Sail downwind faster than the wind!
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From: spock on 1 Aug 2010 12:18 > Think vacuum Think why golf balls have those tiny craters Think wind > going across tall chiminey Curve wing of birds TreBert- Hide quoted text - I already have. Golf balls have dimples to make the surface layer of air stickier and create more surface drag. When the ball is not spinning the stickier air follows the curvature of the ball father around it before exiting leaving a smaller wake and less dynamic drag. Because dynamic drag is the most prevalent on the ball reducing it reduces net drag even though surface drag is increased. When the ball spins while going through the air is like a spinning car tire being pushed into the ground to produce a linear motion. The spinning ball is not pushed into the ground it is pushed into the oncoming air. This surface drag effect is not as dramatic as the car tire but it does produce an effect called the Magnus Effect. Why if the Magnus affect were caused by surface drag any surface preparation that increased surface drag would increased Magnus affect, oh thats right it does. If the Magnus effect is caused by drag why is it called lift. That is a r on the side of the ball still in the flow to travel farther around the ball. The ball diverts the flow as a result of it shape. Hold the back of a plastic spoon in the stream of air coming out of an air nozzle and notice how hard it is to pull out. Now hold a plastic knife to the same low-pressure flow and you will probable not notice any force. If the ball or spoon were being sucked into the flow by low pressure why isnt the knife or many other objects not pulled into the flow? If you dont have an air nozzle the kitchen faucet will also work, what it lacks in pressure it makes up for in viscosity.
From: Androcles on 1 Aug 2010 12:59 "spock" <spock(a)strato.net> wrote in message news:018c8a64-6c6e-4a3f-80ff-bbbb17712940(a)l25g2000prn.googlegroups.com... > Think vacuum Think why golf balls have those tiny craters Think wind > going across tall chiminey Curve wing of birds TreBert- Hide quoted text - I already have. Golf balls have dimples to make the surface layer of air stickier and create more surface drag. When the ball is not spinning the stickier air follows the curvature of the ball father around it before exiting leaving a smaller wake and less dynamic drag. Because dynamic drag is the most prevalent on the ball reducing it reduces net drag even though surface drag is increased. When the ball spins while going through the air is like a spinning car tire being pushed into the ground to produce a linear motion. The spinning ball is not pushed into the ground it is pushed into the oncoming air. This surface drag effect is not as dramatic as the car tire but it does produce an effect called the Magnus Effect. Why if the Magnus affect were caused by surface drag any surface preparation that increased surface drag would increased Magnus affect, oh that�s right it does. If the Magnus effect is caused by drag why is it called lift. That is a r on the side of the ball still in the flow to travel farther around the ball. The ball diverts the flow as a result of it shape. Hold the back of a plastic spoon in the stream of air coming out of an air nozzle and notice how hard it is to pull out. Now hold a plastic knife to the same low-pressure flow and you will probable not notice any force. If the ball or spoon were being sucked into the flow by low pressure why isn�t the knife or many other objects not pulled into the flow? If you don�t have an air nozzle the kitchen faucet will also work, what it lacks in pressure it makes up for in viscosity. ==================================================== Q: What makes a sailboat move? A: The wind. Q: What makes a sailboat stop? A: Friction with the water. Q: What makes the sailboat move North? A: A wind from the South. Q: The wind is from the East. What makes the sailboat move North? A: It can't! Q: Yes it can, set the sail to align SW-NE. What makes the sailboat move North? A: Hmmm... the force of the wind. Q: The wind is blowing from the East. What stops the sailboat moving West? A: The keel, aligned N-S. Q: So the sailboat moves North but the wind is from the East. How fast does the sailboat move North? A: I dunno, let's talk about golf balls and kitchen faucets and plastic spoons instead. They've got dimples.
