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.

When 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 have displacement hulls, allowing them to travel more smoothly through the water.

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 may operate like displacement hulls when at rest or at slow speeds, but they climb toward the surface of the water as they move faster.

Flat-bottomed and vee-bottomed hull shapes act as planing hulls. Most small, power-driven boats have planing hulls, allowing them to travel more rapidly across the water.

Flat-Bottom Hull 

Flat-Bottom Hull

Advantages: This planing hull has a shallow draft, which is good for fishing in small lakes and rivers.

Disadvantages: Rides roughly in choppy waters.

Deep-Vee Hull 

Deep-Vee Hull

Advantages: This planing hull has a shallow draft, which is good for fishing in small lakes and rivers.

Disadvantages: Takes more power to move at the same speed as flat bottom hulls. May roll or bank in sharp turns.

Round-Bottom Hull

Round-Bottom Hull

Advantages: A typical displacement hull, it moves easily through water, even at slow speeds.

Disadvantages: Has a tendency to roll unless it has a deep keel or stabilizers.

Multi-Hull

Multi-Hull

Advantages: Another example of a displacement hull, the multi-hull has greater stability because of its wide beam. Examples include Cathedral hull and Tunnel hull.

Disadvantages: Needs a large area when turning.

Hull content courtesy of www.boat-ed.com

Cathedral Hull

Cathedral Hull

Advantages: This popular hull style has two or more hulls attached closely together for more stability without extra width. The air pocket between the hulls can also help the boat get on plane more easily.

Disadvantages: In choppy waters, the side hulls can cause pounding, resulting in a lot of spray.

Cathedral Hull content courtesy of www.boatus.org