Former Bayesian captain on sinking, vessel ballast and stability
sailingscuttlebutt.com
sailingscuttlebutt.com
The mast of this ship was slightly higher than that of the Preußen, one of the biggest sail ships ever build.
While it clearly worked for a while, it shows how insane the design actually was
It's also interesting because the boat was notable for having the tallest mast of its kind, and then sunk partly (one would guess) because of that. The boat sink quickly because hatches were left open in the warm weather. There was also discussion of weird weather phenomena being the cause.
He was also in the news shortly beforehand for fighting US prosecutors tooth and nail against a fraud case and recently beating them. Of course there are conspiracy theories that the two are connected, especially as his business partner died within a week while out jogging!
The whole thing is pretty interesting overall.
This becomes interesting from a number of facets. Engineering failure, human error, weather.
draught 4m without the moveable keel. The standard ballast is 140t, added 30t - 170t, not 200t. Say center of gravity of that ballast is 3m down from the center of stability - thus 510 tons x meter momentum. The moveable keel - 60t, center of gravity say in the middle or significantly lower (usually it would be very close to the bulb at the bottom end of the keel), i.e. at least 6-7 meters below the center of stability - thus 360-420 tons x meter momentum. So, while technically true, 500 being the major part, having 900 instead of 500 would probably have been much better in that situation.
>The Angle of Vanishing Stability is the angle of heel at which the vessel righting moment reaches zero, meaning that the vessel will not return to upright. Again, I forget the actual numbers for this, but the figures would be around 90 degrees with the moveable keel lowered and 75 degrees with it raised.
yep, and without lowered keel the chances of the gust putting the boat into those 75 degrees is much higher.
If the downflood angle is 45 degrees, that does not matter. He notes that you'd have to turn off the generator & HVAC before closing the vents, and those vents give it the poor downflood angle.
it does matter a lot - the larger momentum, the sooner it will return from the 45 back to 0, and thus less flooding. With less momentum and thus slower return it may though not return at all if the flooding speed would increase the list faster than the momentum would righten the boat back.
Once you've got water pouring in, all the stability angles start changing. Usually very fast. And returning "back to 0" would require both the storm suddenly calming, and floodwaters to be free to (in effect) move to the ship's centerline. (Some hull shape will do that, with limits - but I'm not a naval engineer, and don't have a useful real-world understanding of this.)
I think the critical thing here would a graph showing the ship's righting moment and the storm's heeling moment, both vs. angle of list, with the former shown both with and without the keel extended. Actually, a series of graphs - the wind wasn't constant, and the righting moments changed as the ship flooded. Those could answer the "would extending the keel have saved the ship?" fairly well.
Flip-side, extending the keel would have changed the ship's draft from 4m to 10m. The ship was dragging its anchor. I don't have a chart of the waters the ship was in, but running its deep keel into the bottom could also have ended badly. Has that consideration been mentioned?
EDIT: Here's the former captain's take on this, from the article:
> The Angle of Vanishing Stability is the angle of heel at which the vessel righting moment reaches zero, meaning that the vessel will not return to upright. Again, I forget the actual numbers for this, but the figures would be around 90 degrees with the moveable keel lowered and 75 degrees with it raised.
> The Downflooding Angle is much more important though in the scenario we are talking about. This is the angle of heel at which water will start to enter the vessel (usually through engine room or accommodation ventilation ducts)… once this starts the vessels is in serious trouble as stability is quickly reduced or lost due to the flooding.
> The downflooding angle for Bayesian was around 40-45 degrees… much less than the AVS. So, unless the vent dampers are closed (which with HVAC systems and generator running they would NOT be as they need to be open for that), the vessel will start to flood rapidly if heeled more than the downflooding angle.
My initial response to you was probably based on his strong emphasis on downflooding angle, vs. vanishing stability angle.
It was mentioned in some article that the wreck lies 50m deep, so it seems that even with the keel extended they wouldn't have been in imminent danger of grounding.
Really there should be a 'stabilize' button in the cockpit that drops the keel and does the dozen other things that is probably in the runbook automatically so people don't have to think about what to do.
obviously lowering the keel affects this a lot, as there is much difference in leveraged 60 tons vs non-leveraged.
So the question is not “is it possible to design automatically closing ducting” but “what is the cost of doing it”. And in general everything the guests interact with or experience will be exactly how the owner wants it, while everything else will be done to the minimum quality required by the classification rules.
The most robust solution is to keep things as simple as possible. Any bells and whistles you add will become liabilities very quickly, and if crucial systems depend on these bells and whistles, you can quickly get cascading failures.
