Boats vs. Waves: Riding the Crest, Surviving the Trough
Capt. Heather Francis explores the art of mastering nature’s fury at sea.
January 28, 2025
Waves are a disturbance that travel through water caused by wind blowing across the surface. The size of a wave is affected by many things including how strong the wind is, how long the wind has been blowing, the depth of the water, and the distance the wave can travel without obstruction. The ‘disturbance’, or wave, is energy, and when a wave comes in contact with a boat there is a transference of energy from the wave to the vessel.
Above: A stormy sea. Photo by Matt Hardy via Pexels.
The Art of Mastering Nature’s Fury
Waves become dangerous when they are big enough, that is they have enough energy, to overcome the vessels righting capabilities. When a wave is able to overcome a vessel is dependant on the displacement, length, beam, roll inertia, and centre of gravity of the vessel, not to mention the ability of the crew to control the vessel. All of these factors affect how the vessel reacts in a seaway and how much energy transference is required to push it past it’s righting capabilities.
Strategies for Sailing Through Heavy Weather
In years past it was common practice to set a drogue anchor or hove-to when caught out in heavy weather. When executed properly, these techniques slow a boat down and keep it at a favourable angle to the waves, which potentially avoids the chance to either be caught in a broach or to be pitch poled. Hoving-to and drogue anchors work well for a traditional, heavy, full keel cruising boats but not as successfully on today’s modern fin keel, racing designs and multihulls. These styles of boats have enough speed to ‘keep up’ with the sea state, allowing them to better manoeuvre through dangerous condition. However, speed accelerates rudder adjustments, making it easier to over steer and put the vessel in a compromising position, so the helmsman needs a little more skill to keep the vessel under control.
Understanding Wave Measurements, Terminology And Forecasts
Marine weather forecasts generally include information about wave height, direction, and frequency but it is important to be able to decipher what that information is telling us.
- Wave Height – Since waves are not uniform, statistical analysis is used to forecast ‘significant wave height.’ This is defined as the average of highest one third of waves measured, but the actual wave height a given time or place could be much higher. If the SWH is 10 foot, then 12.7 foot waves will be experienced, and 16.7 foot waves could appear. Wave height is measured between the peak and trough on each wave.
- Crest– The highest point of a wave, sometimes referred to as the peak of the wave.
- Trough- The lowest point, or dip between two waves.
- Wave Length – The distance between two sequential crests or two sequential troughs.
- Wave Period – The time, measured in seconds, it takes the wave to travel the wave length.
- Wave Frequency – The number of wave crests that pass a fixed location in a set amount of time.
Broach vs. Pitch Pole
The two most common problems that occur when navigating in large seas are an accidental broach and a vessel pitch poling. Both involve the boat straying far from it’s proper upright position, and usually result in severe damage to the vessel and crew. Let's take a deeper look at each one.
Broach – A broach is when a vessel is forced to turn violently towards windward, finding itself broadside to the wave and heeled over dramatically. It most often occurs while reaching or running before the wind, but can also happen while sailing to windward. A broach is usually a result of the vessel being overpowered or running at a bad angle to large waves.
A broach is dangerous because while heeled over less of the rudder is in the water, which means the helmsman has significantly less control to right the vessel while it lies broadside to the waves. If the boat is pinned down by the wind, or further rolled by a large wave, it can result in a knockdown, where the vessel is laid down 900, mast in the water. At this point a vessel may still be able to right itself, however, it is now much more venerable to either capsize or roll through completely. Either scenario is dangerous and damaging to the vessel and the crew.
Pitch poling – Pitch poling occurs when a vessel is running directly perpendicular to the waves. When the sea is steep enough the vessel can accelerate down the face of the wave and bury the bow in trough of the next wave, bringing the vessel to almost an immediate stand still. The sudden deceleration causes the stern to cartwheel up and over the bow. Depending on the sea state this end-over-end rotation can happen several times in a row, and often results in a dismasting, severe injury, and the vessel remaining inverted. The size of a wave required to pitch pole a vessel is significantly larger than a wave that involved in a broach.
How large is too large?
The general consensus is that a wave that is higher than your vessel is wide has the potential to cause a knockdown or roll a vessel that has been broached. And, a wave that is more than 30% higher than your vessel is long can cause the boat to pitch pole.
Using this rule of thumb, a typical cruising monohull that measures 40-foot long and 11-foot wide could be in trouble if broadside to waves 12-foot or greater, and waves 14-foot or great could cause it to pitch pole. This isn’t to say that either events are going to happen in heavy conditions. On the contrary, most vessels can navigate in a very large seaway without incident, as long as the crew prepares the vessel for the conditions, and understands how to correctly approach the sea state.
The most dangerous seas are those with large, breaking waves. Breaking waves occur when height of the wave can no longer be supported by the width of the wave at it’s base. When this occurs the classic ‘surfable’ looking waves appear, which tend to break over the vessel rather than allow the boat to ride up and over it. A cubic meter of sea water weights approximately 1 ton, which means the average wave can do a lot of damage.
7 Tips for Sailing in Heavy Conditions
Here are 7 more tips for sailing in heavy conditions:
- Reef sails when conditions deteriorate to avoid the vessel becoming overpowered.
- In gusty conditions have a crew member on the main sheet ready to “dump the main” and de-power the vessel.
- Auto-pilots can get overwhelmed in a large seaway, so try to hand steer. However, rotate the position of helmsman regularly to avoid fatigue.
- Keep large waves on the aft quarter rather directly abeam or behind the vessel.
- Stay on the “good tack” during heavy weather to keep the motion of the boat favourable, even if that means heading away from your destination until conditions improve.
- Check weather reports and avoid going out in bad weather whenever possible.
- Practice, practice, practice. Knowing how to implement the strategies that will enable your vessel and crew perform best in heavy weather is the best way to avoid catastrophe. Practice reefing, hoving-to, and maneuvering in a smaller seaway with lighter winds until everyone is familiar with the techniques.
Wrap Up
Sailing in heavy weather demands a deep understanding of wave dynamics, vessel capabilities, and crew preparedness. By mastering the principles outlined in this guide and practicing essential techniques, you can confidently navigate challenging conditions while keeping your vessel and crew safe. Remember, preparation and experience are the keys to transforming nature’s fury into a manageable adventure. So, whether you’re facing towering waves or planning for the unexpected, stay vigilant, stay informed, and most importantly, stay safe out on the water.
