Calculating Displacement Ratios

[Tom Wood]

When calculating Displacement/Length ratios and Sail Area/Displacement ratios, I can never come up with the answers that appear in articles and boat builder’s literature. Can you help?

Vick.

Tom Wood responds:

Actually, we've already published several articles that explain those formulas, for example, Beth Leonard's Comparing Cruising Boats and Randy Harman's Choosing the Right Boat.

The trouble most people run into when running these numbers is: (1) not using the correct 2,240 pounds for a long ton, (2) not using the correct 64 pounds for the displacement of one cubic foot of seawater, and (3) difficulties calculating displacement to the 2/3 power (the cubic root of displacement in cubic feet, squared), which usually takes either a high-powered scientific calculator or a lot of trial and error.