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Could a fan in front of a sail increase speed?
A question sometimes asked is that if you have a large fan at the
stern on a sailboat blowing forward into the sails would that propel the boat forward? The usual answer given is no because the fan blowing air forward would produce momentum propelling the boat backwards. This would swamp the effect of an effective wind acting on the sails. But suppose instead you had the fan in front blowing rearward into the sails? In this case the momentum would propel the boat forward. Furthermore by using the method of tacking into the wind, the wind blowing into the sails could produce a force with a forward component as well. Then the acceleration forward should be higher than that produced by the momentum flow of the fan alone. The speed could also be higher than the speed of the air created by the fan since tacking into the wind can give you a higher speed than the wind speed. Would this work? Bob |
Could a fan in front of a sail increase speed?
Yes, you won't even need the sail!
http://www.answers.com/topic/air-boat-jpg Scout wrote in message oups.com... A question sometimes asked is that if you have a large fan at the stern on a sailboat blowing forward into the sails would that propel the boat forward? The usual answer given is no because the fan blowing air forward would produce momentum propelling the boat backwards. This would swamp the effect of an effective wind acting on the sails. But suppose instead you had the fan in front blowing rearward into the sails? In this case the momentum would propel the boat forward. Furthermore by using the method of tacking into the wind, the wind blowing into the sails could produce a force with a forward component as well. Then the acceleration forward should be higher than that produced by the momentum flow of the fan alone. The speed could also be higher than the speed of the air created by the fan since tacking into the wind can give you a higher speed than the wind speed. Would this work? Bob |
Could a fan in front of a sail increase speed?
wrote in message oups.com.. .. A question sometimes asked is that if you have a large fan at the stern on a sailboat blowing forward into the sails would that propel the boat forward? The usual answer given is no because the fan blowing air forward would produce momentum propelling the boat backwards. This would swamp the effect of an effective wind acting on the sails. But suppose instead you had the fan in front blowing rearward into the sails? In this case the momentum would propel the boat forward. Furthermore by using the method of tacking into the wind, the wind blowing into the sails could produce a force with a forward component as well. Then the acceleration forward should be higher than that produced by the momentum flow of the fan alone. The speed could also be higher than the speed of the air created by the fan since tacking into the wind can give you a higher speed than the wind speed. Would this work? Of course it will. Haven't you ever watched a Popeye cartoon? SV |
Could a fan in front of a sail increase speed?
Would this work? No, and we promptly removed our GE fan from the swim platform at the start of the season. The fan cost more than Scotty's boat. RB 35s5 NY |
Could a fan in front of a sail increase speed?
Wind blowing on bare poles will make the boat go.
The apparent wind created by a boat drifting withe the current (in still air relative to the ground) will make it go faster than the current. Yes, the fan blown into the sail at the correct locations will increase boat speed. Blowing it from the rear and using ballistic theory will not yield the true answer. Blowing the fan over the sails and correctly applying Bernoulli's Laws shows the sailboat will indeed move forward. Under the right conditions the sailboat will move faster than the windspeed of the fan. I am an intellectual (Mensa member in good standing), look great in Speedos and wonder if LP is available. Kates keeps on standing me up - without Viagra! Jax |
Could a fan in front of a sail increase speed?
Jax wrote:
snip I am an intellectual (Mensa member in good standing), look great in Speedos snip.. Jax Sez who? We've been subjected to the pictures unfortunately. |
Could a fan in front of a sail increase speed?
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Could a fan in front of a sail increase speed?
Somebody said that you died of aids...
Jax typed: Wind blowing on bare poles will make the boat go. The apparent wind created by a boat drifting withe the current (in still air relative to the ground) will make it go faster than the current. Yes, the fan blown into the sail at the correct locations will increase boat speed. Blowing it from the rear and using ballistic theory will not yield the true answer. Blowing the fan over the sails and correctly applying Bernoulli's Laws shows the sailboat will indeed move forward. Under the right conditions the sailboat will move faster than the windspeed of the fan. I am an intellectual (Mensa member in good standing), look great in Speedos and wonder if LP is available. Kates keeps on standing me up - without Viagra! Jax |
Could a fan in front of a sail increase speed?
