1. What is Hull Speed?

Hull speed is the speed at which the wavelength of a boat's bow wave equals the boat's waterline length, creating increased drag. It represents the theoretical maximum speed a displacement hull can achieve without planing.

2. How Does the Calculator Work?

The calculator uses the hull speed formula:

Where:

• \( k \) — Hull speed constant (typically 1.34 for most boats)
• \( \text{Length} \) — Waterline length in feet

Explanation: The formula shows that hull speed increases with the square root of the waterline length. The constant k varies slightly depending on hull design (1.3-1.5).

3. Importance of Hull Speed Calculation

Details: Knowing your boat's hull speed helps in voyage planning, fuel efficiency optimization, and understanding performance limitations of displacement hulls.

4. Using the Calculator

Tips: Enter waterline length in feet and select appropriate k value (1.34 for most monohulls). All values must be valid (length > 0, k between 1.3-1.5).

5. Frequently Asked Questions (FAQ)

Q1: What's the typical k value for different boats?
A: 1.34 for most monohulls, 1.3 for heavy displacement boats, up to 1.5 for some multihulls or fine-hulled vessels.

Q2: Can boats exceed hull speed?
A: Displacement hulls can exceed it with sufficient power but with dramatically increased resistance. Planing hulls can exceed it by rising up on the water surface.

Q3: How do I measure waterline length?
A: Measure the straight-line distance from bow to stern at the water's surface when the boat is normally loaded.

Q4: Does hull speed apply to all boats?
A: No, it mainly applies to displacement hulls. Planing hulls and semi-displacement hulls can exceed this speed.

Q5: Why does hull speed matter for sailboats?
A: It helps sailors understand the maximum efficient speed they can achieve under sail power alone without resorting to surfing or planing.