1. What is Displacement Hull Speed?

The displacement hull speed is the theoretical maximum speed a displacement hull can efficiently travel through water without planing. It's determined by the waterline length of the vessel.

2. How Does the Calculator Work?

The calculator uses the displacement hull speed formula:

Where:

• \( LWL \) — Length at waterline in feet
• 1.34 — Empirical coefficient for displacement hulls

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

3. Importance of Hull Speed Calculation

Details: Knowing a vessel's hull speed helps in designing efficient propulsion systems and understanding fuel consumption patterns. Exceeding hull speed requires significantly more power.

4. Using the Calculator

Tips: Enter the vessel's length at waterline in feet. The value must be greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is length at waterline (LWL)?
A: LWL is the length of the boat from bow to stern where it actually meets the water, which may be shorter than the overall length.

Q2: Can boats exceed hull speed?
A: Yes, but it requires significantly more power and typically involves planing or semi-planing hull designs.

Q3: Does hull speed apply to all boats?
A: No, this formula is specifically for displacement hulls. Planing hulls can exceed this speed with sufficient power.

Q4: Why is the coefficient 1.34?
A: This empirical value comes from wave-making resistance characteristics of displacement hulls in salt water.

Q5: How does water density affect hull speed?
A: The formula assumes salt water. In fresh water, the coefficient might be slightly lower (about 1.31).