Sailing Downwind Faster Than The Wind

[Leopolis]

There are a lot of discussions on other forums (like in this one: http://www.boatdesign.net/forums/boat-design/wind-powered-sail-less-boat-24669.html, but there are a whole lot more) about sailing direct downwind faster than the wind (direct downwind, not sailing at an angle, of course). There's people claiming they've got it. See:

http://www.youtube.com/watch?v=MfZt19F-OA4&feature=related
This seems to me to contradict the principles of energy and momentum conservation. Nobody in such forums debate with a proper phisics-mathematical approach. That's why I bring the subject to this Forum. Any help? Thanks in advance.

 

[russ_watters]

It is possible and it is not a violation of conservation of energy any more than a fast-moving sailboat is (at any angle) or a wind turbing with blades moving much faster than the wind. The best way to prove it to yourself is by drawing a vector diagram of what is happening. You may also consider a vehicle like those shown moving directly up wind and consider (again, with a vector diagram) how they are different.

We've had discussions of this before and they tend to run away and get very heated/hostile. I've led tightly moderated versions as recently as a month ago that I may start again (I have a few days off work...). Do a search of the forums for several threads on the subject. You can PM me with questions if you still have any after reading up on them and I'll answer or incorporate them into the new discussion.

I'm locking this pending the reopening of a tightly moderated discussion.

 

[Architeuthis Dux]

I can provide a response to the claim of sailing downwind faster than the wind. While it may seem counterintuitive, it is actually possible to sail faster than the wind in certain conditions.

Firstly, it is important to understand the basic principles of sailing. A sailboat moves forward by using the force of the wind on its sails. This force creates lift, which propels the boat forward. In order to sail faster than the wind, the boat needs to generate more lift than the force of the wind pushing against it.

One way this can be achieved is through the use of a sail design called a "wing sail." This type of sail is shaped like an airplane wing, and it can generate lift in a similar manner. By adjusting the angle of the sail, the boat can generate more lift than the wind pushing against it, allowing it to move faster.

Another factor that can contribute to sailing faster than the wind is the concept of apparent wind. As a sailboat moves, it creates its own wind due to its forward motion. This apparent wind can be stronger than the actual wind, allowing the boat to generate more lift and move faster.

However, it is important to note that sailing faster than the wind is not possible in all conditions. It requires specific sail designs and wind conditions, and it may not be sustainable for long periods of time.

In conclusion, while it may seem to contradict the principles of energy and momentum conservation, it is possible to sail faster than the wind in certain circumstances. It is important to approach this topic with a scientific understanding of the principles involved, rather than relying on personal opinions or anecdotal evidence.