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    Re: Plotting tools
    From: Greg R_
    Date: 2008 May 27, 21:59 -0700

    --- "Greg R."  wrote:
    
    > The plotter arm can then either be left free or locked to a bearing
    > (it works a lot like a drafting tool, only a lot more versatile and
    > better-suited to navigation work).
    
    That should read "drafting machine" vs. "drafting tool".
    
    And for those on the list who might be too young to know what that is,
    that was one way that we did mechanical drawing back in the bad old
    days before CAD programs. :-)
    
    --
    GregR
    
    
    
    > --- Lu Abel  wrote:
    >
    > > Rotate the front disk by the amount of local variation and tape it
    > > to the back disk.  Draw a course line with any convenient
    > > straightedge, slap the PIN down so the hollow rivet is over the
    > > course line, align it properly with the parallels and meridians on
    > a
    > > chart and you've instantly got your magnetic course.   Way easier
    > to
    > > use than describe.  Nearest currently available equivalent is the
    > W&P
    >
    > > Compute-A-Course that's shown below the Portland plotter.
    >
    > It's a little more elaborate than a garden-variety plotter, but the
    > ChartPak plotter arm has a similar feature - you can lock the degree
    > wheel to either the true or magnetic compass rose (or anything else
    > entirely, I suppose it could also be used for grid navigation if
    > you're
    > in a polar area). The plotter arm can then either be left free or
    > locked to a bearing (it works a lot like a drafting tool, only a lot
    > more versatile and better-suited to navigation work).
    >
    > > Something I can't figure out is why many different designs of
    > really
    > > good plotters (like the PIN) appear, but none seems to stick around
    >
    > > except the traditional 4x15 plotter and parallel rules.
    >
    > As someone mentioned in another thread, a lot of navigation is
    > steeped
    > in tradition, and traditions sometimes apparently die hard.
    >
    > --
    > GregR
    >
    >
    > > Greg R. wrote:
    > > > --- Guy Schwartz  wrote:
    > > >
    > > >
    > > >> Edges are graduated in inches and centimeters
    > > >>
    > > >
    > > > It would be a lot more useful (at least in my opinion) if it also
    > > had a
    > > > scale that matched the plotting sheets, though I guess you could
    > > always
    > > > use the inch scale and "do the math" mentally when plotting.
    > > >
    > > Several of the typically 4 x 15 inch plotters such as the Weems and
    >
    > > Plath plotters do indeed feature distance scales for the common
    > chart
    > >
    > > scales of 1:40,000 and 1:80,000.   But that's useful only if these
    > > are
    > > indeed "common chart scales"   In a cruise along the coast of Nova
    > > Scotia, I was more than a little surprised to discover that their
    > > coastal charts are not of a constant scale (eg, 1:80,000) the way
    > US
    > > charts are scaled, but vary somewhat from place to place.
    > >
    > > On another note, my favorite plotter (for local coastal navigation,
    > > at
    > > least) is a non-longer-available device called the Pocket Instant
    > > Navigator.   Incredibly simple device -- two clear plastic disks
    > > joined
    > > at their centers by a hollow rivet and able to rotate with respect
    > to
    > >
    > > one another.   Disks are inscribed 0-360 degrees.  Back disk also
    > has
    > >
    > > square grid at aligned N-S and E-W.  Rotate the front disk by the
    > > amount
    > > of local variation and tape it to the back disk.   Draw a course
    > line
    > >
    > > with any convenient straightedge, slap the PIN down so the hollow
    > > rivet
    > > is over the course line, align it properly with the parallels and
    > > meridians on a chart and you've instantly got your magnetic course.
    >
    > >
    > > Way easier to use than describe.  Nearest currently available
    > > equivalent
    > > is the W&P Compute-A-Course that's shown below the Portland
    > plotter.
    > >
    > > Something I can't figure out is why many different designs of
    > really
    > > good plotters (like the PIN) appear, but none seems to stick around
    >
    > > except the traditional 4x15 plotter and parallel rules.
    > >
    > > Lu Abel
    > >
    > > >
    > >
    >
    >
    > >
    >
    
    
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