Home
Back
Hull Speed Formula:
| From: | To: |
Hull speed is the theoretical maximum speed that a displacement hull boat can achieve without planing. It represents the speed at which the boat's bow and stern waves synchronize, creating the most efficient wave pattern for displacement mode travel.
The calculator uses the hull speed formula:
Where:
Explanation: The formula is derived from wave mechanics, where hull speed is proportional to the square root of the waterline length. The 1.5 coefficient converts the theoretical wave speed to practical mph values.
Details: Understanding hull speed is crucial for boat design, performance prediction, and fuel efficiency planning. It helps determine the practical speed limits for displacement hull vessels and aids in selecting appropriate propulsion systems.
Tips: Enter the waterline length in feet. This is the length of the boat where it actually meets the water, not the overall length. The value must be greater than zero for accurate calculation.
Q1: What types of boats does this formula apply to?
A: This formula applies specifically to displacement hull boats. Planing hulls and semi-displacement hulls can exceed these theoretical limits.
Q2: Why is waterline length used instead of overall length?
A: Waterline length determines the wavelength of the boat's wake, which directly affects the hull speed. Overall length includes overhangs that don't contribute to wave-making resistance.
Q3: Can boats exceed their hull speed?
A: Displacement hull boats cannot practically exceed hull speed without planing. Semi-displacement hulls may exceed it with sufficient power, but with dramatically increased fuel consumption.
Q4: How accurate is this calculation?
A: This provides a good theoretical estimate. Actual performance may vary based on hull shape, weight distribution, and sea conditions.
Q5: What is the coefficient for knots instead of mph?
A: For knots, use 1.34 instead of 1.5 in the formula: Speed (knots) = 1.34 × √(Waterline Length).