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----- Original Message -----
From: Frank R
To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
Sent: 4/16/2005 5:28:39 PM
Subject: Re: Joshua Slocum's navigational methods


Dan H, you wrote:
"Since Slocum was an experienced see Captain of many years, and based on his
writings. I would say he used Lunars more than once in his voyage."

I think it's important to distinguish Slocum's circumnavigation from his
earlier commercial voyages. The risk, whatever it may have been, was
entirely his own when he was sailing around the world. He had no schedule
to keep, no cargo to deliver, no crew to keep safe and secure...

(Ans) Yes but he was also First Mate,  deckhand, chief cook,  and bottle
washer besides being the navigator. And most likely
          used lunars when he suspected his DR since he doesn't mention any
other method..

And you wrote:
"He most likely use a book of trig tables at best for his calculations."

That's what one would normally use for celestial navigation, lunars or
otherwise, in that era. Or is that what you meant? Those trig tables would
be found in any of the standard navigational manuals of the era. Perhaps he
had Bowditch's "Practical Navigator" or more likely Norie's "Epitome of
Navigation" (since it's established that he taught himself navigation
originally --decades earlier-- from Norie).

(Ans) Or more likely a set of Trig Tables like "six place tables".

And:
"It seems that how many times on a passage he would use lunars would depend
on his confidence in his current Dead Reckoning position."

Perhaps that's the point. Today we are taught that DR was a miserable
burden for early navigators who were always hopelessly uncertain of their
positions because DR was all they had. But the facts seem a little
different. Navigators cherished their dead reckoning. It was the mark of a
true mariner that he could sail an ocean by DR and scientific navigation
"spoiled the fun", you might say. It reminds me of the status of standard
celestial navigation today competing against GPS. The satellite systems
spoil the fun, so some navigators enjoy testing themselves by doing pure
celestial (+DR when the weather doesn't cooperate) to prove their mettle.
The GPS is stowed away but available if confidence fails. Ironically, a
19th century navigator might have seen the finely honed and "scientific"
methods of modern celestial navigation
as something like a GPS today --much too easy and given a few days 'anyone
can do it'.

(Ans) I think it's a matter of culture and familiarity. I don't find
maintaining a DR much work. I do find (on a passage) taking
        SR's a time consuming bother. Also the navigation is about getting
from point A to Point B  the with  best  seamanship
        possible. not navigating with scientific  mathematical precision
since on a small boat so many errors are introduced.

And:
"He only mentions it once in the book"

He also explicitly states in his book that he kept his longitude mostly by
dead reckoning, which was why I originally asked if there was any other
evidence on the matter. Nonetheless, some people who have read SAATW find
all sorts of "clues" that they think point to extensive use of lunars. It
looks like wishful thinking to me...

(Ans) Well the book was meant for the general public. I think loading it
with detailed navigation examples would have been
          defeating to sales at that time.

And you wrote:
"but at least once at mid passage and again sometime before making land
seems prudent."

Sounds about right for a prudent mariner with cargo or lives at risk. Then
again, a prudent man would have gotten his chronometer repaired. Was Joshua
Slocum a prudent man? Did he have anything to lose besides self-esteem? He
was a man setting out to prove himself and make a little fame and money off
it if possible. He succeeded more or less, but I wouldn't call him prudent.
Do you remember reading in the book that he didn't know how to swim?

(Ans) Well Slocum was a very experienced seaman and a LOT of the old time
sailors I knew did not know how to swim.
         Going overboard in the middle of the ocean alone swimming  would
not be much help, probably just prolong the agony.

        In the few passages I have made,  the largest boat was 35 ft. and
there were two of us. I started out
        taking SR's  morning, noon and evening. After a week of this it was
noon sites every other day. Then four days
        before our ETA I stared SR  again. But a DR was always maintained.

        The first 5 years that I sailed I used Mid-Lattiude sailing for my
DR. Breaking it down into 600 mile increments, that is
        what I used on our trip to Hawaii.

Cheers,
-Dan-

   

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