Nautical terms
34 of 469 terms in Docking & boat handling. Show all
B
- Back and fill (Casting) Docking & boat handling
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Turning a single-screw boat in tight space by alternating short bursts ahead and astern: going ahead with the rudder over to swing the bow, then backing and letting prop walk swing the stern, repeating until turned.
- Bank effect (Bank suction, Bank cushion) Docking & boat handling
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In a narrow channel or river, water pressure near a steep bank pushes the bow away from it (bank cushion) while the stern is drawn toward it (bank suction), which can suddenly sheer the boat across the channel.
- Bow line Docking & boat handling
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A dock line led from the bow of the boat to the dock or a piling.
Not to be confused with the bowline knot.
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- Bow thruster (Stern thruster, Thruster) Docking & boat handling
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A small propeller, usually in a tunnel through the hull near the bow (or stern), driven by an electric or hydraulic motor, that pushes the bow (or stern) sideways for docking. With both, a boat can move sideways and turn in place.
Electric thrusters lose much of their thrust if battery voltage drops, and many have limited run times; the maker advises keeping the supply voltage up and changing the thruster's anode.
- Breast line Docking & boat handling
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A dock line run out sideways from the boat to the dock at roughly a right angle, as opposed to a spring line, which runs at a shallow angle along the boat.
- Broach (Broaching) Docking & boat handling
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When a following sea pushes the stern around so the boat is thrown broadside to the waves or surf.
The Coast Guard handbook advises steering quickly into any sideways movement of the stern in following seas.
C
- Cavitation (Ventilation) Docking & boat handling
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When a propeller loses grip because low-pressure bubbles form on its blades, or air is drawn in from the surface: the engine races, thrust drops and the prop can be damaged. Easing the throttle and then building speed gradually restores thrust.
F
- Fender (Bumper) Docking & boat handling
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A cushion hung over the side to protect the hull from the dock, pilings or another boat. The Coast Guard handbook says never to fend off by hand or foot; use a fender.
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- Following sea (Following seas) Docking & boat handling
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Waves coming from astern, moving the same way as the boat. They can lift the stern, make steering hard and lead to broaching.
The Coast Guard handbook notes a transom stern gives these waves a large surface to push on.
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H
- Head sea (Head seas) Docking & boat handling
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Waves coming from ahead, against the boat's course.
- Headway Docking & boat handling
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Forward movement of the boat through the water. The opposite is sternway.
- Heave to (Heaving to, Hove to) Docking & boat handling
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To stop or nearly stop the boat and hold it roughly in place. The Coast Guard uses it to mean stopping when hailed for a boarding; sailors also heave to by setting the sails so the boat makes little headway, to wait or ride out a storm.
- Heel Docking & boat handling
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A temporary lean to one side caused by wind on the sails, waves, or a hard turn at speed.
L
- Leeway Docking & boat handling
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Sideways drift of a boat to leeward caused by the wind (and, loosely, by current), so its track differs from its heading. Sailboat keels help resist it.
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- List Docking & boat handling
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A steady lean to one side caused by uneven weight in the boat. Unlike heel, it doesn't go away when the wind drops or the turn ends.
N
- No-wake zone (Idle speed zone, Slow no wake) Docking & boat handling
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An area, marked by a white regulatory marker with an orange circle or by signs, where boats must go slowly enough to make no significant wake. The markers are maintained by the states.
P
- Pitchpole Docking & boat handling
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Capsizing end over end, when a large wave lifts the stern and the bow buries into the sea ahead.
- Pivot point Docking & boat handling
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The point around which the boat turns. On most boats it is a little forward of amidships at rest, moves forward as the boat gains headway (about one-third of the length back from the bow at normal speed) and aft when backing.
Because the stern swings around the pivot point, check that the stern will clear the dock before you turn away from it.
- Porpoising Docking & boat handling
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A planing boat's bow rising and falling in a steady rhythm at speed. Adjusting trim tabs or drive trim usually corrects it.
- Prop walk (Propeller side force, Side force) Docking & boat handling
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The sideways push of a turning propeller on the stern. With a right-handed propeller (clockwise seen from astern), the stern tends to move to starboard in forward gear and to port in reverse. A left-handed propeller does the opposite.
The Coast Guard handbook's back-and-fill turn relies on it. Know which way your stern walks before backing into a slip.
S
- Slip (Berth) Docking & boat handling
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A boat's parking space at a marina, between two piers, floats or finger docks. "Berth" also means a bed aboard.
- Spring line (Spring, Forward spring, Aft spring) Docking & boat handling
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A dock line that runs at a shallow angle along the boat, from a cleat near the bow or stern to a point on the dock well aft or forward. Springs stop the boat surging fore and aft, and the boat can be powered against one to swing the bow or stern in or out.
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- Springing off (Springing, Spring off) Docking & boat handling
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Using a spring line and the engine to move the boat against the line. With a line from a forward cleat to the dock aft, idling ahead with the wheel turned away from the dock walks the boat in sideways; with a line from a stern cleat to the dock forward, backing swings the bow out.
BoatUS Foundation describes using springs this way to get into or out of tight spots when wind is pinning you to the dock.
- Squat Docking & boat handling
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The stern sinking lower in the water when a boat accelerates hard, because water rushing under the hull reduces the lift under the stern.
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- Steerageway Docking & boat handling
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The lowest speed at which the boat still answers the helm. Below it, the rudder has too little water flowing past to steer.
- Stern line Docking & boat handling
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A dock line led from the stern of the boat to the dock or a piling.
- Sternway Docking & boat handling
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Movement of the boat backward through the water. The opposite is headway.
T
- Trim (Down by the bow, Down by the stern) Docking & boat handling
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How the boat sits fore and aft in the water: level, bow down or stern down. A change in trim changes the drafts forward and aft. On outboards and stern drives, "trim" also means tilting the drive to adjust the running angle.
- Trim tabs (Tabs) Docking & boat handling
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Adjustable plates at the bottom of the transom of a planing boat. Lowering them lifts the stern and brings the bow down, used to get on plane, level the ride, correct a list and reduce pounding or porpoising.
The Coast Guard handbook advises adjusting them in short bursts and warns that over-trimming at high speed makes handling unpredictable.
- Twin-screw (Twin engines, Splitting throttles, Opposed propulsion) Docking & boat handling
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A boat with two engines and propellers, usually turning in opposite directions. Running one ahead and the other astern ("splitting the throttles") twists the boat, and many can turn nearly in their own length.
Backing both engines evenly cancels their side forces, so a twin backs straighter than a single-screw boat.
W
- Wake Docking & boat handling
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The waves and disturbed water a moving boat leaves behind. The Coast Guard handbook says operators are responsible for their wake.
Whether you are liable for wake damage is a matter of state and federal law; the Rules don't excuse neglect such as unsafe speed, and many states set their own wake rules.
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- Windage (Sail area) Docking & boat handling
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The surface of the boat above water that the wind pushes on: hull sides, cabin, flybridge, canvas and rigging. A high bow or foredeck lets the wind swing the bow more easily at low speed.
The Coast Guard handbook notes a single-screw boat will generally back into the wind when it has more "sail" area forward of its pivot point.
Y
- Yaw (Yawing) Docking & boat handling
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Swinging from side to side off course, especially when running in a following or quartering sea; also the swinging of a boat back and forth at anchor.
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General guidance for recreational boaters, researched from the sources listed and written in our own words. Your equipment manuals, local knowledge, the Navigation Rules and a qualified instructor come first.