A change of direction by turning the bow of the boat through the wind. Bottom forward corner of a sail.
Line that attaches the tack of an asymmetric spinnaker to the bowsprit or spinnaker pole. The tack is adjustable to allow the set of the sail to be altered for different wind conditions and to make it easier to take down.
A system of blocks arranged so as to multiply the power being applied to a rope or line. For instance a four to one tackle will increase the force applied by four, at the expense of having to move four times as much rope.
Depth of water above chart datum.
Difference between low and high water.
Direction of the tide's flow.
A horizontal rod, bar or similar device attached to the top of the rudder and used to steer the boat.
The side of the boat the wind is blowing out from.
The side of the boat the wind is blowing onto.
Forces that twist, for example on the keel.
The stable, strong wind which blows both sides of the equator.
Lining up two fixed objects to keep you on course, for example, if the tide is pushing you sideways.
The flat bit across the back – or stern – of the boat.
A moving car, usually with ball bearings, that runs on specially made track to allow a sheet lead to be adjusted.
Keeping the boat level fore and aft.
Crew member with special responsibility for adjusting the sails to every nuance of wind speed or direction.
The direction and strength of the wind when the boat is dead in the water. When underway, instruments calculate the true wind by taking into account boat speed and relative wind.
An emergency sail for very severe wind conditions. Made from heavyweight synthetic sail cloth, usually set without a boom and often tied round the mast so it can be used if there has been a major failure of the mainsail or mast.