Bayesian Interim Report

[Mister E]

My yot doesn't have AC, so hatches would be open.

However, nor does it have a professional skipper, nor night watch when I anchor.
However, I'd generally hope to survive an average night off palermo, and if knocked down my 26ftr would - I believe - withstand that.

I think your "not predicted" may perhaps be a tad over generous?

So you can predict a direct hit from an unforcast tornado can you?

 

[WindyWindyWindy]

So you can predict a direct hit from an unforcast tornado can you?

There was a gale forecast wasn't there? A bit of caution would be wise. had they known the boat could be knocked down so easily they might have made more preparations. The missing info in the stability book is pretty poor when it's an unusually unstable sailing vessel.

There's that whopping awning that it's always pictured with for starters, and the internal watertight doors that must have been open for it to sink, presumably open to get the people out, but they could have been mustered given the level of threat a gale poses to that boat. Had they known.

For an item like that, a sticker on a crane, it would not be material to refusing to class, re-class the vessel to the CA standard. Instead, it would be on a list of items to be addressed within a time frame, all of which can be challenged by the vessel owner, manager. It might not even end up on a list, but be noted as a recommendation, not mandatory.

Yes, the suggestion was the surveyor felt quite strongly about the list of items and that it was a requirement. They do have a lot of power here, possibly more than the surveyor themselves realises.

 

[Mister E]

Windy
do you prepare your boat for a direct hit from a tornado when a gale is forecast?

 

[Mister E]

So just how many yachts are designed for a direct hit from a tornado?

 

[WindyWindyWindy]

Windy
do you prepare your boat for a direct hit from a tornado when a gale is forecast?

I do make some preparations. I might take in the towels and close the hatches if it looks like rain.

If I had a stability book that told me that a gale might knock it down I would be making ready for a knockdown. That's what I meant, that they were in an unusually poorly performing vessel and the information was incomplete. It wasn't intended as a criticism of the crew, but of the lack of important information.

Actually, provided they don't hit anything solid, most yachts will survive that kind of weather.

 

[Mister E]

I do make some preparations. I might take in the towels and close the hatches if it looks like rain.

If I had a stability book that told me that a gale might knock it down I would be making ready for a knockdown. That's what I meant, that they were in an unusually poorly performing vessel and the information was incomplete. It wasn't intended as a criticism of the crew, but of the lack of important information.

Actually, provided they don't hit anything solid, most yachts will survive that kind of weather.

That is not a direct hit from a tornado.
So again do you make provision for that?
If so can you give advice to the rest of the world about this?

 

[Mark-1]

So just how many yachts are designed for a direct hit from a tornado?

In these circumstances pretty much all of them, by virtue of the normal requirements of a yacht. We have video in this thread of a bog standard AWB being knocked flat by a down draft and bobbing straight back up when it passes.

That doesn't mean a Superyacht always has to be designed to be as capable as a Sadler 32 but it would have been be nice if it was!

 

[billskip]

So just how many yachts are designed for a direct hit from a tornado?

If it's keel had been down this whole incident maybe possibly wouldn't exist..
What I'm saying is there are many unknowns and all the experts can not guarantee what might or might not have been...
The fact is it happened...and as people sadly lost their lives there has to be an investigation...who agrees or disagrees with the findings is their choice.

 

[westernman]

I do make some preparations. I might take in the towels and close the hatches if it looks like rain.

If I had a stability book that told me that a gale might knock it down I would be making ready for a knockdown. That's what I meant, that they were in an unusually poorly performing vessel and the information was incomplete. It wasn't intended as a criticism of the crew, but of the lack of important information.

Actually, provided they don't hit anything solid, most yachts will survive that kind of weather.

A moderate gale is up to 33 knots (F7), a fresh gale 40 knots (F8), strong gale 47 knots (F9), whole gale 55 knots (F10).
They were hit by winds of over 70 knots - which is a lot more than a hurricane and is off the beaufort scale.

How many of us expect and are prepared for winds well over hurricane force when anchored in a flat calm of less than 8 knots?

 

[RobbieW]

...
How many of us expect and are prepared for winds well over hurricane force when anchored in a flat calm of less than 8 knots?

Anyone anchoring in the Med with thunder cells about ?

 

[Mister E]

Just for information tornados have the power to demolish concrete buildings.
So a direct hit from one is going to be outside of any designed parameters of any yacht. It is such a low risk in normal life up to now that it would not be cost effective.
Unless you sail in Tornado Alley In America.

For those that still believe that their boat is immune to one. Do some research on Supper Cells.

 

[boomerangben]

Nor me and Google was unhelpful but you only have to look at a ship to determine roughly which permanently open openings would be submerged at 40 degrees and the answer for the 'normal' ships we see around the UK coast the answer is none.

To say none is a bold statement. Neither of us know. All I am saying is that the regulations allow for an angle of downflooding of less than 40 degrees, providing the GZ curve meets certain parameters. I can easily imagine some offshore supply/anchor handling vessels have relatively small angles of downflooding, but I simply don’t know

The fact still remains - the Bayesian (if the information on Google is correct) had an angle of downflooding of 40 - 45 degrees and that meets the minimum requirement laid down by the MCA

 

[boomerangben]

There was a gale forecast wasn't there? A bit of caution would be wise. had they known the boat could be knocked down so easily they might have made more preparations. The missing info in the stability book is pretty poor when it's an unusually unstable sailing vessel.

