1. What Is Hull Speed On A Sailboat?

Definition: Hull speed is the theoretical maximum speed a displacement hull can efficiently travel through water without planing.

Purpose: This calculation helps sailors understand their boat's performance limitations and optimal cruising speed.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

Explanation: The formula calculates the speed at which the boat's bow wave length equals the waterline length, creating maximum wave-making resistance.

3. Importance of Hull Speed Calculation

Details: Knowing your hull speed helps with voyage planning, fuel efficiency, and understanding when additional power becomes ineffective.

4. Using the Calculator

Tips: Simply enter your boat's waterline length in feet. The waterline length is the length of the boat at the surface when normally loaded.

5. Frequently Asked Questions (FAQ)

Q1: Can a boat exceed its hull speed?
A: Yes, but it requires exponentially more power. Some modern hull designs can exceed this speed through planing or semi-planing.

Q2: Why is the constant 1.34 used?
A: This empirical constant accounts for the relationship between wave-making resistance and boat length in salt water.

Q3: Does hull speed apply to all boats?
A: No, it only applies to displacement hulls. Planing hulls can exceed this speed when enough power is applied.

Q4: How does hull shape affect hull speed?
A: While the formula is length-based, hull shape can affect how efficiently a boat reaches its theoretical hull speed.

Q5: What's the typical hull speed for common sailboats?
A: A 30-foot sailboat (25 ft LWL) ≈ 6.7 knots, 40-footer (35 ft LWL) ≈ 7.9 knots, 50-footer (45 ft LWL) ≈ 9 knots.