There are few incidents on board more destructive than a crash gybe. The power unleashed when the wind catches the wrong side of the mainsail is hard to overstate, and the speed with which it occurs makes evasive action impossible in the moment.

There have been several tragic accidents involving crash gybes in the last 20 years which have been analysed by the MAIB and other authorities and the reports are sobering to read.

Studying accident reports is standard practice in aviation, but it’s less common for sailors to study them. They are, however, an important resource for understanding the risks of being on the water, and how accidents happen and absorbing the findings can make us all better skippers. The MAIB’s remit is to analyse the causes of each incident without apportioning blame.

We’ve probably all had an unexpected gybe at some point, though not with such devastating consequences. So rather than hope we’re immune to the same errors, perhaps it’s safer to assume we’re not and take a closer look at the reports to identify common themes, and how to stay safe downwind.

Case study 1 – Liquid Vortex, 2011

In 2011 Beneteau 40.7, Liquid Vortex, was competing in the Myth of Malham Race when a crash gybe seriously injured one crew member. The race starts in the Solent and heads west, rounding the Eddystone lighthouse before finishing back in the Solent.

The boat was running downwind on the return leg in a West Force 6 when her spinnaker tore. The damaged sail was lowered, and the heavyweight spinnaker was prepared, but became wrapped during the hoist. The headsail wasn’t set at the time, and there was no preventer rigged.

The first mate went forward to resolve the issue while the skipper remained in the cockpit but struggled to sort out the wrap. Communication between the cockpit and foredeck was difficult over the noise of the flogging sail. Frustrated with how long the process was taking, the skipper decided to go forwards himself.

He left an inexperienced crew member on the helm, instructing her to steer 040°, which was approximately a beam reach. He’d noticed an approaching fishing boat, but didn’t think it would be a problem. However, the helm and another crew member in the cockpit became increasingly concerned with their converging courses and asked the skipper for instructions. He shouted back to pass ahead of it, gestured to port, and told them not to gybe but the helm turned to starboard instead and gybed unexpectedly.

The traveller on the First 40.7 is just in front of the helm and during the gybe the mainsheet swung aft, striking the helm and knocking her to the cockpit floor, where she lay unresponsive. Another crew member took over the wheel and unintentionally gybed back again. A Mayday was issued and the casualty was evacuated by helicopter, during which the winchman fell overboard and had to be picked up by hi-line from the sea.

MAIB analysis

The report concludes that: ‘Communication between the skipper on the foredeck and the helmswoman in the cockpit was difficult’ and that ‘the helmswoman’s uncertainty about the action the skipper wanted her to take could have been avoided had the skipper remained in, or returned to, the cockpit until the fishing vessel had passed and was clear.’

The MAIB report also found that the skipper was competitive and ‘drove his boat and his crew hard’. Given the presence of novice crew, many of whom were suffering from lack of sleep and seasickness, as well as relatively demanding conditions, ‘a more cautious and encouraging approach was warranted’, the MAIB report said.

Case study 2 – CV21

During the first leg of the 2015 Clipper Round the World Race, CV21, one of a fleet of 12 identical Clipper 70s, suffered a fatal crash gybe 120 miles west of Portugal.

In the lead up to the incident, the boat was on a broad reach with NNE winds of 20 knots and a moderate sea state. They had the full mainsail, Yankee 1 and preventer rigged. The watches changed at 2200 and, according to the report, the oncoming watch leader commented that the boat seemed a ‘bit lively’. The off-going watch leader ‘disagreed and stated that there had been no problem running downwind during his watch’.

By 2330 the wind had increased and was gusting 30 knots. One of the most novice helms was at the wheel. The watch leader and skipper (who was below) agreed to put in a reef. At this point the watch leader left the helm station where he’d been supervising the steering, and crossed over the traveller, which is just forward of the helm, to brief the crew. He remained clipped on aft of the traveller, but was sitting forwards of it in an area which was known as a danger zone when the boat gybed without warning.

The report states that: ‘The helmsman was unable to regain control of the yacht’s heading before a second gybe returned the boom back to port’ and ‘a crew member saw that the boom preventer was flying free’. After the double gybe the watch leader was found lying motionless in the cockpit lying across the traveller and tragically never regained consciousness. The vessel diverted to Portugal and a postmortem revealed that he had died from a broken neck.

