|
how a sail works, who can help me explain?
I need to know your measurements, please. Include the circumference of your neck as that is supposed to be the best indicator of an overweight condition. Fat neck = fat head. "katysails" wrote in message ... How a sail owrks: Big stick...big piece of cloth....wind.....wind pushes boat...what else do you need to know/ |
how a sail works, who can help me explain?
"katysails" wrote in message ...
How a sail owrks: Big stick...big piece of cloth....wind.....wind pushes boat...what else do you need to know/ -- katysails s/v Chanteuse Kirie Elite 32 Ad eundum quo nemo ante iit. http://katysails.tripod.com "Women and cats will do as they please, and men and dogs should relax and get used to the idea." - Robert A. Heinlein Katysails, wind does not push boat, sail causes vacuum on leeward side, sail gets sucked into vacuum, pulls boat with it. Forget all the other stuff, this is all you need to know. Dowra. |
how a sail works, who can help me explain?
"dowra" wrote in message | Katysails, wind does not push boat, sail causes vacuum on leeward | side, sail gets sucked into vacuum, pulls boat with it. | Forget all the other stuff, this is all you need to know. | Dowra. Oh Geee Whizz-z-z-z No wonder I feel like I can't seem to get a breath on that side of the boat. It also explains the oxygen masks deploying on the leeward side on those upgrade high tech boats...... it does nothing to explain why you can't navigate a known channel without going aground. Calling Sea Tow..... calling Sea Tow......... CM |
how a sail works, who can help me explain?
"dowra" wrote in message om... Katysails, wind does not push boat, sail causes vacuum on leeward side, sail gets sucked into vacuum, pulls boat with it. Be very careful the next time you get an itchy ear. The vacuum might "suck" your finger right in! Forget all the other stuff, this is all you need to know. So after you get sucked onto the mud, Sea Tow come and suck you off again???? Regards Donal -- |
how a sail works, who can help me explain?
Some questions on Lift as applied to sail?
If Bernoulli is wrong and Newton's Law of ACTION & REACTION is what creates Lift, why then , when a sail is at maximum lift do the tell-tale at the leech of the sail stream back off the sail, as describe by Bernouli and not fly at a 90 degree angle as described by Newton's downdraft and updraft? If Newton's Law of Action & Reaction is correct (I'm not saying it is wrong) then the action has to be on the convex side of the sail ( Action- downdraft) to create the reaction on the concave side (Reaction- Updraft or Lift) Why then do we look for the tell-tales to be streaming backwards when sailing. Seems to me they should be forced straight into the sail in various direction Also, If Newton's Law is correct that should make the convex side of the sail the windward side and the concave side the Lee side ( Action_Reaction) How can this be if the boat is traveling in the direction of the convex side ( The Newtonian windward side) If, as Pim, logic of a flat sail is the desired shape for upwind performance, then why wouldn't a flat piece of plywood work best when tacking up wind? ( Just maybe, Bernoulli isn't wrong for how a sail works?) These are some question in my mind. Maybe some of you Flight Wizards have answer for me before I completely abandon " Bernoulli" Ole Thom |
how a sail works, who can help me explain?
Lift is to air as Buoyance is to water
Oh Oh! Maybe in lighter than air. Newton's second Law is; Lift= mA. The mA is for; m= mass A= acceleration Buoyance needs no acceleration. Ole Thom |
how a sail works, who can help me explain?
"Simple Simon" wrote in message ... How is measuring the actual length of travel a molecule takes on its journey across the top of the foil as opposed to across the bottom of the foil amount to nonsense? I'm simply pointing out that the air doesn't travel different distances on both sides of the sail. The flow of the air gets interrupted by the sail. As the air hits the sail on the windward side, it gets deflected and slowed down. The energy that has now been removed from the wind has transferred to the sail. i.e. the wind is "pushing" the sail. On the leeward side, the air is trying to flow away from the sail, thus creating "pull". As the angle of the sail comes close to head on to the wind, a point is reached where turbulence decreases and the air flows smoothly across both surfaces, but you still have the "push" and "pull" forces working. This is the point where the sail is working efficiently. You don't need complicated formulae to understand this. You certainly don't need Bernouili. Regards Donal -- |
how a sail works, who can help me explain?
