, floating steel container.) Or …

2. You can have multiple watertight divisions of the vessel spaced out to confine a given hull breach/leak to a single area (contained volume), complete flooding of which would not endanger the vessel.

The first of these would not help in a situation where extreme heeling leads to sudden and massive down-flooding. But the second approach would — provided a) the watertight compartments were in total volume (i.e., buoyancy) sufficient to keep the vessel afloat and b) watertight integrity remained intact against down-flooding. This latter proviso spotlights a common rub in the industry.

Most yacht designers and builders view watertight compartmentalization as intended to protect a vessel from flooding water entering via a hull breach. They rarely, if ever look at providing watertight integrity against a spreading down-flood. Yet down-flooding is probably a greater catastrophic danger to a sailing yacht than water intrusion via a hull beach — because down-flooding causes a positive-feedback chain reaction that leads to an almost instant loss of positive stability.

For a detailed discussion of buoyant stability, see my 2014 article that analyzed the capsize of the 90-foot Baden at launch by her builder, Northern Marine:

➡️ [ Disaster In Anacortes ]

Admittedly, it’s easier to talk about watertight compartments sufficient to float a vessel in the event of serious down-flooding than it is to actually design and build them. Mostly because of the demand buyers and owners put on the industry for not only maximized interior accommodations, but also for maximized convenience of access. In short, buyers and owners don’t generally want to go up and down stairs or ladders to move from one major area of the vessel to another. Which generally leaves everyone relying on so-called “watertight” doors let into watertight bulkheads.

The problem is — and I can tell you this as a former yacht builder — the probability of watertight doors being closed and dogged before they are needed is not much higher than zero. And once the vessel is heeled enough by wind and sea to experience serious down-flooding, it’s almost always too late to close them, even if the flooding would allow it to be done.

No, the only way to provide emergency buoyancy in a vessel that experiences serious down-flooding is to design in and build permanently watertight compartments. Which could be done with some intelligent analysis and design — and, of course, some lessened convenience when moving through the interior of the yacht. To be sure, not a design cakewalk, but possible — with some creative design work. And I submit, potentially well worth the effort. Witness the Bayesian disaster. — Phil Friedman

Copyright © 2024 by Phil Friedman — All Rights Reserved

Author’s Note: The points made in this article concerning watertight compartmentalization may or may not apply to the yacht “Bayesian” or other vessels built by Perini Navi. I don’t have enough information to know. However, notwithstanding that, I believe the question is worth considering because of the potential path to increased safety a robust discussion might produce. And certainly, if such were to come to pass, then some good might also be seen to come out of this otherwise sad, sad occurrence. — PLF