Weather helm is the tendency of sailing vessels to turn towards the source of wind, creating an unbalanced

helm Helm may refer to: Common meanings * a ship's steering mechanism; see tiller and ship's wheel * another term for helmsman * an archaic term for a helmet, used as armor Arts and entertainment * Matt Helm, a character created by Donald Hamilton * ...

that requires pulling the

tiller A tiller or till is a lever used to steer a vehicle. The mechanism is primarily used in watercraft, where it is attached to an outboard motor, rudder post or stock to provide leverage in the form of torque for the helmsman to turn the rudder. ...

to windward (i.e. 'to weather') in order to counteract the effect. Weather helm is the opposite of lee helm. It is generally less troublesome than lee helm.

Overview

Weather helm is the result of a leeward and aft shift of a vessel's vector center of effort (the direction to which the force generated by the sails is pushing). This shift is caused by excess pressure on the

mainsail A mainsail is a sail rigged on the main mast of a sailing vessel. * On a square rigged vessel, it is the lowest and largest sail on the main mast. * On a fore-and-aft rigged vessel, it is the sail rigged aft of the main mast. The sail's foot ...

, which overpowers the windward lateral resistance generated by the

jib A jib is a triangular sail that sets ahead of the foremast of a sailing vessel. Its tack is fixed to the bowsprit, to the bows, or to the deck between the bowsprit and the foremost mast. Jibs and spinnakers are the two main types of headsail ...

(or other head sail) and keel or centerboard. This results in an imbalance of force at the stern from windward, and the craft pivots about the center of drag (often near the center of the keel or centerboard), causing the bow to drive windward. Weather helm does not only result from an overpowered main; when a vessel is heeling to leeward, the aft component of keel drag is moved to windward. This creates a force (a turning moment) that pushes the bow to weather. As both an overpowered main and heavy heel occur in the same circumstances, it is sometimes difficult to determine the source of weather helm. While weather helm occurs on any size of vessel, the physical movement of the craft is often more severe for vessels without a keel. This is a result of the smaller blade being very quickly overpowered by the relatively larger mainsail. In keelboats, despite the fact that weather helm is not as readily felt, it can be just as detrimental, as the lateral drag against the blade still exists, along with the need to pull the rudder to an undesirable position (see Mitigation). A slight amount of weather helm is thought by some sailors to be a desirable situation, both from the standpoint of the "feel" of the helm, and the tendency of the boat to head slightly to windward in stronger gusts, to some extent self-feathering the sails. Other sailors disagree and prefer a neutral helm. Weather helm also provides a form of

dead man's switch A dead man's switch (see alternative names) is a switch that is designed to be activated or deactivated if the human operator becomes incapacitated, such as through death, loss of consciousness, or being bodily removed from control. Originally a ...

—the boat stops safely in irons if the helm is released for a length of time.

Mitigation

Any action that reduces the angle of heel of a boat that is reaching or beating to windward will help reduce weather helm. Racing sailors use their body weight to bring the boat to a more upright position. Reducing or

reefing Reefing reduces the area of a sail, usually by folding or rolling one edge of the canvas in on itself and attaching the unused portion to a spar or a stay, as the primary measure to preserve a sailing vessel's stability in strong winds. Restoring ...

the total sail area will have the same effect and, counter-intuitively, many boats will sail faster with less sail in a stiff breeze once heel and weather helm have been reduced, due to the reduction in underwater drag (see

Over-canvassed sailing A sailing boat that is carrying too much sail for the current wind conditions is said to be over-canvassed. An over-canvassed boat, whether a dinghy, a yacht or a sailing ship, is difficult to steer and control and tends to heel or roll too much. ...

). Easing the sheets on aft-most sails, such as the mainsail in a

sloop A sloop is a sailboat with a single mast typically having only one headsail in front of the mast and one mainsail aft of (behind) the mast. Such an arrangement is called a fore-and-aft rig, and can be rigged as a Bermuda rig with triangular sa ...

or cutter can have an immediate effect, especially to help with maneuvering. Moving or increasing sail area forward can also help, for example by raising the

(and maybe lowering the

staysail A staysail ("stays'l") is a fore-and-aft rigged sail whose Sail components#Edges, luff can be affixed to a stays (nautical), stay running forward (and most often but not always downwards) from a mast (sailing), mast to the deck (ship), deck, the b ...

) on a cutter. Sailing off the wind, weather helm may be caused by the imbalance due to fore-and-aft sails all being sheeted out on the same (leeward) side of the boat. Raising a

spinnaker A spinnaker is a sail designed specifically for sailing off the wind on courses between a reach (wind at 90° to the course) to downwind (course in the same direction as the wind). Spinnakers are constructed of lightweight fabric, usually n ...

or poling out a headsail to windward with a

whisker pole A spinnaker pole is a spar used in sailboats (both dinghys and yachts) to help support and control a variety of headsails, particularly the spinnaker. However, it is also used with other sails, such as genoas and jibs, when sailing downwind wit ...

can help. Yachts making ocean

trade wind The trade winds or easterlies are the permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisph ...

crossings have rigged 'twins' - double headsails poled out to opposite sides from the same forestay for extended downwind passages without a mainsail.

Square rig Square rig is a generic type of sail and rigging arrangement in which the primary driving sails are carried on horizontal spars which are perpendicular, or square, to the keel of the vessel and to the masts. These spars are called ''yards'' and ...

ged sails also provide relatively symmetric drive off the wind. As weather helm requires pulling the rudder through the water at an angle to the intended course, it produces drag and impedes the boat's progress through the water. In the book "Sailing Illustrated", Patrick M. Royce defines weather helm as simply a "heeling sailboat wanting to come head to wind." The principle is the same whether the vessel is steered by tiller or wheel; turning the wheel leeward gives the same rudder effect as pulling a tiller windward.

Discussion

The fundamental cause of "helm", be it weather or lee, is the differential between the center of effort of the

sail plan A sail plan is a description of the specific ways that a sailing craft is rigged. Also, the term "sail plan" is a graphic depiction of the arrangement of the sails for a given sailing craft.> In the English language, ships were usually describe ...

to the center of lateral resistance of the hull. If the center of pressure is astern of the center of lateral resistance, a weather helm, the tendency of the vessel to want to turn into the wind, or to weather-vane, will result. If the situation is reversed, with the center of pressure forward of the center of resistance of the hull, a "lee" helm will result, which is generally considered undesirable, if not dangerous. Too much of either helm is not good, since it forces the helmsman to hold the rudder deflected to counter it, thus inducing extra drag beyond what a vessel with neutral or minimal helm would experience. See ''Sailing Theory and Practice'' by C.A. Marchaj for a mathematical analysis of the dynamics of weather helm.

References

{{DEFAULTSORT:Weather Helm Sailing manoeuvres