Basic Boat Terminology

At first all the terms used in the marine world may seem intimidating and confusing, but mariners use these terms so that everyone working on, or with a vessel can understand each other. In an emergency it is vital that everyone understands each other as quickly as possible. You may be the only crew member on your vessel but in an emergency, you may need to communicate with other vessels and the coast guard who can assist you. In the marine industry there is a lot of jargon and terms that are industry specific, but this is true in many other industries. Whether you are new to the industry or if you have new crew on board the vessel it is important that everyone can effectively communicate when working on or around boats.

Here are some basic boat terms that you should understand:

Abaft – Toward the stern.

Abeam – A direction at right angles, 90o to the side of the boat.

Aft – A directional term, towards the stern of the boat

Ahead – A directional term when the boat is moving forward

Amidships – The central or middle area of a boat

Astern – In the direction of the back of the boat; also, the movement of the boat going backwards.

Athwartships – A line or anything else running from side to side across the boat

Ballast – Added weight in the boat’s bottom to provide stability.

Beam – A measure of a boat’s widest part of the hull, the width of the boat.

Below – Moving from an upper deck to a lower deck.

Bilge – The deepest area inside the hull of a boat

Bow – The front end of a boat

Chine – The angles on the boat’s hull below the water line. It is “soft” if it is rounded and “hard” if it has sharp angles and is squared off. Chine affects the boat’s speed and turning characteristics.

Displacement – The amount of water a boats hull and load pushes aside equal to the weight of its hull and load.

Draft – Is the depth of the boat from the waterline to the bottom of its keel. The draft is the depth of water necessary to float the boat. Watch out for your outboard skeg, it protrudes lower than the draft of the boat!

Fenders – A cushion-type object between a boat and the dock/ or another boat to minimize damage and absorb shock

Forward or Fore– A directional term meaning towards the bow of the boat.

Freeboard – The distance between the waterline and the gunwales or deck openings

Gross tonnage – A volume measurement of the total enclosed space within a boat

Gunwales – Top edge of the side of a boat (pronounced gun ‘al)

Hatch – An opening in the deck or top side of a cabin which usually has a watertight closure.

Heel – The temporary leaning of a vessel to port or starboard caused by wind, seas or turning forces

Hull – The part of the vessel excluding any super structure and determines the performance of a boat and keeps it floating.

Inboard – From either side toward the centreline.

Keel – The central longitudinal beam which the hull is built up from.

Lazarette – A compartment on a boat at the stern end of a boat usually used for storage.

Leeward – The opposite side or direction from where the wind is blowing, away from the wind.

Length Over All (LOA) -The length of the boat from its forward most part to its after most part in a straight line including outboard engines, davits and bow sprits. This does not change according to the way the boat sits in the water.

Lifelines – Lines or railings, erected around the edge of decks.

List – The leaning of a vessel to port or starboard due to uneven weight distribution or bad design

Outboard – From the centreline of the boat toward either port or starboard side.

Pitching – When a boat rocks in a fore and aft movement.

Planing – When a vessels hull is ‘skimming’ along the water’s surface.

Port – The left side of a boat facing forward with a red side light

Quarter – If you are standing at the stern looking forward, you call the right rear section the starboard quarter and the left rear section the port quarter.

Rigid Hull Inflatable Boat (RHIB) – A vessel with additional ‘soft’ floatation tubes attached to a solid hull.

Roll Period – The amount of time it takes for a vessel to roll from one side to the other and back again.

Scupper – An opening in the sides of a boat at deck level to allow water to flow overboard

Semi Displacement – This type of hull uses the characteristics of both a planing and a displacement hull to move through the water.

Starboard – The entire right side of a boat, from bow to stern and has a green sidelight.

Stern – The rear of a boat is the stern. When you move toward the stern, you are going aft. When the boat moves backwards, it is going astern.

Stiff Roll – Is when a vessel has a ‘quick’ roll period and indicates a stable boat

Tender Roll – Is when a vessel has a ‘slow’ or lengthened roll period, it may be quick to roll to one side but slow to come back up right. This type of roll may indicate danger and that the vessels stability is compromised.

Transom – The transom at the stern of the boat is wide, flat, or curved. The shape of the stern affects the speed, hull resistance, and performance of the boat.

Trim – The relationship between a ship’s draft forward and aft.

Underway – When a vessel is not made fast to the dock, not at anchor and not aground

Waterline Length (LWL) – Is the distance from the bow to the stern, measured at the water line when the boat is stationary. Note that this length changes as the boat rides high or low in the water.

Windward – In the direction from which the wind is blowing, toward the wind.

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