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#1
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judging current; rules of thumb?
Here's one for those of you out there without onboard
instruments/knotmeter/gps.... Is there any reasonably accurate (say, within a know or so) way of judging the current, when you are under way, and there are no fixed objects within sight? Shaun |
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#2
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judging current; rules of thumb?
"Shaun Van Poecke" wrote in message
... Here's one for those of you out there without onboard instruments/knotmeter/gps.... Is there any reasonably accurate (say, within a know or so) way of judging the current, when you are under way, and there are no fixed objects within sight? Shaun Yes, there are. -- jlrogers±³© |
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#3
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judging current; rules of thumb?
"Shaun Van Poecke" wrote Is there any reasonably accurate (say, within a knot or so) way of judging the current, when you are under way, and there are no fixed objects within sight? Yes, there is. All you have to do is look on the charts for those little arrow thingies... Or you can look in the tide and tide current books. Cheers, Ellen |
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#4
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judging current; rules of thumb?
Shaun Van Poecke wrote:
Here's one for those of you out there without onboard instruments/knotmeter/gps.... Is there any reasonably accurate (say, within a know or so) way of judging the current, when you are under way, and there are no fixed objects within sight? Shaun No, there aren't. -- jeff |
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#5
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judging current; rules of thumb?
"Jeff" wrote in message
. .. Shaun Van Poecke wrote: Here's one for those of you out there without onboard instruments/knotmeter/gps.... Is there any reasonably accurate (say, within a know or so) way of judging the current, when you are under way, and there are no fixed objects within sight? Shaun No, there aren't. -- jeff Yes, there is. -- jlrogers±³© |
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#6
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judging current; rules of thumb?
"jlrogers±³©" wrote in message
t... "Shaun Van Poecke" wrote in message ... Here's one for those of you out there without onboard instruments/knotmeter/gps.... Is there any reasonably accurate (say, within a know or so) way of judging the current, when you are under way, and there are no fixed objects within sight? Shaun Yes, there are. -- jlrogers±³© I can't think of any way to do it without some kind of instrument. If there's nothing in sight, you have no point of reference. Tell us please.... -- "j" ganz @@ www.sailnow.com |
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#7
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judging current; rules of thumb?
jlrogers±³© wrote:
"Jeff" wrote in message . .. Shaun Van Poecke wrote: Here's one for those of you out there without onboard instruments/knotmeter/gps.... Is there any reasonably accurate (say, within a know or so) way of judging the current, when you are under way, and there are no fixed objects within sight? Shaun No, there aren't. -- jeff Yes, there is. OK, please explain. Maybe this will bring Jax out of the woodwork to tell us that Einstein proved that dead reckoning is impossible. |
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#8
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judging current; rules of thumb?
"Jeff" wrote OK, please explain. Maybe this will bring Jax out of the woodwork to tell us that Einstein proved that dead reckoning is impossible. I can explain it too. I've been thinking about a way off and on since you said there's no way. Remember way back when we were talking about me getting in irons because of wind going the same speed as the current? You said unless there's land there's no way to tell. Well there is and I'm going to tell how. 1-- tie a long string on an empty wine bottle. 2-- throw the wine bottle off the boat when your sailing. 3-- get a stop watch time on how long it takes for the string to go tight and pull the bottle along. 4-- pull the bottle back aboard. 5-- turn around and go the opposite direction 6-- repeat the first three steps. Since the bottle goes with the current it lets you measure the current. The wind is independent. The bottle lets you connect to the current. It lets you see it. Your boat measures the wind speed. It's not as fast as the wind but it's moved by it the same each way. Reaching that is. You have to reach both ways. Cheers, Ellen |
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#9
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judging current; rules of thumb?
Jeff wrote:
jlrogers±³© wrote: "Jeff" wrote in message . .. Shaun Van Poecke wrote: Here's one for those of you out there without onboard instruments/knotmeter/gps.... Is there any reasonably accurate (say, within a know or so) way of judging the current, when you are under way, and there are no fixed objects within sight? Shaun No, there aren't. -- jeff Yes, there is. OK, please explain. Maybe this will bring Jax out of the woodwork to tell us that Einstein proved that dead reckoning is impossible. Use a venturi/pitot boat knotometer and rotate it 360 degrees noting the speed accurately for increments of angle. If it reads 0 knots for all angles your GPS speed is the current speed. If it reads 5 knots forward, 0 knots aft and the GPS speed is 4 knots the current is 1 knot from aft. The same procedure is done for sideways currents but one must use trigonometry, a feat easily accomplished on my Mensa circular mind meld slide rule. I can do all the calculations in my head while wearing just a set of Speedo briefs. I've devised a set of Lorentz contraction gauges to measure all absolute motion precisely in 3 dimensions. Aliens are after me to keep this gift to mankind from falling in human hands so I must travel in disguise. Jax |
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#10
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judging current; rules of thumb?
Nope. Don't work. Not Nohow.
Ellen MacArthur wrote: "Jeff" wrote OK, please explain. Maybe this will bring Jax out of the woodwork to tell us that Einstein proved that dead reckoning is impossible. I can explain it too. I've been thinking about a way off and on since you said there's no way. Remember way back when we were talking about me getting in irons because of wind going the same speed as the current? You said unless there's land there's no way to tell. Well there is and I'm going to tell how. 1-- tie a long string on an empty wine bottle. 2-- throw the wine bottle off the boat when your sailing. 3-- get a stop watch time on how long it takes for the string to go tight and pull the bottle along. 4-- pull the bottle back aboard. 5-- turn around and go the opposite direction 6-- repeat the first three steps. Since the bottle goes with the current it lets you measure the current. but the boat is also going with the current. The boat speed is "through the water," not "over the bottom." The wind is independent. The wind that the boater would call "true wind" is actually the vector sum of the wind and current (adjusting signs as appropriate). The bottle lets you connect to the current. nope. You're connected to the current while you're in the boat. It lets you see it. nope. Your boat measures the wind speed. Nope. The wind it feels actually has a component added by the current. It's not as fast as the wind but it's moved by it the same each way. Reaching that is. You have to reach both ways. And how do you tell the boat speed over the bottom, as opposed to through the water? |
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