Hull Speed Calculator Full Displacement Hull

Hull Speed Formula:

\[ HS_{fdh} = 1.34 \times \sqrt{LWL_{fdh}} \]

Hull Speed (HS_fdh):

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1. What is Hull Speed for Full Displacement Hull?

Hull speed is the theoretical maximum speed a displacement hull can achieve without planing. It's determined by the waterline length of the vessel and represents the point where the wavelength of the boat's wake equals the waterline length.

2. How Does the Calculator Work?

The calculator uses the hull speed formula:

\[ HS_{fdh} = 1.34 \times \sqrt{LWL_{fdh}} \]

Where:

\( HS_{fdh} \) — Hull speed in knots
\( LWL_{fdh} \) — Waterline length in feet
1.34 — Empirical coefficient for displacement hulls

Explanation: The formula is derived from wave-making resistance theory, where hull speed is proportional to the square root of the waterline length.

3. Importance of Hull Speed Calculation

Details: Understanding hull speed is crucial for boat designers, sailors, and marine engineers to predict vessel performance, fuel efficiency, and to optimize hull design for specific speed requirements.

4. Using the Calculator

Tips: Enter the waterline length in feet. The value must be greater than zero. The calculator will compute the theoretical maximum hull speed for a full displacement hull.

5. Frequently Asked Questions (FAQ)

Q1: Why is the coefficient 1.34 used in the formula?
A: The value 1.34 is an empirical constant derived from observations of wave-making resistance for displacement hulls in seawater.

Q2: Can boats exceed their hull speed?
A: Yes, with sufficient power, some displacement hulls can exceed their theoretical hull speed, but it requires exponentially more power and may cause significant increase in wave resistance.

Q3: Does hull speed apply to planing hulls?
A: No, planing hulls can exceed their displacement hull speed by rising up and planing on the water surface rather than displacing it.

Q4: How does waterline length affect hull speed?
A: Longer waterline length generally allows for higher hull speed, as the relationship follows a square root function.

Q5: Are there variations of this formula for different conditions?
A: Yes, some formulas use slightly different coefficients (e.g., 1.3-1.5) based on hull form, but 1.34 is the most widely accepted standard.