As shown below. But that is externally generated wind. So it's not what the OP is asking about.However, if you have a windmill on a boat, driving a water propeller, it can push the boat against the wind.
Yes, with externally generated wind relative to the surface you can put some of its energy into a battery this way.Aah!!
Then you'd have more wind to drive the windmill. . . so you could charge the
battery, too ??
We need to negotiate just what are the boundaries of the system; fan, fan + sail, fan + infinite sail (massless), fan + infinite source of air, fan + finite source of air, energy source, et cetera....It's an open system.
There was a guy in Camden Maine who had such a craft....this must have been thirty years ago. A turnable windmill attached to the boat propellor. It did actually work and would even travel upwind (if memory serves) but it was not very fast and nobody would write poems about her. As I recall I did a calculation at the time which showed you could go upwind at half the windspeed (ignoring hull friction and assuming a "perfect " propeller). I note that the design did not catch on.However, if you have a windmill on a boat, driving a water propeller, it can push the boat against the wind.
You can consider throwing balls to see that the concept doesn't violate momentum conservation. Aerodynamics then just makes it less efficient, but not impossible.The mis-applications of "intuition" to aerodynamics and propulsion systems are a little more common than just mine.
There is no such speed limit for going directly upwind or downwind in terms of true wind multiple. It only depends on the efficiency, which imposes practical limits:As I recall I did a calculation at the time which showed you could go upwind at half the windspeed (ignoring hull friction and assuming a "perfect " propeller).
Very interesting references. I guess I assumed the Betz limit for my calculation...(it was a long while ago and not really my field! I remember wondering at the time why there was no such limit on a sail. ) Thanks much for the clarification.There is no such speed limit for going directly upwind or downwind in terms of true wind multiple. It only depends on the efficiency, which imposes practical limits:
With less resistance on land more than twice the true wind was achieved in both directions:
There is an old paper by Blackford, that derives a speed limit of 2 x windspeed, by assuming that the maximal upwind speed will be achieved at the Betz limit:Very interesting references. I guess I assumed the Betz limit for my calculation.
Yep. Orbur and Wilville tried it both ways. The etymology of "Purple" was cute in that one too.Just for laughs, I'll recommend Niven's Flying Sorcerers. The mis-applications of "intuition" to aerodynamics and propulsion systems are a little more common than just mine.
Jacques Cousteau implemented a not-especially-dissimilar concept on his supplementally-wind-powered (primarily diesel powered) vessel Alcyone.However, if you have a windmill on a boat, driving a water propeller, it can push the boat against the wind.
He probably wasn't the first. The optician Bernhard Schmidt actually build such boats in the 1920s:Jacques Cousteau dreamed up a way to make a wind turbine that could drive a propeller so that a vessel could go directly into a headwind
We tack upwind , and even downwind. It's faster than the wind on either point of sail.. My point is, postulating a motor facing the wrong way on boats that have been perfected over the centuries for their speed, economy and versatility is beyond silly I have gone 30 MPH on the ocean on my 18'. Physics puzzles are fine. But boats were Man's first vehicles. The engineering, banking, insurance and investing industries all relate back to historic water transport. The boat I currently sail used Formula One computer aided design with millions of data points. Then there are cartoon boats with fans on them. Then there is the difference between beating a dead horse, or in some cases, riding one.Apparently, you missed the point.
Sure, but not directly upwind or downwind.
That "apparent wind" is the vector sum of the wind and the boat velocity. There is no new or faster wind generated on the boat. It is still impossible to continue sailing a conventional sail cat directly into the wind, or when there is no wind.On a reaching course, the side-force pushed on the boat and via the centerboards, are converted into forward motion. As the air accelerates over the wing shaped sails, it creates apparent wind.
Just a plain ol sailor here with no prizes.As pertains to the title of the thread, yes sailboats can provide their own wind. Apparent wind. Three times Utah Catamaran State Champion here.
Uh, 40 large high altitude reservoirs, One Pleistocene lake at 6000'that is 104 square miles, 400,000 years old. Three high volume whitewater rivers, Colorado, San Juan, and the Green, Lake Powell, 162,000 acres, 1900 miles of shoreline. We do ok.Wait, isn't Utah a desert?
Hey, but suppose you had a large bent tube on the intake side of the fan arranged so the intake of the fan was drawn from in front of the sail? That is, the intake tube would bend around the sail. I think you could go a lot faster that way.Myth busters did this: