Knot log?

[Nereus32]

In the old days, when mariners used to measure speed with a knotted line thrown into the water, watched it drift by and counted the knots, what was the spacing of the knots? How long was the line? and what was the timing interval (seconds, tens of seconds, etc.)?

[RichH]

1 knot = 1 nautical mile per hour = approx. 100 ft. per minute = 101 ft. per minute (exactly) = 1.7 ft/sec.

Knot your line every 100 ft., count how many knots run out before the sand runs out in your "minute glass".