Sail downwind faster than the wind!
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From: Androcles on 30 Jul 2010 07:50 "John Doe" <jdoe(a)usenetlove.invalid> wrote in message news:4c52ae63$0$9845$c3e8da3(a)news.astraweb.com... | "Cwatters" <colin.wattersNOSPAM TurnersOakNOSPAM.plus.com> wrote: | | > "John Doe" <jdoe usenetlove.invalid> wrote | | >> It is discussed on the website (http://www.physicsforums.com) | >> recently as this year. | >> | >> I see some problems with the idea as argued. They keep talking | >> about wind speed with respect to ground speed as if that is a | >> power generator. They also seem to be pretending that gearing, | >> or the difference between wheel and propeller rotation speeds, | >> is somehow a power source. | > | > That's exactly how it works. The maths proof of how it works and | > a solution for the conditions under which it works is also out | > there on the web. A land based version was recently built and | > tested. It achieved more than twice the wind speed. See Youtube. | > I believe the first working machine to do it was built in the | > 1960's. | > | >> The follow-on argument appears to be that you can sail directly | >> into the wind. | > | > Also possible and has been demonstrated many times, including on | > full size boats. | > | >> I see no prior discussion here on UseNet. On the Internet, I | >> see it is discussed as early as 2007. Apparently the idea was | >> originated by Jack Goodman in 2006. | > | > This has been discussed a million times on different forums. . | > | > Aside: America Cup yachts manage to sail between two points (one | > directly downwind of the other) faster than the wind by | > "tacking" downwind. | | When you are tacking, the wind does not stop blowing against your | sails. I believe it is all part of some joke warfare... | -- A sail is an aircraft wing tipped vertically. The wing is there to fight gravity. The sail produces the same lift but has no gravity to fight against. Tacking makes use of the "lift" to drive the boat "up" except that "up" is now forward. The aerodynamic principle is the same, the terminology is different. Another name for a glider is a sailplane. A yacht is a sailplane tipped on its side. The second "wing" is the keel.
From: Cwatters on 30 Jul 2010 12:24 "John Doe" <jdoe(a)usenetlove.invalid> wrote in message news:4c52b7da$0$8901$c3e8da3(a)news.astraweb.com... > "Cwatters" <colin.wattersNOSPAM(a)TurnersOakNOSPAM.plus.com> wrote: > >> http://www.wired.com/autopia/2010/07/its-settled-downwind-faster-than-the-wind-officially-possible/ > > Lots of things are possible on moderated websites/forums, just > depends on the editor. I am sure there is hype about perpetual > motion machines too. Probably but does that somehow stop you researching this project yourself? If I remember correctly it was sponsored by Google and a few other corporations. >> http://www.youtube.com/watch?v=7SYvg40NHtc >> >> http://www.youtube.com/watch?v=EEuAqq8FINw >> >> http://www.youtube.com/watch?v=PCu9wHvamtI > > YouTube is a valuable resource for me, especially lately while > trying to figure out the best way to build powered inline skates. > But YouTube video is hardly scientific. Oh I agree. Next time you hear they plan to run the vehicle buy yourself a plane ticket and go measure it's performance yourself. It's probably the only way you will believe that it's possible to go down wind faster than the wind.
