By the mid-19th century, many boats had been built with iron or steel frames but still planked in wood. In 1855 ferro-cement boat construction was patented by the French as Ferciment. This is a system by which a steel or iron wire framework is built in the shape of a boat's hull and covered ([[trowell]]ed) over with cement. Reinforced with bulkheads and other internal structure, it is strong but heavy, easily repaired, and, if sealed properly, will not leak or corrode. These materials and methods were copied all over the world, and have faded in and out of popularity to the present.
