# The Sea Demonstrates Again It Doesn't Care - Yacht Bayesian

You idea is a good basic illustration.

The windage area of mast/boom plus the standing rigging must be considered, plus the hull & superstructure.

The force applied by a wind would of course depend on the direction of application and would be reduced as the ship heeled and the horizontal vector of the wind force applied is reduced. So that is a bit of an integrated solution.

The resultant force is not at mast tip although it could be expressed that way.

This will prove an interesting technical investigation and a good defense. No one knows nor can anyone prove what the wind speed was at the time and place of the incident….

I would think the force should be calculated as acting at the center of lateral area of the mast.

Another observation: from this picture, it appears that the cabin deck is at about one meter below the sheer line, and the distance between the opening and the sheer line is half a meter or so. This might have had an effect on when flooding began and what the actual righting moment was after ingress.

Earl

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Someone found the stability booklet:

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I am still interested in, if the Bayesian hull is intact. Has it been checked? My ships float on their hulls, and are not blown upside down and sunk by wind on the mast. Or this typhoon full of water filling the Bayesian from above through the deck? What drunken seaman came up with such idea?

Maybe a Swedish seaman? Off one of “your ships”, maybe?

You?

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This post is from August 24 when fewer details were known. Of particular interest are Roger Long’s remarks.

Roger Long replied, “Seventy-three degrees? There you go. The heeling arm would have again been above the righting arm at about 2/3 of that angle and, without sheets to ease or ability to steer, she would have been committed to capsizing around 50 degrees of heel.”

With the caveat that I’ve no expertise in this area:

Looking at the numbers from post #320, the calculation of 70 kts wind speed, it does look the mast height is multiplied by 0.5 so apparently assuming the force is acting at about half the height of the mast. The righting arm used looks to be in error, the 2.75m about twice what I’ve seen elsewhere.

Using the lower GZ and taking into account 45 degrees of wind heel the two errors about cancel out. It works out to about 70 kts.

Given all the uncertainties there may well have been gusts 100 kts or more. In a downburst there also might have been vertical component to the wind direction.

It’s very possible I’m missing something important or made other errors but 70-100 kts seems like a reasonable guess. Captain Karsten Borner of the Sir Robert Baden Powell estimated hurricane force winds.

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So, as I read in other reports in GDS, they are simply making the distinction from actual drowning as cause.
Also note that any “air pockets” at the surface would reduce to about 1/5 of that volume on the seabed.

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I dont know where he gets that 50 degrees number from without the wind angle and force?

It seems a bit of a guess that exact number. But to my understanding what he’s saying is that the angle of vanishing stability means that they yacht WITHOUT any external forces acting on it would right itself up to a heel angle of 73°. However, if you include the heeling moment of the wind, the heeling moment will overpower the residual righting moment much before the angle of vanishing stability, which he guesses to be about 2/3 of the value of AVS, hence 50°.

it will still right itself after AVS that is just saying the righting moment is not increasing but going down.
My guess would be it would still right itself at 90 degrees ( without any other sustained force)

We need the wind profile of the mast and rigging to know the force that adds per m/sec of wind
It would be a very tender yacht if a bit of wind would knock it over at 50degrees and hold it there

That is not how I was taught AVS works. The AVS of my boat is 125 degrees, which according to the stability chart is where the righting moment is zero.
How most sailors (as in sailing on sailboats) use the term:
In sailing, the limit of positive stability (LPS) or angle of vanishing stability (AVS) is the angle from the vertical at which a boat will no longer stay upright but will capsize,

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This is from the Bayesian’s stability book. Don’t need to know the wind velocity to see that a heel of 50 degrees is at or past the critical angle of heel.

It’s essentially the idea of deck edge immersion. Wind heel is different from a roll because with heel the yacht is at equilibrium wrt heeling force and righting arm. The AVS is not relevant.

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Yup: If X amount of wind will hold your boat over Y degrees and your boat will sink at Z degrees and Y>Z, you need a better boat or less wind.

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From the Bayesien booklet

#### 3. Master Responsibility on Stability Under Sail

Compliance "With reference to Chapter 11.2.1.2. of LY2 Code, the Light Load condition in this booklet results not to have a positive GZ curve range up to 90 degrees. For this condition GZ is positive up to 84.3 degrees.

to me it looks like at about 35 degrees there is no more increasing righting moment and that keeps dropping till 90 ish then its upside down.

If it did go upsidedown would it have floated?
My guess is it sunk before it got there?

That righting diagram is static stability, doesn’t take into account everything actually encountered at sea. How long was parametric rolling not accounted for?

According to Roger Long (from the Loose Cannon Substack, now behind a paywall), from wind tunnel tests the force to heel that large mast to a dangerous angle could be as little as half the calculated.

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It is possible for some sailboats to float inverted or roll 360 degrees. They are much more watertight and would roll faster than this boat. They also roll over because of very large waves, so it is a much faster event than this was.

• there is a survivor bias in these accounts, we don’t know about the ones that sank for the most part. Generally the boat either roll all the way around or another wave rolls them upright soon after. The only ones I know of offhand that stayed inverted are either cats or monohulls that suffered structural failures where the keel departed the boat.
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I raced with a guy that told me years ago pulling out of the Hobart in a 55’er and going back to Melbourne so all relaxed low sail but down wind in huge swells, nose dived and flipped.
He said all slow motion middle of the day so the guys all walked around the main salon.
Then the conversation started, isnt this meant to right itself as they stood on the ceiling…
He said what seemed like forever it slowly came back up, outside 2 guys in cockpit over the side on their harnesses so they pulled them back on, kept going.

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