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MAIB analysis

The MAIB analysis stated that prior to the incident, ‘the apparent wind speed of 15.7 knots was approaching the 16-knots limit recommended by the sailmaker for the Yankee 1 headsail. As the wind speed continued to increase, the helmsman found it increasingly difficult to maintain the yacht’s heading, occasionally veering up to 50° off course.’ They stated that ‘it would have been wise for… [the watch leader]… to replace the helmsman with a more experienced crew member’, but that his ‘decision to reef… was timely.’

Of the watch leader’s position close to the traveller they found that the race training and safety briefs had covered this hazard in detail and it was not known why the watch leader was there. They suggested that perhaps ‘he was preoccupied considering the reefing evolution and the pre-reefing brief he was about to give his team, and so forgot about the zone.’ The skipper did not come on deck for the reef briefing, and whilst this decision was ‘understandable… it resulted in the deck being left unsupervised by him at a time of heightened risk’.

On the failure of the preventer, subsequent tests discovered that it had parted at a partial splice of the Dyneema strop on the foredeck, ‘which might have been exacerbated by uneven loading of the splice, resulting in fewer fibres bearing the load’. They also found that ‘The manufacturer’s data sheet for the D2 Racing rope supplied to the Clipper 70s did not contain information on the loss of strength caused by splices, hitches or knots,’ and that ‘wider promulgation of the limitations of HMPE [known as Dyneema] rope would be beneficial’ for the industry.

Case study 3 – Buccaneer of Upnor

It isn’t always downwind sailing where crash gybes occur. According to an MAIB accident summary of an incident in August 2007, the Elan 333 Buccaneer of Upnor was en route from Weymouth to Poole when she crash-gybed off St Alban’s Ledge from a beam reach. The conditions were Northerly, Force 5-6, gusting Force 7.

According to the MAIB’s accident summary, the skipper had been supervising a novice helm for an hour on a close-reach course. Despite having two reefs and the No. 1 jib set, ‘the helmsman experienced difficulty in keeping the boat on the course, and the mate had to frequently “spill” wind from the overpowered sail by slackening the mainsheet’, the summary states.

When she needed to go below, the skipper instructed the helm to change course to a beam reach, which took them slightly further off St Alban’s Head and the mate remained on deck. Whilst she was below a gust struck and the boat broached. The novice helm put on full rudder to counter it. ‘After a short time,’ the report continues, ‘the gust subsided, but, with the helm still hard over the yacht quickly came round to starboard and continued into a rapid and uncontrolled gybe.’

The traveller on the Elan 333 is at the front of the cockpit, just aft of the companionway. During the gybe the mate, who had been sitting just behind the traveller, was caught in the slack mainsheet and thrown against the coach roof and fatally injured. He was evacuated by helicopter, but died the next day.

MAIB analysis

The MAIB advised the skipper of the need to ‘comprehensively assess the capabilities of each crew member to competently undertake specific tasks in the prevailing weather conditions, particularly when the skipper is absent from the deck.’

They also said that the skipper should ‘ensure that when transferring temporary charge of the deck and navigation that the passage plan is properly understood and adequate precautions are taken to supervise inexperienced crew and maintain overall control of the deck.’

Case study 4 – Platino

Based on Maritime New Zealand report Platino, a privately owned 66ft sloop built in 1997, had undergone a major refit in 2015. After three months of cruising in New Zealand, the two owners and three additional crew set off on a passage to Fiji, over 1,000 miles away. One of the owners, referred to as the skipper in the report, had 60-70,000 miles of experience and the other crew were all seasoned offshore sailors.

The passage started in light winds, but by day three they had 30-35 knots from the south with a confused sea. Fiji lies almost due north of Auckland, so they came onto a broad reach, set the preventer, reduced sail and the autohelm was performing well in the conditions. Suddenly, the boat crash-gybed with the boom following through, before crash gybing back again. The boat was out of control and preventer had failed.

The helm station was aft of the centre cockpit and the traveller lying between the two. No one was by the helm at the time of the incident, but it’s thought that one of the crew members was trying to reach it when the second gybe occurred. He seems to have been thrown to the side deck by the mainsheet and probably died instantly from his injuries.

Worsening situation

The traveller failed, leaving the boom completely unrestrained, with the mainsheet and traveller car still attached. The report stated: ‘The motion of the boom was now only restricted by the boom hitting the shrouds on either side of the mast.’ The rest of the crew were then called on deck.

