Glossary

• apparent wind angle:
  the direction the wind is blowing from the sailboat's point of view. It is different from the true wind angle because of the effect of the boat's speed and direction.

• boom vang:
  an adjustable connection between the boom and the base of the mast which holds the boom down in addition to (and independent of) the main sheet. Its primary function is to control the twist in the leech of the mainsail when sailing on reaches and runs, when the boom is no longer positioned above the traveler track. In some circumstances the vang is used to bend the mast, therefore flatten the main when sailing up wind. It is most commonly a block and tackle system, but hydraulic systems and rigid systems are also available which may hold the boom up as well as pull it down.

• clew:
  The aft lower corner of a sail; the intersection of the leech and foot. In the case of a spinnaker, the corner NOT attached to the spinnaker pole.

• computer aided design:
  The use of computers to aid in the design of some product, in our case sails.

• CAD:
  See computer aided design

• computer aided manufacturing:
  The use of computers to aid in the manufacturing of some product, in our case sails.

• CAM:
  See computer aided manufacturing

• E:
  The mainsail foot. [see drawing]

• Ey:
  The mizzen foot. [see drawing]

• flattener:
  A cringle, grommet, or ring in the leech of a mainsail, placed slightly above the clew ring, which is used to provide more flattening than is available from the outhaul. [see mainsail drawing]

• flat bed plotter:
  A computer controlled carriage which travels along a flat surface or table. The carriage can carry tools which draw, sometimes in different colors, or can cut the material which is lying on the table surface.

• gooseneck:
  the fitting which joins the boom to the mast. It should allow the boom to rotate left and right (port and starboard), up and down, and sometimes to rotate on the long axis of the boom. [see related photos: Santa Cruz 52 ]

• grommets:

• hank:
  Synonym for jib snap, a fitting which attaches a jib its stay.

• head:
  The upper corner of a sail. [see mainsail drawing][see jib drawing][see related photo: Santa Cruz 52 ]

• head board:
  A rigid flat plate at the top of a sail (usually a mainsail), which serves as a reinforcement, an attachment point for the halyard, and an attachment point for the highest luff slider. [see mainsail drawing][see photo: Santa Cruz 52 ]

• head patch:
  The reinforcements, built up as multiple layers of sail cloth, which transfer the stresses in the sail to the head board or head ring, where the halyard is fastened.

• I:
  The vertical distance from the upper point of "I" to the lower point of "I." The upper point of "I" is the intersection of the front face of the mast and the highest jibstay. The lower point of "I" is the shear line abreast the mast. Note that this is not the cabin top. [see drawing]

• J:
  The horizontal distance from the mast to where the forward jibstay intersects the deck. [see drawing]

• jib snap: 
  a fitting which attaches a jib its stay.

• lazy spinnaker guy:
  The non-loaded spinnaker guy connected to the clew of the spinnaker, which is carrying the active spinnaker sheet. [see photograph] [see explanation of dip pole gybes]

• lazy spinnaker sheet:
  The non-loaded spinnaker sheet connected to the tack of the spinnaker, which is carrying the active spinnaker guy where the spinnaker pole is attached. [see photograph] [see explanation of dip pole gybes]

• leech:
  The trailing edge of a sail. In the case of a symmetric spinnaker, the side opposite the spinnaker pole. [see mainsail drawing][see jib drawing]

• leech cord:
  An adjustable cord which runs up the trailing edge of a sail. Intended to control fluttering. "Fluttering" is a phenomenon local to the leech of the sail, as opposed to luffing, wherein the front of the sail is shaking because the wind is impacting on the leeward side of the sail. It will also not control the leech if the jib sheet block is too far aft, which pulls the foot too tight and allows the leech to shake. In mainsails, the leech cord controls fluttering between the battens. [see jib drawing][see related photo: Santa Cruz 52 ]

• luff sliders:
  The fittings on the luff of a mainsail which allow the sail to slide along a track or groove on the back edge of the mast. [see mainsail drawing]

• mainsheet:
  The line used to trim the back edge (leech) of the mainsail.

