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| Safe Overhead Clearance |
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A distance that needs to be kept between the mast and overhead electrical lines to prevent electrical arcing.
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| Safety Harness |
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A device worn around a person's body that can be attached to jack lines to help prevent a person from becoming separated from the boat.
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| Safety Pin |
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(1) Any pin that is used to prevent a fitting from falling open. (2) A pin used to keep the anchor attached to its anchor roller when not in use.
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| Sail |
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(1) A large piece of fabric designed to be hoisted on the spars of a sailboat in such a manner as to catch the wind and propel the boat. (2) The act of using the wind to propel a sailboat.
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| Sail Shape |
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The shape of a sail, with regard to its efficiency. In high winds a sail would probably be flatter, in low winds rounder. Other circumstances can cause a sail to twist. Controls such as the cunningham, boom vang, outhaul, traveler, halyards, leech line, sheets, and the bend of the mainmast all can affect sail shape. Also see sail trim.
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| Sail Track |
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A slot into which the bolt rope or lugs in the luff of the sail are inserted to attach the sail. Most masts and roller reefing jibs use sail tracks. Systems with 2 tracks can allow for rapid sail changes.
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| Sail Trim |
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The position of the sails relative to the wind and desired point of sail. Sails that are not trimmed properly may not operate efficiently. Visible signs of trim are luffing, excessive heeling, and the flow of air past telltales. Also see sail shape.
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| Sailboat |
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A boat which uses the wind as its primary means of propulsion.
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| Sailcloth |
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A fabric, usually synthetic, used to make sails.
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| Sailing Directions |
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Books that describe features of particular sailing areas, such as hazards, anchorages, etc.
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| Sampson Post |
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A strong post used for to attach lines for towing or mooring.
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| Sand Bar |
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An area in shallow water where wave or current action has created a small, long hill of sand. Since they are created by water movement, they can move and may not be shown on a chart.
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| Satellite Navigation |
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Navigation using information transmitted from satellites. See Global Positioning System.
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| Scend |
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The distance that the trough of a wave is below the average water level. With large waves in shallow water the scend is important to help determine whether a boat will run aground.
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| Schooner |
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A sailboat with two or more masts. The aft mast is the same size or larger than the forward one(s). Also see ketch and yawl.
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| Scope |
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The length of the anchor rode relative to the depth of the anchor. For example 100 feet of anchor rode in 20 feet of water would be a scope of 5:1. A scope of 7:1 or more is usually used depending on the holding ground. Too little scope can cause the anchor to drag. Increased scope increases the swinging room.
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| Scow |
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A boat with a flat bottom and square ends.
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| Scud |
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To run before the wind in a storm.
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| Scull |
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A method of moving a boat by using a single oar at the stern.
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| Scupper |
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An opening through the toe rail or gunwale to allow water to drain back into the sea.
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| Scuttlebutt |
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Gossip. People talking about things that may or may not be true, usually about other people or events. The term scuttlebutt evolved from the name of a keg containing water and alcohol that sailors used to gather about before meals.
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| Sea |
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(1) A body of salt water. A very large body of fresh water. (2) Any body of salt water when talking about its condition or describing the water around a boat. Heavy seas for example.
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| Sea Anchor |
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A drogue designed to bring a boat to a near stop in heavy weather. Typically a sea anchor is set off of the bow of a boat so that the bow points into the wind and rough waves.
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| Sea Buoy |
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The last buoy as a boat heads to sea.
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| Sea Cock |
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A valve used to prevent water from entering at a through hull.
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| Sea Kindly |
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A boat that comfortable in rough weather.
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| Sea Level |
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The average level of the oceans, used when finding water depths or land elevations.
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| Sea Room |
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Room for a boat to travel without danger of running aground.
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| Seagoing |
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A vessel designed to be able to cross oceans.
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| Seamanship |
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The ability of a person to motor or sail a vessel, including all aspects of its operation.
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| Secondary Port |
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A port that is not directly listed in the tide tables but for which information is available as a difference from a nearby standard port.
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| Sector |
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An arc of a circle in which certain types of navigational lights known as sector lights are visible.
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| Sector Light |
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A navigational light that is visible only for a specific sector or arc of a circle, enabling a boat to determine that it lies within that sector. Sector lights might mark the entrance to a channel.
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| Secure |
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To make fast. To stow an object or tie it in place.
