[Boatanchors] Radio transmitter ranges

[Grant Youngman]

> Who came up with 
> Knots anyhow, surely not Mark Twain! (LOL!) 

He may knot [sic] have thought it up, but used it no doubt.

The device that sailors used to make their speed measurement was called the
"chip log".  Chip as in chip of wood, and log as in to record in a log.  The
chip was a wedge of wood about 18" in size; it was tied to one end of a rope
on a large spool.  The rope had knots tied into it about every 47'3" (more
about how that was calibrated below).  This is related to modern speed
determining devices (air or water) that are still called "logs"

The wooden chip was thrown overboard at the ship's stearn (back end).
Because of its wedge shape, it would "grab" the water and start pulling out
rope as the ship moved forward at some yet unknown speed.  One man would
hold the spool of rope as it played out; another man would start a sandglass
filled with 30 seconds of sand; and a third man would count the knots as
they passed over the stearn board.  When the 30 seconds of sand expired, the
time keeper would call out and the counting of knots would stop.

The number of knots in the rope that were counted in 30 seconds was then
equal to the speed of the ship in nautical miles per hour.  

There's a picture and explanation at
http://www.tallshipbounty.org/Demos_ChipLog.html.  Pretty ingenious,
actually.

Most "boatanchor" like, to stay at least remotely on the forum's topic :-)

Grant/NQ5T