No!
As soon as it reaches the speed of the wind it cannot get more energy from it. More energy would be necessary to push thru the friction from the then slower wind.
100% efficiency matching the speed of the wind is highly improbable.
Brain teaser: wind power conundrum
- Thread starter Arthur Smith
- Start date
No!
As soon as it reaches the speed of the wind it cannot get more energy from it. More energy would be necessary to push thru the friction from the then slower wind.
100% efficiency matching the speed of the wind is highly improbable.
Arthur Smith
Registered Member
No question sailboats can exceed wind speed. Ice yachts more so. What neither can do is sail directly downwind at greater than windspeed.
Again, they definitely can. I've done it. It all has to do with the difference between windspeed and water speed.
Arthur Smith
Registered Member
Are you sure about the precise constraints I'm setting? Wind heading
Let me be clear as I can. The wind is blowing consistently from East to West at 10 knots. You steer a consistent straight course of due West. There is no current. You can sail faster than 10 knots?
Arthur Smith
Registered Member
Ah we have a skeptic. Have you glanced at any previous comments?
Ah - if there is no current then you can't.
I regularly went faster downwind than the wind speed by launching in light winds during the outgoing tide.
Arthur Smith
Registered Member
Sure. But no wind-powered vehicle on land, water or ice with any arrangement of sails can exceed windspeed going directly downwind. Agreed?
Mostly yes. There are two exceptions:
-A current that is with the wind or
-A wind turbine/propeller system similar to the land vehicle mentioned above.
I don't think so. Some sailing boats can travel faster than the wind, but not when travelling directly downwind.
Edit to add: it is not entirely clear what you mean by "powered only by the wind". For instance, the propeller-powered car mentioned previously can travel directly downwind faster than the wind, but that relies on a power transfer from the wind-driven propeller to the wheels (which are in contact with the ground, obviously).
DaveC426913
Valued Senior Member
Although that is still, by definition, "powered only by the wind", since the wind is the only power source.
Arthur Smith
Registered Member
What Dave said.
Think about it. If the wind were not blowing, in still air (relative to ground surface) the cart will not move. The energy in moving air is effectively limitless provided you can harvest or exploit it. The power source for the cart is wind, exploited by the propellor "drilling" into the wind, gearing up the force from the ground on the wheel.
Well, the power source is the difference in speed between the wind and the ground. Take away either one and the thing doesn't work.
Arthur Smith
Registered Member
δος μοι που στω και κινω την γην
In fact, much work was done with models in still air using exercise treadmills.
DaveC426913
Valued Senior Member
If you take way the wheels it doesn't work either, but that doesn't make them a power source.
Right. The power source is the difference in speed. The wheel (and prop, and belt drive) are just the things that harvest that power.If you take way the wheels it doesn't work either, but that doesn't make them a power source.
Arthur Smith
Registered Member
In Classical Greek
δός μοι πού στω και κινήσω την γην
Apologies for "incorrect" post. Classical=>Attic=>Doric
But the sentiment is the same. With a lever and a fulcrum, you can move anything.
ETA: and somewhere to stand, of course!
δός μοι πού στω και κινήσω την γην
Apologies for "incorrect" post. Classical=>Attic=>Doric
But the sentiment is the same. With a lever and a fulcrum, you can move anything.
ETA: and somewhere to stand, of course!
Arthur Smith
Registered Member
Anyway, thanks fellow sciforums members for the feedback. My sudden appearance here was not due to chance. It was prompted by reading a comment elsewhere by someone using the handle "AnssiH". AnnsiH (for reasons that are not clear to me) started a thread here at scienceforums. The mod/admin/owner, oceanbreeze, took the unshakeable view that Blackbird is a con and Rick Cavallaro is a crackpot, closing the thread and dumping it in "Silly Claims Forums". Judging by the many other threads that exist elsewhere there with, shall we say, questionable content that are not in "Silly Claims", one has to wonder about arbitrary or capricious decisions.
Anyway, I decided to see if there was a way back to reason. I was previously unaware of scienceforums.com, scienceforums.com nor sciforums.com prior to contact with AnnsiH, who was also new to me as an internet presence but all three sites cropped up so I decided I could make a similar approach on all three and see what transpired. The results from sciforums and scienceforums.net were reasonable, if a little disappointing in that there was no serious doubt that the claim is solid and supported. Scienceforums.com produced a different result.
https://www.scienceforums.com/topic/38816-brain-teaser-the-shell-game/
Anyway, I decided to see if there was a way back to reason. I was previously unaware of scienceforums.com, scienceforums.com nor sciforums.com prior to contact with AnnsiH, who was also new to me as an internet presence but all three sites cropped up so I decided I could make a similar approach on all three and see what transpired. The results from sciforums and scienceforums.net were reasonable, if a little disappointing in that there was no serious doubt that the claim is solid and supported. Scienceforums.com produced a different result.
https://www.scienceforums.com/topic/38816-brain-teaser-the-shell-game/
English translation?