Parts of a Boat Hull – Labeled Diagram and Hull Shapes

All 18 parts on the diagram

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Outside of the hull 8

Keel The main centerline of a vessel. On some boats it reaches down into the water to steady the boat.
Stem The most forward part of the bow. It runs up from the keel and joins the planks of the two sides.
Transom It closes the back of the hull. On a small boat it may carry a rudder or an outboard motor.
Skeg A sternward extension of the keel. It can protect the propeller and the rudder.
Waterline Everything below it is under water when the boat floats.
Topsides The part of the hull between the waterline and the deck.
Sheer line Sheer is the upward curve of the hull's lines toward the ends. It curves up most toward the bow.
Strake Each strake runs from the stem to the transom. The strake next to the keel is the garboard.

Shape and structure 6

Gunwale It is usually stiffened with an extra strip along the top. Generally pronounced gunnel.
Frames Frames are also called ribs. The planking is fastened to them.
Stringers A stringer is a lengthwise part of the hull's framework. It crosses the frames, which run from side to side.
Chine A chine is a sharp change of angle in the hull's cross-section. A hull with this corner is a hard-chine hull.
Bilge Water that gets into the boat collects here. It is on either side of the keel.
Deadrise It is measured on either side of the keel. A hull with a lot of deadrise has a clear V shape.

Hull shapes 4

Flat-bottomed hull A planing hull with a shallow draft. It is good on small lakes and rivers. It rides roughly in choppy water.
Round-bottomed hull A displacement hull that moves easily at slow speeds. It tends to roll without a deep keel or stabilizers.
Deep-vee hull Rides more smoothly in rough water than a flat bottom. It is a planing hull and takes more power to push.
Multi-hull A wide beam makes a multi-hull very stable. It needs a large area to turn.

How this list was compiled: Every name checked on 2026-09-30 against at least two independent sources, a name kept only where two use it. (1) Boat Ed, a state boater-education course (Indiana): Parts of a Boat From a Side View and From a Front View, Displacement Hulls, Planing Hulls and Descriptions of Hull Shapes, https://www.boat-ed.com/indiana/studyGuide/Descriptions-of-Hull-Shapes/10101602_35113/ (hull, keel, gunwale; displacement and planing hulls; flat-bottomed, deep-vee, round-bottomed and multi-hull). (2) Nine Motorboats and How to Build Them (Motor Boating, 1913), full text at https://archive.org/details/ninemotorboatsho00motorich (keel, stem, transom, skeg, chine, strakes, garboard, sheer, frames, stringers, bilge, topsides, dead-rise); with C. P. Kunhardt and W. P. Stephens, Canoe and Boat Building (1889), https://archive.org/details/canoeboatbuildin00stepiala (gunwale, deadrise, strakes, sheer). (3) Wikipedia, text only: Hull (watercraft), Chine (boating), Strake, Skeg, Transom (nautical), Stem (ship), Bilge, Gunwale, Rib (nautical) and the Glossary of nautical terms (deadrise, frame, sheer, stringer, topsides, waterline). Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's boat, nothing traced. Licence: own work

How it works

These are the parts of a boat hull with the deck and engine left off. Most of the names also serve for the parts of a sailboat hull and the parts of a ship hull.

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Three views of one hull

From the side you see the outline: the stem at the bow, the keel along the bottom, the transom at the stern, and the strakes of planking between. Cut across, the same hull shows how it is built: frames run from gunwale to gunwale, stringers run fore and aft, and the bottom meets each side at the chine. The third view sets four hull shapes side by side.

Deadrise is an angle, not a part: it says how steep the V of the bottom is.
Gunwale is generally said gunnel.

Questions and answers

What are the main parts of a boat hull?

The keel along the bottom, the stem at the bow and the transom at the stern. The sides rise from the chine to the gunwale. Inside, frames run across the hull and stringers run along it, and the bilge is the lowest space.

What is the chine on a boat?

The corner where the bottom of the hull meets the side. A hull with this sharp change of angle is a hard-chine hull; a round-bottomed hull curves smoothly and has none.

What is deadrise on a boat hull?

The angle of the bottom up from level, measured on either side of the keel. A flat-bottomed hull has almost none. A deep-vee hull has a lot, which gives a smoother ride in rough water and takes more power.

What are the two basic types of boat hull?

Displacement and planing. A displacement hull pushes the water aside and is limited to slower speeds; round-bottomed hulls work this way. A planing hull rises and glides on top of the water when it has enough power; flat-bottomed and vee-bottomed hulls plane.