Chuck Husick: Techno-Talk, January 2003 BoatUS Magazine
This months column may surprise those readers who believe that
we are interested only in things powered by electricity. Surprise! The
subject of this column works without batteries. It is a compass, specifically
a hand-bearing compass. Every boater should have one and know how to
mariners agree that every boat that sails beyond view of a shoreline
should have a properly compensated magnetic steering compass, the steering
compass cant provide the navigation facilities available from
a modest investment in a hand-bearing compass.
you are proceeding on a constant heading when you notice a distant vessel
on your starboard bow. Being a prudent mariner you want to keep an eye
on the other boat to determine the possible need to alter your course.
You note the other vessels position in relation to a flyspot on
your windscreen, knowing that you can then check for a change in relative
bearing to determine if you will pass clear, have a close encounter
or a collision. Unfortunately the flyspot was, in fact, a fly and it
has moved on, depriving you of your calibrated reference point. You
need a new visual sight reference. Lacking a grease pencil with which
to mark the windscreen, you look for some other reference point, a scratch
in the glass or some point on the windscreen frame.
were carrying a hand-bearing compass you could have made a note of the
other vessels magnetic relative bearing and checked it again every
few minutes. If you change your heading, first make a note of both your original heading and the relative bearing so that you can use the information when assaying the new relative bearing to the target vessel. Whatever pucker factor might have been present disappears
with the knowledge that you are properly tracking the movement of the
take the relative bearing on the first boat you note that the waters
have become crowded, including commercial traffic, some of which consists
of tugs with barges in tow. You know the danger involved in misjudging
an encounter with this type of traffic and begin to take bearings, noting
the identity of the target, the time and the relative bearing of each.
In a few minutes and using a pencil and a piece of paper, you will have
created a reasonably comprehensive picture of the nautical world around
you, all thanks to a compass that works without batteries.
survived the voyage through the weekend traffic you reach your destination,
a quiet anchorage. You select the ideal place to carefully lower the
anchor (having learned long ago that dropping the anchor results in
an anchor uselessly buried under a pile of chain). It is quiet, the
breeze has dropped to a mere zephyr. You are set for the night, unless
the wind picks up and/or the tidal current causes your anchor to drag.
You have set the anchor watch function on your GPS or Loran to alert
you if something goes awry during the night. GPS can be squirrelly under some circumstances, including problems created by the interaction of strong TV
signals with some types of marine TV antennas, plus the occasional government
denial of service exercise that may block or jam GPS signals. If you are using a Loran receiver you are aware of the position fix changes that can occur at dusk (and at dawn) and when a weather front approches.
In pursuit of self-reliance, you take out the hand-bearing compass and
take a round of sights on distinctive objects on the shore. You try
to choose objects that will still be visible when the sun sets, knowing
that if something does occur to interrupt a quiet night, it will be
when it is black as proverbial pitch. Now you can relax.
additional uses for the hand-bearing compass beyond those mentioned.
Its an obvious back-up for the main steering compass. It can be
used to determine if DC current is flowing in a circuit by moving it
up against one of the two wires in a circuit and watching for a movement
of the compass card. (This works best when the current is at least few
amperes). Some solo sailors take the hand-bearing compass with them
when they make the daily pilgrimage to the home of the porcelain god,
allowing them to check on any change in the boats heading during
their brief time off watch. With prices starting at $25, the value is