Jax (which I doubt)
Jax doesn't subscribe to Bernoulli's Theory but believes in Newton's Law. (For each and every force there is a egual AND opposite force created) I have to admit my own acceptance (Maybe) to this theory. The question does a lot to bisporove Bernoulli and adds to Newton. With Newton's law the force created (and this is my own observation, right or wrong I don't know) is the force deflecting the with the leading edge of the sail away from the curved side of the sail. The reaction of the air, not the deflected air but the normal atmospheric air to rush in and equalize the reduced air on the curved side, which is moving and slides off the trailing (Leech) edge. This courses the tell-tales to stream, sometimes even hooking to the windward side. This is my reasoning and why I don't think the fan theory would make the boat move faster. It would be a a disruption to the Action/Reaction of the Sail surface by introducing a independent air supply. For any of the racing sailors that have ever stopped a windward boat from the leeward side by getting close enough to put the exhaust air from your sails to the curved side of their sail will know what I'm talking about. http://community.webtv.net/tassail/ThomPage |
Could a fan in front of a sail increase speed?
Larry wrote:
wrote in news:1153667730.918826.254080 @p79g2000cwp.googlegroups.com: Would this work? No. Airboats with just the fan go 70 mph, even over wet grass. I haven't seen any sails on any of them to increase speed. Let's think....If we put an airboat engine/fan on the bow blowing through all that wind resistance of rigging and sails and tackle and measure the speed.....then, clean the deck of all sailing paraphenalia and let the airboat fan power the boat with no sailing equipment, its drag, its weight, its moment pulling the boat over... Which do YOU think would be faster? I'm picking Door Number Two! Thanks for the response. I didn't know airboats could go that fast. The key fact that makes me think it could go faster is that with a motor driven boat there is created apparent wind from its motion even in still air. The wind speed of this apparent wind is the speed of the boat of course (in still air.) But it is known that sailboats can *exceed* the wind speed: The physics of sailing. "How can boats sail faster than the wind? Lots of boats can---especially the eighteen footer skiffs on Sydney Harbour. Ask a sailor how, and he'll say "These boats are so fast that they make their own wind", which is actually true. Ask a physicist, and she'll say that it's just a question of vectors and relative velocities." .... "The faster that the boat goes, the greater the relative wind, the more force there is on the sails, so the greater the force dragging the boat forwards. So the boat accelerates until the drag from the water balances the forward component of the force from the sails." .... "Why are eighteen footers always sailing upwind? In a fast boat, there's no point going straight downwind: you can never go faster than the wind. So you travel at an angle. But if your boat is fast enough, then the relative wind always seems to be coming mainly from ahead of you, as these arrows show. So the eighteen footers never set ordinary spinnakers: they have asymmetrical sails that they can set even when they are travelling at small angles to the apparent wind." http://www.phys.unsw.edu.au/~jw/sailing.html Furthermore it has been proven that propeller driven boats that have sails can achieve higher speeds with the sails than from the propeller alone: Motorsailing - Some Thoughts. "Based on my experience the motorsailer is the most practical and comfortable vessel for serious ocean passagemaking. However these days power-only long range cruising yachts seem to be the rage. We sell about 8 power boats for each motorsailer we build. I personally can not understand the long range powerboat skipper generating a beautiful 7 to 9 knot wind, at some cost, and than just throwing it away - while worrying about fuel?" .... "Plus the sailing rig increases the speed of the vessel so less fuel capacity is needed. This weight savings coupled with the additional propulsion power available results in faster passages and excellent fuel economy. "How can this be? Well most power-only trawler yachts cruise at around 6 to 8 knots per hour depending on power, weight, hull shape and water line length. All these vessels are creating, at some expense, a wind equal to their speed. This wind, a vital and reliable source of energy, combines with and adds to the true wind to create an apparent wind across the boat which is just thrown away. The motorsailer, on the other hand, uses its rig to regain this energy resulting in increased boat speed, up to 25% above a stabilized powerboat, without increasing fuel use." http://www.seahorseyachts.com/seahor...emarine_3.html So a fan at the stern blowing *rearward* with the sails forward, so the fan does not blow over the sail, could likewise increase speed, just as with the motorsailers. What I'm asking is if in fact you did put that fan in front of the sails so the air did blow over them, would this increase speeds even better than the fan at the stern case. Bob Clark |
Could a fan in front of a sail increase speed?
