Saturday, April 19, 2008

Sail Trim and Shape

Hoisting the sails: Before leaving the dock, you should determine the amount of sail needed. If high winds are expected, it is best to reef or decrease sail area at the dock than forced to reef while underway. The mainsail usually has between one and three reefing points that allow its size to be decreased. The jib might have roller furling (a foresail that can be rolled around the headstay) which can be used to reduce its size. If not, the size of the jib hoisted will have to be determined before setting sail.

Mainsail: If you leave the dock under power, secure the halyard to the head of the mainsail and remove the mainsail's cover. This allows rapid hoisting of the sail, if the motor dies. Make sure the boom vang and sheets are loose to allow the boom to elevate to the proper height. If hoisting a full sail, make sure the Cunningham and reefing lines are also loose. You should also adjust the outhaul before hoisting the mainsail. Once the mainsail is hoisted, loosen the boom toping lift so the mainsail can assume the proper shape and swing freely from side to side. Do not turn off your motor until after the sails are hoisted.

Jib: There many sailboats, and most charter boats, now use a roller furling system for the jib. The roller furling line is uncleated and pulling the jib's sheets the jib is unfurled. Tension should be kept on the roller furling line to keep the line from tangling as it is rolled on the drum. If the jib has to be hoisted, it is usually attached to the forestay using "hanks". The size of the jib is based upon wind conditions.

Control of the sails: The two most commonly used lines by the sailor to control the sails are the halyards and sheets. The halyard is mainly used to hoist the sails and the sheets used to control sail position in relation to the wind. Both of theses lines will also change the sail's shape. Other lines are present to adjust the sail's shape as the sail is eased out or trimmed toward midline. The angle of the sailboat in relationship to the wind is called the point-of-sail. When turning a sailboat, the boat is taken from one point-of-sail to another by adjusting the rudder and sail trim. The closer you sail to the wind, the closer the sails are pulled or trimmed to the midline of the boat. As you sail away from the wind, the sails should be let out.
Winches are used to help trim the sail and adjust lines under the force of the wind. Many winches have a self-feeding cleat on the top, which allows you to pull a line in under force without slippage. Be careful using a winch to pull in a line which should be pulled in by hand, the jib's roller furling line. If these lines are not pulled in easily, it usually means that they are caught.

Taking down the sails: Before you take down the sails the motor should be turned on. The halyard should not be removed and the sail cover should not be placed on the mainsail until the boat is at dock. If the motor fails, the sails can be quickly hoisted. There are two basic methods of taking down the mainsail, heading into the wind and heaving-to.

First method, the boat is first placed in a deep broad reach sailing almost directly away from the wind so the mainsail is shielding the jib's front sail's wind. This decreases the wind pressure on the jib and allows for easier furling. The jib is rolled in, keeping some tension on the sheets to tighten the roll and to keep the sail from flogging (strong whipping of the sail caused by the wind). Under power, the boat is then headed into the wind and the mainsail is lowered and flaked over the boom.

Second method, the boat is heaved-to and the mainsail is let out until it is luffing. In this method, the mainsail is lowered first over the boom. Since the boom is out over the water, the mainsail is taken straight down and may be flaked after the boat reaches the dock or once the mast is secured back to midline. The jib is then furled. When heading into the wind, the wind may forcefully pull the jib out. In a strong wind, the boat is placed into a deep broad reach. The sheets are loosened and the jib furled.

In heaving-to, the forward motion of the boat is slowed, the bow of the boat is turned through the wind but the jib is not released on the windward side the jib is backed. The mainsail is then eased out and the boat is now turned into the wind. Two opposing forces now exist. The jib pushes the boat away from the wind but the rudder pushes the boat into the wind. The boat comes to a near standstill, drifting slowly to leeward.