Bilge keel

When designing a bilge keel there are important decisions to consider. To minimize hydrodynamic drag the bilge keel should be placed in way of a flowline where it does not oppose crossflow. For such a usage the ends of the bilge keel should be tapered and properly faired into the hull. Also, a bilge keel should not protrude from the hull so far that the device could be damaged when the vessel is alongside a pier, even with a few degrees of adverse heel. Bilge keels on commercial vessels should not protrude below the baseline either, where they could be damaged or fouled by grounding. Note that small bilge keels are often fitted to smaller fishing boats precisely to protect the hull on drying moorings and to help keep the vessel upright. ==Effectiveness==

A bilge keel is constructed from flat plate so as to present a sharp obstruction to roll motion. The roll damping provided by a bilge keel is more than that of a barehull ship, but falls short of other roll damping devices. Nevertheless, it is considered prudent naval architecture to install a bilge keel whenever possible as it is the only device effective in the severest of seas. Bilge keels can also be used in conjunction with other roll damping devices. ==On sailing yachts==

Bilge keels are often fitted to smaller sailing yachts. Bilge keels minimise the draft of the vessel compared to a single fin keel thus enabling it to negotiate shallower water. Bilge keels on sailing yachts extend below the lowest point of the hull extending slightly outwards. Such an arrangement also enables the vessel to stand upright on firm sand or mud at drying moorings without the need for detachable legs, and is simpler than retractable fin keels while giving the hull greater protection. Bilge keels are not as effective as central fin keels in preventing leeway (sideways slippage) caused by crosswinds but are preferred by many small craft owners due to their other advantages. ==History==

The first ship to be equipped with bilge keels was , which was launched in Scotland in 1880. ==See also==