Foils became more hydrodynamic, especially after the availability of tank test models. Wood was dropped as a foil material in the 1980s and replaced by stiffer synthetic materials such as fibreglass then kevlar and carbon fibre. By 1970 hollow wooden spars were replaced by tapered aluminium of much smaller section and lighter weight. These in turn were replaced by much stiffer and lighter carbon fibre masts in the 1990s. Sail area got progressively larger especially when wings were added. This enabled small crews to sail with extremely large sails in stronger wind strengths. As most boats were sponsored they could have multiple rigs to match the wind strength.