Joe wrote:
wrote: A question sometimes asked is that if you have a large fan at the stern on a sailboat blowing forward into the sails would that propel the boat forward? The usual answer given is no because the fan blowing air forward would produce momentum propelling the boat backwards. This would swamp the effect of an effective wind acting on the sails. But suppose instead you had the fan in front blowing rearward into the sails? In this case the momentum would propel the boat forward. Furthermore by using the method of tacking into the wind, the wind blowing into the sails could produce a force with a forward component as well. Then the acceleration forward should be higher than that produced by the momentum flow of the fan alone. The speed could also be higher than the speed of the air created by the fan since tacking into the wind can give you a higher speed than the wind speed. Would this work? Yes it works! I'm in the process of mounting this fan on my bow pulpit. Making the swivel braket is the hardest part, air flow entry angle is important. I hope to gain 13kts: http://www.superiorairparts.com/Wall...er1024x768.jpg Joe Have you performed any tests that lead you to believe the speed can be greater than by putting the fan at the stern? That is, will the fan in the front blowing over the sails increase speed more than when it is at the rear and not blowing over the sails? Bob Clark |
Could a fan in front of a sail increase speed?
This brings back memories of long and
heated discussions about whether a windmill on a boat could propel the boat directly into the wind. Assume either electric power generated by the windmill or direct mechanical connection to the prop. Have at it! Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Could a fan in front of a sail increase speed?
wrote in message oups.com... A question sometimes asked is that if you have a large fan at the stern on a sailboat blowing forward into the sails would that propel the boat forward? The usual answer given is no because the fan blowing air forward would produce momentum propelling the boat backwards. This would swamp the effect of an effective wind acting on the sails. But suppose instead you had the fan in front blowing rearward into the sails? In this case the momentum would propel the boat forward. Furthermore by using the method of tacking into the wind, the wind blowing into the sails could produce a force with a forward component as well. Then the acceleration forward should be higher than that produced by the momentum flow of the fan alone. The speed could also be higher than the speed of the air created by the fan since tacking into the wind can give you a higher speed than the wind speed. Would this work? Bob Okay, here's what you do: Install a high-efficiency air compressor belowdecks. Connect this to a modified luff foil into which precisely sized holes have been drilled at an angle which allows for maximum efficiency of turbulated airflow across both the back and front of the sail, with the speed at the back being greater than that at the front (precise differential you will have to calculate yourself for your specific sail). Do this for all sails. Report back. :-) Karin Conover-Lewis Rawson 30 ketch "Escapade" Marinette WI |
Could a fan in front of a sail increase speed?
chuck wrote in news:1153691380_100797
@sp6iad.superfeed.net: This brings back memories of long and heated discussions about whether a windmill on a boat could propel the boat directly into the wind. Assume either electric power generated by the windmill or direct mechanical connection to the prop. Have at it! Jacques Cousteau did it. The windmill was vertical so it ran the propulsion with apparent wind from any direction. There were 4 of them as I remember on a good-sized ship. http://openweb.tvnews.vanderbilt.edu...21-CBS-19.html IT worked but had mechanical problems. |
Could a fan in front of a sail increase speed?
Actually, someone from Australia did just that. Well engineered, and
successful. Would go about the same speed in all directions. I wish I could remember where I read about it but it must have been 20 years ago. "chuck" wrote in message ... This brings back memories of long and heated discussions about whether a windmill on a boat could propel the boat directly into the wind. Assume either electric power generated by the windmill or direct mechanical connection to the prop. Have at it! Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Could a fan in front of a sail increase speed?
Questions like this remind me of the old Popeye cartoons, where Popeye thows an old bathtub into the sea, and then, whith a shower head on the end of a pipe, crams it into the drain. viola! Instant water jet! town pressure on tub forces water through shower head, and instant propulsion. Another Idea that looks good on paper....... wrote: A question sometimes asked is that if you have a large fan at the stern on a sailboat blowing forward into the sails would that propel the boat forward? The usual answer given is no because the fan blowing air forward would produce momentum propelling the boat backwards. This would swamp the effect of an effective wind acting on the sails. But suppose instead you had the fan in front blowing rearward into the sails? In this case the momentum would propel the boat forward. Furthermore by using the method of tacking into the wind, the wind blowing into the sails could produce a force with a forward component as well. Then the acceleration forward should be higher than that produced by the momentum flow of the fan alone. The speed could also be higher than the speed of the air created by the fan since tacking into the wind can give you a higher speed than the wind speed. Would this work? Bob |
Could a fan in front of a sail increase speed?
like the cartoon axiom which states, "cartoon characters may be unaffected
by gravity and may be supported by thin air, but only so long as they are unaware of their current, unsupported status." Scout wrote in message ups.com... Questions like this remind me of the old Popeye cartoons, where Popeye thows an old bathtub into the sea, and then, whith a shower head on the end of a pipe, crams it into the drain. viola! Instant water jet! town pressure on tub forces water through shower head, and instant propulsion. Another Idea that looks good on paper....... wrote: A question sometimes asked is that if you have a large fan at the stern on a sailboat blowing forward into the sails would that propel the boat forward? The usual answer given is no because the fan blowing air forward would produce momentum propelling the boat backwards. This would swamp the effect of an effective wind acting on the sails. But suppose instead you had the fan in front blowing rearward into the sails? In this case the momentum would propel the boat forward. Furthermore by using the method of tacking into the wind, the wind blowing into the sails could produce a force with a forward component as well. Then the acceleration forward should be higher than that produced by the momentum flow of the fan alone. The speed could also be higher than the speed of the air created by the fan since tacking into the wind can give you a higher speed than the wind speed. Would this work? Bob |
Could a fan in front of a sail increase speed?
