At 06:55 PM 3/31/99 +0100, you wrote:
Hello Evans
>Slawek Grzechnik wrote "During WWII convoy navigators, whatever their
>civilian backgrounds, became superb sextant users." Well, some of them
>did and it was always an astonishment to me that anyone could
>successfully command, say, a Liberty ship with so little practical
>experience. American ships of necessity had relaxed requirements
>regarding sea time for navigators and many Liberty ships in convoy
>simply repeated the Commodore's signal flags for the noon position. Who
>could blame them? It takes time to become a competent astro-navigator
>(quicker with help from able companions).
Things happen during the war. This is inevitable. Trainning was very fast.
According to Nicholas Monsarrat ("The Cruel Sea") training of a corvette
officer was 6 weeks if I remember well. The only requirement was that the
candidate had a college degree or more. Many of them became old salts after
a time. For you Evans it would be easy to find more on the subject. There
was also some friction between merchant ships and their Navy escorts. Add
to that that even experienced navigators have blunders in their careers.
I have another proof that one week training may be sufficient. In one of my
yacht cruises I had two candidates for captain rank. They were very good
terrestrial navigators and wanted to learn astronavigation. It took them a
week to grasp it, which means that after a week they were able to take
sightings, correct them, use the Almanach and tables sensibly, and finally
plot lines and obtain position. At such point the trainees are given a
license to study and practice on their own, mastership of the subject still
being far away. They were exceptional guys however, already experienced
navigators and highly motivated.
Later during this cruise they took sightings on every occasion, whether
necessary or not, just for practice, and not only Sun but Moon and stars
too. Explanation: Sun is the body used most. It is hard to confuse with
other bodies which may occasionally happen with stars, they look more or
less the same in the sextant view. There are of course "tricks" to prevent
the confusion. Besides that stars may be measured only during twilights
when both stars and horizon are visible. Position by stars is less
accurate. Moon is very good body but time measurements have to be exact
because of its fast motion, there are also more corrections to apply so
navigators sometimes avoid shooting the Moon. Shooting only the Sun forces
you to make two sighting separated by few hours and moving the line from
the first sighting by the distance you made good ("running fix" is the
English name?). This introduces some error of course too. You know neither
your course, nor speed, nor leeway, nor currents set exactly but what to
do. Navigation is an art after all.
During this cruise when the coastline was visible and we could determine
the position by terrestrial methods (bearings, distances) or by radar (this
was the only cruise I had the yacht equipped with radar) we made a
competition. Each of us took one line and the winner was the guy whose line
was closest to radar position if we had one. It happened that lines went
through. Sometimes for fun, just before entering a harbour we took one line
to check if this was our destination (imagine faces of people walking on
the sea wall). Somewhat reverse method was being used by plane pilots in
good old days. They used to fly over railway stations to read the name of
the place.
Slawek
Slawek Grzechnik
32 57.4'N 117 08.8'W
http://home.san.rr.com/slawek
