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?

"Jeff" wrote in message
. ..
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.


You're right Jeff... but Neal is an idiot, so what do you expect.

--
"j" ganz @@
www.sailnow.com

"Jeff" wrote
Nope. Don't work. Not Nohow.

but the boat is also going with the current. The boat speed is "through the water," not "over the bottom."

It will work. Where you go wrong is saying the boat is going with the current.
It is if it's dead in the water. When it's sailing it's also going with the wind.
You never want to give the wind any credit. So the current goes two or three
knots. And the wind makes the boat go double that. You can use the boat motion
caused by the wind to measure the current. You just have to go back and forth.
You don't need instruments to measure the wind. You can use Beaufort. The
wind becomes your reference point. It's better if you go back and forth at least
every forty-five degrees to really tell what's going on with the current.

The wind that the boater would call "true wind" is actually the vector sum of the wind and current (adjusting signs as
appropriate).

And if there's no boat around? There's still apparent wind if you have
a bottle drifting with the current.

nope. You're connected to the current while you're in the boat.

Only if your just drifting along. Once your sailing the wind makes your boat
move independently of the current. The current still affects it but it affects it
different in different directions.

Your boat measures the wind speed.

You just contradicted yourself.

And how do you tell the boat speed over the bottom, as opposed to through the water?

The bottom's got nothing to do with this. He just wanted to know if you could know the
current with no outside landmarks and the bottom is an outside landmark.

Cheers,
Ellen

Sorry Ellen, its basic physics. Galileo figured it out about 400
years ago. He called it the Principle of Relativity. (Einstein used
the word "relativity" as a homage to Galileo.)

Here's a portion of his writings n the subject:
http://physics.syr.edu/courses/modul...E/galileo.html


Ellen MacArthur wrote:
"Jeff" wrote
Nope. Don't work. Not Nohow.

but the boat is also going with the current. The boat speed is "through the water," not "over the bottom."

It will work. Where you go wrong is saying the boat is going with the current.

Your boat isn't affected by the current? That's quite remarkable!

It is if it's dead in the water. When it's sailing it's also going with the wind.
You never want to give the wind any credit.

The boat moves according to the wind it feels. Its not the same as
the wind it would feel if there were no current.

So the current goes two or three
knots. And the wind makes the boat go double that.

That's speed over the bottom, which you can't determine.

You can use the boat motion
caused by the wind to measure the current.

No, you'll measure the speed through the water as the same in both
directions.

You just have to go back and forth.

Won't help - you'll measure "zero" current

You don't need instruments to measure the wind. You can use Beaufort. The
wind becomes your reference point. It's better if you go back and forth at least
every forty-five degrees to really tell what's going on with the current.

You might be able to guess that there's a strong current against a
strong wind if the steepness of the chop doesn't match the wind, but
this is only a guess and certainly not accurate to a knot. Otherwise,
what you're saying is just gibberish.



The wind that the boater would call "true wind" is actually the vector sum of the wind and current (adjusting signs as
appropriate).

And if there's no boat around? There's still apparent wind if you have
a bottle drifting with the current.

Sure, but there's no way to determine the components.


nope. You're connected to the current while you're in the boat.

Only if your just drifting along. Once your sailing the wind makes your boat
move independently of the current. The current still affects it but it affects it
different in different directions.

How is that? Do you have some sort of "magic" current? Up here, the
current affects you the same no matter what direction you're pointing.


Your boat measures the wind speed.

You just contradicted yourself.

Never.


And how do you tell the boat speed over the bottom, as opposed to through the water?

The bottom's got nothing to do with this. He just wanted to know if you could know the
current with no outside landmarks and the bottom is an outside landmark.


If you know the current, and the speed through the water, then you
know the speed over ground. If you can't determine the speed over
ground, then you can't determine the current.

"Jeff" wrote \
Sorry Ellen, its basic physics. Galileo figured it out about 400 years ago. He called it the Principle of Relativity.
(Einstein used the word "relativity" as a homage to Galileo.)

Here's a portion of his writings n the subject:
http://physics.syr.edu/courses/modul...E/galileo.html

Your just trying to confuse me with the relativity stuff. That's got nothing to
do with sailing. It's all about mass and energy and the speed of light. Physics and
the galaxy.
But, darn you, you had me thinking about it all night and I tried to think of some
way to prove it. But my bottle on a string doesn't work. Your right all it does is tell
the boat speed through the water. I was getting confused because I just kept thinking
about land and the current vs. land and it made sense. But he asked how to tell current
when no land's in sight and no instruments allowed. So I had to totally get rid of land.
I thought about that Star Trek episode where they found a planet that was just a
big ball of water all the way to the center. No land. So, if your sailing there you'd
never know if there was a current because you only have the water and the air.
There's no way to know (you can't use a sextant for a star sight) which is moving,
the water or the air. Your right on the edge between the two. You can't know.
So I was ready to say I lose and you win but I had a dream and in the dream
I saw big waves in the Gulf Stream which were really really big and breaking because
the wind was blowing like a hurricane against the current. Ah ha! That's it.
All you need is a table with wave heights and periods. If the waves are larger and
have different periods than they'd have in still water then there's a current.
So you CAN tell after all. No instruments needed just wave tables.

Cheers,
Ellen

Ellen MacArthur wrote:
"Jeff" wrote \
Sorry Ellen, its basic physics. Galileo figured it out about 400 years ago. He called it the Principle of Relativity.
(Einstein used the word "relativity" as a homage to Galileo.)

Here's a portion of his writings n the subject:
http://physics.syr.edu/courses/modul...E/galileo.html

Your just trying to confuse me with the relativity stuff. That's got nothing to
do with sailing. It's all about mass and energy and the speed of light. Physics and
the galaxy.

No, not at all. That's Einstein Theories of Special and General
Relativity. Galileo's Principle of Relativity is much more mundane.
Read that link again - its an interesting scientific observation made
almost 400 years ago.

But, darn you, you had me thinking about it all night and I tried to think of some
way to prove it. But my bottle on a string doesn't work. Your right all it does is tell
the boat speed through the water. I was getting confused because I just kept thinking
about land and the current vs. land and it made sense. But he asked how to tell current
when no land's in sight and no instruments allowed. So I had to totally get rid of land.
I thought about that Star Trek episode where they found a planet that was just a
big ball of water all the way to the center. No land. So, if your sailing there you'd
never know if there was a current because you only have the water and the air.
There's no way to know (you can't use a sextant for a star sight) which is moving,
the water or the air. Your right on the edge between the two. You can't know.
So I was ready to say I lose and you win but I had a dream and in the dream
I saw big waves in the Gulf Stream which were really really big and breaking because
the wind was blowing like a hurricane against the current. Ah ha! That's it.
All you need is a table with wave heights and periods. If the waves are larger and
have different periods than they'd have in still water then there's a current.
So you CAN tell after all. No instruments needed just wave tables.

Too late, I already mentioned this possibility twice. However, this
only works in limited situations, and is highly variable. The wind
has to be strong, and against a real current for a significant period
of time before the chop is measurable. "Wave tables" would be of
little use, it would take someone with serious local knowledge to be
able to determine the current to one knot accuracy even in the most
favorable situation.