Re: [RCSE] Sailboat Wings
I saw a TV show filmed at North Sails showing how they make one of those A Cup mainsails. They form a solid plug of wood, or similar, then lay laser pre-cut pieces of kevlar, etc on the plug and sew it together with a giant moving sewing needle on a CNC controlled machine in 3D. The amazing thing to me is how close they can haul the sail in and not stall it. They call the "foils". Go DC! Rich Hollyday At 10:13 PM 01/03/2000 -0800, you wrote: Hi Guys, Anybody been paying any attention to the "Luis Vuitton Cup?" Notice the shape of the mainsails. Can you say elliptical? They seem to be running fairly high aspect ratio with really close to elliptically shaped sails.(Or should I call them wings?) I'm not a sailor (but I'd like to be), but I found this interesting. In a game where efficiency is everything, they could probably teach us something. Just an observation. Keep those planforms efficient! Daryl - I need a new hobby - Perkins RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
Re: [RCSE] Sailboat Wings
OK, here we go. There is true wind and there is apparent wind. Apparent wind is the wind you feel if there is no wind and you're on a bike and you start moving forward. It feels like there is wind, right? Sailboats use wind and forward motion to work. Proper sail trim is extremely important to achieve maximum efficiency from any given boat. You are manipulating your "wing/sail" with many different lines. OK. A close hauled (point of sail into the wind) mono hull sail boat can pretty much only go what is called hull speed. Now, you crack off the sails a little, head off the wind a bit and you start generating more of your own wind by gaining more speed. This is the true wind and your forward motion combined, hence more apparent wind and hence more speed. Anytime you sail past where the apparent wind is on your beam you throw up your spinnaker (big pretty sail) and you go even faster. Your sails are still working as a wing and you are being "lifted". That is until you are running down wind and then you only go as fast as the true wind is blowing. You cease getting lifted by your sails anymore. Your are "running before the wind". It doesn't matter what kind of a boat you are on either unless you are in a situation where you have a planing hull or there are waves and you break-loose and start surfing. ULDB's (ultralight displacement boats) which became extremely popular in the 70's can surf the ocean bay waves very well. Once down wind its only as fast as the wind is blowing for most boats. Its a pretty scary point of sail in a blow too. In sailboat racing, un-wanted jibes while running down wind result in what is commonly know as the "death roll" and you can be pinned on your side if you "round down". OK, in the medium of the ocean there is a lot of drag from the water. On land with only three wheels on the ground there's a lot less friction. On ice its even less. That is why extreme speeds can be achieved in a realitivly light wind. Its can pretty much be summed up by saying " the faster you go, the faster you go ". OK, so now if you want to sell all of your gliders and buy a sailboat and want to live on the wild side, buy a mutli-hulled sailboat and go real fast. Be prepared to get wet though. I am sure there is a much more scientific explanation and I'm looking forward to the many theories forthcoming on this glider exchange. Cliff Lindgren Brett Jaffee wrote: Well, as others have pointed out, there are sail powered vehicles that can go faster then the actual wind (I'm still not quite sure how that works, but apparently it does). As for flat areas with lots of wind, you've got places like the Bonneville Salt Flats in Utah, or even Rogers Dry Lake near Edwards AFB in California. At 10:25 PM 01/04/2000 -0800, Tracy R Reed wrote: On Tue, Jan 04, 2000 at 04:45:34PM -0800, Brett Jaffee wrote: stab. Supposedly, it could go 120mph. In a 120mph wind? Where do they find such wind with flat land to race on that isn't covered in dunes? -- Tracy Reed http://www.ultraviolet.org The idea that Bill Gates has appeared like a knight in shining armour to lead all customers out of a mire of technological chaos neatly ignores the fact that it was he who, by peddling second-rate technology, led them into it in the first place. - Douglas Adams in Guardian, 25-Aug-95 Brett Jaffee: [EMAIL PROTECTED] Brett's Slope and Power Home Page: http://home.earthlink.net/~jaffee OnTheWay Quake 2 server utility: http://www.planetquake.com/ontheway The Unoffical Extra 300 Home Page: http://www.bayarea.net/~nathan/extra300/ RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
Re: [RCSE] Sailboat Wings
Hit the delete key if your not interested, sorry, but I find this fascinating. Boy, during the winter, you guys will go on about anything. ;-) Honestly, I think there are a lot of applicable principles here, and I am amazed at the number of RC soaring guys who are/have been sailors. (I rec'd a lot of private responses also) I saw the same program as Brett. The landsailer in question was VERY impressive. It was designed and built for one thing - to get the land speed record for land yachts. It was all composite, with long flowing lines. Even the cockpit was enclosed. It was very clean. The sail/wing was VERY high aspect ratio, all composite/molded. They were driving this thing on what looked like a runway, (it wasn't the salt flats) but this was not the record attempt. They said they had already gone faster than the current record of (I believe) 88 or 89 mph, and I seem to recall them saying they had been over 100 mph. The driver was impressed with its ability to go very fast in light winds. It was impressive to watch the "boat" accelerate. I now wish I was paying more attention so I could give you guys more accurate figures. I'll do a little "surfing" so I can offer some pics. C-ya D Brett Jaffee wrote: At 11:06 PM 01/04/2000 -0800, Scobie Puchtler or Sarah Felstiner wrote: In reaction to a submission about a landsailer that could make speeds of 120mph, Tracy recently wrote: I should note that the car in question hadn't reached these speeds as of the time the show was filmed. It was hoped it would go that fast, though. While sailcraft are often seen as 'simply being pushed along by the wind', this