Should we break the Taboo?
With the confusion of genres caused by the super-powerful ocean racing multihulls, the conservatism of monohull sailors and the high commercial stakes, the risk of capsizing is still a taboo subject for many people in the world of two or three-hull sailing boats. However, rather than just focusing on hearsay, Multihulls World suggests a rational approach to the subject in order to get a better understanding of the situation.
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Publié le
25/05/2023
Par
François Trégouët
Numéro :
190
Parution :
Jul.
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Aug.
2023
Misunderstanding and confusion have allowed such prejudices to persist. Regattas and offshore racing have largely contributed to this (bad) reputation. But you really can’t compare those racing machines with our cruising multihulls. Even among extreme vessels there are differences. An Ultim trimaran takes off in around 16 knots of wind. An Ocean Fifty sails on one float from 13-14 knots of wind, while an Orma 60-footer makes do with 11.5 knots. Even more extreme, the BMW Oracle trimaran in the America’s Cup rises up from 7 knots: a real lake boat! Moreover, on board a Decision 35, if the wind rises to 20 knots on Lake Geneva, the boat becomes unmanageable. Out on the open sea, alone, the risk is tenfold because the reaction time is longer, whereas anticipation is more necessary than ever. But let’s concentrate on our cruising multihulls. Even if it is statistically insignificant - in recent times there have only been 1 to 5 capsizings of multihulls over 30 feet per year out of 15,000 cruising multihulls that are currently sailing (we are not talking about shipwrecks or total losses caused by hurricanes like Irma). That means the risk is 0.017% per year. Over the lifetime of a boat – say 40 years - this amounts to 0.67%. Compare this with the risk of a car accident - 1 every 70,000 km in France, according to the Road Safety Department, or 1 every 7 years (the average mileage of a car being 10,000 km/year globally). So, a 0.017% risk of capsizing for a multihull every year, against 14% of having an accident on the road for a car, certainly raises a few questions don’t you think?
However, even if it is insignificant, the risk of capsizing on a large production catamaran or trimaran does exist. The proof? It is regulated by the standard that all manufacturers must respect. Thus, at the helm stations of all good modern multihulls, three small yellow triangular pictograms prevent any temptation to turn a blind eye. The first one, an exclamation mark, draws our attention to a crucial point. The second, representing an overturned boat, leaves no doubt about the subject. As for the third - an open book - it instructs us to refer to the owner’s manual, and in particular to its recommendations for reducing sail, which, if respected, will protect against any risk of capsizing or dismasting. Only a few multihulls (the largest and heaviest) are subject to a sail reduction warning.
“A ship is a highly unpredictable entity”
Renaud Bañuls, naval architect
Whatever the type of boat, the risk of capsizing increases with the wind, the sea state, the speed of the boat and, most importantly, the fatigue of the crew. Even if sailing a multihull is much less tiring than aboard a monohull, the time spent sailing in difficult conditions, the repetition of maneuvers and of course the constraints of night watches can all impair our judgment, lower our level of attention and increase reaction times. In the end, these elements can become a significant risk factor. A boat capsizes when the rotational forces exceed stability. Capsizing can occur in three ways: longitudinally (pitch-poling), diagonally (in this axis, there is less mast rigidity and less buoyancy) and finally laterally. The latter is perhaps, wrongly, the one that’s most present in the imagination of the yachtsman, by association with beach cats or racing multihulls.
“Going at 20 knots is uncomfortable. The goal is to sail at 12 knots all the time, easily, without risk and without effort”
Christophe Barreau, naval architect
The co-factor of the risk of overturning is the height of the center of gravity. The lower the center of gravity, the lower the risk of capsizing. The three major risk factors are the following: a narrow boat, light weight, and a high center of gravity. This is typical of a sports catamaran, which easily climbs on «one leg». For a Hobie 16 for example, the risk of capsizing is taken for granted. In the owner’s manual of one of them, we can read the following: “Although a catamaran is a particularly stable platform, a capsize can happen, even to the best of us”. But just as Aristotle said there were three kinds of men, there are also three kinds of multihulls for the sailor: those for quiet cruising (the most numerous), those for fast cruising with a more favorable length/displacement ratio, and finally competition multihulls that can have the impudence to expose their underside to the wind. The risk of overturning is close to zero for the first two categories, but for different reasons. For the more sedate vessels, especially the larger ones, their ratios including weight, length, beam, volume of the floats or sail area make them practically uncapsizable. They can even be declared as such by the regulations, which explains the absence of escape hatches on some boats.
