The 12 Metre Rule
This formula inputs speed producing factors (length (L), sail area (Sa), freeboard (F), and a girth measurement (2D)) through a simple mathematical formula. In order for a yacht to be a Twelve Metre the results of this formula must not exceed 12 Metres. To limit the likelihood that one 12 Metre design would be vastly superior to another and promote fair and competitive racing there are other restrictions on design measurements of 12 Metre racing yachts. Maximum and minimum parameters on mast height, draft, beam and headsail height are applied to 12 Metre racing yachts to ensure that there is not too much diversity among boats.
A 12 Metre under construction at the Luders Marine Construction Company in Stamford, Connecticut, in 1958.