Addition Of Results From Zig - Zag Tests To The Pilot Card
And The Wheel House Poster
Proposal By Hans Hederstrom
The present Pilot Card
does not contain any information regarding the course keeping and
yaw checking abilities of the vessel. This information is often
missing from the Wheel House Poster.
Available information is
normally limited to turning circles for loaded and ballast
conditions of the vessel. The data for those turning circles are
obtained in deep water, at full speed and with the rudder hard over.
This is circumstances that seldom apply to the working conditions of
a marine pilot.
Further more it should be emphasized that the
turning circle itself could give a false impression of the
manoeuvrability of the vessel. There are several test results where
the turning circle tests have indicated very good results but in
practice the vessels have proved to be very difficult to handle due
to poor course keeping and yaw checking abilities often combined
with poor dynamic stability. This is a result of modern hull design
in shipbuilding where the figure of the length / beam ratio has been
reduced and made even worse when the stern shape of vessels often
are designed similar to a barge.
Accidents have occurred due
to the fact that pilots have not been aware of the poor course
keeping and yaw checking abilities. In many cases the pilot made the
vessel build up a Rate of Turn, which later proved to be very
difficult to check and thereby resulted in an accident. This problem
has become even more pronounced with the increasing fitting of high
lift rudders.
If Zig - Zag test results were included on the
Pilot Card as well as on the Wheel House Poster, pilots would be
able to identify a vessel with poor course keeping and yaw checking
ability.
SUGGESTION.
The following
information should be made available on the Pilot Card:
The following information should be made available on the Wheel
House Poster:
- Diagram of 10 / 10 Zig-Zag test results with the first execute
to starboard as well as to port indicating ‘time to second
execute’ and the ‘first and second overshoot angles’.
- Vessel complies with ‘Interim Standards For Ship
Manoeuvrability’, Res. A.751(18) Yes / No
The Zig-Zag test should be repeated with the first execute to
starboard as well as to port, as large differences can occur due to
the type of propeller.
The Zig-Zag test should also be
repeated for ballast and loaded conditions.
There are no
special instruments needed to conduct those tests.