Question.

State, with reasons, the locality and extent of damage which may be sustained by the hull structure of a ship being driven hard through heavy seas.

Describe how such damage stated in (a) can be made good.

Answer.

Most likely to be damaged are:

Pounding region

This is the bottom shell for the forward 0.25 of the length of the vessel, three strakes of plating either side of the keel. This region is subject to severe impact stress.

Panting region

This is the forward 0.15 of the length of the vessel, but especially the forward 5% to 71\2% of the length (i.e. forward of the collision bulkhead). The panting stresses are cyclic and arise due to the fluctuations in water pressure as the forward end immerses/emerges during pitching.

At end connections/discontinuities

There is a susceptibility to cracking and failure at end connections and other discontinuities due to the stress concentrations that arise.

Damage may be made good as follows:

Pounding region

Any indented shell plating/frames should be 'faired' back to shape if possible (using wedges, shores, strong backs and heat if necessary). If this is too difficult, replace the bottom shell longitudinal grinders and floors as required.

Panting region

The same procedure as with pounding damage should be followed. Repair/replace shell plates, frames, stringers and panting beams as required.

At end connections/discontinuities

•Gouge or grind aft end connection welding and re-weld.

Drill the ends of cracks, gouge and weld if safe to do so.

If watertight integrity is threatened can use a cement box as a temporary repair.