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 a hull coefficient that accounts for hull shape.

2. How Does the Calculator Work?

The calculator uses the hull speed formula:

Where:

• \( Speed \) — Hull speed in knots
• \( k \) — Hull coefficient (typically 1.34 for most boats)
• \( L \) — Waterline length in feet

Explanation: The formula shows that hull speed increases with the square root of the waterline length. Longer boats can theoretically go faster than shorter ones.

3. Importance of Hull Speed Calculation

Details: Knowing your boat's hull speed helps in understanding performance limits, fuel efficiency, and when planning passages or races.

4. Using the Calculator

Tips: Enter waterline length in feet and select appropriate hull coefficient (1.34 for average hulls, higher for performance hulls). All values must be valid (L > 0, k between 1.3-1.5).

5. Frequently Asked Questions (FAQ)

Q1: What is a typical hull coefficient value?
A: Most displacement hulls use 1.34. Racing sailboats might use 1.5, while heavy barges might use 1.3.

Q2: Can boats exceed hull speed?
A: Yes, with sufficient power some boats can plane or semi-plane, exceeding theoretical hull speed.

Q3: How do I measure waterline length?
A: Measure the length of the boat at the water's surface from bow to stern at normal load.

Q4: Does hull speed apply to all boat types?
A: No, it primarily applies to displacement hulls. Planing hulls can exceed this speed.

Q5: Why is hull speed important for sailboats?
A: It helps sailors understand when additional sail area becomes inefficient for speed gain.