"Thomas Stewart" wrote in message ... These are some question in my mind. Maybe some of you Flight Wizards have answer for me before I completely abandon " Bernoulli" You may as well abandon Bernouilli (note correct spelling) because you have already abandoned reason. Your motor sailer proves it. |
how a sail works, Windtunnel Tests.
Maybe this will help everybody:
http://www.wb-sails.fi/news/99_4_Win...es/Movies.htm# "Thomas Stewart" wrote in message ... Lift is to air as Buoyance is to water Oh Oh! Maybe in lighter than air. Newton's second Law is; Lift= mA. The mA is for; m= mass A= acceleration Buoyance needs no acceleration. Ole Thom |
how a sail works, Windtunnel Tests.
Movies don't work.
"jlrogers" wrote in message ... Maybe this will help everybody: http://www.wb-sails.fi/news/99_4_Win...ies/Movies.htm |
how a sail works, Windtunnel Tests.
Must be something in your settings. They work for me.
"Simple Simon" wrote in message ... Movies don't work. "jlrogers" wrote in message ... Maybe this will help everybody: http://www.wb-sails.fi/news/99_4_Win...ies/Movies.htm |
how a sail works, who can help me explain?
"Simple Simon" wrote: That's precisely why I give more credence to Venturi. I like to keep it simple as my name suggests. Why clutter a good physical reality with extra theories that may or may not be applicable? In my opinion the theory: "air tends to follow the sail (also on the leeward), and thus deflects the air, and for that deflection you need a force, and that force is the sailforce" is easier as explaining: "the path on the leeward is longer, so the air has to move faster" continued with "fast moving air has a lower pressure" "just like in a venturi in a pipe" Please note that I do not make air molecules bounce of the sail, I am deflecting a flow of air. To check if that flow has not separated from the sail I also reccomend telltales. Please read www.sailtheory.com/sail.html for more details. What might be confusing: Bernoulli never had a theory for a wing. He had a theory for explaining how high a fountain would spray. Newton never had a theory for a wing, his theory was about bouncing balls and planets etc. Euler, Kutta and Joukofski, and Prandtl all had some theories about flow around a wing. For some strange reasons they are not often mentioned. (I am promoting Ludwigs Prandtl "lifting line theory" if you want to know) I quit this discussion, I think the "longer path gives higher speed, and thus lower pressure" theory really sucks. If you do not need a theory, please do not use a theory. It is better to use no theory as to use a stupid one. Thank you for giving your opinion. Best Regards, Pim -- Posted by news://news.nb.nu |
how a sail works, Windtunnel Tests.
If you use GuardIE, Zone Alarm, and Spybot, you can control all of those very well, though I too removed realplayer and used the
minimal install of Quicktime.(Version 6.3 of Quicktime is easy to control). Guardie allows one to activate it by URL. Using Spybot allows one to reroute defined internet requests to 127.0.0.0. Real just thinks it's calling home. "Simple Simon" wrote in message ... I see the problem. The movies are Quicktime. I removed all that horrible Quicktime crap from my computer. It made it crash everytime I attempted to use it and it was constantly trying to load ads and other crap from the Quicktime server. It's almost as bad as RealPlayer which I also removed every vestige of. "jlrogers" wrote in message ... Must be something in your settings. They work for me. "Simple Simon" wrote in message ... Movies don't work. "jlrogers" wrote in message ... Maybe this will help everybody: http://www.wb-sails.fi/news/99_4_Win...ies/Movies.htm |
how a sail works, who can help me explain?
"Simple Simon" wrote in message ...