The increase in recent years of the volume of the floats in general and of the bows in particular, which obviously benefits the accommodation, is also a positive safety factor. Forward cockpits may also have been perceived as an aggravating risk factor, but in reality, the volumes involved are small. Moreover, architects do not hesitate to double the requirements of the standard in terms of onboard water evacuation. Let’s now turn to the high-performance cruising multihulls. With their center of gravity and sails lowered and moved aft, their bows with studied volumes and above all lightened, their minimal windage, their sometimes-retractable daggerboards (see elsewhere) and finally their high average speeds allowing in most cases to choose the weather, these units are also on the safe side of statistics - except in extreme use or conditions.
As for racing multihulls, they are best handled by experts and seasoned crews, as any moment of inattentiveness or any technical problem can turn into a fatal capsize. Capsizing just because of the wind is therefore impossible with a cruising multihull aimed at the general public. This is less true in particularly rough seas, where a breaking wave hitting the side of the float can cause a capsize, with the fixed leeward skeg tripping the boat up. In these extreme conditions (see our chart showing risk areas), multihulls equipped with daggerboards can raise them and thus slide sideways, which reduces the risk of overturning.
“The bigger and heavier the boat, the less likely it is to capsize”
Hervé Piveteau, Excess Catamarans product manager
But what if respecting these recommendations would cause the log to lose a few tenths of a knot? This is actually not necessarily the case, as a bit of practice will show that reducing the sail area allows the leeward hull to be less loaded, favoring performance. But isn’t this a paltry price to pay to be in total safety? Of course, this goes against the dream of a giant Hobie Cat balanced on one float... but isn’t that idea of a multihull a heresy for pure cruisers?
“The risk of capsizing is intrinsically addressed by the official standard”
Damien Cailliau, CEO of Marsaudon Composites
Shipyards and riggers are going even further in risk management: the standing rigging can be calculated not to resist the maximum moment of resistance of the boat, making the mast a sacrificial element - dismasting is rightly considered a lesser evil compared to the risk of capsizing. But the overall dimensioning is a difficult exercise as it needs to be weak enough to break before capsizing when the boat is light, and strong enough not to break at the slightest strong wind when the boat is loaded, and the displacement has increased to 140%. But as good as these systems are, they should never be taken as an absolute guarantee. They are simply the last chance to make up for a situation that is out of control and that, without them, would inevitably lead to an emergency. The more integrated they are, the more intelligent they are, and one could be tempted to say that the human factor will have less influence, and therefore these systems will be more relevant. The human being is made in such a way that, for the sake of performance, out of ignorance or carelessness due to fatigue, it can bypass a safety device, close a clutch or take too many turns on a winch during an emergency maneuver. New tools are appearing, and these should help to move in the right direction, such as tension sensors in the rigging which allow an alarm to be sounded well before the maximum RM (righting moment), i.e., before the float starts to lift on a catamaran.
Madintec, from La Rochelle, have been involved in ocean racing for the past ten years. Their ambition is to offer sailors a central calculation and piloting solution that is not very far from what they can offer to racing skipper François Gabart, for example. These pilots, which have been made smarter by the use of control units, integrate all the data from an inertial unit. They know the physical design of the multihull and take into account its acceleration in all possible dimensions. The objective is to avoid the untimely triggering of automatic release systems, whereas fine-tuned piloting obtained through high-frequency calculations can make the situation totally manageable. A human can steer to around five degrees, especially downwind in heavy seas, while a good autopilot can steer to within one degree. These high-performance pilots do not deviate from their route by more than a tenth of a degree, with a reaction time of well under a second. Even better, the same system has the ability to release the mainsail or the genoa, or even both, simultaneously if the situation requires it.
10 tips to stay safe
2. Reduce sail before it is necessary
3. Whenever possible, the weather dictates the schedule
4. Remain vigilant in all circumstances
5. Do not overload the multihull
6. Limit the weight aloft and at the bow
7. Respect the watertightness of the bulkheads
8. Do not make any structural or rigging modifications without the agreement of the architect or the shipyard
9. Sail according to your abilities and respect the program for which the multihull was designed
10. Get trained and informed... by reading Multihulls World for example!
The pictograms visible at the helm station leave no doubt as to the commitment of the manufacturers and certification bodies.
Only the largest and heaviest multihulls are exempt from taking into account the risk of capsizing.
This hart highlights the relationship between high latitudes and the risk of very strong winds and seas (in red), which are factors that can lead to capsizing. The intermediate latitudes are a little more favorable. Then, between 45° N and 30° S, there is a vast zone that is statistically calmer - except for hurricanes, of course.
Les préconisations de réduction de voilure du Leopard 50 sont visibles à côté du tableau électrique.
If you don’t have a fully automated system, good old reefing remains the most efficient safety system...
The brand new Fustec load release system is featured in our Shopping pages in this issue.
The wind is not necessarily the only thing responsible for a capsize; it can be due to the sea state and particularly the waves...
