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    Re: Sumner's Line (Navigation question)
    From: Fred Hebard
    Date: 2006 Feb 10, 00:15 -0500

    On Feb 9, 2006, at 8:40 PM, Bill wrote:
    
    > Ken wrote:
    >
    >> But someone made it (perhaps only for dramatic effect), so
    >> I still want to pursue it a little further.  Several posts agreed
    >> that it
    >> was not perilous since he was 31 min west of his DR, etc..  But, has
    >> everyone missed this, as my reading puts him 31.8min EAST (or
    >> closer to The
    >> Smalls light, and the rocks), or am I wrong?  Is it reasonable to
    >> make a
    >> case that being closer than he thought was courting disaster had
    >> he not
    >> discovered the LOP?
    >
    > Not George, but here is my two cents worth:
    >
    > It is a tough read, and I find it somewhat ambiguous.  Printed out
    > the chart
    > from Bowditch so I could play with it.  My measurements put his
    > 10am DR
    > approx. 41' longitude west of Small's light. What is shown as the
    > 10am DR is
    > indeed 40nm from Tusker light, and roughly 27+nm from Small's light
    > as the
    > crow flies.  The text does state that the time sight put him 15'
    > longitude,
    > or 9 miles further east than his DR, so his sight put him 31'
    > longitude west
    > (approx 19nm) of Small's light. (My comfort level would definitely be
    > decreased by the time sight.)
    >
    > Further, it is difficult for me to tell exactly how much ground he
    > covered
    > after his 10 AM sight until the elapsed time stated to complete the
    > leg to
    > the light.  While the line of position may have become clear at
    > "once" (once
    > the calculations were done), how long did it take to make them?
    > All I can
    > tell for sure from the account is that "...the ship was kept on her
    > course,
    > ENE,..."  So I presume she was sailing ENE after the sight and while
    > calculations were being made.  Once the LOP was clear, she then
    > made the
    > light in less than an hour.
    >
    > Unfortunately there is not enough information in this account to do
    > time
    > time/speed/distance calculations, but a SWAG says they didn't cover
    > 27+ nm
    > in the time it took to do the calculations, plus less than an hour
    > more of
    > sailing.
    >
    > From the account, and the SWAG, it would appear that Ken's
    > reasoning is
    > headed in the right direction.
    >
    > Bill
    
    
    Well yes, he was courting disaster had he kept his course up to the
    moment of spotting Small's light, lacking the LOP.  But lacking the
    LOP, I expect that he would have stood off or similar, and lost time.
    
    
    

       
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