Mainsheet, Traveller, and Traveller Car

Mainsheet, Traveller, and Traveller Car

The mainsail needs to be controlled from the mast and the boom. Here are the basic controls used most often by the sailing crew.

Mainsheet

You need a way to control the sailboat boom. The mainsheet consists of blocks--or pulleys--that attach to the end or middle of the boom and deck. You ease (let out) the mainsheet to allow the boom to swing away from the boat. You trim or sheet (pull in) the boom with the mainsheet to bring the boom closer to the boat.

Traveller

A flat, thin bar, installed athwartships (side to side), upon which the traveller car slides. The traveller helps to adjust the position of the boom.

Traveller Car

The bottom block on most mainsheets attaches to a device called a mainsheet car. The mainsheet car slides along the traveler to allow more control on the mainsail.

Genoa Sheet, Lead Block, and Sheet Winch

The headsail - which may be a jib or Genoa - needs line and winches to keep control and make adjustments to shape the headsail for maximum performance.

Genoa Sheet

Each headsail has two control lines called sheets that attach to the clew of the sail.

Lead Block

After you attach the headsail sheet, lead each sheet along the side of the boat. Thread it through the lead block. This block sits atop a Genoa track, and directs (leads) the line back to the cockpit sheet winch.

Sheet Winch

Each sheet leads from the sheet block back to a sheet winch on each side of the boat. Because the loads on a jib or Genoa filled with wind are so high, you need the power of a winch to provide many times more mechanical advantage to pull in (grind) on each Genoa sheet. Make sure that you take three or more clockwise wraps on the winch before you start to grind the winch.

Other Control Devices

Some controls are common to both sails, such as halyards, halyard winches, and winch handles.

Halyards

You hoist each sail with the halyard. The end of each halyard has a shackle that attaches to the head of the sail. Haul (raise) each sail all the way to the top of the mast before you tie it off (cleat it).

Halyard Winch

Similar to the sheet winch, each sail halyard has its own winch so that you can place enough tension along the luff to shape the sail. Make sure that you take three or more clockwise wraps on the winch before you start to grind the winch.

Winch Handle

Each winch handle has a ratchet shaped end that fits into the center of the winch drum. The handle should be long enough to enable you to grind on the winch without excessive effort. Stow the winch handle in a winch handle pocket, or keep it in the cockpit to prevent loss.

Boom Vang

When the end of the boom goes out past the side of the boat, the mainsheet will not have enough "umph" to pull down on the leech of the mainsail. That's where the boom vang takes over. It's a simple block and tackle--much like the mainsheet--but it attaches to the bottom of the mast and then to the underside of the sailboat boom.

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A boom vang is used on a sailboat to pull down the boom on off-wind points of sail when the wind in the mainsail would lift the boom. Proper use of a boom vang helps keep the sail full and drawing well.
What a Boom Vang Does

When a sailboat sails downwind, the mainsail is let out for best sail trim, and the boom is typically 50 to 80 degrees from the centreline out to the leeward side. Because of this angle, the mainsheet has little downward pull on the boom, which freely rises and falls with wind changes and when the boat rolls on waves from behind. When the boom rises, the mainsail billows out, twists, and spills wind, then may snap back - over and over. This motion makes the sail less efficient.

A boom vang prevents this motion by pulling downward on the boom regardless of its position in relation to the centreline. A traditional block-and-tackle vang (photo) mounts between the base of the mast and mid-boom. The control line is typically led back to the cockpit, where pulling the line exerts force to pull the boom down.

A number of commercial rigid boom vangs are also available. This is essentially an adjustable pole that mounts similarly to hold down the boom. While more expensive than a block-and-tackle vang, rigid vangs have the added function of also holding the boom up when the mainsail is lowered, such that a topping lift is not needed.
How to Use a Boom Vang
When to tighten the vang:

When sailing downwind on a broad reach or a run, tighten the vang to keep the boom down and minimize mainsail twist that spills air from the sail.
If the boat does not have a traveller, which is used to pull the boom down on a beam reach, use the vang even on a beam reach (the wind directly over one side).

When to ease or release the vang to allow the boom to rise:

When sailing downwind in light air, the mainsail generally has better shape if the vang is not tight. Let the sail bag out some.
When sailing downwind in a strong wind, ease the vang to de-power the mainsail by allowing the boom to rise and the sail to spill air high up (mainsail “twist”). Bring in the mainsheet if needed to prevent chafing of the sail against the shrouds and spreaders.
After dropping the mainsail, raise the boom to give more headroom in the cockpit.

Boom Vang as Preventer

If your boat lacks a boom preventer, an important piece of safety gear, it may be possible to improvise with the vang as a preventer when needed, if its lower connection can be easily released and moved forward of the mast. See How to Rig a Preventer.