From: jbriggs444 on 30 Jul 2010 12:46 On Jul 30, 6:11 am, "Cwatters" <colin.wattersNOS...(a)TurnersOakNOSPAM.plus.com> wrote: > "John Doe" <j...(a)usenetlove.invalid> wrote in message > > news:4c529e1b$0$21228$c3e8da3(a)news.astraweb.com... > > > It is discussed on the website (http://www.physicsforums.com) > > recently as this year. > > > I see some problems with the idea as argued. They keep talking > > about wind speed with respect to ground speed as if that is a > > power generator. They also seem to be pretending that gearing, or > > the difference between wheel and propeller rotation speeds, is > > somehow a power source. > > That's exactly how it works. The maths proof of how it works and a solution > for the conditions under which it works is also out there on the web. A land > based version was recently built and tested. It achieved more than twice the > wind speed. See Youtube. I believe the first working machine to do it was > built in the 1960's. > > > The follow-on argument appears to be that you can sail directly > > into the wind. > > Also possible and has been demonstrated many times, including on full size > boats. > > > I see no prior discussion here on UseNet. On the Internet, I see > > it is discussed as early as 2007. Apparently the idea was > > originated by Jack Goodman in 2006. > > This has been discussed a million times on different forums. . > > Aside: America Cup yachts manage to sail between two points (one directly > downwind of the other) faster than the wind by "tacking" downwind. If they > can do it the rest is just engineering. [Apologies -- my first time seeing the conundrum] Let me see if I can reason through it from first principles... So if you were going upwind you'd be drawing power from the propellor in the air and generating thrust from the propellor in the water (or from the tires on the road). And if your efficiency was bad, you could just gear things down until the propellor in the air is spinning madly while the propellor in the water (or the tires on the road) barely turns. Sure, that's not just plausible. That direction is freaking obvious. If you are going down-wind you [eventually] need to reverse things. Now you are using the propellor in the air for thrust and you are drawing power from a lesser backward drag at a higher relative speed. [Below wind speed you can use the propellor for power and the tires for thrust because the drag on the propellor points in a favorable direction, but that way of doing things is a trap] Sounds, good, but the intuition wants a sanity check. So *build's a mental picture*. You're cruising down the road on a bicycle. It's downwind and you're just barely keeping up with the wind. You have this huge propellor in the air, but it's not turning yet. It's just pulling you downwind at wind speed. You have a little generator that you can snap down so that it spins against the sidewalls of your tires. It generates enough current to run your headlight when you're riding at night. So you snap the generator down and you wire the output into the propellor in the air. Your relative speed with respect to the air is zero. You can generate a large thrust from a small power input. Your relative speed with respect to the ground is large. You can generate a large power output from a small amount of drag. OK. I'm convinced. The intuition tried valiantly to use the "there's no power available when you're moving at wind speed" argument. But that's because the intuition was still trying to run the thing the wrong way.
From: Richard Henry on 30 Jul 2010 13:13 On Jul 30, 2:40 am, John Doe <j...(a)usenetlove.invalid> wrote: > It is discussed on the website (http://www.physicsforums.com) > recently as this year. > > I see some problems with the idea as argued. They keep talking > about wind speed with respect to ground speed as if that is a > power generator. They also seem to be pretending that gearing, or > the difference between wheel and propeller rotation speeds, is > somehow a power source. > > The follow-on argument appears to be that you can sail directly > into the wind. > > I see no prior discussion here on UseNet. On the Internet, I see > it is discussed as early as 2007. Apparently the idea was > originated by Jack Goodman in 2006. The first notch on the bullshit meter is conservation of energy.
From: Cwatters on 30 Jul 2010 13:17
"Cwatters" <colin.wattersNOSPAM(a)TurnersOakNOSPAM.plus.com> wrote in message news:dNWdnUaLmrg8Yc_RnZ2dnUVZ8oidnZ2d(a)brightview.co.uk... > > "John Doe" <jdoe(a)usenetlove.invalid> wrote in message > news:4c52b7da$0$8901$c3e8da3(a)news.astraweb.com... >> "Cwatters" <colin.wattersNOSPAM(a)TurnersOakNOSPAM.plus.com> wrote: >> >>> http://www.wired.com/autopia/2010/07/its-settled-downwind-faster-than-the-wind-officially-possible/ >> >> Lots of things are possible on moderated websites/forums, just >> depends on the editor. I am sure there is hype about perpetual >> motion machines too. > > Probably but does that somehow stop you researching this project yourself? > If I remember correctly it was sponsored by Google and a few other > corporations. > Here you go.. http://www.fasterthanthewind.org/ It was designed by "Thin Air Designs" in collaboration with the San Jose State University Aero department and sponsored by Google and others. They have some data suggesting that >3x the wind speed is possible. If you want to see the maths that was published here... http://www.boatdesign.net/forums/propulsion/ddwfttw-directly-downwind-faster-than-wind-25527.html See this post by Guest625101138... "Mark Drela has provided the theory of operation of a DDWFTTW boat using an air propeller and a water turbine. In the attached papers he provides the necessary conditions on efficiency and drag to achieve the objective"... http://www.boatdesign.net/forums/attachments/propulsion/28167d1231128492-ddwfttw-directly-downwind-faster-than-wind-ddw2.pdf http://www.boatdesign.net/forums/attachments/propulsion/28168d1231128492-ddwfttw-directly-downwind-faster-than-wind-ddwe.pdf |