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Why Do Catamarans Capsize? (The 2 Main Reasons)

Don’t let the appearance of a catamaran sitting in the water fool you. It’s one of the safest vessels you can travel in, whether on a waterway or the open ocean. Talk about stability, comfort, and spaciousness. A cat has it all.

Now, that doesn’t mean there haven’t been mishaps when it comes to catamarans. Cat incidents are very few and far between. However, why do catamarans capsize? To avoid capsizing, it is important to keep the boat from getting caught in rotating forces. 

When a cat capsizes, it might do so in one of two ways. One is when the catamaran’s side gets struck by a breaking wave having similar height and length, forcing it to roll over. Pitch-poling occurs when the boat’s bow lowers into a wave right after riding a previous wave.

catamaran size

1. Pitch-poling

Pitch-polling head-over-heels forward (i.e. “burying” the bow and “tripping” over it) is by far the most common method for catamarans to capsize. Slender hulls are common on racing catamarans because they reduce wetted surface area, which ultimately decreases drag and boosts speed. 

Their rigs are big and extremely efficient, and they frequently use daggerboards and square topsails hard wing sails on AC72s) as well as rotating rigs and sails with spinnakers or screechers. 

When the boat’s rig, which is both powerful and efficient, is coupled with the hulls’ low water resistance, it may reach high speeds and generate its own “apparent wind.” Once a boat can keep up with a seemingly infinite amount of perceived wind, things go awry for many sailors.

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How is the Catamaran tripped by its hulls?

catamaran

In this case, the boat can be “tripped” by raising the rig’s speed past the speed limit of the hull, which will then continue to sail over the top as well as push the boat into the water. This happens most commonly when a boat’s leeward hull is dipped.

Catamaran racers must either depower or rig the boat to avoid this point or sail deeper to little apparent wind. However, this is pushed to its utmost bound when racing. Depowering the catamaran or rig is the crew’s responsibility.

Catamaran pitch-polling Example

After taking off the foils, the AC72 pitch-polled at a boat speed of more than 30 knots in 25 knots of wind during a race. Following that, the AC72 began tearing into everything in its path. 

The highest point of risk for racing cats is the “bear-away” (moving away from working into wind, to a reach) due to huge apparent wind generated by the rig, which creates a significant acceleration of the hulls. Oracle’s crew failed miserably, as evidenced by the fact that they went over.

Why Do Cruising Cats Not Capsize?

The fact that production cruising catamarans rarely capsize is due to their thoughtful design, which combines big living spaces with level sailing for a safe and enjoyable experience. Pitch-poling is unlikely to occur due to its inability to generate enough apparent wind. 

All of this is true even if the boats have been specifically designed for speed unless they have extremely thin hulls, rotating rigs, or sails with high aspect ratios.

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A production cat’s bows can be buried in the sand if it comes down a large wave at a high speed (more than 20 knots) with too much sail. Although cruising cats are designed with considerable spare buoyancy inside the bows to counteract this issue.

High freeboards, fat bows plus flared hulls all achieve the same outcome, but with different levels of windage and general performance, in cats of diverse shapes and sizes. There is just too much buoyancy for the bows to nose dive, so the goal is to keep them above the water.

How Does Reefing Help Prevent Pitch-rolling?

Reefing also reduces the likelihood of a cat capsizing by limiting the rig’s ability to generate too much force in heavy following seas. 

Single-line reefing systems are common on production cats, making them simple to operate from the cockpit. These conditions are ideal for using drogues, which can reduce the boat’s speed to less than 15 knots.

2. Wind Break (Heeling)

Another less common situation is the boat flipping over on its side because of too much wind (or sail space) and high waves from the side. Sailing towards or away from waves, instead of squarely on their side, can decrease risk by reefing the sails but also reducing sail area. A shattered wave

When it comes to healing, the apparent wind direction and the amount of sheeting in the sails are two of the most important factors. This means that if the sails are sheeted in tightly, a cat (and every other sailboat) will have a stronger rotating force. 

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Sails and Masts’ Role in Heeling

Sails and masts are directly affected by these forces since the wind is “caught” in them, and they are directly affected by these forces as well as those of the hull. 

Instead, if the sails were made more “sloppy,” less wind would be “captured,” allowing more wind to move through the sails and reducing the heel.

Forces are especially important in wind angles in which they are in direct opposition to an object’s beam. Aerodynamic efficiency decreases away from the beam, which is mostly to blame for this.

The Two Types of Waves

There are two types of large waves: breaking waves and non-breaking waves. The latter is a type of breaking wave, which occurs when the amplitude of a wave reaches a point where it begins to break apart.

Non-breaking waves, sometimes known as rolly waves, fall under this group. These are kinder, and they don’t have the power to shape-shift in an uncontrolled or aggressive way.

When it comes to non-breaking waves, a cat will usually follow the motions and waveform as it rises and falls uniformly, and this action shows no signs of being harmful, according to the findings of the study.

Which Cats Are Affected Most by Breaking Waves? 

Monohulls are prone to pendulum-like behavior since they rock from side to side.

Breaking waves, on the other hand, can be a danger, especially if you’re in a smaller catamaran. The results of the test demonstrated that to avoid capsizing, there must be an adequate beam-to-wave ratio.

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It is typical for the length of the catamaran to be at least twice as wide as the beam. It appears that breaking waves, in conjunction with wind forces, play a substantial role in determining the likelihood of capsizing.

In some cases, waves that break at a height equal to or less than the beam of a catamaran might produce a capsize. Vulnerability is greater on smaller or narrower boats.

What Makes Breaking Waves Dangerous?

Breaking Waves

The incline of the wave contributes significantly to the risk posed by breaking waves, which can easily push a boat beyond its normal range of stability. There is a difference between a non-breaking wave that’s 30ft and a 15ft breaking wave when it comes to the English countryside and the French ski resorts.

Moving past the tipping point of a boat requires a smaller amount of effort as the boat approaches it. So the combination of circumstances is critical; strong breaking waves, high apparent wind forward of the beam, and even a slight inaccuracy from the cockpit, and danger is just around the corner.

Keel Effects (centerboards and daggerboards)

Having the capacity to slide sideways when hit by a breaking wave is one element that decreases rotational forces when the catamaran is slammed from the side.

In most cases, this is undesirable because it restricts the cat’s windward mobility; however, small keels, daggers, or centerboards can alleviate this problem.

In the event of a heavy breaking wave, keels pose a safety risk because the crew is unable to remove them from the hull to lessen drag. According to research, this will make it more difficult to slide sideways and raise the chance of capsizing.

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Can Cats Handle Rough Weather?

how well does a catamaran handle a storm

Catamarans are a great option for long-distance travel because they are both comfortable and spacious. The question is whether or not catamarans can handle rough seas.

Catamarans are indeed capable of handling rough seas. This is because sailors have the choice of steering from the inside in poor weather. Furthermore, even in less-than-ideal sea conditions, the catamaran’s bridge clearance, bridge, and size make it a joy to drive.

Having a huge dinghy with a powerful motor is always a smart idea on rough seas because of the catamaran’s wide hull. There are several other things to keep in mind when operating a catamaran on strong seas.