1. What is the Boat Speed Formula?

The boat speed formula, also known as Crouch's formula, estimates a boat's speed in knots based on horsepower, displacement, and a constant factor that accounts for hull type and efficiency.

2. How Does the Calculator Work?

The calculator uses Crouch's formula:

Where:

• \( V \) — Boat speed in knots
• \( C \) — Crouch constant (dimensionless)
• \( HP \) — Horsepower (hp)
• \( D \) — Displacement in pounds (lbs)

Explanation: The formula shows that boat speed is proportional to the square root of the power-to-weight ratio, with the Crouch constant accounting for hull efficiency.

3. Importance of Boat Speed Calculation

Details: Accurate speed estimation helps in boat design, performance prediction, engine selection, and fuel efficiency planning. It's essential for marine engineers, boat builders, and enthusiasts.

4. Using the Calculator

Tips: Enter Crouch constant (typically 150-250 for planing hulls), horsepower, and displacement in pounds. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical Crouch constant values?
A: Common values range from 150 for heavy displacement hulls to 230 for high-speed planing hulls. Racing boats can have constants up to 250.

Q2: How accurate is Crouch's formula?
A: It provides good estimates for planing hulls but may be less accurate for displacement hulls operating below hull speed.

Q3: What is hull speed for displacement boats?
A: Hull speed = 1.34 × √(waterline length in feet). Displacement boats cannot exceed this speed efficiently.

Q4: Can this formula be used for sailboats?
A: Primarily for powerboats. Sailboat speed depends more on sail area, wind conditions, and hull shape.

Q5: How does boat weight affect speed?
A: Heavier boats require more power to achieve the same speed. The relationship follows the square root function in the formula.