sailboat capsize ratio explained

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EXCLUSIVE Why did the Bayesian capsize? Prosecutors to probe keel of £30m superyacht and speak to boat's designer as unearthed clip from 2019 tornado shows what SHOULD happen in stormy conditions

By Nick Pisa and Elizabeth Haigh

Published: 03:51 EDT, 22 August 2024 | Updated: 06:40 EDT, 22 August 2024

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Italian prosecutors will analyse the keel of the capsized £30million superyacht and speak to its designers as an investigation gets underway.

This morning five bodies recovered from the wreck of the doomed vessel were identified, including the ship's owner British tech tycoon Mike Lynch.

The underwater search is continuing for one person still missing, believed to be 18-year-old student Hannah Lynch.

Twenty two people, comprising 12 guests and 10 crew members, were on the luxury boat when it was ravaged by a 'black swan' waterspout and sank off the coast of Italy just before 5am on Monday. 

Fifteen of the 22 people who were on board managed to escape and make it onto a life raft.

However six people, Mr Lynch, his daughter Hannah, Morgan Stanley International chairman Jonathan Bloomer and his wife Judy and Clifford Chance lawyer Chris Morvillo and his wife Neda remained unaccounted for.

The body of the boat's chef Recaldo Thomas, was found shortly after the boat sank on Monday. 

Italian prosecutors will now look to explain why the Bayesian sank when other nearby boats managed to stay afloat during the freak storm.

Part of that investigation will centre on the ship's keel, which was partially elevated at the time of the storm.

The keel, which extends like a giant fin underneath the boat and acts as a counterweight to the tall mast, was not fully down despite poor weather being forecast hours earlier.

It comes as an unearthed video from 2019 shot in Auckland, New Zealand , showed what should happen when a ship like the Bayesian overturns in stormy weather. 

Earlier today,  the Mail's Robert Hardman  revealed CCTV footage of a tornado pushing a  large superyacht with a similar mast style to the Bayesian onto its side. 

But rather than capsizing, the mast quickly flips straight back up to its upright position.

As the search operation continues on Thursday, other developments are: 

• The Italian coastguard confirmed Mike Lynch's body was among the five recovered from the wreck, but his daughter Hannah is still missing
• Two hostesses, aged 20 and 22, who survived the disaster said they are 'alive by a miracle' 
• The Mail's Robert Hardman explores unanswered questions about what could have caused the tragedy  
• A resurfaced interview one week before the tragedy reveals how Chris Morvillo dedicated his career to getting Mike Lynch acquitted on US fraud charges.

The Bayesian (pictured) overturned during a severe thunderstorm on Monday morning

The CCTV footage shows a tornado pushing a large superyacht with a similar mast style to the Bayesian onto its side

But rather than capsizing, the mast quickly flips straight back up to its upright position

Experts told the Mail that it is fairly standard for the keel not to be fully lowered while a ship is at anchor, but with storms forecast and portholes reportedly left open, it raises questions over the cause of the tragedy.

Bayesian yacht sinking RECAP: Hannah Lynch remains lost at sea as father is identified

Prosecutors are seeking to speak with the ships' designers, after captain James Cutfield was questioned for two hours on Wednesday.

The company which manufactured the boat has now claimed human error was to blame.

Amid increasing questions as to how such a robust ship, which had previously sailed in Antarctica and was described as 'bulletbroof', could have sank Giovanni Costantino, CEO of Italian Sea Group, has spoken out on the tragedy.

ISG bought the Bayesian's constructors Perini Navi two years ago. Mr Costantino said: 'This was human error, the yacht sank because it took on water. From where exactly the investigators will tell us. The dynamic of the sinking is seen and read from AIS (Automatic Identification System) data and lasted sixteen minutes.

'We have given this data to the prosecutors at Termini Immerse. From the images it looks as if the yacht had been taking on water for four minutes. 

'All it took was another gust of wind to turn her over, that meant more water coming in. She then straightened very briefly before going down.'

