1. What is Displacement Speed?

Displacement speed is the theoretical maximum speed a displacement hull can achieve without planing. It's determined by the waterline length of the vessel and represents the point where the hull creates a single wave equal to the waterline length.

2. How Does the Calculator Work?

The calculator uses the displacement speed formula:

Where:

• \( Speed \) — Displacement speed in knots
• \( Waterline\ Length \) — Length of the boat at waterline in feet
• 1.34 — Empirical coefficient for displacement hulls

Explanation: The formula is derived from wave-making resistance theory, where hull speed is limited by the wavelength a hull can efficiently produce.

3. Importance of Displacement Speed

Details: Knowing a boat's displacement speed helps in voyage planning, fuel efficiency calculations, and understanding the vessel's performance limitations.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Can boats exceed displacement speed?
A: Yes, but only with planing hulls that rise up and plane on the water surface, which requires significantly more power.

Q2: Why is the coefficient 1.34?
A: This empirical value accounts for the relationship between wave formation and hull speed in displacement vessels.

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

Q4: How accurate is this calculation?
A: It provides a theoretical maximum; actual speed may vary based on hull shape, load, and sea conditions.

Q5: What's a typical displacement speed for sailboats?
A: Most cruising sailboats (30-50 ft waterline) have displacement speeds between 6-9 knots.