samoht.com - The Formulas Used to Calculate Sailboat Metrics
The Formulas Used to Calculate Metrics
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Hull speed (measured in knots) is the theoretical limit at which your (displacement)
hull can move through the water. It doesn't matter how much sail is in use, your boat
can't go any faster than this in normal conditions. If you can plane, or are surfing,
then you can/will exceed this speed, but then these aren't normal conditions, are they?
Displacement to Length at Waterline
This is a measurement of how heavy your boat is in relation to its length. Higher
numbers mean you have a heavier boat. On the calculation page, and in my software,
I give pithy comments on the probable performance characteristics of your boat
depending upon this calculation.
Beam to Length on Deck
This number doesn't really have much to do with performance per se, but allows
you to calculate the relative "beaminess" of a given vessel.
Sail Area to Displacement
This number measures the size of your sails versus the displacement of your boat.
This is a measure of how likely you are to be able to get your boat to it's hull speed,
but a good sail area to displacement ratio doesn't guarantee it. This figure, along
with the displacement/LWL metric probably give you your best feel for the relative
performance capacity of a given boat.