COMPARING DESIGN RATIOS

You can learn a lot about a boat from its published ratios

By the SAIL staff

When buying a boat, consider how its ratios compare with those of similar boats in its category. DISPLACEMENT-LENGTH RATIO The displacement-length ratio (D/L) is a nondimensional expression of how heavy a boat is in relation to its waterline length. A D/L is calculated by dividing a boat’s displacement in long tons (2,240lb) by one one-hundredth of the waterline length (in feet) cubed. Since the displacement in long tons can be expressed as a volume (in cubic feet of seawater), and since length-cubed is also volumetric, the D/L formula is nondimensional—the units of the numerator and the denominator are the same, feet cubed. The advantage of this is that the D/L can be used to compare the relative heaviness of boats no matter their size. A boat with a 25ft waterline and one with…

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Sail - New Boat & Gear Review (Digital) - 1 Issue, 2019

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