1. What is the Horsepower to Speed Formula?

The horsepower to speed formula (Crouch's formula) calculates boat speed based on horsepower, displacement, and a constant specific to the hull type. It's widely used in marine engineering to estimate vessel performance.

2. How Does the Calculator Work?

The calculator uses Crouch's formula:

Where:

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

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

3. Importance of Speed Calculation

Details: Accurate speed estimation is crucial for boat design, performance prediction, fuel efficiency planning, and comparing different vessel configurations.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What are typical Crouch constant values?
A: Displacement hulls: 120-150; Semi-displacement: 150-200; Planing hulls: 200-250; High-speed racing boats: 250+.

Q2: How accurate is this formula?
A: Very accurate for similar hull types when proper C values are used. Less accurate for unconventional hull designs.

Q3: Does this work for all boat types?
A: Best for monohulls with conventional propulsion. Less accurate for catamarans, trimarans, or boats with unusual propulsion systems.

Q4: What affects the Crouch constant?
A: Hull shape, length-to-beam ratio, weight distribution, and hydrodynamic efficiency all influence the C value.

Q5: Can I use this for sailboats?
A: Primarily for powerboats. Sailboat speed depends more on sail area and wind conditions than engine power.