A Nice Little Conundrum - SailNet Community
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post #1 of 67 Old 02-15-2011 Thread Starter
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A Nice Little Conundrum

Boats A and B are identical and sailed by equally skilled crew.

Both are same distance from finish line.

Both are in a ten knot current flowing in the same direction as the boats.

Boat A has ten knot true wind from astern, Boat B no wind.

What will be the result ? A B Tie

Why ?

(Boat A's True Wind is towards the finishing line. . Current is also running towards the finishing line.)

Andrew B

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Last edited by tdw; 02-16-2011 at 08:15 PM.
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post #2 of 67 Old 02-15-2011
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Because the effect of 10 knots of wind and 10 knots of current from the same direction would not be additive.....there would be a tie.

10 knots of true wind, when you have 10 knots of current already would equal zero apprarent wind on the vessel, and therefore have zero effect upon boat A over and above the current B is benefitting from.

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Last edited by chall03; 02-15-2011 at 10:30 PM. Reason: written better
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post #3 of 67 Old 02-15-2011
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A has no wind relative to the boat 10-10=0 so travels at 10 knots over the ground with the current.
B has no true wind but 10 knots apparent wind from ahead from the relative motion of the boat versus the air, against which it can tack at say 5 knots increasing the wind a bit. In any event it can make way relative to the current so must be travelling at more than 10 knots over the ground so will get there first.
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post #4 of 67 Old 02-15-2011
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When both are travelling with the current, Boat A has no apparent wind, but Boat B will have about 10 knots apparent wind from dead ahead, so Boat B would get there later.
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post #5 of 67 Old 02-15-2011
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Is there a prize??

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post #6 of 67 Old 02-15-2011
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BOTH boats A and B have zero kts of apparent wind and 10 kts of true wind. They should drift over the line together.

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post #7 of 67 Old 02-16-2011
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Boat b will win if it tacks up the course since it will have a 10 kts apparent head wind to help it if it tacks at let's say 40 degs.
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post #8 of 67 Old 02-16-2011
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In the real world boat X will win by 1 second as this scenario has happened to us in real life on Zzzoom to finish a 10 race series winning by 1 second and 1 point

I do believe are bottom was a bit cleaner to allow the one second win after a 4 leg W/L event

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post #9 of 67 Old 02-16-2011
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A wins. B cannot possible move as fast as the current because the apparent 10kt wind from ahead will cause windage and slow it down.

This assumes they cannot change course. Can they?

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Last edited by Tim R.; 02-16-2011 at 03:28 PM.
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post #10 of 67 Old 02-16-2011
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Quote:
Originally Posted by treilley View Post
A wins. B cannot possible move as fast as the current because the apparent 10kt wind from ahead will cause windage and slow it down.
Boat B actually has 10 knots apparent wind which should allow her to move through the water towards the destination, essentially beating on a treadmill going the same way, while Boat A can only wait for the treadmill to get her there.

kinda like one person riding an escalator and the other walking up the steps on the same escalator....

Ron

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".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
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