True Wind vs. Apparent Wind
We’ve created an interactive animation here so that you’ll instantly “get” what everyone tries to explain laboriously on a blackboard without much success.
Click and drag on the slider bar. As the car speeds up, the wind increases in velocity and the direction of origin feels like it moves forward. That’s apparent wind – it’s what your hand feels out of the window and on a boat it’s what the sails feel. If you stop the car, the apparent wind goes back to be the same as the true wind. The true wind stays the same regardless of your speed. That’s it! Now you understand true versus apparent wind.
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Figure 1.2-1 Animation of a Car Moving in Wind
Just one thing to note which you’ll use later on in this sailing course. Observe that the true wind is always coming more from the back end of the car. It’s the same on a boat. When you’re moving along and point to where the apparent wind is coming from, the real true wind will be coming from further towards the back of the boat. As a general (really general) rule of thumb (unless you’re going downwind), if you point about 15 degrees back from the apparent wind – that’s about (double about) the direction of the true wind. The true wind is said to be “Aft” of the apparent wind.
