High speed crafts (HSC)
TOOLS TO HELP EVALUATE BOATS
If you are in the market for a boat or just want to comparison shop, you can use a few computational tools to help make comparisons. Since these numbers are nondimensional, they can be applied to any size boat. A word of caution, however: don't let the spread between boat sizes get too large, or the comparisions will be distorted. Try to keep a maximum range of about 8 to 10 feet (2.4-3 m) between the smallest and the largest.
Speed - Length ratio
The speed- length (S/L) ratio is derived from the froude number, an S/L of less than the boat is in the displacement mode. Above 2.5 (and sometimes even higher) the boat is planing. Between 1.5 and 2.5, the boat is operating in a semidisplacement mode.
Displacement - Length ratio
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