We are having so much fun in the other physics threads I thought I’d bring something else up. This is a discussion I have seen in several forums over the years and I never saw it settled. The question is:
**If I design a boat that has a windmill facing into the wind which moves a propeller in the water… could this boat sail directly into the wind? ** (Note “directly into the wind” not just upwind)
The intuitive answer is “NO”. (If your intuition is saying “yes” there’s a one in a million chance you are a genius but there’s an almost certainty that you are not understanding the problem or you are really dense. In this last case please think twice before posting).
In past discussions there seemed to be a consensus that this was not possible. And yet, there was a consensus that a car on a solid track could sail upwind if fitted with a similar windmill. I was never comfortable with this state of things but really could not find a better answer.
While I was having lunch today I was thinking about this and suddenly it hit me! It is possible! It has to be possible. It does not go against anything we know, only our intuition.
Of course our intuition is often wrong. I still remember when I did not understand that sailing directly downwind is not the most efficient point of sail. In fact, it is quite inefficient. I also remember there was a time when I did not understand how a boat could sail faster than the wind. It seemed quite impossible. And yet, now, after some thinking and learning I understand both points perfectly and my intuition tells me something different than what it did before.
So, today I have had one of those revelations and I now firmly believe it is possible to sail upwind in a boat fitted with a windmill. I m not saying it would be very fast or efficient, just that it is theoretically possible, at least under a certain range of conditions. I mean wind speed in the range that boats use for sailing. In fact, with an optimized design it may be more efficient than a “traditional” sailboat.
OK, now I want to hear arguments for and against this hypothesis. Feel free to use the railroad car with a windmill as a comparison to support your argument. But I would like to hear some solid argument pro or con. You do not need to tell us what your intuition says as we all agree on that.
As a side issue I will relate that, some years ago, some other yatch guy was intent at explaining to me at a party his theory about “free flying” sails, this is to say sails with no spars, like a kite. At the time I did not know enough and he got me thinking. Today it is obvious to me that such sails would only be of any use downwind and could never allow tacking into the wind as traditional sparred sails do.