It does depend on the length difference as stated in the principles of the venturi effect. The speed of the air is increased when it is forced through a smaller area. The sail acts like one side of a venturi in that the air has a smaller area to go through because of the extra length. The air above that air on the surface of the foil acts like a venturi also to a small degree. The net effect is the air moves faster, the molecules become spaced farther apart and the pressure is decreased. This decreased pressure is a greater factor causing lift than the air pushing up on the windward side of the sail. You might know a lot but you need to learn more when it comes to the practical application of single-surface foils used on sailboats. Dear Simple Simon! NASA Glenn Research shows on their website that you are totally wrong about Lift due to "Longer pathlenght and Half Venturi lift theory"!: http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html Professor em. of Physics Weltner shows here how misunderstood Bernoulli equation can be: http://www.rz.uni-frankfurt.de/~weltner/Mis6/mis6.html Aerodynamist Martin Ingelman-Sundberg ownsite with articles : http://www.marv.nu/undersajtm.html Jan-Olov Newborg |
how a sail works, who can help me explain?
Comments interspersed. "Jan-Olov Newborg" wrote in message om... Dear Simple Simon! NASA Glenn Research shows on their website that you are totally wrong about Lift due to "Longer pathlenght and Half Venturi lift theory"!: http://www.grc.nasa.gov/WWW/K-12/airplane/wrong1.html Not a good example. The simulator uses a symetrical, double-surface wing and talks of powered flight. We are talking about a sail which is a single-surface foil here. Proof that the Venturi effect is what provides the lion's share of the lift in the system is the fact that the sail is shaped by the pressures on either side. Because the sail's convex side is always facing the area of lowest pressure proves the venturi effect is in action. (This is not true only on a dead run where the shape is caused by wind action on the windward side of the sail) Professor em. of Physics Weltner shows here how misunderstood Bernoulli equation can be: http://www.rz.uni-frankfurt.de/~weltner/Mis6/mis6.html The good professor is confusing a descriptive term (longer path) for a causative agent (lower pressure). The longer path is not the cause of the lower pressure. The lower pressure is caused by the speeding up of the air molecules because of the SHAPE of the path. Use the wrong shape and you will not get lowered pressure. The shape is the key to lowering the pressure efficiently and without excess drag - not the longer path. Because the shape confers a longer path does not mean it is the longer path that is the cause. The shape of the foil is important not the longer path. The so-called longer path descriptor is ONLY a descriptor. This seems to go over the heads of so many professorial types who are all too involved with nomenclature. Aerodynamist Martin Ingelman-Sundberg ownsite with articles : http://www.marv.nu/undersajtm.html And, this chap is talking only of airplanes and probably has never sailed in his life and is also unfamiliar with single-sided foils that are shaped by the wind. Thanks for the links but I still know I'm right when it comes to sailboats. Capt. Neal http://www.homestead.com/captneal/index.html ~~~~~~~~~~~~~ |
how a sail works, who can help me explain?
Donal.
Your reasoning is FLAWED. You are using two different sails, which cancel out your statement. However, there is a easier proof that holds true. Use a performance curve and you will see that your statement may be correct, with the exception off the wind "Bernoulli" is much more logical. Off the wind we are getting greater lift from a looser, baggier sail and the tell-tales streaming back as indicating Bernoulli's description of flow and recovery area. I know you have seen this while reaching. That is if you are using leech tell-tales. If not, why not? Newton's 1st & 3rd laws say the tell-tales shouldn't be streaming to windward and if Pim Example of the blown paper is correct, the Coanda Effect should be curling the tell-tales back around the to the windward side of the sail Again, If I'm wrong and my eyes are deceiving me, please explain and give an example. Ole Thom |
how a sail works, who can help me explain?
I think poor PIM has bowed out of the discussion or at least
that is what he said in another thread. He probablY thought he could come in here and cherry pick but he quickly found there are some fine minds at work here. We may carry on like a bunch of drunks the majority of the time but we know our sailing!!! "Thomas Stewart" wrote in message ... Pim, Your example of Coanda on the paper, if true, Should wrap the tel-tales around the sail rather than let them stream back. I find fault with your reasoning Ole Thom |
how a sail works, who can help me explain?
Donal.
On your measurement; gain flawed. The measurement should be reflexing the dymanics of the moving sail. If the sail's measurement of the convex side thru the air is measured as compared to the distance across the moving sides of the concave side there would be a great difference. The faster the movement the greater the delta length Again I'm open to any example that makes sense Ole Thom |
how a sail works, who can help me explain?