is only the case when travelling downwind. When travelling more like perpendicular to the wind, on a 'point of sail' referred to as a 'broad reach', sailcraft become a rather sophisticated balance of vectors, taking wonderful advantage of lift over the foil section of the winglike sail to produce speeds potentially surprisingly higher than the wind itself Well, that makes some sense. I can see that, with the wind coming from the side, the sail is under a constant force from the side, which can being redirected to push/pull the craft forward, no matter how fast the wind the craft is moving. Since F=MA, the boat/car should continue to accelerate until the frictional or drag forces equal the force on the wing/sail. OTOH, if going directly downwind, the force on the wing/sail would drop to zero as the craft approached the speed of the wind. Is that close to being correct? Brett Jaffee: [EMAIL PROTECTED] Brett's Slope and Power Home Page: http://home.earthlink.net/~jaffee OnTheWay Quake 2 server utility: http://www.planetquake.com/ontheway The Unoffical Extra 300 Home Page: http://www.bayarea.net/~nathan/extra300/ RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
RE: [RCSE] Sailboat Wings
In reaction to a submission about a landsailer that could make speeds of 120mph, Tracy recently wrote: In a 120mph wind? Where do they find such wind with flat land to race on that isn't covered in dunes? While 120mph is extreme speed for any sailcraft, it would not require winds of 120mph. The viability of sailcraft of various kinds to travel significantly faster than windspeed is well documented and happens every day with windsurfers, kitesurfers, iceboats, landsailers, sailboats with hydrofoils, etc. While sailcraft are often seen as 'simply being pushed along by the wind', this is only the case when travelling downwind. When travelling more like perpendicular to the wind, on a 'point of sail' referred to as a 'broad reach', sailcraft become a rather sophisticated balance of vectors, taking wonderful advantage of lift over the foil section of the winglike sail to produce speeds potentially surprisingly higher than the wind itself, especially when the medium of travel is low friction (as in an iceboat or wheeled landsailer) as opposed to high friction (as in a traditional displacement hull of a large sailboat). Even not particularly sophisticated iceboats can sail at sixty miles per hour in a 30 or 40 mph wind. Lift, Scobie in Seattle. -- Tracy Reed http://www.ultraviolet.org The idea that Bill Gates has appeared like a knight in shining armour to lead all customers out of a mire of technological chaos neatly ignores the fact that it was he who, by peddling second-rate technology, led them into it in the first place. - Douglas Adams in Guardian, 25-Aug-95 RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
Re: [RCSE] Sailboat Wings
Just think of ground wind speed the level sailvehicle is the thermal rise speed to our sailplane. YK Chan Seatte area In a message dated 1/4/00 10:55:44 PM Pacific Standard Time, [EMAIL PROTECTED] writes: Well, as others have pointed out, there are sail powered vehicles that can go faster then the actual wind (I'm still not quite sure how that works, but apparently it does). As for flat areas with lots of wind, you've got places like the Bonneville Salt Flats in Utah, or even Rogers Dry Lake near Edwards AFB in California. RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
RE: [RCSE] Sailboat Wings
At 11:06 PM 01/04/2000 -0800, Scobie Puchtler or Sarah Felstiner wrote: In reaction to a submission about a landsailer that could make speeds of 120mph, Tracy recently wrote: I should note that the car in question hadn't reached these speeds as of the time the show was filmed. It was hoped it would go that fast, though. While sailcraft are often seen as 'simply being pushed along by the wind', this is only the case when travelling downwind. When travelling more like perpendicular to the wind, on a 'point of sail' referred to as a 'broad reach', sailcraft become a rather sophisticated balance of vectors, taking wonderful advantage of lift over the foil section of the winglike sail to produce speeds potentially surprisingly higher than the wind itself Well, that makes some sense. I can see that, with the wind coming from the side, the sail is under a constant force from the side, which can being redirected to push/pull the craft forward, no matter how fast the wind the craft is moving. Since F=MA, the boat/car should continue to accelerate until the frictional or drag forces equal the force on the wing/sail. OTOH, if going directly downwind, the force on the wing/sail would drop to zero as the craft approached the speed of the wind. Is that close to being correct? Brett Jaffee: [EMAIL PROTECTED] Brett's Slope and Power Home Page: http://home.earthlink.net/~jaffee OnTheWay Quake 2 server utility: http://www.planetquake.com/ontheway The Unoffical Extra 300 Home Page: http://www.bayarea.net/~nathan/extra300/ RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
Re: [RCSE] Sailboat Wings
At 10:47 PM 1/4/00 -0800, you wrote: Well, as others have pointed out, there are sail powered vehicles that can go faster then the actual wind (I'm still not quite sure how that works, but apparently it does). As for flat areas with lots of wind, you've got places like the Bonneville Salt Flats in Utah, or even Rogers Dry Lake near Edwards AFB in California. Brett, Having owned and built a couple of landsailers, they are capable of 2-3 times the speed of the prevailing wind. This speed potential occurs during a tack or a run whose direction is very close to being perpendicular to the prevailing wind. We regularly achieved speeds of 30-40 mph with out much difficultly. We spent most of our time along the shore of the Great Salt Lake which is smooth like the Salt Flats and allowed plenty of room for extended racing. The mass of a landsailer compared to a sailboat is much lower resulting in spectacular acceleration. I found as a teenager, that landsailers were a whole lot cheaper to operate than dirt bikes and embodied alot of the same "magic" that I've experienced with hang gliding and soaring (R/C and full-size). Tom Hoopes ([EMAIL PROTECTED]) RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
