Watertight doors provided to increase the damage stability of the ro-ro ship by restricting the movement of any water along the deck and therefore reducing the free water surface area. Flood control doors divide a vehicle deck into separate sections to limit the extent of flooding. Different types are in use, each adapted to specific needs: side-stowed jalousie doors; top-stowed jalousie doors; side-rolling doors; and hemicyclic doors.
- Sliding link doors – The sliding link doors comprise three panels. In the stowed position, the door is placed along the side or along the centre line casing. When the door is closed, the sections run on a track, which is radius, shaped at the ship side and then transversely across the ship. The panels are powered by a hydraulic motor with rack and pinion or by jigger winches with wire. The joints between sections are hydraulically-locked when the door is in the closed position to allow it to take horizontal load.
- Concertina door – A vertical curtain door. It consists of a number of aluminium profiles shaped and dimensioned to be connected along the edges in a zigzag configuration. In use, the door’s storage cassette is lowered from its stowed position under the deck to the floor and the profiles are drawn out to form a “corrugated” bulkhead.