Speed / Length Ratio (S/L)
This ratio allows you to determine hydrodynamically similar speeds for yachts with different waterline lengths.
S/L Calculator
The formula
S/L = Speed in knots / sqrt(WL in feet)
Speed in knots
LWL in decimal feet
S/L Ratio =
One common use of the S/L ratio is to determine the maximum speed of a displacement hull. Generally under normal sailing conditions, any boat with a D/L ratio much over 150 will be limited to a maximum S/L ratio of about 1.34
Hull Speed Calculator
The formula
Hull Speed = 1.34 x sqrt(WL in feet)
LWL in decimal feet
Hull Speed =
Caution & Warning....
The waterline length should be for the hull in an upright (non-heeled) condition.