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Hull Speed Formula:
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Hull speed is the theoretical maximum speed that a displacement hull can achieve without planing. It represents the speed at which the wavelength of the boat's wake equals the waterline length, creating significant wave-making resistance.
The calculator uses the hull speed formula:
Where:
Explanation: The formula calculates the speed at which a boat's bow and stern waves synchronize, creating maximum wave-making resistance. The constant 1.34 is derived from wave theory and empirical observations.
Details: Understanding hull speed helps sailors optimize performance, predict voyage times, and manage expectations about a boat's maximum efficient speed under sail power alone.
Tips: Enter the waterline length in feet. This is the length of the boat at the waterline, not the overall length. The value must be greater than zero.
Q1: Can boats exceed their hull speed?
A: Yes, modern designs with fin keels and spade rudders can exceed hull speed through planing or surfing down waves, but it requires significantly more power.
Q2: How accurate is the hull speed formula?
A: It's a theoretical maximum for displacement hulls. Actual performance depends on hull shape, sail area, sea conditions, and other factors.
Q3: Does hull speed apply to powerboats?
A: Only to displacement powerboats. Planing hulls and semi-displacement hulls can exceed this speed with sufficient power.
Q4: What is the significance of waterline length?
A: Longer waterline length generally means higher potential speed, as the wave-making resistance increases more slowly than the boat's length.
Q5: How can I increase my boat's hull speed?
A: The only way to increase theoretical hull speed is to increase waterline length, though optimizing sail trim and hull cleanliness can help achieve maximum potential.