A wake is the track of disturbed water a boat leaves behind it as it moves: the smoothed, swirling path directly astern and the diverging V of waves spreading from the bow and the stern. A beginner sees the wake as proof the boat is moving and a way to judge whether the helm is steering a straight line. An experienced sailor reads far more in it. The angle of the wake to the centreline shows leeway; the size of the stern wave shows how hard the hull is working against its own wave-making resistance; a wake that bubbles and eddies behind the transom means the boat is trimmed too deep aft; and the wake of another vessel, its wash, is a hazard to be anticipated and a duty to be minimised when you are the one making it.
What makes a wake
A moving hull pushes water aside at the bow and lets it close in again at the stern. That displacement sets up two wave systems. The divergent waves fan out from the bow and stern at a fixed angle to the course, about 19.5 degrees either side in deep water for any hull at any speed, giving the familiar V. The transverse waves run across the track behind the boat, and their length is set by boat speed: the faster the hull moves, the longer the wave it makes. Between the bow and stern of a displacement yacht, the hull rides on its own wave system, and when boat speed rises to the point where the transverse wave is as long as the waterline, the boat is sitting in a trough between its own bow and stern waves and can go no faster without climbing the bow wave. That is hull speed, roughly 1.34 times the square root of the waterline length in feet, in knots. The wake grows dramatically as a displacement hull approaches it.
Reading your own wake
- Leeway: upwind, look astern at the line of smooth water the hull leaves. The angle between that line and the boat’s heading is leeway, typically three to six degrees on a cruising yacht and more when overpressed or pinching. A wake that trails off to windward of dead astern tells you the keel is losing its grip.
- Helm balance: a snaking wake means the helmsman is oversteering or the boat is unbalanced. A straight, quiet wake is the mark of a well-trimmed boat and a relaxed hand on the tiller.
- Trim: gurgling, eddying water behind the transom in light air means the stern is too deep. Move crew forward until the transom edge just clears the surface and the noise stops.
The sailmaker’s view
The wake is the honest witness to what the sails are doing. When we sail with an owner to check a new suit, one of the first things we watch is the wake. Excess heel shows as a fat leeward quarter wave and a wake trailing to windward; overtrimmed sails show as a turbulent rudder wake and a helmsman fighting the tiller. Flatten the main, ease the traveller, move the jib lead, and the wake narrows and quietens as the boat stands up and tracks straight. A sail that is well matched to the boat and well trimmed leaves a smaller wake for the same speed, because less of the driving force is being converted into heel and sideways slip.
Other vessels’ wakes and your own wash
The wake of a passing vessel is called its wash when it reaches you, and it is one of the most common causes of damage and injury in harbours and estuaries. A displacement motor yacht at nine knots throws a far bigger wash than the same boat at six or at twenty. Skippers are responsible for their wash, and many harbours enforce speed limits for that reason. When you meet a large wash under sail, turn to take it at an angle on the bow rather than beam-on, warn the crew, and secure anything below that will fly. Under power at slow speed, turning into the wash reduces rolling. Racing sailors also use wakes tactically: sitting in the disturbed water directly astern of a competitor is slow, and a boat crossing another’s wake will lose speed as it climbs the stern wave.
Frequently Asked Questions about Wake
Why does my wake get much bigger above six or seven knots?
Because the hull is approaching its hull speed and the transverse wave it makes is stretching to the length of the waterline. Beyond that point a displacement hull is trying to climb its own bow wave and the extra power goes into making waves.
Am I responsible for damage caused by my wake?
Yes. Skippers are expected to control their wash, and harbour byelaws and the general duty of good seamanship both apply. Slow down near moorings, small craft and river banks.
The wake is the one part of your sailing that the boat writes down for you. A straight, narrow, quiet wake tells you the sails are trimmed, the boat is balanced and the helm is steady; a wide, churning, wandering one tells you something needs attention. Look over the stern as often as you look up at the sails, and both your boat speed and your neighbours will thank you for it.