1. What is Crouch's Formula?

Crouch's formula is a fundamental equation in naval architecture that estimates a boat's speed based on its horsepower and displacement. It provides a practical way to predict performance characteristics during boat design and evaluation.

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 optimization, engine selection, and understanding the relationship between power, weight, and speed for different hull types.

4. Using the Calculator

Tips: Enter horsepower in hp, displacement in lbs, and select the appropriate Crouch constant based on your boat type. All values must be positive numbers.

Crouch Constant Guidelines:

• 150: High-speed racing boats
• 190: Light planing hulls and performance boats
• 210: Average runabouts and pleasure boats
• 220: Heavy cruisers and displacement hulls

5. Frequently Asked Questions (FAQ)

Q1: What is the Crouch constant and how do I choose it?
A: The Crouch constant represents hull efficiency. Higher values indicate more efficient hulls. Choose based on your boat type - racing boats use lower values, while efficient cruisers use higher values.

Q2: How accurate is Crouch's formula?
A: It provides good estimates for planing hulls but may be less accurate for displacement hulls or unusual hull forms. Actual performance can vary due to factors like propeller efficiency and hull condition.

Q3: Can I use this formula for sailboats?
A: Crouch's formula is primarily for powerboats. Sailboat speed is more influenced by sail area, wind conditions, and hull shape rather than engine power.

Q4: What if my boat has multiple engines?
A: Use the total combined horsepower of all engines in the calculation.

Q5: How does displacement affect boat speed?
A: Higher displacement requires more power to achieve the same speed. The relationship is inverse - doubling displacement while keeping power constant reduces speed by about 30%.