![]() |
|
I think I get the gist of that gem of a sentence, hopefully everyone has
gleaned just a little from your self-professed knowledge, they're probably psychics. "JAXAshby" wrote in message ... certainly no expects you to understand, ac, one liners or ten thousand. From: "AC" Date: 8/23/2004 12:13 AM Eastern Daylight Time Message-id: Are you the "ng"? I hope not, since if you are, that would make you some sort of one-sentence-replying dictator, expecting everyone else to understand your prophetic one-liners. "JAXAshby" wrote in message ... ac, you lack totally and utterly ANY understanding of what is going on -- airfoilwise -- on either or, same same, a sailboat sail. ac, the ng askes that you NEVER post on this subject again. for the obvious reason. From: "AC" Date: 8/21/2004 5:50 PM Eastern Daylight Time Message-id: The answer to your question, is yes. Sails are made from dacron for ease of handling & shortening, and cost. Many examples of rigid-wing vessels exist, I suggest doing a search on that. They often use fairings at the leading edge, or movable trailing edges to fine tune the foil. An aircraft can fly inverted, because its angle-of-attack changes to suit the correspondingly lower efficiency of the foil in this position. As others have noted, acrobatic craft often employ nearly symmetrical foils for this reason. A normally profiled foil will fly inverted, but inefficiently, and at a much lower VMG due to the increased drag from the higher angle of attack. Try some "Bernoulli experiments for kids",and you will reach a better understanding. "Axel Boldt" wrote in message om... Hi, I'm trying to understand how a boat can sail against the wind. Explanations on the internet usually go like this: "The sail has an airfoil shape, the air goes faster on one side than on the other, creating lift by Bernouilli's principle." But I know that for flying planes, the wing's airfoil shape is not essential (otherwise planes couldn't fly on their back): it's the angle of attack that matters. So I'm wondering if the same is true for sailing: would it be possible to sail against the wind with a sail that's a rigid flat surface, not an airfoil-shaped piece of cloth? Thanks, Axel |
You've completely lost me there... paaaaLOnk
"JAXAshby" wrote in message ... little boy, you don't understand. *YOU* are not worth proofreading for grammar or spelling. From: "AC" Date: 8/25/2004 1:06 AM Eastern Daylight Time Message-id: Oooohh, great - name calling. Now, we're really expressing ourselves well, aren't we? I can tell the limitation of your cred's by your grammar. I bet you can't tell what mine are... You can click on as many hyperlinks as you want, and be a wannabe pilot all your life, but still not receive basic physics training, that's a two-way experience. "JAXAshby" wrote in message ... just dipsquats who pretend to know things they utterly and knowingly ignorant of. ac, you lack totally and utterly ANY understanding of what is going on -- airfoilwise -- on either or, same same, a sailboat sail. ac, the ng askes that you NEVER post on this subject again. for the obvious reason. Jax, Do you intend to annoy people, or is it just by accident? |
what a surprise. you are lost all too often.
From: "AC" Date: 8/26/2004 10:58 PM Eastern Daylight Time Message-id: You've completely lost me there... paaaaLOnk "JAXAshby" wrote in message ... little boy, you don't understand. *YOU* are not worth proofreading for grammar or spelling. From: "AC" Date: 8/25/2004 1:06 AM Eastern Daylight Time Message-id: Oooohh, great - name calling. Now, we're really expressing ourselves well, aren't we? I can tell the limitation of your cred's by your grammar. I bet you can't tell what mine are... You can click on as many hyperlinks as you want, and be a wannabe pilot all your life, but still not receive basic physics training, that's a two-way experience. "JAXAshby" wrote in message ... just dipsquats who pretend to know things they utterly and knowingly ignorant of. ac, you lack totally and utterly ANY understanding of what is going on -- airfoilwise -- on either or, same same, a sailboat sail. ac, the ng askes that you NEVER post on this subject again. for the obvious reason. Jax, Do you intend to annoy people, or is it just by accident? |
"AC" wrote in message ...
