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?