I learned in about 2 months that you want the most crude, easy to repair and reliable solution to important parts and you want them cheap - because you'll be replacing them regularly. Expensive solutions will provide very little relief from this (if any at all). If the TVs in the guest rooms break regularly because of constant vibrations, that'll annoy the guests, but the ship will float and go forward. If your fancy fly by wire engine controls corrode and you are out at sea, it's mayday time. A lot of smaller boats still use mechanical wire actuation because it can be mended literally with a string.
If the simple valve is not reliable enough you can design a more reliable one. It will cost you a lot. Maintenance is a cost too. (It costs you in crew time, crew training, materials, and tools.) And when it predictably goes wrong and that causes the ship downtime, and they have to cancel a guest visit because of it that is a cost too.
So all of the things you list there (very good points each!) can be either mitigated by spending more on the initial cost of the valves, or by spending more on maintenance, or paying the price when it breaks.
And I also agree with you that it very well might be the case that the benefits are not worth the costs. (Especially since when you are designing the yacth you can't know what kind of disaster will strike it. We could, in an alternative reality, very well be sitting here and talking about how they should have installed more automatic fire-extinguishers, or more redundant navigation, or protection from prop-fouling.) Engineering is hard.
In other words, spending more on fancier equipment didn't really minimize the main pain point of failures: the ship being unavailable for sailing due to maintenance. It was worse in fact, because more expensive equipment wasn't more reliable usually. Shiny lcd touch panels looked great but were a ballache to use when there was a swell. I had chunky 800hp mercury engines fitted to crack that magical 100mph barrier, but because they were fly by wire, we had constant issues with electrical contacts that were difficult to diagnose out at sea (unlike the older mechanically actuated throttles).
Even worse, the more "over-engineered" a piece of equipment becomes, the more difficult it tends to be to reason about it's boundary conditions. More moving parts, heavier weight, more exotic materials - these all add further unknowns to an already very chaotic system that is seafaring. To come back to my electronic vs simple mechanical throttle system, the former is difficult to repair with a set of pliers, the other is trivial. Even though the former may have redundancies and fancy recovery modes, if it does fail, you are SOL.
So you are right, ultimately it's a cost question in the sense that if the more expensive components aren't more reliable, why spend money on them. I was keen to make the point that I'd have gladly spent more money on said equipment to make it more reliable, but there seemed to be no correlation between the two aspects :D
Automatically closing vents must be considered down-flooding points, so when calculation the down-flooding angle, you must consider them to be open (for SOLAS purposes).
The only exception (which is rarely granted) is for ball-type automatic closing air vents, which are not suitable for cabin ventilation as they close with negative pressure.
We went to the moon. :) Or more pertinently we have diesel submarines with snorkel masts which automatically close (and even more importantly the diesel engine automatically shuts off) when submerged.
So we know it can be done. I can't even imagine how expensive those things are on a submarine, and how expensive all the maintenance must be.
I know this sounds crazy but changing regulations (or rather realistically obtaining exemptions) is "just a cost" too. A huge cost for sure. And an uncertain cost. But it can be done, especially when one does all the requires engineering work to show that the new solution is safer than the old one.
I understand that most people when they say "at any cost" what they mean is "at any cost reasonable within our means for this kind of thing". But when taken literally "at any cost" is quite expansive.
> Automatically closing vents must be considered down-flooding points, so when calculation the down-flooding angle, you must consider them to be open (for SOLAS purposes).
Presumably the SOLAS calculations were already fine with the down-flooding angle as is. So we can still treat the vent as open (for SOLAS purposes) while at the same time have an auto-closing feature on them.
What a non-sequitur. The issue isn't whether it can be built - but whether you can certify and insure it. Apollo couldn't have been run as a commercial pleasure spacecraft, either.
> Presumably the SOLAS calculations were already fine with the down-flooding angle as is. So we can still treat the vent as open (for SOLAS purposes) while at the same time have an auto-closing feature on them.
At anchor, but not at sea, where to achieve it's CE rating, the offending vents would be required to be closed.
That's the misunderstanding then. Because I'm specifically answering whether it can be built or not. This was the original question which started the thread: "So it's not possible to design ducting for HVAC/engine exhaust that either closes automatically at a certain angle, or has some mechanism that lets out gases without letting in water?"
> but whether you can certify and insure it.
You said "at any cost". At any cost I buy Lloyds, instruct them to work with my army of engineers until they find a way to satisfy their requirements, and we insure it. That's within the "at any cost" budget you set.
> At anchor, but not at sea, where to achieve it's CE rating, the offending vents would be required to be closed.
Okay. I'm not seeing the problem with that. You will have to explain to me why does that prevent us from making the vents automatically close at anchor when the boat is capsizing. Where do you see the problem with this?
