"Jeff" wrote |
Hello?! If the boat is moving 4 mph over ground, but the current is
| only 2 mph, then the boat must be moving 2 mph through the water!
| Thus the rudder works.

Well, it doesn't work very good. :-O~

| Consider also: you've been plopped in the ocean with no position
| revealing instruments, but you do have speed and wind gauges. You
| sail for some time and then get rescued. Your rescuers ask if you
| encountered any current. What can you tell them?

Nothing but I can tell them if my rudder worked or not. If there's wind
but no current then it will work in irons because the boat goes backwards.
Look at it this way. The rudder feels a current going by it. (if it could feel).
How fast the current goes past land doesn't matter. Only what matters
is current passing the rudder. If the wind is pushing you back at the same
speed the current's going back the rudder feels no current. Oh, and it's
the same for trying to back the sail by hand. Even if the wind's blowing
10 mph if you're pushed backwards at 10 mph the sail won't feel any wind.
It'll think it's calm out.

Cheers,
Ellen