There is a broad diversity of keel types found within the boating spectrum. By far the most common type used for sailing yachts is the bolted-on fin keel, usually made of cast iron, which is bolted through the underside of a GRP hull with substantial stainless steel bolts.
Other types of keel include bilge keels, shoal keels, encapsulated keels, lifting keels and canting keels, as used on racing yachts. While iron is the most common type of ballast, lead is also widely used.
Cement or concrete is sometimes used in combination with scrap iron as ballast for wooden and steel boats, but this can lead to steel rusting from the inside and is not considered good practice.
Some modern racing yachts have water ballast which can be pumped into tanks to help counterbalance any heeling.
Whatever the shape and type, the job of a sailing boat’s keel is to control sideways movement through the water and to provide a counterweight to the sideways force of the wind on the sails, which causes a boat to heel over. Keels are designed to act as underwater foils that generate lift as the boat moves through
