Next message: Russell: "lv-ab: resinated sand core?"
Have you actually done this?
I tried something similar with a half filled water bottle (simulated log) on
the end of a string. Using the idea that 1 nautical mile is about 1800
meters, I tied knots in the string every 3 meters. Then I let the bottle go
and started my stopwatch. I counted how many knots passed through my
fingers during 6 seconds (3meters / 6seconds = 1 knot speed). If 5 knots
passed in 6 seconds I was doing 5 x 3meter / 6sec x 3600sec/hr = 9km/hr = 5
knots.
Drawbacks:
- You want to use small diameter rope/string cause more than 20 meters of it
is a lot to manage.
- Good luck feeding it out at 6 knots without getting it fouled.
- My results were never repeatable nor anywhere near the speed on the GPS.
Maybe a longer string would reduce error, but increase the likelihood of
fouling. Thank God for GPS!
-Aharon
> Since a nautical mile is about 6000 feet, at a speed of one
> knot we travel 100
> feet in one minute. So, all that is required is 100 feet of
> light line, and an
> object which floats in water, but well submerged so it exerts
> reasonable drag.
> A block of heavy wood works fine as a drogue. Tie one end of
> the line to the
> boat, and the other to the drogue, and flake or coil the line
> loosely on deck.
> As a timing device, the stop watch built into most cheap
> digital wristwatches
> works well.
> Drop the drogue from the stern into the water, and
> simultaneously start the
> timer. When all the line has run out, and it snatches taut,
> stop the watch.
> Now simply divide 60 by the elapsed time in seconds, and the
> result is your
> speed in knots. For example, if all the line runs out in 12
> seconds, your
> speed is 60/12=5 knots.
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