Sail downwind faster than the wind!
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From: John Doe on 30 Jul 2010 16:49 "Androcles" wrote: .... > A sail is an aircraft wing tipped vertically. No it is not. A sail does not have a flat surface opposite the curved surface. > The wing is there to fight gravity. The sail produces the same > lift No. Wind on either side is moving at the same speed as the other. The only reason the sail is curved is because it is made of fabric. -- > 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. > > > > > > > > Path: news.astraweb.com!border1.newsrouter.astraweb.com!indigo.octanews.net!news-out.octanews.net!mauve.octanews.net!news-out1.kabelfoon.nl!newsfeed.kabelfoon.nl!xindi.nntp.kabelfoon.nl!news2.euro.net!novso.com!69.16.177.242.MISMATCH!cyclone02.ams2.highwinds-media.com!news.highwinds-media.com!npeersf01.ams.highwinds-media.com!newsfe17.ams2.POSTED!7564ea0f!not-for-mail > From: "Androcles" <Headmaster Hogwarts.physics_z> > Newsgroups: sci.physics > References: <4c529e1b$0$21228$c3e8da3 news.astraweb.com> <QbSdnX9E88HPOM_RnZ2dnUVZ8tGdnZ2d brightview.co.uk> <4c52ae63$0$9845$c3e8da3 news.astraweb.com> > Subject: Re: Sail downwind faster than the wind! > Lines: 57 > MIME-Version: 1.0 > Content-Type: text/plain; charset="iso-8859-1" > Content-Transfer-Encoding: 7bit > X-Priority: 3 > X-MSMail-Priority: Normal > X-Newsreader: Microsoft Outlook Express 6.00.2900.5931 > X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5931 > Organization: virginmedia.com > Message-ID: <I0z4o.8720$bS5.6938 hurricane> > NNTP-Posting-Date: Fri, 30 Jul 2010 11:51:04 UTC > Date: Fri, 30 Jul 2010 12:50:40 +0100 > >
From: John Doe on 30 Jul 2010 16:53 "Androcles" <Headmaster Hogwarts.physics_z> wrote: > Tacking makes use of the "lift" to drive the boat "up" except > that "up" is now forward. If that were true, the sail would invert.
From: jimp on 30 Jul 2010 17:17 John Doe <jdoe(a)usenetlove.invalid> wrote: > "Androcles" wrote: > > ... > >> A sail is an aircraft wing tipped vertically. > > No it is not. A sail does not have a flat surface opposite the > curved surface. Neither do all airfoils on airplane wings. >> The wing is there to fight gravity. The sail produces the same >> lift > > No. Wind on either side is moving at the same speed as the other. > The only reason the sail is curved is because it is made of > fabric. There are airplanes flying with fabric wings not much different than a sail. -- Jim Pennino Remove .spam.sux to reply.
From: John Doe on 30 Jul 2010 19:17 jimp specsol.spam.sux.com wrote: > John Doe wrote: >> "Androcles" wrote: >> >> ... >> >>> A sail is an aircraft wing tipped vertically. >> >> No it is not. A sail does not have a flat surface opposite the >> curved surface. > > Neither do all airfoils on airplane wings. Right. >>> The wing is there to fight gravity. The sail produces the same >>> lift >> >> No. Wind on either side is moving at the same speed as the >> other. The only reason the sail is curved is because it is made >> of fabric. > > There are airplanes flying with fabric wings not much different > than a sail. There is no such thing as a flexible fabric aircraft wing like on a sail boat. If somehow there were less pressure on the forward side, a sail would invert. The forces that lift an aircraft wing do not exist against a sail because wind attacks an airplane wing at a different angle than wind pushes against a sail. But the direction of the proposed lift is not even correct for a sail on a sailboat. That imaginary lift would push the sailboat backwards, not forwards. -- > > > > -- > Jim Pennino > > Remove .spam.sux to reply. > > > Path: border5.newsrouter.astraweb.com!news.astraweb.com!border1.a.newsrouter.astraweb.com!news.netcologne.de!ramfeed1.netcologne.de!newsfeed.freenet.ag!news.k-dsl.de!aioe.org!not-for-mail > From: jimp specsol.spam.sux.com > Newsgroups: sci.physics > Subject: Re: Sail downwind faster than the wind! > Date: Fri, 30 Jul 2010 21:17:32 -0000 > Organization: Aioe.org NNTP Server > Lines: 28 > Message-ID: <c4sbi7-aqe.ln1 mail.specsol.com> > References: <4c529e1b$0$21228$c3e8da3 news.astraweb.com> <QbSdnX9E88HPOM_RnZ2dnUVZ8tGdnZ2d brightview.co.uk> <4c52ae63$0$9845$c3e8da3 news.astraweb.com> <I0z4o.8720$bS5.6938 hurricane> <4c533ac9$0$30344$c3e8da3 news.astraweb.com> > NNTP-Posting-Host: 5FQzpG9PgxCHgWX2ynv4yg.user.speranza.aioe.org > X-Complaints-To: abuse aioe.org > User-Agent: tin/1.8.3-20070201 ("Scotasay") (UNIX) (SunOS/5.10 (i86pc)) > X-Notice: Filtered by postfilter v. 0.8.2 >
From: Sam Wormley on 30 Jul 2010 19:40
On 7/30/10 4:40 AM, John Doe 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. In 2009, the world speed sailing record on water was set by a hydrofoil catamaran sailing at 1.71 times the speed of the wind. See: http://en.wikipedia.org/wiki/Sailing_faster_than_the_wind |