The answer to your question, is yes. Sails are made from dacron for ease of handling & shortening, and cost. Many examples of rigid-wing vessels exist, I suggest doing a search on that. They often use fairings at the leading edge, or movable trailing edges to fine tune the foil. An aircraft can fly inverted, because its angle-of-attack changes to suit the correspondingly lower efficiency of the foil in this position. As others have noted, acrobatic craft often employ nearly symmetrical foils for this reason. A normally profiled foil will fly inverted, but inefficiently, and at a much lower VMG due to the increased drag from the higher angle of attack. The profile of the wing only handles the Drag, not Lift. Angle of attack handles Lift (see the Cl/Alfa diagram)! Try some "Bernoulli experiments for kids",and you will reach a better understanding. Bernoulli experiments are all due to other physical effects like boundary layer (asymmetric) separation, entrainment of air, Coanda effect etc. The thought that " a change in air velocity will change the pressure" is not real, only mathematic relations. Jan-Olov Newborg |
The profile of the wing only handles the Drag, not Lift.
ah, no. |
Try some "Bernoulli experiments for kids",and you will reach a better
understanding. no, you won't. wings/sails do not have lift because of "Bernoulli" inspite of the fact you can read such in thousands of kiddie books. |
Hi Axel, there is a nice flash movie explaining this on www.bmw-yachtsport.com, look for "Physik des Segelns". It's in german but I think that's no problem for you :-) Have a nice weekend, Joachim Axel Boldt schrieb: Hi, I'm trying to understand how a boat can sail against the wind. Explanations on the internet usually go like this: "The sail has an airfoil shape, the air goes faster on one side than on the other, creating lift by Bernouilli's principle." But I know that for flying planes, the wing's airfoil shape is not essential (otherwise planes couldn't fly on their back): it's the angle of attack that matters. So I'm wondering if the same is true for sailing: would it be possible to sail against the wind with a sail that's a rigid flat surface, not an airfoil-shaped piece of cloth? Thanks, Axel |
Jax,
How much have you studied the response of sails? By studied, I mean with real data from instruments calibrated to accepted standards and in standardized conditons. If not Bernoulli, Then perhaps you will explain to the readers how the Kutta-Zhukovsky Theorem can explain everything without assistance of the equations set out by Daniel Beroulli. Or, did you have something else in mind? Matt Colie (CV by request only) JAXAshby wrote: Try some "Bernoulli experiments for kids",and you will reach a better understanding. no, you won't. wings/sails do not have lift because of "Bernoulli" inspite of the fact you can read such in thousands of kiddie books. |
|
|
|
Jax,
This is so much like when I was a GA. "Yes" is not a complete answer. So...I Repeat If not Bernoulli, Then perhaps you will explain to the readers how the Kutta-Zhukovsky Theorem can explain everything without assistance of the equations set out by Daniel Beroulli. Or, did you have something else in mind? Please elaborate, we are waiting Oh so patiently. There are two DC's here wait to hear. Matt Colie - See Prior Sig JAXAshby wrote: yes. From: Matt Colie Date: 8/28/2004 4:30 PM Eastern Daylight Time Message-id: Jax, How much have you studied the response of sails? By studied, I mean with real data from instruments calibrated to accepted standards and in standardized conditons. If not Bernoulli, Then perhaps you will explain to the readers how the Kutta-Zhukovsky Theorem can explain everything without assistance of the equations set out by Daniel Beroulli. Or, did you have something else in mind? Matt Colie (CV by request only) JAXAshby wrote: Try some "Bernoulli experiments for kids",and you will reach a better understanding. no, you won't. wings/sails do not have lift because of "Bernoulli" inspite of the fact you can read such in thousands of kiddie books. |
Matt,
