The National 12 is a development class where within a set of rules (and with occasional considered changes to those rules) the boats have been able to evolve over time, moving from wood and clinker construction to high-performance glass and carbon fibre-foam composite boats. One of the most noticeable changes in the boats is the steady increase in beam over the history of the class – early examples were less than 5 ft while modern ones are usually at the maximum 6 ft 6 in to provide maximum righting moment for the crew. The Twelve has developed into a racing boat which performs well in all conditions being highly manouvreable and challenging to sail in windy weather.