deadrise

Deadrise is a nautical term describing the angle formed between the hull bottom and a horizontal reference plane. It is a measure of how V-shaped the hull is, and it varies along the length of the vessel.

In practice, deadrise is specified at particular stations along the hull, such as the keel, chine, or transom. In V-hull designs, the deadrise is larger toward the bow and shallower toward the stern, yielding a pronounced forward V that helps slice through waves. Flat-bottom craft have little or no deadrise.

The deadrise affects performance and ride characteristics: higher deadrise improves ride in chop and reduces spray but increases wetted surface area and drag, limiting top speed and fuel efficiency. Lower deadrise reduces drag and can improve straight-line speed but yields a rougher ride in waves and less stability in cross-sea conditions. The precise values depend on hull shape and size; typical recreational V-hulls range roughly from 15 to 25 degrees, with higher values in specialized speed or offshore designs.

Terminology note: Some sources distinguish deadrise (one word) from dead-rise (two words), which refers to the rise of the bow bottom relative to the keel and can be related but is not identical to deadrise. Designers specify deadrise to characterize hull form and its expected performance.