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    Re: Joshua Slocum's navigational methods
    From: Dan Hogan
    Date: 2005 Apr 17, 10:39 -0700

    ----- Original Message -----
    From: Frank R
    To: NAVIGATION-L{at}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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