1. What is Hull Speed?

Hull speed is the theoretical maximum speed a displacement hull can achieve without planing. It's determined by the waterline length of the boat and represents the point where the boat's bow wave equals the length of the waterline.

2. How Does the Calculator Work?

The calculator uses the hull speed formula:

Where:

• \( \text{LWL} \) — Waterline length in feet
• 1.34 — Empirical coefficient for displacement hulls

Explanation: The formula shows that hull speed increases with the square root of the waterline length. The 1.34 coefficient is derived from observations of wave-making resistance characteristics.

3. Importance of Hull Speed Calculation

Details: Knowing your boat's hull speed helps in sail trim optimization, fuel efficiency calculations, and understanding performance limitations. Exceeding hull speed requires significantly more power.

4. Using the Calculator

Tips: Enter the waterline length in feet (measure from bow to stern at the waterline). The value must be greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: Can boats exceed hull speed?
A: Yes, but it requires significantly more power. Planing hulls can exceed hull speed by rising up on top of the water rather than pushing through it.

Q2: Does hull speed apply to all boats?
A: No, it primarily applies to displacement hulls. Planing hulls and semi-displacement hulls can exceed this theoretical limit.

Q3: How accurate is the hull speed formula?
A: It's a good rule of thumb but actual performance depends on hull shape, weight, and other factors. Modern designs may exceed this by 10-20%.

Q4: Why is waterline length important?
A: Longer waterline creates longer waves, allowing higher speeds before wave-making resistance becomes prohibitive.

Q5: How does hull speed affect sailing?
A: Sailboats typically perform most efficiently near hull speed. Exceeding it requires exponential increases in wind power.