Chine (boating)

A chine in boating refers to a sharp change in angle in the cross section of a hull. A hull without chines has a gradually curving cross section. The term hard chine indicates an angle with little rounding, where a soft chine would be more rounded, but still involve the meeting of distinct planes. Chine log construction is a method of building hard chine boat hulls. Hard chines are common in plywood hulls, while soft chines are often found on fiberglass hulls.

The oldest type of engineered boats are dugout canoes, which were built by hollowing out a log. These designs generally had rounded bottoms, which made best use of the round shape of the logs. Traditional planked hulls in most cultures are built by placing wooden planks oriented parallel to the waterflow and attached to bent wooden frames. This also produced a rounded hull, generally with a sharp bottom edge to form the keel. Planked boats were built in this manner for most of history.

The first hulls to start incorporating hard chines were probably shallow draft cargo carrying vessels used on rivers and in canals. The barge and later the scow used a flat bottom and near vertical sides, which provided the maximum cargo carrying capacity (in both space and displacement) available for a given depth of water.

Once sufficiently powerful marine motors had been developed to allow powerboats to plane, it was found that the flat underside of a chined boat provided maximum hydrodynamic lift, while the sharp discontinuity at the chine enabled spray to be deflected away as opposed to riding up the sides of the boat. Consequently, almost all boats designed for high speed on the plane are nowadays of hard chine construction.

The scow in particular, in the form of the scow schooner, was the first significant example of a hard chine sailing vessel. While the squared off scow hulls were ugly to sailors accustomed to the sleek, rounded hulls of the time, a scow could carry far more cargo, and while a laden scow was slow and difficult to sail, when not heavily laden it would keep up with the traditional schooners sailing to windward. While sailing scows had a poor safety reputation, that was due more to their typical cheap construction and tendency to founder in storms. As long as it sailed in the protected inland and coastal waters it was designed to operate in, however, the sailing scow was an efficient and cost effective solution to transporting goods from inland sources to the coast. A good example of this is the gundalow.

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