Question

Suggest, with reasons, why EACH of the following courses of action arc appropriate if a ship

a. Begins to wallow in heavy seas:

b. Frequently sound all hold bilges;

c. Frequently sound bilges in chain locker, peak tanks, cofferdams and other void -spaces;

d. Sound all fuel, fresh water and ballast tanks;

If satisfied with Q, (a), (b) and (c) trim ship by the stern and correct any list.

e. Reduce speed of main engine.

Answer.

(a) If the ship is wallowing (heavy wallowing) in heavy seas there is more likelihood of structural damage to the hull, hatch covers, ventilators etc.

This would allow water ingress which could reduce stability (free surface effect) and cause cargo damage. Frequent soundings of the bilges will give an indication of any such damage.

(b) Again, checking these spaces for water ingress, will indicate any structural damage affecting watertight integrity e.g. chain (spurring) pips covers to the chain locker, air pipes and sounding pipes to tanks.

The effect on stability would be the same as in (i) and there may also be a problem of increased trim by the head with more green seas being taken on forward, exacerbating the problems.

(c) Checking for watertight integrity problems, particularly with fuel tanks which has given major problems in the past. Sea water contamination of fuel has lead to engine failure with all the serious consequences.

(Ref. Braer incident and Ml 171).

Free surface in ballast tanks could be eradicated by pumping out or pressing up (load condition permitting).

(d) Generally, even keel is the desirable sailing condition, but if there is a trim, it is better to be by the stern. In this condition, there would be less likelihood of propeller/rudder emerging, thus giving better power/steering.

A trim by the head would cause more green seas to be taken over the bows making the condition worse.

Any list would reduce the roll angle at which deck: edge immersion would occur, hence any list should be corrected to provide the maximum angle off heel to deck edge immersion.

(e) Reducing main engine speed would lessen the impact effect of the seas and thus reduce the possibility-of-structural damage, particularly at the fore end. Ship motion behaviour would generally be better and the change in speed would cause a change in the periodic time of wave encounter which would reduce resonant motions if they had been occurring.