1. What is a Sailboat Propeller Size Calculator?

Definition: This calculator estimates the optimal propeller diameter for a sailboat based on engine horsepower and a design constant.

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

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( D \) — Propeller diameter (inches)
• \( HP \) — Engine horsepower
• \( C \) — Design constant (typically 10 for sailboats)

Explanation: The formula calculates the cube root of the horsepower-to-constant ratio to determine propeller diameter.

3. Importance of Proper Propeller Sizing

Details: Correct propeller sizing ensures optimal engine performance, fuel efficiency, and prevents engine strain or underutilization.

4. Using the Calculator

Tips: Enter the engine horsepower and design constant (default 10 for sailboats). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is the design constant (C)?
A: It's an empirical value that accounts for boat type and hull characteristics. 10 is typical for sailboats.

Q2: When would I change the constant value?
A: Adjust for different boat types: use 12-14 for planing hulls, 8-9 for heavy displacement boats.

Q3: Does this consider pitch and blade count?
A: No, this calculates diameter only. Pitch should be determined separately based on boat speed and engine RPM.

Q4: What about high-performance boats?
A: High-speed boats may need different calculations that consider cavitation and slip percentages.

Q5: Should I round the result?
A: Yes, propellers typically come in standard sizes, so round to the nearest available size.