the secret is in the reading of the rest of his insightful replies to the group. I know, not a pleasant thought - but essential. The Bernoulli quote was from me, and the refutation "do not have lift because of "Bernoulli" inspite of... blah, blah" says a lot more about him than it does about physics. The earth doesn't have gravity because of Newton, and dark matter isn't necessarily a figment of someone's imagination, just because JAXAshby can't hold it in his hands. Try not to feed the guy! Feel free to respond to the original post, though... "Matt Colie" wrote in message ... Jax, How much have you studied the response of sails? By studied, I mean with real data from instruments calibrated to accepted standards and in standardized conditons. If not Bernoulli, Then perhaps you will explain to the readers how the Kutta-Zhukovsky Theorem can explain everything without assistance of the equations set out by Daniel Beroulli. Or, did you have something else in mind? Matt Colie (CV by request only) JAXAshby wrote: Try some "Bernoulli experiments for kids",and you will reach a better understanding. no, you won't. wings/sails do not have lift because of "Bernoulli" inspite of the fact you can read such in thousands of kiddie books. |
"Jan-Olov Newborg" wrote in message om... "AC" wrote in message ... The answer to your question, is yes. Sails are made from dacron for ease of handling & shortening, and cost. Many examples of rigid-wing vessels exist, I suggest doing a search on that. They often use fairings at the leading edge, or movable trailing edges to fine tune the foil. An aircraft can fly inverted, because its angle-of-attack changes to suit the correspondingly lower efficiency of the foil in this position. As others have noted, acrobatic craft often employ nearly symmetrical foils for this reason. A normally profiled foil will fly inverted, but inefficiently, and at a much lower VMG due to the increased drag from the higher angle of attack. The profile of the wing only handles the Drag, not Lift. Angle of attack handles Lift (see the Cl/Alfa diagram)! You didn't read the post properly. I'd suggest going back and doing so. Nowhere did I say a wing's profile "handles" lift. What the #$@ is a Cl/Alfa diagram? and where has anyone other than you referred to such? Try some "Bernoulli experiments for kids",and you will reach a better understanding. Bernoulli experiments are all due to other physical effects like boundary layer (asymmetric) separation, entrainment of air, Coanda effect etc. Since when is an experiment ever due to an effect? Maybe due to the effect of higher funding by a benefactor... [I hope this is due to a language gap]. As a scientist, I usually like to credit my experiments to myself, rather than some mis-quoted phenomenon that is dubiously applied to the situation. The thought that " a change in air velocity will change the pressure" is not real, only mathematic relations. Jan-Olov Newborg |
Thanks, spock.
It's good to see someone actually talking about something they've studied, rather than "heard about"... A voice of reason in an echoey kinda place... "spock" wrote in message om... (JAXAshby) wrote in message ... Try some "Bernoulli experiments for kids",and you will reach a better understanding. no, you won't. wings/sails do not have lift because of "Bernoulli" inspite of the fact you can read such in thousands of kiddie books. Yes you will. Been there done that. Its fun and will definitely teach you allot of how aerodynamics works in the real world. These simple "Bernoulli experiments for kids" can show you exactly how a wing or most any solid object can generate lift as a result of the Bernoulli effect. You could write a book on what these experiments will teach you. In a feeble attempt to prove the misconception that an airplane wing (while in normal flight) produces lift as a result of Bernoulli effect, these kiddy and adult books give perfect examples of Bernoulli effect lift. My favorite is the levitating ball. The large problem with this is that a wing in flight is not partially influenced by a stream of air that has reduces internal pressure as a result of its increased velocity. A wing in flight is totally submerged in the relative airflow that is influencing it and many times this relative airflow has no velocity at all because the aircraft is flying in still air. So to generate Bernoulli effect lift from a wing simply direct a jet of air over the top of it. If you want a wing in normal flight to produce Bernoulli effect lift your are pretty much crap out of luck as you apparently already know. |
matt, give it up. beernoulli is not part of any theory of flight. none.