That reminds me of: If from the top of your mast you drop a hand tool when
your boat is sailing a 5 - 6 knots where will it land? The answer is right on you boat. I wonder why? Could the same phenomena applies to a fan attached on a boat blowing on its sail to provide propulsion? "Scout" wrote in message ... like the cartoon axiom which states, "cartoon characters may be unaffected by gravity and may be supported by thin air, but only so long as they are unaware of their current, unsupported status." Scout wrote in message ups.com... Questions like this remind me of the old Popeye cartoons, where Popeye thows an old bathtub into the sea, and then, whith a shower head on the end of a pipe, crams it into the drain. viola! Instant water jet! town pressure on tub forces water through shower head, and instant propulsion. Another Idea that looks good on paper....... wrote: A question sometimes asked is that if you have a large fan at the stern on a sailboat blowing forward into the sails would that propel the boat forward? The usual answer given is no because the fan blowing air forward would produce momentum propelling the boat backwards. This would swamp the effect of an effective wind acting on the sails. But suppose instead you had the fan in front blowing rearward into the sails? In this case the momentum would propel the boat forward. Furthermore by using the method of tacking into the wind, the wind blowing into the sails could produce a force with a forward component as well. Then the acceleration forward should be higher than that produced by the momentum flow of the fan alone. The speed could also be higher than the speed of the air created by the fan since tacking into the wind can give you a higher speed than the wind speed. Would this work? Bob |
Could a fan in front of a sail increase speed?
wrote:
That reminds me of: If from the top of your mast you drop a hand tool when your boat is sailing a 5 - 6 knots where will it land? The answer is right on you boat. I wonder why? Could the same phenomena applies to a fan attached on a boat blowing on its sail to provide propulsion? Sorry to break this to you, but any hand tool dropped while on a boat will immediately and directly land in the water, regardless of from where it is dropped. Chuck ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Could a fan in front of a sail increase speed?
wrote: Joe wrote: wrote: A question sometimes asked is that if you have a large fan at the stern on a sailboat blowing forward into the sails would that propel the boat forward? The usual answer given is no because the fan blowing air forward would produce momentum propelling the boat backwards. This would swamp the effect of an effective wind acting on the sails. But suppose instead you had the fan in front blowing rearward into the sails? In this case the momentum would propel the boat forward. Furthermore by using the method of tacking into the wind, the wind blowing into the sails could produce a force with a forward component as well. Then the acceleration forward should be higher than that produced by the momentum flow of the fan alone. The speed could also be higher than the speed of the air created by the fan since tacking into the wind can give you a higher speed than the wind speed. Would this work? Yes it works! I'm in the process of mounting this fan on my bow pulpit. Making the swivel braket is the hardest part, air flow entry angle is important. I hope to gain 13kts: http://www.superiorairparts.com/Wall...er1024x768.jpg Joe Have you performed any tests that lead you to believe the speed can be greater than by putting the fan at the stern? That is, will the fan in the front blowing over the sails increase speed more than when it is at the rear and not blowing over the sails? Bob Clark Here's another way to look at the scenario. Suppose you had your giant fan on a raft with no sail or keel. This raft is connected to the sailboat by a rope. Suppose this rope initially is slack. You turn on the fan directed towards the sailboat. The wind produced by the fan allows the sailboat to move forwards by tacking into the wind. The raft and fan also move forwards separately due to the momentum thrust of the fan. The instant the rope is about to become taut you turn off the fan. When the rope tightens, the sailboat will get a higher speed because of the forward momentum of the raft. The raft will also be pulled backward but it won't affect the forward speed of the boat as long as it does not contact the boat. You make the rope long enough so this doesn't happen. Once the rope is slack again. You turn on the fan again. The process repeats. You see the result will be that the sailboat will wind up having a speed due to *both* the wind produced by the fan acting on the sails and from the momentum thrust produced by the fan. Bob Clark |
Could a fan in front of a sail increase speed?
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