Roundbilge

Roundbilge refers to a specific type of hull construction used in boats and ships. In a roundbilge hull, the hull planks are bent and shaped to form a continuous, smooth curve from the keel to the widest part of the beam, known as the bilge. This contrasts with hard-chine hulls, which have distinct angles or chines where the hull planks meet.

The design of a roundbilge hull typically results in a softer, more rounded underwater shape. This shape is often associated with good seakeeping qualities, allowing the vessel to slice through waves more easily and with less slamming compared to a flatter-bottomed or hard-chine hull. This can lead to a more comfortable ride, particularly in rougher waters.

Historically, roundbilge construction was common in wooden boats, where skilled shipwrights could steam and bend timbers to achieve the desired curves. Modern roundbilge hulls are still built, often using materials like fiberglass, steel, or aluminum, where the hull form is molded or welded into the characteristic smooth, rounded shape.

The performance characteristics of a roundbilge hull can vary depending on the specific proportions of the vessel, such as its length-to-beam ratio and the degree of roundness. However, generally, they are favored for vessels where comfort and seakindliness are priorities, such as cruising yachts, traditional fishing boats, and some types of commercial vessels. The smooth curves also contribute to efficient hydrodynamics, which can positively impact fuel efficiency and speed.