British tech tycoon Mike Lynch with his wife Angela Bacares, who survived the disaster

The superyacht (pictured left) was docked off the coast of Porticello, near Palermo, when it was hit by an over-sea tornado, known as a waterspout 

Search efforts are back underway this morning to find Hannah Lynch, after five bodies were recovered from the wreckage

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Earlier a spokesman for the company told MailOnline 'procedures were not followed' on the luxury vessel and the sinking was down to 'portholes being left open despite bad weather being forecast hours earlier'.

A spokesperson said: 'The Bayesian was built to a very high standards and it would not have sunk if proper procedures had been followed by the crew.

'A storm had been forecast earlier, no fishing boats went out and yet the portholes were not shut, the yacht sank because it was engulfed by a massive amount of water through open portholes.'

The spokesperson added: 'The Bayesian would have remained afloat in any weather, even if it was being swung from left to right in gale force winds but it could never have remained in the water with open port holes.

EXCLUSIVE Why did all but one crew member of Bayesian superyacht survive while passengers remain missing?

'The design made the yacht extremely sturdy, but it couldn't stay up because there had been a huge intake of water though open portholes.

'The yacht was built to withstand whatever the conditions were. The mast has nothing to do with what happened, it was built that way when it was launched and it had a refit in 2020 in Spain, the yacht sank because procedures in bad weather were not followed.'

The Bayesian was 56m long, had a 74m mast and was built in 2008 with David Hutchinson, captain of its sister ship Rosehearty, telling Boat International 'she was bulletproof'.

He told the specialist publication: 'We've been to Antarctica and Chile, and we've had her in 70knots of wind ' but they had never been put in a situation that he felt was unmanageable.

The Bayesian went down in a matter of minutes after being struck by the tornado while anchored off the coast at Porticello, near Palermo Sicily on Monday.

Bayesian's captain James Cutfield, 51, survived and is currently in hospital.

Prosecutors are looking into the theory that the yacht's portholes and hatches were not closed in time ahead of the storm, despite bad weather being forecast, and if any of the crew are liable.

Italian Sea Group completed the buyout of Perini Navi for 80 million Euros in 2022 and a press release at the time said they were 'extremely satisfied' with the purchase complementing its 'expertise in the sailing yacht sector'.

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Capsize Index?

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Hello, Does anyone know where I can find a list with the capsize factors of modern sailboats. I understand anything below 2.0 is a "Bluewater" vessel.This will help my search for the correct sailboat. Thanks, JerryO  

go to: http://www1.iwvisp.com/jholtrop/Articles/best.htm and follow the links from there.  

Simplified indexes, such as the so-called ''Stability Index'', really is of very little real use in determining whether a particular boat is indeed suitable as a ''bluewater'' vessel. For example, two of the most critical factors in determining how safe a boat will be offshore or its inherrent stability is the vertical heights of the center of gravity and center of buoyancy. No where do either of these appear in the ''capsize index''. The EU developed a very sophisticated ''stability index'' (STIX). These series of formulas were intended to help determine the relative safety of a vessel in any given venue. But even the STIX formulas were merely ''sorogate formulas''. Sorrogate formulas are common in yacht design. These are formulas intended to predicty the behavior of a vessel using simple measurements. There are a helpful tool in comparing very similar types of boats. They do not produce specific accurate for an individual design. To explain further, one of the key factors in the so-called ''Capsize Index'' is weight, but weight in and of itself has no bearing on a boat''s likelihood of capsizing. (Visuallize a equal weight boats but one boat with a 50% of its weight in its teak decks, overhead, ceilings and bulkheads vs another boat with 50% of its weight in a lead bulb deep below the boat.) The Capsize index also has no way to compare different hull forms which of course affects stability as well as comfort at sea. So as you can see these simplified indexes really have little or no use in determining whether a particular boat will do offshore. All of that said you can find a calculator for a number of surogate formula indexes at Sail Calculator: http://www.image-ination.com/sailcalc.html#bbb The EU standards are available at: http://europa.eu.int/comm/dg03/directs/dg3d/d5/reccraft.htm Good luck Jeff  

Thanks for all the input.There is alot of knowledge here.I am simply trying to shop for a boat that is 35k or less in price,able to handle bad weather(in case it comes up).As much as I like the J30 series I really don''t think they are suitable for my needs.(Limited cockpit space from pics I have seen).I would like to spend winter months cruising the Carribean.(6 months or so approx).I only hope to make the wise choice in purchasing my sailboat. Thanks again for all the help, JerryO  

