Deadrise is a term used to describe the angle of the hull bottom of a boat. It is the amount of angle that forms between the boat bottom and a horizontal plane on either side of the center keel. The angle is measured in degrees and is the angle between a horizontal plane and the hull surface. A boat with a deeper, sharper V-shaped hull has a higher deadrise angle, while a flat-bottom boat has a deadrise angle of zero degrees.
The deadrise angle affects the boats performance and ride quality. Generally, the flatter the deadrise, the worse the boat will slide in corners, while a boat with a higher deadrise will turn sharper without slipping. The deadrise angle also affects the boats stability, speed, and fuel efficiency.
The answer to what is a good deadrise on a boat depends on how the boat is used. For someone who spends their time on protected waterways where waves aren’t usually an issue, a boat with no deadrise may be the best choice. Flat-bottom boats offer the very best stability to minimize rocking and rolling, they tend to draw very little water, and they don’t need much power to get onto plane. Displacement boats or models which don’t rise out of the water and plane out very much, like trawlers and some motor yachts, may have very low or even no deadrise. Multi-hull powerboats are another example, since they spread the areas of impact between two different hulls. In cases like these, adding deadrise might serve only to increase rocking and rolling, without having an appreciable effect on reducing wave impacts.
To measure the deadrise angle, a boat builder or owner can use a digital inclinometer or a deadrise angle gauge.
