Lee helm, sometimes referred to as weather helm, is a condition that occurs when a sailboat wants to turn up into the wind. There are several potential causes of lee helm which boaters should be aware of.
Boat Design
The design and shape of the hull can contribute to lee helm. Here are some hull characteristics that may cause a boat to develop lee helm:
- A wide, flat stern – This provides less lateral resistance in the stern and makes the bow want to come up into the wind.
- Insufficient keel depth – A shallow keel provides less resistance to leeway and allows the bow to blow off.
- A skeg-hung rudder – This puts the pivot point forward, making the rudder act like a weather vane.
- A long keel with a short forefoot – The long keel provides lateral resistance while the short forefoot reduces directional stability.
Boats with these design elements tend to develop lee helm more easily, especially when sailing upwind. Modifications like deepening the keel, adding a skeg, or lengthening the forefoot can help improve directional stability.
Sail Trim
Improper sail trim is one of the most common causes of lee helm. Here are some tips on sail trim to reduce lee helm:
- Ease the mainsheet – Let the boom out to spill wind from the mainsail. This depowers the mainsail and reduces heel.
- Depower the jib – Flap the jib luff or use the jib sheet to depower. Reduce heel from the jib.
- Move crew weight aft – Shift crew back to induce a bit of weather helm.
- Reef the mainsail – Reduce sail area to depower and improve balance.
Proper sail trim is essential to maintaining balance. The goal is to reduce heeling forces that cause lee helm. Start by easing sheets, then try other adjustments to find the best sail trim for the conditions.
Rudder Alignment
A rudder that is not properly aligned can also cause lee helm. Here are some indicators of a rudder alignment issue:
- Boat pulls to one side under sail
- Helmsman must hold significant weather helm
- Boat is difficult to steer on runs and broad reaches
To check rudder alignment:
- Head up into the wind under power.
- Let go of the helm and see which way the boat wants to turn.
- Adjust the rudder angle to reduce turning tendency.
A small amount of toe-in (1-2 degrees) can help with tracking on modern fin-keel boats. But too much will cause lee helm. Rudder alignment should be checked annually and after a grounding.
Keel Damage
Damage to the keel can also allow a boat to develop lee helm. Signs of a damaged keel include:
- Increased rate of leeway when sailing upwind
- Tendency for the boat to “trip over its keel” and round up
- Difficulty tacking or staying on line upwind
Keel damage often occurs from running aground. The keel may be bent, the tip damaged, or the keel-to-hull joint compromised. Any impact serious enough to damage the hull-to-keel joint requires urgent inspection. Even minor damage can degrade sailing performance.
Mast Issues
Problems with the mast can also potentially contribute to lee helm:
- Rake: Too little rake angles the mast forward, moving the center of effort forward and inducing lee helm.
- Rig tension: Loose rig tension allows the mast to bend and develops lee helm. Tight rigs perform better upwind.
- Mast step: A worn or shifting mast step moves the mast base aft, increasing lee helm.
Mast problems are most common on older boats. Checking and correcting rake, rig tension, and the mast step can help improve upwind performance.
Heavy Conditions
Finally, heavy air and wave conditions can cause even a well-tuned boat to develop lee helm. As boats heel over and are pushed by waves, the underwater profile changes and lee helm tends to increase. In very heavy air:
- Reef early and frequently to depower
- Shift crew weight as far aft as practical
- Ease mainsheet and traveler to de-power and open leech
- Consider a storm jib to balance helm
Some lee helm is unavoidable in heavy air. The goal is to reduce heel and weather helm to maintain control.
Conclusion
Lee helm has many potential causes. Careful boat inspection, sail trim, and tuning can help identify and address underlying issues. While some lee helm may be unavoidable in very heavy conditions, a well-tuned boat should sail upright and resist lee helm in most conditions.
Being aware of the causes of lee helm allows skippers to make adjustments and keep their boat sailing optimally across the wind range.