Ahoy, Jerry039. You didn''t indicate how you got the number you refered to, the 2.0. I assume it is from the Capsize Screening Formula developed by the U.S. Yacht Racing Union in conjunction with the Society of Naval Architects and Marine Engineers. This is a simpler way to estimate the positive stability range of a boat than the various complicated stability indexes that are usually done by architects and, on racing boats envolves measuring under the International Measurement System. Briefly, the formula that your 2.0 refers to is a two step formula. Take the total weight of your boat and divide by 64 (wt. of a cubic foot of sea water,62.2 for fresh water). This gives you the boat''s volume in cubic feet in sea water. Second, take the cube root of that number (almost any hand held calculator) and divide that into the beam of the boat. If the number is 2 or less, then the boat is pretty safe from capsize. There was an exhaustive study done on the Fastnet disaster and, believe it or not, the boat that came out of that as the benchmark boat was the Contessa 32. Find a picture or drawing of her and look at it. She has relatively low freeboard, does not have a very high aspect ratio rig. Getting a boat with a shorter mast and longer boom for the same given sail area lowers the center of effort, shortening the lever that produces heeling moment. She has adequate ballast to displacement ratio which is very important. In addition to these qualities, you want a swept back forefoot, not a straight entry, so you can deflect and or ride up on objects you might strike at sea. You want a moderately long keel for tracking and steering control in a sea, cut away aft, and you want a rudder and skeg so your rudder will not be so vulnerable. Thirty five feet is generally recommended as the minimum length for blue water cruising and I prefer a boat with moderate beam to a fat one. All this having been said, JeffH is right about the location of weight,etc. This assumes reasonable construction. Finally, it is the skill of the crew that is the single most overriding factor. The smallest sailboat to cross the Atlantic was under five feet long. People have sailed oceans in open boats, in production "lake boats" and just about every thing else. You have to know your boat and you have to know what your routine is for a given set of conditions. Crewing on a blue water boat is a good way to get experience. In today''s market, if you search diligently, you can get a lot of boat for the 35K you have to spend. It will be older, but the late 60''s and early 70''s grp boats are bullit proof because they were over built out of anxiety generated by the lack of overall experience with fiberglass. Look for the qualities I mentioned, keep it at 2.0 or below, a minimum of 40% ballast to displacement ratio, and she will get you home if you know how to help her. Finally, talk to people who actually cruise and read Cruising World and other cruising magazines. Good luck. dhartdallas.  

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capsize ratio

• Thread starter Harvey
• Start date Jun 20, 2006
• Brand-Specific Forums

Can anyone tell me what the capsize ratio of a G23 would be?Thanks,Harvey  

ratio Go to www.image-ination.com then click sail calc. It says the cap ratio for a G23 is 2.21It will tell you alot of other useful stuff.  

I don't mind displaying my ignorance will someone please explain " capsize ratio" for me. I under stand "righting moments", "angle of positive stability" but I haven't before heard of "capsize ratio".  

Ross - this site explains it for you. (NM)  

JimQ, If I read this correctly My capsize ratio is 1.73 the screening stability value is 18.69 and the angle of vanishing stability is 156 So I guess that she is going to be hard to knock down and will come back up on her feet is she does go down.  

OK - if you say so. I thought the information was interesting, but way over my old head to fathom.If it's blowing stink (anything over 20 knots) on my 33 year old boat we put in the lower hatch boards, hoist a 110 jib, and throw a single reef into the main.I'm not interested in trusting a theory that says - "yeppers, you're going to pop right back up after you get knocked down".Read where it goes on about a 40 ft. boat not being able to withstand 20 ft. waves? Sounds very similar to that 41 footer Free Spirit that was lost with all hands last week off the coast of Halifax while underway to Europe.  

Jimq, in 20 kts you are still way over canvased with a single reef and a 110 jib. 20 kts blows 4 times as hard as ten kts and twice as hard as 15 kts.  

jimq, you sail in much more sheltered water than I. 15-20 kts kicks up much rougher water than that on the Bay.  

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