Forget all the other stuff, this is all you need to know. Dowra. U'll remember that next time I Hoover down the lake.... -- katysails s/v Chanteuse Kirie Elite 32 Ad eundum quo nemo ante iit. http://katysails.tripod.com "Women and cats will do as they please, and men and dogs should relax and get used to the idea." - Robert A. Heinlein |
how a sail works, who can help me explain?
Hoover? Like the vacuum cleaner? Katy, I'm shocked that you would admit it. But, it does make for better fantasies! "katysails" wrote in message ... Forget all the other stuff, this is all you need to know. Dowra. U'll remember that next time I Hoover down the lake.... |
how a sail works, who can help me explain?
He's not saying air has a fixed structure. Rather, he is saying
there is some depth to the flow of the air around the shape of the foil. It is not just a couple of molecules thick and as one increases the distance from the foil the air molecules are still existing at increased distances from each other and the pressure is lowered because of this lower density. "Oz1" wrote in message ... On Tue, 08 Jul 2003 22:44:16 GMT, "Wally" wrote: If the same lump of air that was split at the leading edge is reconstituted at the trailing edge, then those molecules that passed around the outer surface 100mm away *must* have travelled faster than those that passed the inner surface 100mm distant. And that's where your theory falls down! You assume that the air is some kind of lego block toy that has a fixed structure and that after passing over the foil it must once again lock back into that same structure. If that were so how would you explain turbulence and vortices Oz1...of the 3 twins. I welcome you to crackerbox palace,We've been expecting you. |
how a sail works, who can help me explain?
"Oz1" wrote in message
If the same lump of air that was split at the leading edge is reconstituted at the trailing edge, then those molecules that passed around the outer surface 100mm away *must* have travelled faster than those that passed the inner surface 100mm distant. And that's where your theory falls down! You assume that the air is some kind of lego block toy that has a fixed structure and that after passing over the foil it must once again lock back into that same structure. That bit isn't a theory, it's a qualified proposition. If that were so how would you explain turbulence and vortices Summink to wiv fings gettng in the way. -- Wally I demand rigidly-defined areas of uncertainty! www.art-gallery.myby.co.uk |
how a sail works, who can help me explain?
Suck Dowra Suck!! Blow is only a figure of speech G G
Yap, the old ways are the best way??? Are you sure Newton's first three laws do not apply??? Ole Thom |
how a sail works, who can help me explain?
"Thomas Stewart" wrote: Us sailors use tell-tales which tend to confirm Bernoulli to our own eyes If we(I) am wrong please tell me and give a visual example. Ole Thom If sail is set optimal according to the theory I use, the tell-taless at the leech will stream nicely to astern. Because that is what we(I) want, direct as much wind to astern, so pushing yourself forward. If your tell tales on the leech are not streaming to astern, it means that the wind is not directed to astern, and that you could do better. I use the Coanda effect only to explain why the airflow follows (or separates) the sail on the leeward side. And yes, the air on leeward moves faster, Not because the path is longer, but because the air upwind from the sail is being sucked to the lower pressure on the leeward, and pushed away from the higher pressure on the windward part of the sail, what ofcourse will result in more airflow at leeward, and thus a higher speed on leeward. (This is called "circulation" in most theories) so, tell-tales do not only confirm "Bernoulli", but also the theory I use. I do not use the classic "newtonian" theory. but again, what I use is on www.sailtheory.com/sail.html Best regards, Pim -- Posted by news://news.nb.nu |
how a sail works, who can help me explain?
maybe I should get drunk to understand the "bernoulli" theory ;-) %-)
"Donal" wrote: "Simple Simon" wrote in message ... . We may carry on like a bunch of drunks the majority of the time but we know our sailing!!! How True! I am drunk! Regards Donal -- -- Posted by news://news.nb.nu |
how a sail works, who can help me explain?
