DAVIS Hand Bearing Compass - Manual (Page 2)

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211_Engl.pdf October 2005
by the time equals both your distance offshore (A) and the distance
run (B). Tip: Another method to determine distance offshore is to
take two sightings off the same object exactly 60 minutes apart and
plot the two lines of position. Open a pair of dividers to match your
distance traveled in 60 minutes. Draw your actual travel line of posi-
tion (A) parallel to the compass course you are steering at the point
where the angle is the same width as your distance traveled (figure
5).
Predicting Collision Course. Take a sighting on any mov-
ing or stationary object that you suspect might be on a collision
course and note its bearing. If repeated sightings yield the same
bearing, you are on a collision course (figure 6). Note that a collision
course with a stationary object means that your are being "set" by
drift or tide and you must alter course to avoid a collision. Tip: These
types of sightings are extremely useful in sailboat racing when two
boats are converging on different tacks.
Checking Drift While at Anchor. Take sightings on any two
or more objects on shore and write them down. Radical changes in
their magnetic bearings could indicate that your anchor is dragging.
Tip: The closer you are anchored to the objects on shore, the
greater the chances that simple swinging on the anchor will cause
these bearing to change.
Caring for Your Compass. The Davis Hand Bearing
Compass is a precision instrument. It is designed for rugged use and
built to last a lifetime, but must not be dropped or exposed to severe
shock trauma. It can be cleaned with fresh water or alcohol; do not
use any other solvents. Continuous vibration or exposure to magnet-
ic influences can damage the pivot bearing or magnetism of the
compass and lessen its accuracy.
Factory Overhaul. Contact Davis Instruments if you would like
to have your Hand Bearing Compass overhauled.