‘Soon after arriving on deck,’ the report continues, ‘the first crewmember to arrive called out to the skipper to duck, which she did before glimpsing something going overboard on the port side. The skipper then saw the crewmember in the water some distance from the yacht with his arm raised as the yacht continued on out of control.’ Tragically, the crew member who was overboard was never recovered.

One of the owners made it to the helm station but struggled to gain control of the yacht. He just managed to hold the boat head to wind for long enough to furl most of the mainsail. The mainsheet and traveller car, which were still attached to the 678kg boom and mainsail, were described as ‘acting like a wrecking ball’, smashing the helm console which included the hydraulic furling controls before the mainsail could be completely stowed. The cockpit table and bimini were also ripped off, and wheel bent, which made it more difficult to regain control of the yacht.

The crew were unable to secure the boom and were convinced that its motion would bring down the rig, which it did several hours later. The three survivors were rescued the following afternoon, more
than 24 hours after the incident.

The yacht was later recovered and investigations revealed that the header tank for the hydraulic fluid on the rudder drive unit was almost empty, and a slow leak was the likely cause of the steerage problem which had initiated the gybes.

The investigations also discovered that the preventer had failed in two places: the line parted, and the deck fitting that it was attached to had sheared off. On the failure of the mainsheet traveller, the report concluded that the design and installation of the traveller system exceeded the recommended specifications, but that ‘it would be unreasonable to expect that the traveller arrangement would definitely hold when subjected to one or more completely uncontrolled gybes’.

Platino accident report

Whilst the loads on a 60-footer are exponentially larger than those on a 40-footer, the Platino report gives valuable insight into the technicalities of preventer design. It explains that the angle between the preventer and the boom is the key to reducing the load on the preventer.

Hypothetically, if you could rig a preventer at 90° to the boom, this would mean that the load on the preventer would be equal to that of the force acting on the boom (a 1:1 ratio).

However, it’s not possible to rig a preventer at this angle, and the best that could have been achieved on Platino was a 27° angle if the preventer had been rigged to the bow. This would increase the load on the preventer by a factor of 2.4. Platino’s preventer had not been rigged to the bow, but to a block on the toe rail just aft of the shrouds. The angle between the preventer and the boom was only 6° which increased the load on the preventer by a factor of 10.

A computer simulation found that static loads on the preventer, when rigged to the bow in 35 knots of wind, would have been 1,100kg. Rigged as it was, this was increased to 4,600kg. With an additional 10 knots of wind, so 45 knots, these loads would increase to 1,700kg and 7,000kg respectively. Whilst the figures derived from a computer simulation may not represent all the real-world factors such as shock-loading, and the downward angle from boom to deck, they do explain why it’s important to take your preventer line as far forward as possible.

Platino’s preventer consisted of two parts: a pennant attached to a strong point on the boom, and a long extending line. It was the extending line which parted. Whilst the pennant was specifically for use as a preventer, the extending line was an old line which had been re-purposed. Even new, it would have been considerably weaker than then pennant. The pennant and the extending line were connected using bowlines. This is identified as the likely point of failure – a bowline can reduce the strength of a line by up to 70%.

Platino’s preventer also failed on the deck fitting. The bolts holding the padeye for the block onto the toe rail sheared off. The report found that this padeye had not been intended to be part of the preventer system and was not strong enough for this purpose.

The report also included figures from Harken, showing that a block deflecting a line by 30º will experience 52% of the force on the line, while at 60º this is 100% (the same load) and at 180º this is 200%, or double the load. With Platino’s preventer rigged to the shrouds, this would increase the load on the deck fitting and block to nearly 9 tonnes.

Lessons learned from accidents at sea

These reports make detailed investigations into the causes of each accident and are well worth reading. Each incident is different, and there are a combination of factors including interactions between crew members, the weather, and unforeseen gear failure which contribute to each one. As well as the individual conclusions drawn in the reports there are some lessons we can draw from looking at the incidents as a whole.

1 Mainsheet hazard

It’s a misconception that the boom is the main hazard of downwind sailing. Whilst being struck by the boom during a crash gybe on a yacht would probably be fatal, on most modern cruisers it’s well above head height.

It is the metres of slack in the mainsheet which is more likely to injure people. This is not always appreciated by novice crew, who may position themselves near the traveller, not realising the potential for the mainsheet to swing through this area. Crew need to keep clear of the danger zone, and crew can assist each other by speaking out when someone is in an unsafe position. Identifying a safe line, such as forward of the primary winches, makes it easier for crew to follow.