Donal,
"Bernoulli" says an increase in velocity produces a lower pressure. That is also what you are saying. Isn't it? Ole Thom |
how a sail works, who can help me explain?
"Oz1" wrote in message
If that were so how would you explain turbulence and vortices Summink to wiv fings gettng in the way. You sure it's not the lego blocks playing 'end of intermission at the theatre' and struggling to get into exactly the same place they were in before they were seperated by the foil I'm no fluid dynamicist and my sailing experience is limited, but I'm willing to have a go at working it out. I'm not in the slightest bit sure, offering naught more than a qualified hypothesis. I make no more elevated claim than that. -- Wally I demand rigidly-defined areas of uncertainty! www.art-gallery.myby.co.uk |
how a sail works, who can help me explain?
"Donal" wrote in message ...
"dowra" wrote in message I have made my statement about vacuum, can either of you assholes prove me wrong? I don't think so! ONCE AGAIN I AM DOWRA THE GREAT! PS. Donal, don't even bother to post, you are more of a dolt than yf moron(oo) go back to grade school science, both of you. Dowra the all knowing! |
how a sail works, Windtunnel Tests.
Don't work for Ole Thom either. What are they trying to show? It seem to
indicate an over trim of both jib and main. If the maun was eased and the slot open some I think things would clear up? As it is, what are we looking at.. Is the votex being caused by the slot? Is the tell-tales showing separation on the windward side. The way the tails are behaving there is no sign of coanda effect, they are lifting but still pointing back???? Ole Thom |
how a sail works, Windtunnel Tests.
"Simple Simon" wrote: The prime motive force occurs on the leeward side of the sail and not on the windward side as PIM is attempting to suggest. I am not suggsting that the sailforce comes from the windward side alone, The leeward side is also very effective in deflecting the wind. (Actually I suggest the leeward side is a little more important, because there is more air on the leeward, because it has been sucked to the leeward side.) again, this is on my website under www.sailtheory.com/sail.html Under PIMs scenario there would be no tip vortex. I explain tipvortex! www.sailtheory.com/sail.html#tipvortexes Again you suggest I wrote things I have never wrote. please read my site a little more thoroughly, before you commment its contents wrongly. Best regards, Pim www.sailtheory.com -- Posted by news://news.nb.nu |
how a sail works, who can help me explain?
Your theory is just too simple even for Simple Simon.
You cannot just take one side of a sail and claim it does all the work. There is much more to it than that. If your simple theory was correct all one would need is sheets of plywood set at an angle to the wind and sailboats would go just as fast as those with dacron sails that are cut to produce the correct shape to cause the venturi effect to produce lift. "PIM" wrote in message ... I did not really leave the discussion completely, it was just a slip of the keybord when I was too irritated about a stupid theory that is based on: "things on a longer path go faster" combined with some quicktime videos that did not work My emotion took over. :-( And I am always lurking. Thanks, Pim who knows the theory on www.sailtheory.com is better as simple mc neals "Ventulli" theory. -- Posted by news://news.nb.nu |
how a sail works, who can help me explain?
PIM,
I for one, hope you stick around. You are an asset to the group. We may be a bit Harsh in reply but; "we call'em as we see'em!" I kind of like it that way. We do have probably more than our share of asshole but that is to be expected in an unmoderated group. They can be ignored and and sometimes played with. You, though have something to contribute. Hang around and get to know us. We liken ourselves to a cross section of a public bar, where everyone is allowed to have an opinion (Good or Bad) AND NOW; Your posting. Bernoulli is incomplete as far as sail function is concern. So is Newton. That is why the designers use Coanda and circulation. You as much said there are voids in the Theories, and you're right. Remember humans were using sails centuries before Bernoulli and Newton were born and they designed and used some pretty different sails that worked well. Damn well. Those that come to mind; The Vikings, Egyptian, Polynesians, the traders in the Indian Ocean and China Seas. They had square sails, fore and aft Lateen and Junk sails,Claw Sails and a triangular sail on the Nile before Christ was born. It get hard , sometimes to remember the sails came first and the theories much later. It's no wonder these theories are incomplete. The thinkers didn't have sail in mind and certainly not wings. I do believe that all theories, though incomplete, if usable should not be abandon. Bernoulli works well for sailboaters but fall way short on Hvy Than Aircraft. With powered flight even Newton's Laws need modification. I truly don't see a need for Newton's 2nd Law; (Lift=mA) in sailing So, in conclusion let's use what works for us and keep all that applies Stick with us, you thick headed Dutchman, I'm getting to like you AND: "I'LL DRINK TO THAT!" Ole Thom SV "Pneuma" Gulf 29 Pilothouse Sloop |
how a sail works, Windtunnel Tests.