There's that whopping awning that it's always pictured with for starters, and the internal watertight doors that must have been open for it to sink, presumably open to get the people out, but they could have been mustered given the level of threat a gale poses to that boat. Had they known.


Yes, the suggestion was the surveyor felt quite strongly about the list of items and that it was a requirement. They do have a lot of power here, possibly more than the surveyor themselves realises.

Why do you say there’s information missing from the stability book? There have been no findings that said as much as far as I can read. There may be stuff missing that people think should have been there, but a stability book is a document that needs to be approved by a certified authority. It must have been approved. And why do you say it is an unusually unstable vessel? It met all the stability requirements

I might be wrong here but water tight doors provide assurance of damaged stability ie where the hull itself is breeched. If there are openings in each watertight compartment which might lead to downflooding, water tight doors will make very little difference. I have no idea of the lay out of the vessel so don’t know if water tight doors were open or closed or if a closed one would impede exit. (I doubt there is a single means of escape from a compartment

 

[Biggles Wader]

Just for information tornados have the power to demolish concrete buildings.
So a direct hit from one is going to be outside of any designed parameters of any yacht. It is such a low risk in normal life up to now that it would not be cost effective.
Unless you sail in Tornado Alley In America.

For those that still believe that their boat is immune to one. Do some research on Supper Cells.

Make sure you have dinner first.

 

[Mark-1]

I can easily imagine some offshore supply/anchor handling vessels have relatively small angles of downflooding,

Hence I said 'normal'.

 

[Mark-1]

Why do you say there’s information missing from the stability book? There have been no findings that said as much as far as I can read.

From the MAIB report:

The SIB contained Curves of Maximum Steady Heel Angle to Prevent Downflooding in Squalls. These
curves provided a safe operating range for a sailing vessel, indicating the maximum heel angle it could
withstand before there was a risk of downflooding occurring in a sudden gust or squall. The SIB did not
contain such curves for when Bayesian was operating in the motoring condition where the centreboard
was raised and no sails were up

Rightly or wrongly, there were no keel up stability numbers.

 

[Mark-1]

Just for information tornados have the power to demolish concrete buildings.
So a direct hit from one is going to be outside of any designed parameters of any yacht. It is such a low risk in normal life up to now that it would not be cost effective.
Unless you sail in Tornado Alley In America.

For those that still believe that their boat is immune to one. Do some research on Supper Cells.

Yachts are absolutely designed to survive a knockdown, I've been knocked down on a Summer's day in Poole Bay and seen dozens of boats knocked down in normal use. A yacht doesn't care if it's knocked down in a freak downdraft under bare poles or due to crew error with the kite up in a Sunday afternoon race. Either way it doesn't sink fast, and it comes back up. (As we can see in the video posted above.)

...and a yacht is far less prone to wind damage from these extreme events than a building - I've never seen the roof blown off an AWB.

 

[boomerangben]

Hence I said 'normal'.

If you live in Aberdeen, offshore supply boats are very normal! I think if you look at the range of vessels operating around the UK at any one time, there is nothing normal.

Thinking about it and what little I know about openings and downflooding etc, but reading the various (but limited) information on the internet, any opening counts, even ones that can be sealed, eg pilot access doors, so any high sided vessel might have an opening that counts, reducing the downflooding angle to smaller values. Operational procedures clearly assure an acceptable level of safety though.

Perhaps it’s time I had a pint with a surveyor buddy (big ship)!

 

[boomerangben]

Yachts are absolutely designed to survive a knockdown, I've been knocked down on a Summer's day in Poole Bay and seen dozens of boats knocked down in normal use. A yacht doesn't care if it's knocked down in a freak downdraft under bare poles or due to crew error with the kite up in a Sunday afternoon race. Either way it doesn't sink fast, and it comes back up. (As we can see in the video posted above.)

...and a yacht is far less prone to wind damage from these extreme events than a building - I've never seen the roof blown off an AWB.

Aren’t you trying to compare apples and pears though? An AWB is as different to a super yacht as a super yacht is to a super tanker. Hence the different rules that govern each

For instance, you don’t need to consider damage stability for your leisure vessel…one hole = sinking (unless you can pump/bail fast enough). Having said that, I don’t know what you sail, but AWB in general don’t need to consider damage stability

 

[Mark-1]

If you live in Aberdeen, offshore supply boats are very normal! I think if you look at the range of vessels operating around the UK at any one time, there is nothing normal.

Thinking about it and what little I know about openings and downflooding etc, but reading the various (but limited) information on the internet, any opening counts, even ones that can be sealed, eg pilot access doors, so any high sided vessel might have an opening that counts, reducing the downflooding angle to smaller values. Operational procedures clearly assure an acceptable level of safety though.

Perhaps it’s time I had a pint with a surveyor buddy (big ship)!

Are you saying Offshore Supply Boats have unsealable openings that are submerged at 40 degrees? I can't see any. I've never seen one first hand I've googled and they look like massive flat bed trucks and it all looks sealed to me up to the bridge. Looks to me like a giant could grab it, submerge it up to the bridge and it would just bob back up. Which is what you'd expect given their role.