Hull Speed Calculator

Calculate:

Waterline Length:

Desired Hull Speed:

1. What is a Hull Speed Calculator?

Definition: This calculator determines the theoretical maximum speed (hull speed) of a displacement vessel based on its waterline length, or the required waterline length for a desired hull speed.

Purpose: It helps boat designers, sailors, and enthusiasts estimate the maximum efficient speed of a vessel or design a boat to achieve a specific speed.

2. How Does the Calculator Work?

The calculator uses the following formulas:

\( V_{\text{hull}} = 1.34 \sqrt{L_{\text{waterline}}} \)

\( L_{\text{waterline}} = \left( \frac{V_{\text{hull}}}{1.34} \right)^2 \)

Where:

\( V_{\text{hull}} \): Hull speed (in knots, mph, or km/h, converted to/from knots).
\( L_{\text{waterline}} \): Length of the waterline (in feet, meters, or inches, converted to/from feet).

Steps:

Select the calculation mode: Hull Speed or Waterline Length.
Enter the Waterline Length (for Hull Speed) or Desired Hull Speed (for Waterline Length) and select the unit.
Validate inputs to ensure they are positive.
Compute the result using the appropriate formula, converting units as needed.
Display the result to 3 decimal places with the unit dropdown next to it.

3. Importance of Hull Speed Calculation

Calculating hull speed is crucial for:

Boat Design: Helps designers ensure a vessel meets speed requirements efficiently.
Fuel Efficiency: Operating near hull speed minimizes fuel consumption for displacement boats.
Performance Planning: Assists sailors in planning trips and understanding vessel capabilities.

4. Using the Calculator

Example 1: Calculate the hull speed for a boat with a waterline length of 25 feet:

Waterline Length: 25 feet
Hull Speed: \( 1.34 \sqrt{25} = 1.34 \times 5 = 6.7 \, \text{knots} \)
Result in mph: \( 6.7 \times 1.15078 \approx 7.710 \, \text{mph} \)

Example 2: Calculate the required waterline length for a hull speed of 8 knots:

Desired Hull Speed: 8 knots
Waterline Length: \( \left( \frac{8}{1.34} \right)^2 \approx (5.970)^2 \approx 35.641 \, \text{feet} \)
Result in meters: \( 35.641 / 3.28084 \approx 10.866 \, \text{meters} \)

5. Frequently Asked Questions (FAQ)

Q: What is hull speed?
A: Hull speed is the theoretical maximum speed a displacement vessel can achieve efficiently, based on its waterline length.

Q: Why does hull speed depend on waterline length?
A: Hull speed is related to the wave created by the boat; longer waterlines allow for faster wave propagation, increasing the maximum efficient speed.

Q: Can a boat exceed its hull speed?
A: Yes, but it requires significantly more power and may cause the boat to plane, which is less efficient for displacement hulls.