except in kiddies books. And kiddies books aren't used at the college level. If you dont understand that, you don't understand even the first semester. google to your hearts content is you want. add the words astrology and tele-kenesis to your google and see how many hits you get. Jax, This is so much like when I was a GA. "Yes" is not a complete answer. So...I Repeat If not Bernoulli, Then perhaps you will explain to the readers how the Kutta-Zhukovsky Theorem can explain everything without assistance of the equations set out by Daniel Beroulli. Or, did you have something else in mind? Please elaborate, we are waiting Oh so patiently. There are two DC's here wait to hear. Matt Colie - See Prior Sig JAXAshby wrote: yes. From: Matt Colie Date: 8/28/2004 4:30 PM Eastern Daylight Time Message-id: Jax, How much have you studied the response of sails? By studied, I mean with real data from instruments calibrated to accepted standards and in standardized conditons. If not Bernoulli, Then perhaps you will explain to the readers how the Kutta-Zhukovsky Theorem can explain everything without assistance of the equations set out by Daniel Beroulli. Or, did you have something else in mind? Matt Colie (CV by request only) JAXAshby wrote: Try some "Bernoulli experiments for kids",and you will reach a better understanding. no, you won't. wings/sails do not have lift because of "Bernoulli" inspite of the fact you can read such in thousands of kiddie books. |
|
|
ac, you have never studied anything even remotely concerned with this
discussion. And no, a CNN sound bite does not qualify as "study". Neither does reading a Popular Mechanix article. From: "AC" Date: 8/29/2004 2:47 AM Eastern Daylight Time Message-id: Thanks, spock. It's good to see someone actually talking about something they've studied, rather than "heard about"... A voice of reason in an echoey kinda place... "spock" wrote in message . com... (JAXAshby) wrote in message ... Try some "Bernoulli experiments for kids",and you will reach a better understanding. no, you won't. wings/sails do not have lift because of "Bernoulli" inspite of the fact you can read such in thousands of kiddie books. Yes you will. Been there done that. Its fun and will definitely teach you allot of how aerodynamics works in the real world. These simple "Bernoulli experiments for kids" can show you exactly how a wing or most any solid object can generate lift as a result of the Bernoulli effect. You could write a book on what these experiments will teach you. In a feeble attempt to prove the misconception that an airplane wing (while in normal flight) produces lift as a result of Bernoulli effect, these kiddy and adult books give perfect examples of Bernoulli effect lift. My favorite is the levitating ball. The large problem with this is that a wing in flight is not partially influenced by a stream of air that has reduces internal pressure as a result of its increased velocity. A wing in flight is totally submerged in the relative airflow that is influencing it and many times this relative airflow has no velocity at all because the aircraft is flying in still air. So to generate Bernoulli effect lift from a wing simply direct a jet of air over the top of it. If you want a wing in normal flight to produce Bernoulli effect lift your are pretty much crap out of luck as you apparently already know. |
Mr. Jax,
You STILL have not answered the question. I would not stand for this then and I still won't. If you have a contrary point to make, you have to defend it. I never said you were wrong or right and I even tried to help. Actually, I guess I won't try any longer as we are not getting anything of value covered here today. Dismissed Matt Colie JAXAshby wrote: matt, give it up. beernoulli is not part of any theory of flight. none. except in kiddies books. And kiddies books aren't used at the college level. If you dont understand that, you don't understand even the first semester. google to your hearts content is you want. add the words astrology and tele-kenesis to your google and see how many hits you get. Jax, This is so much like when I was a GA. "Yes" is not a complete answer. So...I Repeat If not Bernoulli, Then perhaps you will explain to the readers how the Kutta-Zhukovsky Theorem can explain everything without assistance of the equations set out by Daniel Beroulli. Or, did you have something else in mind? Please elaborate, we are waiting Oh so patiently. There are two DC's here wait to hear. Matt Colie - See Prior Sig JAXAshby wrote: yes. From: Matt Colie Date: 8/28/2004 4:30 PM Eastern Daylight Time Message-id: Jax, How much have you studied the response of sails? By studied, I mean with real data from instruments calibrated to accepted standards and in standardized conditons. If not Bernoulli, Then perhaps you will explain to the readers how the Kutta-Zhukovsky Theorem can explain everything without assistance of the equations set out by Daniel Beroulli. Or, did you have something else in mind? Matt Colie (CV by request only) JAXAshby wrote: Try some "Bernoulli experiments for kids",and you will reach a better understanding. no, you won't. wings/sails do not have lift because of "Bernoulli" inspite of the fact you can read such in thousands of kiddie books. |
All times are GMT +1. The time now is 12:45 AM. |
|
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
Copyright ©2004 - 2014 BoatBanter.com