What Is A Sailing Knockdown & Why Does It Happen?

One of the most troubling – and potentially dangerous – events that can happen to a sailor is to experience a knockdown.

So what is a knockdown? Why does it happen, and how much danger does it pose to the boat’s crew?

Here’s What a Knockdown is:

A knockdown happens when the sailboat is knocked over on its side to roughly 90 degrees. The mast will touch the water in a knockdown. In dinghies, the term is called flipping. Knockdowns are when waves overpower the boat. Often, a keelboat will begin to right itself almost immediately.

What Exactly is a Knockdown in Sailing?

The definition of knockdown can vary from one source to the next. Most authorities agree that it is a situation where a keelboat is knocked over to the point that its mast nearly parallels or even touches the water.

It is a form of capsizing. Capsizing can refer to a boat being knocked over 90 degrees or totally upside down. So a knockdown is essentially a less severe form of capsizing.

A knockdown has the potential to occur in bad weather, as either the wind strength or the waves will cause a boat to get knocked on its side.

A keelboat will usually start righting itself when a knockdown occurs due to the inherent righting momentum of the keel.

If the boat does not start righting itself, a knockdown can be dangerous, and the crew will have to aid the boat as it tries to recover.

In this case, the boat may continue to roll over, and the boat will lose all righting momentum from the keel. This can lead to the sailboat going turtle (completely upside down).

What Causes a Knockdown for a Sailboat?

There are two primary causes for a boat experiencing a knockdown, and sometimes they will act in concert.

The first is wind. A sailboat in a storm or hurricane can experience a larger gust or surge in wind strength. If the sails are not eased quickly, the force of the wind can cause the boat to have a knockdown.

The other cause is waves. A boat that takes a wave at the wrong angle can cause the boat to get rolled over on its side. This is usually a wave that hits straight across the beam.

This is why some boats when they are overwhelmed by the weather, will drop all their sails and throw out a sea anchor. The sea anchor keeps their bow pointed into the waves to cut through them rather than take them amidships.

These can act in concert, as well, and often do. Knockdowns often occur to sailboats under spinnaker, running before the wind.

The stern can be raised high by a particularly large wave, and if a gust accompanies it, the sailboat can get overpowered and be forced by the combination of wind and wave to head up and then get knocked over.

How Do you Avoid a Knockdown?

While many sailors find that taking a knockdown in certain situations is unavoidable, there are things you can do to minimize the risk of taking one.

The most obvious is to make sure you do get overpowered in a squall. Many sailors will tell you that it is already past time if you are thinking about reefing your sails (reducing the sail area).

So you will want to reef early, long before you find yourself overpowered.

Make sure you are not taking the waves on the boat’s beam. Sail into or away from the waves to minimize their influence on the boat’s heeling.

You will want to pay close attention to your helming, particularly downwind. When you ride over the crest of a wave, the rudder may clear the water partially or even entirely, leading to a loss of steerage and the boat turning sideways into the waves and making a knockdown much more likely.

You Might Deploy a Drogue:

A drogue is similar to a sea anchor but is deployed off the stern to keep the stern facing the wind and the waves.

This evolved from the old technique many mariners would employ during squalls or storms of dragging long lines behind their boats. If you have trouble keeping your stern into the waves and do not have a drogue, you can employ this technique.

Dragging 200 feet of line behind you can provide a little help in such conditions.

Finally, if you are overwhelmed by the storm and need to ride it out, drop all the sails and deploy your sea anchor. 

This is a small parachute-like object that is tied to the bow. It drags the bow around and keeps it pointed into the wind, making sure waves never strike amidships.

Sometimes a knockdown is inevitable, particularly on lengthy storm sailing and the threat of rogue waves, but doing what you can to minimize the chances and the impact is what every sailor needs to understand.

What Do you Recover from a Knockdown?

Even in higher winds, less severe knockdowns are generally easy to recover from.

Just make sure your sails are eased, and let the keel’s natural righting momentum do the work. Within moments your boat will be upright, and you will be on your way again.

If the knockdown was bad, you might have other problems.

If water got into the cabin, your bilge pump might not be enough to clear out the water. Excessive water down below can keep the boat from righting itself.

In this case, start bailing – vigorously. The longer the boat stays on its side, the more water will start pouring in, so you need to get it out fast. Handheld bilge pumps can be effective, but good old buckets can work fast, too.

Once the bulk for the water that flooded the boat has been removed, the boat should begin to right itself.

There is the possibility that your sails might be keeping the boat on its side. This is particularly the case if you were under spinnaker when you were knocked down. A spinnaker can fill with water and get wrapped around itself, acting as an anchor on your rigging.

So you may have to cut away some sails for your boat to recover from the knockdown. An expensive loss, but better than the alternative.

You might also have damage to your rigging. The worst-case here is if you are dismasted. This means the mast has been torn out of the deck or the hull.

In this case, the danger is still not over, as the shrouds will still be holding the mast to the boat and potentially keeping you from righting, or may even be dragging you into a turtle.

You may need to cut away the mast in this situation. Using bolt cutters on the shrouds may be the only efficient option.

Again, this is the worst case, but it might be necessary not to damage the boat further. Your survival is paramount if the situation has deteriorated to this point.

Final Thoughts:

In most conditions, knockdowns are not too difficult to recover from. But in certain conditions, like short-handed sailing in a gale offshore, a knockdown can be a life-threatening situation.

The best things a sailor can do is to minimize the risk of one happening and sail smart in conditions where one might occur.

Sources

How to Survive A Knockdown – Sailing Today