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| Securite |
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A type of warning message transmitted by radio. Securite messages are used to warn of impending storms, navigational hazards and other potential problems that are not immediately life threatening by themselves. MAYDAY and PAN PAN are used for more immediate problems.
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| Seizing |
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Tying two lines, or a spar and a line together, by using a small line.
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| Self Bailing |
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Said of an area, such as the cockpit, that is capable of rapidly draining away any water that may fill the area.
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| Self Draining |
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A locker or other area equipped with a drain capable of allowing any water that may collect in it to leave, such as from wet clothes or equipment.
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| Self Steering Gear |
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A device used to keep a sailboat on the same heading relative to the wind without aid of a person. Self steering gear is a mechanical system using a wind vane instead of electrical power as does an autopilot.
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| Semaphore |
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A method of signaling using two flags held in position by the signaler.
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| Sentinel |
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A weight hung from the anchor chain in order to keep the anchor lying as flat as possible to prevent dragging.
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| Separation Zone |
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A region drawn on a chart to separate two lanes that have shipping vessels moving in opposite directions.
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| Serve |
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To wind small line around a rope to protect it from chaffing and weather.
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| Set |
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(1) To put an object in place, as in "set the anchor." (2) The manner in which an object is in place. "Are the sails set correctly?" (3) The direction that a current is moving.
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| Sextant |
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A navigational instrument used to determine the vertical position of an object such as the sun, moon or stars. Used with celestial navigation.
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| Shackle |
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A metal U-shaped connector that attaches to other fittings with the use of a pin that is inserted through the arms of the U.
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| Shakedown |
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An initial trip with a boat to make sure that everything is operating properly.
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| Shank |
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The long bar part of an anchor. The flukes are at one end of the shank and the stock is at the other.
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| She |
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All boats are referred to as female. "She is at anchor." "Her sails are set."
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| Shear Pin |
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A pin attaching one part to another that is designed to break if excessive loads are applied. For example to connect the propeller to the propeller shaft so that the pin can break if the propeller strikes something, preventing damage to the propeller and engine.
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| Sheathing |
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A covering to protect the bottom of a boat.
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| Sheave |
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A wheel used to change the direction of a line, such as in a block or at the top of the masthead.
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| Sheepshank |
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A knot used to temporarily shorten a line.
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| Sheer |
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(1) The fore and aft curvature of the deck. (2) A sudden change of course.
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| Sheer Strake |
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The top plank on the side of a wooden boat that follows the sheer of the deck.
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| Sheet |
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A line attached to the clew of a sail and is used to control the sail's trim. The sheets are named after the sail, as in jib sheets and main sheet.
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| Sheet Bend |
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A type of knot used to tie two lines together.
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| Ship |
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(1) A large vessel. (2) To take an object aboard, such as cargo, or water. (3) To put items such as oars on the boat when not in use.
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| Shoal |
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(1) Shallow water. (2) An underwater sand bar or hill that has its top near the surface.
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| Shore |
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The edge of the land near the water.
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| Short Splice |
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A quickly made splice joining two lines together. A short splice is wider than the original line and will not fit through blocks or fairleads.
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| Shove Off |
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To push a boat, as from a dock or another boat.
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| Shroud |
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Part of the standing rigging that helps to support the mast by running from the top of the mast to the side of the boat. Sailboats usually have one or more shrouds on each side of the mast.
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| Side Lights |
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Green and red lights on the starboard and port sides of the boat required for navigation at night. Each light is supposed to be visible through an arc of 112.5°, beginning from directly ahead of the boat to a point 22.5° aft of the beam.
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| Sideslip |
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The tendency of a boat to move sideways in the water instead of along its heading due to the motion of currents or leeway.
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| Sight Reduction Tables |
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Tables containing information about the position of the sun, moon, planets and stars. When using celestial navigation these tables help find the position of a boat.
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| Single Sideband |
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A type of radio carried on a boat to transmit long distances.
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| Sink |
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(1) To go to the bottom of the water. (2) To cause an object to go to the bottom of the water.
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| Skeg |
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Any flat protrusion on the outside of the hull that is used to support another object such as the propeller shaft or rudder.
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| Skin |
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The outside surface of a boat. Usually used when describing a fiberglass or other molded hull.
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| Slack |
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(1) A line that is loose. (2) To ease a line.
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| Slack Water |
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A period of almost no water movement between flood and ebb tides
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| Slide |
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Also called a lug. Metal or plastic pieces attached to a sail's luff that slide in a mast track to allow easy hoisting of a sail.
