Boats come in many styles and shapes, but the names of the different parts remain the same. As a boat operator you should know the following terms and definitions.
Bow: Front of a vessel
Stern: Rear of a vessel
Starboard: Right side of a vessel
Port: Left side of a vessel
Hull: Body of a vessel
Gunwale: Upper edge of vessel's side (pronounced gunnel)
Cleat: Metal fitting on which a rope can be fastened
Navigation lights include all-round white light and red and green sidelights
Beam: Maximum width of a vessel
Freeboard: Distance from water to lowest point of the boat where water could come on board
Draft: Depth of water needed to float a vessel
Propeller: Rotates and powers a boat forward or backward
Keel: Main centerline of a vessel or the extension of hull that increases stability in the water
There are two basic types of boat hulls, displacement and planing.
Displacement Hulls
Boats with displacement hulls move through the water by pushing the water aside and are designed to cut through the water with very little propulsion. If you lower a boat into the water, some of the water moves out of the way to adjust for the boat. If you could weigh that displaced water, you would find it equals the weight of the boat. That weight is the boat's displacement.
Boats with displacement hulls are limited to slower speeds. A round-bottomed hull shape acts as a displacement hull. Most large cruisers and most sailboats have displacement hulls, allowing them to travel more smoothly through the water.
Displacement Mode - A planing hull, when operated at very slow speeds, will cut through the water like a displacement hull.
Plowing Mode - As speed increases, a planing hull will have a raised bow, reducing the operator's vision and throwing a very large wake. Avoid maintaining a speed that puts your boat in plowing mode.
Planing Mode - Your boat is in planing mode when enough power is applied so that the hull glides on top of the water. Different boats reach planing mode at different speeds.
Planing Hulls
Boats with planing hulls are designed to rise up and glide on top of the water when enough power is supplied. These boats can operate like displacement hulls when at rest or at slow speeds but climb towards the surface of the water as they move faster.
Boats with planing hulls can skim along at high speed, riding almost on top of the water rather than pushing it aside. Flat-bottomed and vee-bottomed hull shapes act as planing hulls. Most small power-driven vessels, including personal watercraft (PWCs), and some small sailboats have planing hulls, allowing them to travel faster across the water.
Length of a Vessel
A vessel's length overall dictates the equipment the vessel must have to comply with federal and state laws. Length overall is measured from the tip of the bow in a straight line to the stern of the vessel. Bow sprits, rudders, outboard motors and motor brackets, handles, and other fittings, attachments, and extensions are not included in this measurement.
Length Classes
Some states have laws that refer to vessel lengths as "classes." The U.S. Coast Guard no longer uses these designations to indicate length.
Class A: Less than 16 feet
Class 1: 16 feet to less than 26 feet
Class 2: 26 feet to less than 40 feet
Class 3: 40 feet to less than 65 feet
