Lee Helm is a sailing boat’s tendency to turn away from the wind – to bear off to leeward – when the helm is released. It is the opposite of weather helm, and to hold a straight course the helmsman must keep the tiller pushed to leeward or the wheel turned toward the wind. The beginner should understand that lee helm is generally a fault: it feels lifeless, it costs speed, and it is unsafe because a boat with lee helm left to herself will bear away, gather speed and may jibe. The experienced sailor knows that lee helm is a symptom of the sail plan’s centre of effort being too far forward of the hull’s centre of lateral resistance, that it is common in light air on boats tuned for a breeze, and that it is one of the clearest signals a rig-tuner or sailmaker can be given.
The Physics: Centre of Effort and Centre of Lateral Resistance
Imagine all the sideways force from the sails acting at one point, the centre of effort (CE), and all the sideways resistance of the hull, keel and rudder acting at another, the centre of lateral resistance (CLR). If the CE is behind the CLR, the sails try to pivot the bow into the wind: weather helm. If the CE is ahead of the CLR, they pivot the bow away from the wind: lee helm. Designers place the CE a little ahead of the CLR on the drawing board – a “lead” of a few percent of waterline length – because heel moves the effective CE outboard and to leeward of the hull’s centreline, which adds a turning moment toward the wind. In light air there is little heel, so that correction disappears and a boat that carries a comfortable touch of weather helm at 15 knots may show lee helm at five.
What Causes Lee Helm
- Mast too far forward or raked forward: the entire sail plan, and so the CE, moves ahead. A mast stepped a few centimetres forward of its design position, or a forestay lengthened without adjusting the backstay, is a classic culprit.
- Too much headsail relative to mainsail: a big genoa with the main reefed or flogging puts the effort well forward. Motor-sailing on the jib alone always produces lee helm.
- Light air: no heel, no leeward shift of the CE, and the designed lead shows up as lee helm.
- Centreboard or daggerboard too far aft, or partly raised: on a dinghy, raising the board moves the CLR aft and can swing the balance from weather to lee helm.
Why It Matters
Speed first. A rudder held to leeward to counter lee helm is dragging without generating useful lift; a small amount of weather helm, by contrast, has the rudder angled a few degrees so that it adds lift to windward and helps the keel. Boats with lee helm point poorly and feel dead in the hand, because the helmsman gets no feedback from the wind. Safety second. A boat with weather helm rounds up and stops if the helmsman lets go or falls; a boat with lee helm bears away, accelerates and can gybe all standing, bringing the boom across the cockpit. Solo sailors and cruising couples especially want a boat that heads up when unattended. Autopilots and wind vanes also struggle on a boat with lee helm.
Curing Lee Helm
- Trim the main harder and bring the traveller up. Adding power aft moves the CE back. Check that the mainsail is not over-flattened by outhaul or backstay in light air.
- Rake the mast aft. Tighten the backstay adjuster or shorten the forestay a turn or two at a time and lengthen the backstay to match. This is the most powerful permanent fix and most one-design tuning guides give a target rake for exactly this reason.
- Balance the sail plan: reef or change down the headsail before reefing the main; on a fractional rig, do not sail on the genoa alone.
- Talk to your sailmaker: a mainsail that has gone flat and lost its leech return, or a genoa cut fuller than the main, shifts the balance forward. A recut or a new main with the draft where it belongs often removes lee helm that rig adjustments could not.
Frequently Asked Questions about Lee Helm
How do I tell whether I have lee helm or weather helm?
Sailing on the wind with a steady breeze, let go of the tiller or wheel for a moment. If the bow swings toward the wind you have weather helm; if it swings away, lee helm. Do it with sea room and a hand ready to catch the helm.
Is lee helm ever a good thing?
Very rarely. A neutral helm in drifting conditions is fine, and some racers tolerate a touch of lee helm in light air to free up the rudder, but any noticeable lee helm in a breeze is a fault to be tuned out.
Lee helm is the boat telling you that the sails are pulling ahead of where the hull resists. Move the effort aft with rake, trim and sail selection until the tiller carries a light, steady pull to windward, and the boat will be faster, safer and a great deal more pleasant to steer.