1. What is a Prop Size and Pitch Calculator?

Definition: This calculator estimates the optimal propeller diameter based on power input, rotational speed, water density, and a design constant.

Purpose: It helps marine engineers and boat designers determine the appropriate propeller size for efficient propulsion.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( D \) — Propeller diameter (meters)
• \( k \) — Design constant (dimensionless)
• \( P \) — Power input (Watts)
• \( n \) — Rotational speed (revolutions per second)
• \( \rho \) — Water density (kg/m³)

Explanation: The formula calculates the optimal diameter that balances power absorption with hydrodynamic efficiency.

3. Importance of Proper Propeller Sizing

Details: Correct propeller sizing ensures optimal fuel efficiency, prevents engine overload, and maximizes boat performance.

4. Using the Calculator

Tips: Enter the power in Watts, rotational speed in rev/s, water density (default 1025 kg/m³ for seawater), and design constant (typically 0.8-1.2). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical value for the constant k?
A: For most marine propellers, k ranges between 0.8 and 1.2 depending on the design.

Q2: How does water density affect the calculation?
A: Higher density water requires more power to turn the propeller, affecting the optimal diameter.

Q3: What units should I use for rotational speed?
A: The calculator requires revolutions per second (rev/s). Convert from RPM by dividing by 60.

Q4: Does this include pitch calculation?
A: This calculates diameter only. Pitch is typically determined separately based on desired speed.

Q5: How accurate is this calculation?
A: It provides a theoretical optimum. Real-world factors like hull design may require adjustments.