Development classes: Most dinghy classes have a fairly fixed layout of sails and hull design, and changes are very infrequent. However, some classes can compete and sail with less rigid definitions and measurements. This encourages experiment which often leads to innovation in techniques and construction. Examples are the International 14, National 12, the 18ft Skiff, the Puddle Duck Racer and the Moth. The International Moth is worth noting because of its use of lifting foils on the rudder and daggerboard. These generate enough lift to push the hull above the water, significantly reducing friction and allowing speeds in excess of .