Jofra wrote:

Am I right in assuming "rhumb-line" is therefore the shortest
distance between two points on the surface of a sphere?
I think the word is being mis-used in this thread and would like an
authority to comment.

I don't know for sure that any authorities are reading or writing to this
thread, so I'll substitute until one comes along. No, you are _not_ "right"
in your assumption. Re-read the definition posted earlier.

However leaving that aside we should be thinking of the most
desirable course to sail and this may or may not be the direct
course to the destination.

If you were to say "the fastest course is the best," or "the most
comfortable course is the best," or ... etc., etc., then perhaps there would
exist some basis for discussion. Otherwise it is very difficult to make
progress on this subject using vague generalities. In addition I am still
under the impression that the discussion concerned steering error rather
than piloting technique.

... To give an example, I crewed on an American yacht last century from
New Caledonia to Bundaberg in
Australia. After leaving Noumea the skipper put a line on the chart
direct towards Bundaberg. "We follow that line" he said. Well there
is a current that runs south down near the coast of Australia. The
"shortest" distance by pencil did not equate to the shortest
distance in a yacht. We started off heading west and as we got
nearer our destination we were heading WNW. I partly blame his
background - fast power boats - for this situation.

I cannot say for sure that I understand your example since there are quite a
few details that have been omitted, but what you _seem_ to be saying is that
no allowance was made for current when setting a course. As mentioned
earlier, this has little _direct_ relation to steering error, although using
the broadest definition of "steering error" would include in many cases the
effects of unidentified or unquantified currents.

I don't know that anything I have written has been much help to you, but I
am afraid that I've pretty much run out of ideas at this point, old sport.

--
Good luck and good sailing.
s/v Kerry Deare of Barnegat
http://kerrydeare.home.comcast.net/