• outhaul:
  The adjustment which moves the clew of the mainsail fore and aft along the boom; controls foot tension. A primary control of sail fullness. [see mainsail drawing]

• P:
  The mainsail hoist. [see drawing]

• Py:
  The mizzen hoist. [see drawing]

• pre-determined mark:
  a mark placed on running rigging and the mast or deck to serve as a reference to help get the sails trimmed faster. For instance a mark on the main halyard which shows when the sail is hoisted to the band at the top of the mast, or a mark on the spinnaker pole topping lift to indicate when the pole will pass over the bow pulpit and below/behind the forestay during gybes.

• preventer:
  Analogous to a boom vang, a line which holds the boom straight down to the edge of the boat and is rumored to 'prevent' gybes...a good sail trimming tool in light air, because it holds the boom still. Dangerous when used in windy conditions because (a) it instills a false sense of security in the crew, because they think the boom can't gybe, (b) if the mainsail backs, the boat will gybe far more violently than if the boom gybed without the preventer, resulting in the boat laying on its side with mast horizontal on water, boom sticking straight up in the air...boat will remain in this position until boom is allowed to rotate down onto the water, (c) either the preventer, or worse, the boom will then break where the preventer is attached.

• reef clew:
  The part of a sail which contains the reinforcement patches which will become the clew when the sail is reefed. [see mainsail drawing]

• reef clew patch:
  The reinforcements, built up as multiple layers of sail cloth, which transfer the stresses in the sail to the reef clew ring, where the reef clew line is fastened. [see mainsail drawing]

• reef points:
  The small grommets between the reef tack and the reef clew which are used to tie the bulk of the sail loosely around the boom [see mainsail drawing]

• reef tack:
  The part of a sail which contains the reinforcement patches and the ring which will become the tack when the sail is reefed. [see mainsail drawing]

• reef tack offset:
  The position of the hardware/running rigging which constrains the reef tack ring when the sail is reefed.

• reef tack patch:
  The reinforcements, built up as multiple layers of sail cloth, which transfer the stresses in the sail to the reef tack ring, where the reef tack line is fastened. [see mainsail drawing]

• roach:
  In a mainsail (or a jib), the sailcloth which extends aft of a straight line between the head and the clew. Generally battens are required to support the roach. [see photo]

• sail slide stop:
  A fitting at the bottom of the mainsail luff slide track which prevents the luff sliders from coming off the bottom of the track. Occasionally they can be found at the top of the track too.

• sailmaker's yard:
  An English/American unit of area for measuring the weight of sailcloth. It is 28.5 inches wide by 36 inches long. To say a piece of cloth is 6.5 ounce means a piece measuring 28.5" by 36" would weigh 6.5 ounces. This rather strange "yard" seems to be a remnant from the days when it was universally agreed that no one would ever be able to build a loom wider than 28.5 inches which would weave sail cloth. (Today 54 inches is common.)

• slab reefing:
  A type of reefing wherein a horizontal piece of the sail (a 'slab') is removed by lowering the halyard and retrimming the sail using the reef tack and the reef clew. This is distinct from forms of roller reefing.

• spur grommets:

• standing rigging:
  wires which hold up a mast but which are not easily adjustable in length, i.e. they are usually adjusted with turnbuckles.

• tack:
  The front lower corner of a sail; the intersection of the luff and the foot. In the case of a spinnaker, the corner connected to the spinnaker pole. [see mainsail drawing][see jib drawing][see related photograph: Santa Cruz 52 ]

• tack hook:
  A hook adjacent to the gooseneck, used for holding the reef tack of a mainsail while reefed.

• tack horn:
  see 'tack hook'

• topping lift:
  A control line used to hold up various spars: the main boom and the spinnaker pole are two common examples.

• UV border:
  A treatment on the leech and foot of sails which are stored outdoors, intended to protect the sails from UV radiation which rapidly deteriorates the sailcloth. Found typically on roller furling jibs and external roller furling mains. [see related article]