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Boat Speed Formula:
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The boat speed formula, also known as Crouch's formula, estimates the theoretical top speed of a displacement hull boat based on horsepower and weight. It provides a practical way to predict boat performance during design and planning stages.
The calculator uses Crouch's formula:
Where:
Explanation: The formula shows that boat speed is proportional to the square root of the power-to-weight ratio, scaled by the Crouch constant which varies by boat type.
Details: Accurate speed estimation helps in boat design, engine selection, performance prediction, and safety planning. It's essential for marine engineers, boat builders, and enthusiasts.
Tips: Enter Crouch constant (typically 150 for runabouts, 180 for racing boats, 220 for high-speed runabouts), horsepower, and displacement weight. All values must be positive numbers.
Q1: What are typical Crouch constant values?
A: Common values: 150 for standard runabouts, 180 for light racing boats, 190-220 for high-performance boats, 120 for heavy displacement hulls.
Q2: How accurate is this formula?
A: It provides good estimates for displacement hulls but may be less accurate for planing hulls or unusual boat designs. Real-world factors like hull condition and water conditions affect actual speed.
Q3: What is displacement weight?
A: Displacement refers to the total weight of the boat including hull, engine, fuel, passengers, and cargo - essentially the total weight the boat must push through water.
Q4: Can this formula be used for all boat types?
A: It works best for displacement hulls. For planing hulls, semi-displacement hulls, or multi-hull boats, additional factors need consideration.
Q5: Why use knots instead of mph?
A: Knots (nautical miles per hour) are the standard speed unit in marine navigation worldwide, as they relate directly to latitude measurements.