Chichester Yacht Club Magazine November 2016 | Page 10

Te c h ni ca l & S af e t y
The second is that recreational vessels can
only transmit the lower specification Class B
AIS signals. These signals can be filtered out
by vessels using Class A equipment in order to
reduce clutter on the screens and a
proliferation of alarms on the bridge. As the
number of Class B transmitting AIS fitted
increases it is more likely that ships will need to
filter the signals. In the Solent we often have
our plotter screens covered in Class B targets –
many of which are tied up in marinas – and it
would be difficult to criticise those who felt the
need to filter them out.
2. VHF radio calls not part of ColRegs
CHIRP considers that, given the imminence of
the potential collision, it was not a good idea to
spend time on attempting VHF contact. The
time would have been better spent taking
avoiding action. It has apparently become an
issue among professional seamen that VHF
contact is being used in lieu of following
ColRegs, and is the subject of another report in
CHIRP’s latest issue.

angles of visibility.
CHIRP also suggested that high power LED
lighting is fitted, which is eminently sensible
and was covered in the March edition of this
magazine.
4. Radar Visibility
CHIRP considered radar visibility and
suggested that passive radar reflectors are
unreliable and that radar target enhancers
(RTE) should be considered. The merits of
reflectors and RTEs were discussed by John
Barfoot in his “Crossing the Channel” talk in
March (summary in the April edition of this
magazine).

John’s view was that RTEs return the best
echo beyond the ship’s sea clutter region (more
than 6 Nm) but the size of the echo will stay the
same whatever distance from the ship. A radar
reflector should also be fitted to give a larger
echo when closer to (within 1 or 2 Nm). He also
explained that ships usually have two types of
radar X band and S band. S band may
3. Navigation Lights
sometimes be preferred by watchkeepers due
to its ability to penetrate rain, snow and sea
CHIRP drew attention to the difficulty of seeing clutter.
sailing vessel navigation lights and has drawn
some conclusions that seem to your
Radar reflectors work better with X band – their
correspondent to be wrong.
effective size as a target is 10 times smaller on
S band. Most RTEs work on X band though
Firstly they state that as sailing vessel
dual band ones are available.
mastheads are subject to pitch and roll the
navigation lights will appear as flashes.
Apart from cost the biggest problem with RTEs
Fortunately ColRegs takes this into account
is the power they consume although the engine
and require sailing vessel lights to be visible at can usually be started to power them if
+/- 25 degrees from the horizontal, unlike other necessary, such as when crossing shipping
vessels where the angle is +/- 7.5 degrees.
channels.
Details in ColRegs Annex I.
Being in a small boat at sea may be likened to
Secondly they conclude that yachts should
being on a bicycle on the road. Although the
consider burning “normal” navigation lights
boat is in plain sight a proportion of ships just
instead of the masthead tricolour. Presumably do not see it, probably because they are not
they mean a combination of the port and
looking out for such vessels.
starboard lights fitted for motoring and a stern
light. This seems a dangerous conclusion. Mast
head lights have the benefit that they cannot
be shielded by sails, that they are at a height
nearer the sightline of the ship’s watchkeepers
and they have the aforementioned greater

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