From: bert on 1 Aug 2010 15:45 On Aug 1, 9:51 am, Hayek <haye...(a)nospam.xs4all.nl> wrote: > Tom Roberts wrote: > > Y.Porat wrote: > >> about "sailing agisnst the wind' > >> it is an illusion!!! > > > You know as little about sailing as you do about physics or math -- i.e.. > > NOTHING AT ALL. > > > There is no "illusion" about sailing upwind, and sailors do it all the > > time. Not directly upwind, mind you, but a good boat and crew can > > approach 45 degrees from directly upwind. Using alternate tacks the boat > > can have a long-term path going directly upwind. > > > BTW a modern sailboat on a reach can sail considerably faster than the > > wind. But no boat can do so when running before the wind. > > Are you sure ? Sometimes you can go faster by slightly > downward tacking. Especially if you follow wind shifts, > also a supreme tactic when going upwind. > > I remember they laughed at my compass. When I beat them > for the first time, they all ran at the shop and > installed one too. (Laser class) > > Uwe Hayek. > > > > > If you don't know what these terms mean, look them up. They are > > standard sailing terms. > > > Tom Roberts > > -- > We are fast approaching the stage of the ultimate > inversion : the stage where the government is free to do > anything it pleases, while the citizens may act only by > permission; which is the stage of the darkest periods of > human history. -- Ayn Rand > > I predict future happiness for Americans if they can > prevent the government from wasting the labors of the > people under the pretense of taking care of them. -- > Thomas Jefferson. > > Socialism is a philosophy of failure, the creed of > ignorance, and the gospel of envy, its inherent virtue > is the equal sharing of misery. -- Winston Churchill. Go to Boston harbor visit Old Ironsides go below its deck and there you will see how the crew could turn the mast so it would have the propper angle to tack. Yes a power boat can go directly into the wind(straight line) A sail boat has to zig zag.and that makes getting from A to B a greater distance. However that 16 year old girl knew to go round the world she had to sail. Sailing is green. Someday those 1500 foot oil tankers carrying 10 million gl. of oil will also have a sail What's their hurry. TreBert
From: spock on 1 Aug 2010 16:01 On > ==================================================== > Q: What makes a sailboat move? > A: The wind. > Q: What makes a sailboat stop? > A: Friction with the water. > Q: What makes the sailboat move North? > A: A wind from the South. > Q: The wind is from the East. What makes the sailboat move North? > A: It can't! > Q: Yes it can, set the sail to align SW-NE. What makes the sailboat move > North? > A: Hmmm... the force of the wind. > Q: The wind is blowing from the East. What stops the sailboat moving West? > A: The keel, aligned N-S. > Q: So the sailboat moves North but the wind is from the East. How fast does > the sailboat move North? > A: I dunno, let's talk about golf balls and kitchen faucets and plastic > spoons instead. They've got dimples. Wind and water current can both make a sailboat move (accelerate) initially. It takes a force for an object to acceleratinreplyto=0Oh5o. 37279$gM.14334(a)hurricane
From: Androcles on 1 Aug 2010 18:01
"spock" <spock(a)strato.net> wrote in message news:95a06261-9d6f-4c9b-8f00-f3f0c014937e(a)s17g2000prh.googlegroups.com... | On | > ==================================================== | > Q: What makes a sailboat move? | > A: The wind. | > Q: What makes a sailboat stop? | > A: Friction with the water. | > Q: What makes the sailboat move North? | > A: A wind from the South. | > Q: The wind is from the East. What makes the sailboat move North? | > A: It can't! | > Q: Yes it can, set the sail to align SW-NE. What makes the sailboat move | > North? | > A: Hmmm... the force of the wind. | > Q: The wind is blowing from the East. What stops the sailboat moving West? | > A: The keel, aligned N-S. | > Q: So the sailboat moves North but the wind is from the East. How fast does | > the sailboat move North? | > A: I dunno, let's talk about golf balls and kitchen faucets and plastic | > spoons instead. They've got dimples. | | | Wind and water current can both make a sailboat move (accelerate) | initially. It takes a force for an object to acceleratinreplyto=0Oh5o. | 37279$gM.14334(a)hurricane What does the speed of the boat have to do with the force of the wind? | |