1. What is the Displacement Hull Speed Formula?

Definition: This formula calculates the theoretical maximum speed of a displacement hull (the point where the hull's wave resistance increases dramatically).

Purpose: It helps boat designers and sailors estimate the practical speed limit for traditional, non-planing boats.

2. How Does the Formula Work?

The formula is:

Where:

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

Explanation: The 1.34 constant comes from wave physics, representing the speed/length ratio where wave-making resistance increases significantly.

3. Importance of Hull Speed Calculation

Details: Knowing hull speed helps in boat design, fuel efficiency planning, and understanding performance limitations of displacement vessels.

4. Using the Calculator

Tips: Simply enter the waterline length of your boat in feet. The calculator will output the theoretical hull speed in knots.

5. Frequently Asked Questions (FAQ)

Q1: What types of boats does this apply to?
A: Traditional displacement hulls (sailboats, trawlers, ships). Not for planing hulls (speedboats) or semi-displacement hulls.

Q2: Can a boat exceed its hull speed?
A: Yes, but it requires exponentially more power and typically involves planing or semi-planing.

Q3: Why is waterline length important?
A: Longer waterline creates longer waves, allowing higher speeds before wave resistance becomes prohibitive.

Q4: Does hull shape affect this calculation?
A: The formula is a general rule. Fine hulls might slightly exceed it, while full hulls might not reach it.

Q5: How accurate is this formula?
A: It's a theoretical maximum. Actual maximum efficient speed varies based on hull design, power, and sea conditions.