The D/L ratio is a non-dimensional figure derived from the displacement in tons (of 2240 lbs) divided by .01 LWL cubed, or, Dt/(.01 LWL)3.
The SA/D ratio is the sail area in sq. ft. divided by the displacement in cubic feet to the 2/3 power, or SA/D.667 . 
The formula is the maximum beam divided by the cube root of the displacement in cubic feet; B/Displ.333. The displacement in cubic feet can be found by dividing the displacement in pounds by 64, of course.
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