Single-skin glass-reinforced plastic (GRP) was the first craft in the early 1940s. Sandwich construction - a pair separated by and bonded to a thicker, lightweight core - is used in small marine Of thin, strong skins relatively new in the marine industry. Sandwich construction in general was introduced at about the same time as GRP in other industrial areas, namely aircraft, and structural engineering. Today, fiber-reinforced plastic (FRP) single-skin construction is employed in almost 80 percent of marine small craft design. Sandwich construction with balsa or foam cores is a much smaller percentage but is used almost exclusively in the construction of larger power vessels both private and commercial. The largest cored sandwich vessels built to date in North America are LOA 130 feet in length and are built of FRP skins and foam-cored construction.