On page 27, "The Annapolis Book . . .
of Seamanship", it states: SA/D is equal to the sail area divided by the displacement in cubic feet to the 2/3rds power. To find displacement in cubic feet divide the true displacement by 64 in salt water or 62.2 in fresh water. Example of a Sabre 30: 462 divided by ((9400/64), that result squared and the cube root of that result is equal to 29.7. Then 462 / 29.7 equals your SA/D.