Semi-Displacement Vessel

A type of boat or ship designed to operate efficiently in both displacement and planing modes, offering a balance between speed and fuel efficiency.

A semi-displacement vessel is a hybrid design that combines characteristics of displacement and planing hulls, allowing it to operate effectively across a range of speeds. Unlike a pure displacement hull, which is limited by its hull speed and relies on buoyancy to support its weight, a semi-displacement hull can partially rise out of the water as speed increases, reducing drag and enabling higher speeds. However, it does not fully plane like a planing hull. This design is often achieved by incorporating a rounded or modified V-shaped hull with a flatter stern section, which provides stability and lift while maintaining good seakeeping abilities.

These vessels are particularly popular for long-range cruising, as they offer a compromise between the fuel efficiency and smooth ride of displacement hulls and the speed capabilities of planing hulls. Semi-displacement vessels are typically powered by inboard engines and are often used for motor yachts, trawlers, and patrol boats. They are well-suited for those who require moderate speed without sacrificing comfort or the ability to handle rough seas. The design also allows for greater payload capacity compared to planing hulls, making them versatile for a variety of recreational and commercial applications. However, they may not achieve the extreme speeds of planing vessels or the ultra-efficient low-speed performance of pure displacement designs.