Dictionary of Nautical terms used in the recreational craft and boating industries

BOATSTATS

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Glossary

This Glossary of Terms is here to assist in a general understanding of boating terms, please note that it is not intended to be a definitive guide.

If you have a boating term that you think should be included here, please contact us.

Backstay
This is the name given to the rigging wire that stops the mast from falling forwards. It runs from the stern, on the centreline of the boat to top of the mast.
Ballast Type
To balance a sailing boat or power boat, heavy weights made of iron or lead called ballast has to be placed in the bottom of the boat. In sailing boats these may be on the outside of the hull and called Keels (See keels). The keels can be bolted (see keel bolts) to the bottom of the boat or they can be encapsulated (see keel type) usually in Fibreglass as part of the hull structure.
Beam
This is the width of a boat at its widest part.
Boat Survey
A formal inspection & assessment of a boat’s condition, carried out by a qualified professional marine surveyor. Marine surveys may be required by insurers or lenders to supply their services to you. If you are buying a boat, for your own piece of mind, you should contract a qualified marine surveyor to carry out a survey to ensure your purchase is sound.
Boat type
For the purposes of BoatStats, boats are either sail or motor boats. Motor sailors are listed as sail boats.
Chainplate
A chain plate is a piece of metal which acts as a foundation to which the rigging wires, that support masts, stanchions, the pushpit or the pulpit to the boat’s structure. (See backstay, forestay and shroud).
Channel Handicap System, CHS
This is a system to rank boats in a race, also found in horse racing. By providing a handicap boats of different sizes and capabilities can be entered in the same race.
Davit
A small crane used to hoist a boat or dinghy or other object out of the water. These are generally found at the back (stern) of the boat but can be at the side in larger sailing vessels and powerboats.
Deck Fittings
Deck fittings are any mechanical devices that are attached to or go through the deck of the boat.
Deck Structure
Any part of the deck, coach roof or cockpit which is part if structure of the boat.
Depth of centre of buoyancy, DCB
Archimedes' principle of buoyancy states that the buoyant force exerted on a floating body is equal to the weight of the volume of water which is displaced by that body. The depth of centre of buoyancy is the point of the boat where this occurs. As a boat tilts or rolls in the water the centre moves.
Displacement
This is the amount of water displaced by a boat when it is in the water. The displacement of a boat is calculated when the boat is empty and only contains the permanent structure and contents of the boat it excludes fluids, crew and removable items and equipment.
Draft
The draft of a boat is the distance from the waterline, when the boat is afloat, to the deepest part of the boat. Essential to know when the boat is in shallow water.
Fendering
Fendering is the permanent fitting around the edge of a boat to protect it from collision or wear; it is sometimes called a rubbing strake. Fenders are also used to increase the protection of the boat.
Fenders
To provide protection from collision and wear when a boat is tied up next to another object which could cause damage to your boat. They are made from a soft material or inflatable tube.
Forestay
The forestay is the rigging wire that stops the mast from falling backwards. It runs from the bow to top of the mast.
Frame
The frame is the series of reinforcing beams which give strength, stiffness and structure to a boat. It looks like a skeleton in a wooden boat when the hull is removed.

Glossary

Hatch
The hatch is a doorway to provide access to the inside of a boat. In larger boats there may be secondary hatches which provide alternate access. They can be sliding, or hinged depending on the design of the boat. Secondary hatches can also be clear to provide light into a forward or stern cabin.
Hull below the waterline
This refers to any part of the boat which is below the waterline when the boat is afloat.
Hull form
A ‘hull’, or bottom of a boat, comes in several different forms. Each form has a unique shape that gives it certain handling and performance characteristics. In general, hull forms fall into two categories.
Planing Hulls
Planing hulls are designed to ride on top of the water.
Displacement Hulls
Displacement hulls are designed to sit in the water and ‘displace’ or move, the volume of water equal to the weight of the boat (See displacement). There are a number of hull shapes which fit into these two forms, namely: flat, round, deep V,
Cathedral, and tunnel. Internal structure
Any fitting that forms part of the boat’s furniture.
Keel
The keel or keels are weights attached to the bottom of the boat to give it balance and stability. These are generally found on Sailing Boats (See keel type and ballast type).
Keel bolts
These are substantial bolts used to fix an external keel onto the hull of a boat (See ballast type).
Keel Type
The type of keel depends on the number of keels and the design of a boat, they are classified as follows:
Fin Keel
A short, deep keel that sticks out below the centreline of a hull.
Long Keel
A keel that extends part or the full length of a hull along the centre line, it does not go as deep as a fin keel and is suitable for shallow water.
Bilge Keels
Two keels which stick out either side of the centre line of the hull to enable the boat to stand up when the tide goes out. These are suitable for boats kept in a tidal estuary or where there big tides.
Lifting Keel
A keel that can be partially or wholly lifted through the hull to allow access to shallow waters; these can be fin or bilge.
Length on the waterline (LWL)
This is the measurement of the length of the boat at the boats waterline.
Length over all (LOA)
This is the measurement of the full length of the boat, including any projections from the front or back such as a bowsprit at the front or davits at the back.
Porthole
A porthole is an opening in the topsides or deck structure of a boat that allows light in, some may be opened for fresh air. Portholes are usually small, and may have a hinged glass cover called a portlight which can be shut against a gasket to make it watertight.
Recreational Craft Directive, RCD
This is European Union legislation that requires all boats between 2.5m long and 24m long to be certified to show that they meet minimum European safety criteria. Compliant boats must also display a ‘Design Category’ i.e. the category of weather for which the boat was designed:
A = Ocean B = Offshore C = Inshore D = Sheltered waters
Rig type
There are many type of sailing rig around the world and for clarification purposes the rigs in BoatStats reports are defined as follows:
Cutter
More than one foresail attached to the main mast.
Sloop
A single mast boat with a single foresail.
Ketch
A sailing boat with two masts the main mast sitting forward of a smaller ‘mizzen’ mast.

Pulpit
The Pulpit is the Forward deck and railing structure at the bow of a boat. The railing is an important safety structure and generally well constructed.
Pushpit
The pushpit is the stainless steel framework aft of the cockpit. The railing is an important safety structure and generally well constructed.
Rubbing strake
A rubbing strake is used to provide extra protection on a boat from collision and wear when in contact with other boats or objects in the water such as pontoons and quay walls.
Rudder
The rudder is a partially or fully submerged plane at the back of a boat which is used to steer. Some power boats steer by rotating the drive unit and do not have rudders.
Shroud
A permanently installed line or wire that leads from the masthead to chainplates on the hull in the middle of the boat to support the mast (see stays).
Skin fitting
A skin fitting is a through hull fitting which requires a hole to be made into the skin or hull of a boat. Skin fittings can include cooling water from the engine, bilge pump outlets, sink outlets and instrument devices such as the echo sounder.
Stanchion
These are vertical posts that support guard rails/wires around the deck.
Stays
This is a generic term for the various rigging wires including forestays, backstays and Shrouds that are fitted to support the mast.
Stern gear
This is the term given to the external fittings that form part of the propulsion for the boat other than the engine. They include any mechanical devices at the back of the boat such as the propeller shaft, propeller tube, and the stern bearing.
Transom
The transom is the flat part of the boat at the back from the waterline to the deck.