"PIM" wrote in message ...
"Simple Simon" wrote: The prime motive force occurs on the leeward side of the sail and not on the windward side as PIM is attempting to suggest. I am not suggsting that the sailforce comes from the windward side alone, The leeward side is also very effective in deflecting the wind. (Actually I suggest the leeward side is a little more important, because there is more air on the leeward, because it has been sucked to the leeward side.) again, this is on my website under www.sailtheory.com/sail.html And why is it sucked to leeward? Because it causes a vacuum and nature abhores a vacuum, thus it sucks the sail forward. Capt. Dowra,ESQ |
how a sail works, Windtunnel Tests.
Guess thats why you get sucked aground eh?
Cheers MC dowra wrote: And why is it sucked to leeward? Because it causes a vacuum and nature abhores a vacuum, thus it sucks the sail forward. Capt. Dowra,ESQ |
how a sail works, who can help me explain?
We are talking about a sail which is a single-surface foil here.
Proof that the Venturi effect is what provides the lion's share of the lift in the system is the fact that the sail is shaped by the pressures on either side. Because the sail's convex side is always facing the area of lowest pressure proves the venturi effect is in action. (This is not true only on a dead run where the shape is caused by wind action on the windward side of the sail) Professor em. of Physics Weltner shows here how misunderstood Bernoulli equation can be: http://www.rz.uni-frankfurt.de/~weltner/Mis6/mis6.html The good professor is confusing a descriptive term (longer path) for a causative agent (lower pressure). The longer path is not the cause of the lower pressure. The lower pressure is caused by the speeding up of the air molecules because of the SHAPE of the path. Use the wrong shape and you will not get lowered pressure. When it comes to producing low pressure there is no wrong shape. Pressure differentials are a characteristic of lift and dynamic drag. What shape object wrong or otherwise does not generate an area of low pressure when moving thru the air? Low pressure is simply caused by a solid object (regardless of its shape) in a relative airflow. Low pressure alone does little to cause lift. Low pressure from a relative airflow does little to pull or suck the solid object or allow the higher pressure to push the object in the direction of the low pressure. The shape of the object allows this low pressure to generate a substantial amount of lift. This is very easy to prove. The shape is the key to lowering the pressure efficiently and without excess drag - not the longer path. Because the shape confers a longer path does not mean it is the longer path that is the cause. The shape of the foil is important not the longer path. The so-called longer path descriptor is ONLY a descriptor. This seems to go over the heads of so many professorial types who are all too involved with nomenclature. Aerodynamist Martin Ingelman-Sundberg ownsite with articles : http://www.marv.nu/undersajtm.html And, this chap is talking only of airplanes and probably has never sailed in his life and is also unfamiliar with single-sided foils that are shaped by the wind. Thanks for the links but I still know I'm right when it comes to sailboats. Capt. Neal http://www.homestead.com/captneal/index.html ~~~~~~~~~~~~~ |
how a sail works, Windtunnel Tests.
Why? Do you have experience getting sucked off by men?
You keep mentioning this sort of thing, and eventually one begins to wonder. Why not just admit you're gay. I'm sure you can find like-minded individuals in Florida. "Simple Simon" wrote in message ... "Oz1" wrote in message ... On Thu, 10 Jul 2003 15:05:41 +1200, The_navigator_© wrote: Guess thats why you get sucked aground eh? Cheers MC Nah, that's Ground Effect! Well, knock me over with a feather. I thought getting sucked around was the GANZ effect. |
how a sail works, who can help me explain?