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| Sling |
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(1) Lines used to hoist heavy or awkward objects. (2) The act of using such lines to hoist heavy or awkward objects. (3) Ropes used to secure the center of a yard to the mast.
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| Slip |
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A space between two docks or piers where a boat can be moored.
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| Sloop |
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A style of sailboat characterized by a single mast with one mainsail and one foresail. Also see cutter.
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| Slot |
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The opening between the jib and the mainsail. Wind passing through this opening increases the pressure difference across the sides of the mainsail, helping to move the boat forward.
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| Small Stuff |
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Small lines used when whipping and serving.
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| Snap Hook |
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A metal fitting with a arm that uses a spring to close automatically when connected to another object.
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| Snatch Block |
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A block that can be opened on one side, allowing it to be place on a line that is already in use.
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| Snub |
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To suddenly stop or secure a line.
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| Soft Eye |
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An eye splice that does not use a protective insert.
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| Sound |
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Signals required by navigation rules describing the type of vessels and their activities during times of fog.
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| Sounding |
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The depth of the water as marked on a chart.
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| South |
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One of the 4 cardinal compass points. South is the direction toward the South Pole and is at 180° on a compass card.
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| South Pole |
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The "bottom" point of the line about which the earth rotates.
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| Southern Cross |
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A constellation in the shape of a cross used to determine the direction of the South Pole when traveling in the southern hemisphere.
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| Spar |
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A pole used as part of the sailboat rigging, such as masts, booms, and gaffs.
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| Spar Buoy |
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A tall buoy used as a navigational aid.
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| Spell |
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To relieve someone when taking turns at a task, such as manning the helm.
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| Spider Band |
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A metal band around a spar with an eye to take the shackles used on the running rigging.
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| Spill the Wind |
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To head up into the wind or loosen a sail, allowing the sail(s) to luff.
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| Spinnaker |
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A very large lightweight sail used when running or on a broad reach.
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| Spinnaker Pole |
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Sometimes spinnaker boom. A pole used to extend the foot of the spinnaker beyond the edge of the boat, and to secure the corner of the sail.
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| Spinnaker Pole Lift |
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Also spinnaker lift. A line running from the top of the mast, used to hold the spinnaker pole in place.
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| Spitfire |
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A storm jib. A small jib made out of heavy cloth for use in heavy weather. Sometimes brightly colored.
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| Splice |
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The place where two lines are joined together end to end.
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| Spreader |
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Small spars extending toward the sides from one or more places along the mast. The shrouds cross the end of the spreaders, enabling the shrouds to better support the mast.
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| Spring |
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To begin, as in "to spring a leak."
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| Spring Line |
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Docking lines that help keep the boat from moving fore and aft while docked. The after bow spring line is attached near the bow and runs aft, where it is attached to the dock. The forward quarter spring line is attached to the quarter of the boat, and runs forward, being attached to the dock near the bow of the boat.
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| Spring Tide |
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The tide with the most variation in water level, occurring during new moons and full moons. This is the time of the highest high tide and the lowest low tide. The opposite of a neap tide.
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| Squall |
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A sudden intense wind storm of short duration, often accompanied by rain. Squalls often accompany an advancing cold front.
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| Square Knot |
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Reef knot. A simple knot that can slip. Often used on sailboats when reefing.
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| Square Rigged |
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A sailboat having square sails hung across the mast.
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| Square Sail |
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A square sail hung from a yard on the mast. Best used when sailing down wind.
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| Ssb |
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Single sideband radio. A type of radio used on a boat to transmit for long distances.
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| Stability |
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Ability of a boat to keep from heeling or rolling excessively, and the ability to quickly return upright after heeling.
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| Stall |
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(1) To stop moving. (2) Air is sail to stall when it becomes detached from the surface it is flowing along. Usually air travels smoothly along both sides of a sail, but if the sail is not properly trimmed, the air can leave one of the sides of the sail and begin to stall. Stalled sails are not operating efficiently.
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| Stanchion |
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A post near the edge of the deck used to support life lines.
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| Stand on Vessel |
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The vessel that is required to maintain its course and speed when boats are approaching each other according to the navigation rules. Also known as the privileged vessel.
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| Standard Port |
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A port for which information is listed in the tide tables. Other ports known as secondary ports have information listed as a difference from the standard port rather that having complete tables.
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| Standing |
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The part of the line that will carry the load after a knot has been tied in it.
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| Standing Rigging |
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The rigging of a boat that does not normally need to be adjusted.
