Doc No:

RF0152

Navigation In Heavy Weather

Reference Material

Version:

2

UNCONTROLLED DOCUMENT

Page 1 of 2

Navigation In Heavy Weather

It is of utmost importance to watch the pattern and character of the waves. Large long waves with
rounded tops might not be as dangerous as the short high ones with collapsing crests. Trains of
waves should be watched carefully as any cross patterns might lead to wrong decisions concerning
timing of manoeuvres.

The object of any manoeuvre in heavy weather is to take on as little water on board the vessel as
possible. Large amount of water on board causes damage if its energy is not dissipated before
encountering resistance of the ship’s structure. It also alters the stability of the vessel at a critical
period.

Manoeuvring towards wind/sea

• In general, the most favorable conditions can be found when manoeuvring with bare

steerageway, with the wind and sea about 15-20 degrees on either bow.

• Masters must consider the effect on sea conditions when winds are contrary to the current or

swell patterns. Freak wave phenomena may be encountered in the Agulhas current and the Gulf
Stream.

Manoeuvring with the weather

• When manoeuvring with the weather, adjust the speed so that the ship speed is appreciably

different to that of the swell. This will reduce the rolling effect.

• The speed should be adjusted to avoid shipping heavy seas over the poop. Pooping can cause

serious damage to the accommodation and machinery space structures as their large flat
surfaces offer great resistance to waves.

Turning

• If it becomes necessary to turn the vessel around on to a reciprocal course, carry out such a

turn very carefully. First reduce the speed to the minimum where by one can still maintain
steerage.

• Ensure that the whole crew is well informed about this critical manoeuvre well in advance and

that optimum engine response is absolutely assured.

• Observe the wave pattern carefully in order to choose the correct moment to start the

manoeuvre. Usually, waves seem to follow each other in groups of three with relatively calmer
periods in between two groups. A vessel might pick up the speed during one of these calm
periods and slam into the next wave group with too much momentum. Even if the vessel
manages to escape the first wave, one or both of the next two may end up causing severe
damage. Control of the ship’s head with minimum headway, therefore, is of utmost importance.
Consider choosing the beginning of the third wave to plan the turn.

• The idea is to start the turn when the bow is just rising from a trough and climbing the wave. Use

adequate engine power with wheel hard over, so that the vessel turns parallel to the wave
before reaching it’s top.

• Once the vessel is almost parallel to the wave, use maximum power with the wheel still hard

over, to effect the final part of the turn as quickly as possible. At all costs, avoid waves breaking
over the ship while it is parallel to the wave.

Doc No:

RF0152

Navigation In Heavy Weather

Version:

2

UNCONTROLLED DOCUMENT

Page 2 of 2

Disabled in heavy weather

• If a large tanker is disabled in heavy weather, it can drift down wind at a speed in excess of 4

knots. This can have disastrous ramifications if the vessel is close to a lee shore.

• A vessel with a stern trim of 5 metres and rudder amidships, if heading east with wind from the

north, it can drift in a 150 degree direction. If however, the tanker is heading west with wind from
the north, it drifts in a 210 degree direction. By swinging the ship through 180 degrees before
propulsion is lost, her drift direction can be changed by nearly 60 degrees.

DANGER

WIND

WIND

• Walking back an anchor to about 4 shackles of chain might swing her bows towards the wind

and alter her sailing direction yet again. The anchor and chain act as a sea anchor in such
situations. Streaming out entire lengths of floating fibre ropes over the bow with one end
secured on deck, also serve to give control over the ship’s head.

• If no options available and the ship is running into lee shore, it is better to lower one anchor to

say 9 shackles and secure it by cable stopper. Then stand by to use the second anchor as a
back up.

Alerting

• Send a security message. If heavy weather conditions are experienced, which have not been

forecasted, notify the MRCC.

• Advise Teekay management via

First Alert - Incident Notification for Personnel / Ship /

Environment Procedure (SP0268)

.