NavList:

Frank, you wrote 

"then the values under "knots" and "fathoms" are effectively nautical miles and sixth parts of miles (which you can confirm by noticing that the value under "F" ranges from 1 to 5"

Looking at your attached example I read, at H=1 hours (the second one), K=6 and F=6. This contradicts your statement.

The original meaning of F is somewhat unclear. Bowditch, 20th edition, 1851, states on page 126 "Each of these knots [i.e. the knots on the log-line] is divided into 10 fathoms, of about 5 feet each." 

According to a note in The Journal of Navigation, vol. 27, page 536, 1974, Duncan Henderson claims that F means fractions, i.e. tenth of a knot.

I have a personal note made some ten to fifteen years ago that in the logbook of Bounty, from 1788, F seems to be the number of ⅛ knot, which corresponds quite well to a fathom of 6 feet for a length of around 48 feet between the knots on the log-line. Then the eights could be easily "fathomed" from the nearest knot on the line.

Lars