Wind and Math in the Sails

Now that the competition for the America’s Cup is in full swing, we are reminded that the term 12-meter yacht is the greatest misnomer since Columbus called the people he met on this continent Indians.

A 12-meter yacht is not a boat that is about 39 feet long, which would be logical but wrong. It turns out, in fact, that most 12-meter yachts are 65 to 70 feet from stem to stern.

The 12 meters refers to the outcome of a formula combining four dimensions of the yacht. As a public service, we herewith print the formula and urge you to commit it to memory or clip it for future reference as the America’s Cup competition heats up: L + 2D - F + S divided by 2.37 equals 12 meters.

L is the length of the yacht, which is measured along a specified height above the waterline. D is the girth difference, which is the difference between the length of a vertical line along the contour of the yacht’s hull from a certain point above the waterline to a certain point below it, minus the straight-line distance between the two points.

F is the freeboard, which is the height of the deck above the waterline measured at a certain point along the length of the boat.

S is the square root of the sail area.

Got that?