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| Starboard |
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The right side of a boat, from the perspective of a person at the stern of the boat and looking toward the bow. The opposite of port.
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| Starboard Tack |
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A sailboat sailing on a tack with the wind coming over the starboard side and the boom on the port side of the boat. If two boats under sail are approaching, the one on port tack must give way to the boat on starboard tack.
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| Stateroom |
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Sleeping quarters for the boat's captain or guests.
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| Statute Mile |
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A mile as measured on land, 5280 feet or 1.6 kilometers. Distances at sea are measured as nautical miles.
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| Stay |
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Lines running fore and aft from the top of the mast to keep the mast upright. Also used to carry some sails. The backstay is aft of the mast and the forestay is forward of the mast.
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| Staysail |
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A triangular sail similar to the jib set on a stay forward of the mast and aft of the headstay.
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| Steadying Sail |
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Also stability sail or riding sail. Any small sail set to help the boat maintain its direction without necessarily moving, as when at anchor or in heavy weather.
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| Steaming Light |
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Also known as a masthead light. The steaming light is a white light that is visible for an arc extending across the forward 225° of the boat. When lit the steaming light indicates that a vessel under power, including sailboats with engines running. Steaming lights are usually located halfway up the mast rather than at the top.
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| Steep Seas |
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Tall and short waves caused by water current and wave directions being opposite to the direction of the wind.
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| Steerage Way |
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In order for the rudder to be able to properly steer the boat, it must be moving through the water. The speed necessary for control is known as steerage way.
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| Stem |
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The forward edge of the bow. On a wooden boat the stem is a single timber.
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| Step |
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(1) A fitting for the bottom of the mast (mast step.) (2) The act of placing the foot of the mast in its step and raising the mast.
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| Stepped |
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(1) A mast that is in place is stepped. (2) Where the mast is stepped, as in keel stepped or deck stepped.
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| Stern |
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The aft part of a boat. The back of the boat.
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| Stern Light |
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A white running light placed at the stern of the boat. The stern light should be visible through an arc of 135°, to the rear of the boat.
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| Stern Line |
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A line running from the stern of the boat to a dock when moored.
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| Stern Pulpit |
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Pushpit. A sturdy railing around the deck at the stern.
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| Stiff |
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A boat that resists heeling.
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| Stock |
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A crossbeam at the upper part of an anchor.
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| Stopper |
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A mechanical device or knot used to keep a rope from running.
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| Stopper Knot |
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A knot used in the end of a line to prevent the end from running through a block or other narrow space. Stopper knots prevent a line that slips from unthreading itself and getting lost.
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| Storm Jib |
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Sometimes called a spitfire. A small jib made out of heavy cloth for use in heavy weather. Sometimes brightly colored.
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| Storm Sail |
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The storm jib and storm trysail. Small sails built from heavy cloth for use during heavy weather.
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| Storm Trysail |
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A very strong sail used in stormy weather. It is loose footed, being attached to the mast, but not the boom. This helps prevent boarding waves from damaging the sail or the rigging.
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| Stow |
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To put something away.
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| Strakes |
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A row of wooden planks on the hull of a wooden boat.
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| Strum Box |
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A strainer in the bilge so that the bilge pump doesn't get clogged.
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| Stuffing Box |
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A fitting around the propeller shaft to keep the bearing lubricated and to keep water out of the boat.
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| Surf |
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(1) The breaking waves and resulting foam near a shore. (2) The sport of riding breaking waves on a board.
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| Survey |
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An inspection of a boat to determine its condition.
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| Surveyor |
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A person who is qualified to inspect a boat in order to determine its condition.
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| Swab |
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(1) A mop made from rope. (2) To use such a mop.
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| Swallow |
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The place between the sheave (roller) and housing of a block, through which the line is run.
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| Swamp |
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To fill with water.
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| Swell |
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Large smooth waves that do not crest. Swells are formed by wind action over a long distance.
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| Swim Platform |
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A platform, usually on the transom, allowing swimmers to easily climb back onto a boat.
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| Swing a Compass |
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The act of checking compass readings against known headings in order to determine the compass error.
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| Swinging Bridge |
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A bridge that swings away from the waterway so that boats may pass beside it.
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| Swinging Circle, Swinging Room |
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The distance a boat can move around its anchor. Swinging room is important because if other boats or objects are within a boat's swinging circle they may collide.
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| Swivel |
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A rotating fitting used to keep a line from tangling.
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