2 Helm experience

In the first three incidents the helmsperson was inexperienced. Downwind sailing, especially with any kind of wave or swell conditions, is challenging and novice sailors cannot be left unattended.

Even an experienced helm may struggle on a new boat, or in new environments, such as making the transition to ocean sailing.

If in doubt, the sail plan and course can be adjusted to better match crew competence.

3 Cockpit layout

It’s noticeable that none of these incidents occurred on a yacht with a coachroof-mounted mainsheet. The location of the traveller in or aft of the cockpit considerably increases the risk of an injury
to crew in the event of a crash gybe. Many modern yachts used in charter fleets and sailing schools now have such centre mainsheets.

However, many performance cruisers, racing yachts and older boats often don’t, and extreme vigilance is required when sailing them. Sailors who have predominantly sailed yachts with centre-mainsheet yachts may not be so familiar with the risks of the traveller and mainsheet, and will need additional briefings.

4 Distraction

In the case of Liquid Vortex and CV21, there was activity going on outside the cockpit: attempting to unwrap the spinnaker in the case of Liquid Vortex, and the pre-reef briefing in the case of CV21.

Whilst helm distraction is not explicitly mentioned in either report, in my experience any other event occurring on deck can draw the helm’s attention away from the task in hand and needs to be recognised as a risk factor. Autopilots won’t get distracted, but they may also struggle in strong winds or large sea states.

5 Double gybe

In three of these incidents there was more than one gybe reported. In the immediate shock of a crash gybe the helm may not have regained control of the vessel, or they may instinctively return to the original course. Whatever the reason, the risk of a second crash gybe needs to be recognised by those on deck. If there’s a preventer on, and it holds, then quickly gybing back again is the best way to recover the situation.

During a crash gybe where the boom follows through it is much safer to stabilise the boat on the new gybe whilst checking for injuries and damage before attempting a controlled gybe back again.

6 Sail plan

Winds over Force 5 were present in all of the accidents. CV21 was making 11 knots SOG prior to the accident, so the apparent wind would have been much less than the true wind. Whilst this it isn’t mentioned in the reports, the difference between true and apparent wind can lull us into a false sense of security.

Reefing early and reducing the power of the mainsail reduces the loads on the preventer in the case of a crash gybe and gives it the best chance of working. Dropping the main entirely and running under headsail alone is an option which is often favoured by short-handed, novice or cruising crews.

7 Being over-powered

Being over-powered is also a risk factor for losing control of the boat. If the boat is continually broaching, a novice helm will often over-steer. As was the case in the incident aboard Buccaneer of Upnor, when a gust subsides and the vessel starts to respond to the rudder, the helm needs to straighten up quickly.

In gusty conditions an extra reef may slow the boat down in the lulls, but it should mean that things are more controlled in the gusts.

8 Early warning signs

Train your crew to recognise the early warning signs of a crash gybe: the helm feeling lighter; the vessel coming upright and perhaps heeling the wrong way; and the headsail collapsing. Let them know the safe way to turn when in doubt. Turning into the wind too much is noisy and annoying, but turning away from the wind too much is dangerous. Let them err on the side of caution and if they can’t safely sail the course you want, then change the helm, the sail plan, or the route.

9 Dropping the mainsail downwind

Whilst dropping the mainsail to eliminate the consequences of a crash gybe is a good idea, it’s difficult once a large following sea has developed, and these are the exact conditions under which you would want to drop it in. Rounding up enough to drop the mainsail could be dangerous in certain conditions. Coming up onto a beam reach with the headsail sheeted in hard might be enough to back-wind the mainsail and push it off the shrouds, but the sea state might not allow this.

Dropping the mainsail downwind is possible on smaller yachts, but you need to physically drag the luff down as the sail will press against the shrouds. On larger yachts it’s extremely difficult to do unless you have downhauls ready-rigged on the reefing points. So it might be that on longer offshore passages you’re committed to having the mainsail up.

Rules to remember

• Brief the crew on the hazard of the mainsheet and traveller
• Use experienced helms during any manoeuvre, including the briefing
• Identify and enforce ‘Danger Zone’
• Supervise novice helms
• Sail safer angles (such as 120° instead of 150° apparent) when other activities are taking place
• Reef early even though the apparent wind strength may be low
• Drop the mainsail and proceed under headsail alone
• Set a preventer with strong lines and well-thought-through layout

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