Physics of Sailing Video 4: True and Apparent Wind

This video, the forth in my videos about the Physics of Sailing, describes the True Wind and the Apparent Wind when you are under sail, what they are, and how they affect your sailing.
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Thanks again for watching!

[@alanjm1234]

The extreme fast foiling boats make all this stuff truly mind boggling. They sail upwind even when they're sailing downwind. And do so at around 4 times as fast as the true wind!

[@gnocchi.artyst]

Very clear explanation and diagrams. It’s easy to “see” the winds with the diagrams in your head when on water. Thank you!

[@peterworsley4699]

It's been proved that you can sail downwind faster than the wind. But only on land so far.

[@abdulkkhan5095]

Best explanations I have heard so far. Awesome.

[@jordiegundersen1465]

Thank you. At last a tutor that explains it well and effectively to a total beginner. 🎉❤

[@basedonprinciple]

Finally! You explicitly answered my question regarding trim: which wind do we trim to? As a beginner I didn’t get a straight answer to this.

[@marioandresheviacavieres1923]

Gracias

[@jackgalloway8314]

OK. That's alrite. Thankyou

[@TheEvade84]

Super clear, thankyou. A question I am sruggling to answer: Im pondering what is minimum drag coefficient from the keep and hull in water to make a sail work? A sail boat that floated in air wouldn't work too well. I presume you need two mediums 1 for the sail another for the body to gain traction and create momentum.

[@DabskieDabs]

Thanks for sharing this very informative knowledge .

[@jwebster5840]

Well done Owen, many thanks!

[@keithlittlebury2986]

I always wondered did my burgee/wind vein indicate the true or apparent wind? Now I know thank you, It's quite apparent.

[@erents1]

Well done lecture. 👍🏼👍🏼

[@humlakullen]

I’m confused… At 6:00 you said you can’t sail downwind, because there will be no wind to fill your sails..? I thought the whole purpose of sailing was to have the wind push the sails, right?

[@alanjm1234]

What he said was that you can't sail dead downwind at the same speed as the wind. This is correct, because if you travel at the same speed and direction as the wind, you will feel no wind, so there would be no pressure on your sails. Most boats can only manage about 50% or less of wind speed dead down wind. Big downwind sails like spinnakers can improve this, but you still can't match the wind speed because the hull(s) have drag in the water. (A hot air balloon can actually match wind speed dead downwind because it has no drag against the land.)

[@humlakullen]

@@alanjm1234 👍

[@space_speaker]

While your words are correct, your diagram and equations are not. At 6:47 your diagram is not correct. The induced wind vector is pointed at the nose, say south (say boat is traveling north). So the equation is still Induced + True = Appearant. Sure, induce subtracts from your true like you say when going downwind, but that's evident by the math. Just let the math do the work. Why arbitrarily reverse the induced wind's vector's direction, then change the sign to a negative (i.e. subtracting), introducing a second equation to remember, to make the math work? Just let Induced + True = Appearant for ALL times. It seems your making is overly complicated. Am I wrong?