MARITIME – AILING PERFORMANCE CALCULATOR
Apparent Wind From True
A precise tool.
What is the Apparent Wind From True & How does it work?
The wind you feel on a sailing vessel is a combination of the true wind blowing across the water and the wind generated by the boatβs own motion. This resultant wind is called the apparent wind and it determines the aerodynamic forces on the sails. To predict performance you must convert the true wind vector (speed and angle) into the boatβreferenced frame, then subtract the boatβs velocity vector. The magnitude of this vector is the apparent wind speed, while its direction relative to the bow is the apparent wind angle. Mathematically the apparent wind speed (Va) is derived from the true wind speed (Vt), true wind angle (ΞΈ) and boat speed (Vb) using trigonometric decomposition. This relationship is essential for sail trim, polarβplot calculations and tactical decisions on the water.
\sqrt{(V_t \cos theta – V_b)^2 + (V_t \sin theta)^2}
V_t = true wind speed (knots)
V_b = boat speed (knots)
theta = true wind angle relative to bow (degrees)
V_a = apparent wind speed (knots)
V_b = boat speed (knots)
theta = true wind angle relative to bow (degrees)
V_a = apparent wind speed (knots)
Parameters
Result
β
Frequently Asked Questions
What is the difference between true wind and apparent wind?
True wind is the actual wind speed and direction measured relative to the ground. Apparent wind is what a sailor feels on the boat, influenced by both the true wind and the boat’s motion.
How do I use this calculator for my sailboat?
Input your sailboat’s velocity, the true wind speed, and its angle relative to the bow. The calculator will output the apparent wind speed and direction.
Why is it important to know the apparent wind on a sailboat?
Knowing the apparent wind helps sailors adjust their sails for optimal performance, ensuring they harness the wind effectively for navigation and speed.
Can this calculator handle different types of sailboats?
Yes, the calculator can be used for various sailboat types as long as you input accurate velocity and true wind data specific to your boat’s situation.
What units should I use when entering data into the calculator?
Use consistent units such as knots for speed and degrees for angles. The calculator will provide results in the same units used for input.
Is there a way to save my calculations for later reference?
While the calculator itself may not have a built-in save feature, you can manually record your inputs and outputs for future reference.
Can this calculator also be used for kitesurfing or windsurfing?
Yes, the principles of apparent wind apply to kitesurfing and windsurfing as well. You can use similar calculations to optimize your equipment settings based on wind conditions.
Results are for informational purposes only and do not constitute professional advice.