And then buy the IMO and your own country to certify.
> Okay. I'm not seeing the problem with that. You will have to explain to me why does that prevent us from making the vents automatically close at anchor when the boat is capsizing.
There are no automatically closing vents certifiable for human ventilation, so you cannot have an automatically closing vents and just manually cover it when necessary.
> Where do you see the problem with this?
I think the problem is with you, who cannot seem to believe that marine engineering with centuries of experience could have found reasonable trade-offs in the regulations.
You are putting something in my mouth which I did not say. Can it be done? Yes. Physically it can be built. Is it a reasonable trade-off? I don't think so, and I didn't said that it is.
I think the exaust has possitive pressure when the engine is running which would prevent water from entering. OTOH water entering the engine air intake.. would be quite bad for the engine I guess, so there'd be protection against that. Also both of these (exhaust & intake) are not free to the inside of the vessel, but form a closed circuit with the engine, so there's no way to flood the vessel through those.
So probably we're talking about the engine room *ventilation* openings that would let water in.
Imagine a (say) 5cm diameter exhaust pipe, at a 45 degree angle - with exhaust gasses blowing out through the top 3cm, while water runs in through the bottom 2cm. At some point, the cold water starts hitting thicker and hotter pieces of metal. As you put it, "quite bad for the engine".
But from the article, about what happens when the Bayesian heels over too far: "water will start to enter the vessel (usually through engine room or accommodation ventilation ducts)… once this starts the vessels is in serious trouble".
Don't know about this yacht specifically, but as I understand it a common solution is for the engines to suck in ambient air from the engine room.
> So probably we're talking about the engine room ventilation openings that would let water in.
Likely yes. And probably(?!) there were watertight bulkheads around the engine room, so by itself the engine room flooding might not have sunk the boat (assuming doors/hatches were closed), but if combined with other downflooding into the living quarters (doors, ventilators etc.) it would have accelerated how quickly it sank.
Especially for sailing yachts, the exhaust is almost always wet (below the waterline).
I've seen quite a few sailing yachts, but never one with the exhaust below the waterline. Pretty low yes (typically maybe 10-20cm above the waterline?), but not below. When underway, the exhaust can be partially submerged due to waves.
'Wet exhaust' means that the engine cooling water is pumped into the exhaust pipe, which muffles the exhaust noise and cools the exhaust so that rubber tubing can be used.
To a rounding error, every luxury sailing yacht built in the last 20 years and most new designs of all classes will have underwater exhausts.
The fact is that marine engine exhaust systems in good repair are not down-flooding points and certainly not on the yacht in question, where it almost certainly was below the waterline.
Merely expression surprise at your statement, considering my experience is so different. I have no experience of 'luxury' yachts though, just regular sailing boats. So maybe those superyachts are different?
> The fact is that marine engine exhaust systems in good repair are not down-flooding points and certainly not on the yacht in question, where it almost certainly was below the waterline.
Well I agree with that, but because, again in my experience, sailing yacht exhaust systems tend to have an S curve where the exhaust goes relatively high up. Whether the exhaust opening itself is just over or under the waterline doesn't really matter for downflooding.
This is a boat that was never designed to weather a bad storm, where unpredictable things are very likely to happen.
And it starts to flood at 45 degrees while in normal operating trim? That is just nuts. It’s not that hard to put all of the ventilation on the centerline, and a diesel engine won’t flood a boat through its exhaust.
So many design compromises on what could have been a real seagoing vessel you could trust to carry your family anywhere in comfort and safety, just for the sake of some misguided idea of opulence. In ships, beautiful is as beautiful does. A sleek coffin is an ugly ship indeed.
I would not have felt safe sailing that vessel in anything other than well timed passages with no weather nearby.
It really drives home the difference between a boat that is designed to stand up to whatever it might encounter vs a showpiece that is designed to look impressive but cannot face the kind of adversity that a working ship will be exposed to on a routine basis.
Clearly these yachts are designed to be operational in pleasant conditions only and to hide in shelter when the sea shows it’s teeth. What a stupid waste of resources. A fake ship.
Looking at some random ships in roughly that size one can see e.g.
- https://en.wikipedia.org/wiki/Stavros_S_Niarchos sailing ship of 59m, 635 tons
- https://en.wikipedia.org/wiki/Gepard-class_fast_attack_craft German naval ship, 58m, 390 tons.
Considering it was a yacht with relatively fine lines, even taking into account the ballast, 540 tons seems about ok.
What sank the Bayesian superyacht in Italy? (nytimes.com)
157 points by rediguanayum 4 days ago | 276 comments