1. What is Hull Speed?

Definition: Hull speed is the theoretical maximum speed a displacement hull can achieve without planing.

Purpose: It helps boat designers and sailors understand the speed potential of a vessel based on its waterline length.

2. How Does the Hull Speed Formula Work?

The calculator uses the formula:

Where:

• \( HS \) — Hull speed (knots)
• \( LWL \) — Waterline length (feet)

Explanation: The formula relates a boat's maximum efficient speed to the square root of its waterline length, with 1.34 being the empirical coefficient for displacement hulls.

3. Importance of Hull Speed Calculation

Details: Understanding hull speed helps in boat design, performance prediction, and fuel efficiency calculations.

4. Using the Calculator

Tips: Simply enter the waterline length in feet. The value must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: Why is hull speed important?
A: It indicates the speed at which wave-making resistance increases dramatically, making higher speeds inefficient for displacement hulls.

Q2: Can boats exceed hull speed?
A: Yes, but it requires significantly more power. Planing hulls can exceed it by rising over their bow wave.

Q3: Does hull shape affect the 1.34 coefficient?
A: Yes, fine-lined hulls might use 1.25-1.3, while fuller hulls might use 1.4-1.5.

Q4: How do I measure waterline length?
A: It's the length of the boat at the water's surface from bow to stern at normal load.

Q5: Does this apply to all boats?
A: No, it's primarily for displacement hulls. Planing hulls and multihulls behave differently.