CLIVE LOUGHLIN
SEAMANSHIP
Finding your
way in fog
In this new series of
articles Clive Loughlin will
T
his month we’re looking at ways of instruments in more detail in a later issue,
getting into a safe haven in thick fog but Box A shows the main principles for
without the benefit of GPS – which is depth calibration.
be looking at the various
often referred to as Blind Nav. The only We also need to know the hour by hour
tasks that a budding RYA
tools at our disposal are paper charts, tide height of tide at our location and the
tables, a compass, a boat speed (through strength and direction of the tidal stream.
Yachtmaster might be the water) indicator, a watch and (most With practice these only take a few
expected to undertake in
importantly) a depth sounder. minutes to work out using the tide heights,
We have no radar, but we shall assume curves and streams in the almanac, and
the exam and
we have an engine and choose to use it, it’s a good idea to mark these up at the
which are both great
and are following all the recommended start of the day. In all that follows we
fun to practise and of
procedures for the conditions. assume that height of tide has been taken
away from the depth of water to give us
potentially life-saving
KNOW THY DEPTH AND SPEED
the charted depth and that our speed is
benefit. This first article
Before we start on our passage there are speed over the ground after allowing for
two very important things that we need the tidal stream.
on blind navigation
to have working in advance to a good
techniques is co-authored
level of accuracy. Our depth sounder
AVOIDING TRAFFIC
with Charles Wylie, a
needs to show the depth of water (as If we’re in a shipping lane, then one
opposed to ‘depth below the keel’ or priority is to get our boat out of it. This
Royal Navy Dagger
other abominable variations) and we need means getting somewhere shallow, so that
Navigation instructor.
to know our speed/distance travelled the big ships can’t get us.
through the water. We’ll cover calibrating If you think this means 10m depth,
98 Sailing Today July 09
ST147 Seamanship
FOG_RTG.indd 78 13/5/09 13:52:00
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