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] Ideal wing surface texture
Message text written by "Derek Boyer" The moral of the story is that Im being led to believe that smoother is better even in our low-Re environment. Pretty well unsupported reasoning, but beliefs arent always reasonable or wrong. For what it's worth, as this is purely second-hand... I have heard from God on this topic, in a discussion about very, very low Reynolds numbers, specifically micro-hand launch. Smoother is better. Period. John Roe Laguna Hills, Ca www.martialartsacademy.org "Wise men STILL seek Him." 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]
