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. For power boats, it's an important factor in determining efficient cruising speed.

2. How Does the Calculator Work?

The calculator uses the hull speed formula:

Where:

• \( Speed \) — Hull speed in knots
• \( k \) — Hull speed constant (1.3-1.5)
• \( L \) — Waterline length in feet

Explanation: The formula shows that hull speed increases with the square root of the waterline length. The constant k varies based on hull design (1.34 for displacement hulls, higher for semi-displacement hulls).

3. Importance of Hull Speed Calculation

Details: Knowing your boat's hull speed helps determine the most fuel-efficient cruising speed. Exceeding hull speed significantly increases fuel consumption due to increased wave-making resistance.

4. Using the Calculator

Tips: Measure your boat's waterline length accurately. For displacement hulls use k=1.34, for semi-displacement hulls use higher values up to 1.5.

5. Frequently Asked Questions (FAQ)

Q1: Why does hull speed matter for power boats?
A: Even power boats experience increased resistance at hull speed, making it an important efficiency threshold.

Q2: Can power boats exceed hull speed?
A: Yes, but it requires significantly more power and fuel to overcome the increased wave-making resistance.

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

Q4: What's the difference between displacement and planing hulls?
A: Displacement hulls push through water, while planing hulls rise up and skim the surface at higher speeds.

Q5: Does hull shape affect the constant k?
A: Yes, more efficient hull designs can have slightly higher k values, allowing greater speeds for their length.