PIM,
You asked for help in explaining your description of the action of a sail and we only gave you negative comments. Let me give a try to put you thoughts into my words and we'll let Neal pick at both of us. It isn't going to be easy as sailors have always gotten good results with sailing by tell-tales and stream lined flows and the Bernoulli Theorem; But, let's give it a try------ So, the difference in your thoughts is that the sail pushes the boat by using the reaction of the action caused by the bending of the air on the curved lee side of the sail. ( Action and Reaction) This happens by the curved sail passing thru the air, or more precisely, the air passing around the curved sail. The action being the bending back of the air causing a drafting effect towards the windward side of the sail. This action, created by curved section creates a reaction to the windward side of the sail causing a drafting force to push the sail and the boat. With the help of the Keel this reactive force is converted to an angular force driving the boat forward. Now, why does this happen? The cause of this leeward action is the DEFLECTION of the air away from the curve leeward side of the sail. This deflection creates a void which causes the air in front of the sail to rush into the void created by the deflected air. This in turn creates the backward draft that creates the reactive. equal and opposite, forward draft on the windward side of the sail. This is the pressure that drives the boat forward Does that sound correct, PIM? That would satisfy the tell-tales and give reason for the upper windward tell-tale to be dancing as tell-tale sailor know is sailing in the "GROVE" The only difference now is we are using positive pressure to push rather negative pressure to pull. We still create a higher velocity of air on the lee side but replace it with new air, which doesn't have to accept the Equal Transit Time I hope you notice I made no mention of a wing! OK! I'm ready for the flaming replies Ole Thom |
how a sail works, who can help me explain?
Kinda makes sense in a way.... I had full battens installed a few years ago
on my bagged main and noticed a big difference in point and speed. The full battens induce a nice curve even in the lightest air. CM "PIM" wrote in message ... | I am suggesting a curved plate works better! |
how a sail works, Windtunnel Tests.
"Simple Simon" wrote in message ...
"Oz1" wrote in message ... On Thu, 10 Jul 2003 15:05:41 +1200, The_navigator_© wrote: Guess thats why you get sucked aground eh? Cheers MC Nah, that's Ground Effect! Well, knock me over with a feather. I thought getting sucked around was the GANZ effect. Your moniker says it all! Simple salutations, DOWRA(Superior) |
how a sail works, who can help me explain?
"PIM" wrote in message ...
"Simple Simon" wrote: That's precisely why I give more credence to Venturi. I like to keep it simple as my name suggests. Why clutter a good physical reality with extra theories that may or may not be applicable? In my opinion the theory: "air tends to follow the sail (also on the leeward), and thus deflects the air, and for that deflection you need a force, and that force is the sailforce" is easier as explaining: "the path on the leeward is longer, so the air has to move faster" continued with "fast moving air has a lower pressure" "just like in a venturi in a pipe" Please note that I do not make air molecules bounce of the sail, I am deflecting a flow of air. To check if that flow has not separated from the sail I also reccomend telltales. Please read www.sailtheory.com/sail.html for more details. What might be confusing: Bernoulli never had a theory for a wing. He had a theory for explaining how high a fountain would spray. Newton never had a theory for a wing, his theory was about bouncing balls and planets etc. Euler, Kutta and Joukofski, and Prandtl all had some theories about flow around a wing. For some strange reasons they are not often mentioned. (I am promoting Ludwigs Prandtl "lifting line theory" if you want to know) I quit this discussion, I think the "longer path gives higher speed, and thus lower pressure" theory really sucks. If you do not need a theory, please do not use a theory. It is better to use no theory as to use a stupid one. Thank you for giving your opinion. Best Regards, Pim Very good webpage about physical Sail/Lift Theory Pim! The best I have seen so far on the web! Mikko in Finland has a very good page also with airflow computer animations. It´s only Navier-Stokes Lift calculations that comes close to the real physics! Prandtl "Lifting Line Theory" is only useful for a physical non existing "ideal/perfect fluid" created only by mathematical equations! Jan-Olov Newborg |
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