The collision (forepeak) bulkhead is the first transverse watertight bulkhead, fitted near the bow. Its purposes are:

• To limit the flooding in the event of a bow collision, so that the water is confined to the forepeak and the ship retains sufficient buoyancy and stability to survive.
• To provide a watertight boundary at the forward end of the cargo/machinery spaces, protecting them from flooding.
• To give the bow structural strength and to resist the impact loads of a collision and the pounding/panting loads.
• To provide a strong transverse member that stiffens the fore end and supports the stem and the forepeak structure.

The collision bulkhead is a strong transverse watertight bulkhead, built of plating with vertical stiffeners (or horizontal stringers) and a strong boundary connection. Sketch: a vertical transverse bulkhead at the forepeak, with the plating connected to the shell, the deck and the keel, and stiffened by vertical frames (or horizontal stringers) and a top and bottom stool. The bulkhead is made watertight and is connected to the stem and the side shell with continuous welds; the stiffeners are connected to the shell and deck to transmit the loads. The bulkhead is often corrugated or flat with vertical stiffeners, and is heavily constructed because it must resist the impact of a collision and the hydrostatic pressure of flooding. The attachment to the adjacent structure (shell, deck, keel) is made with continuous fillet or butt welds and the stiffeners are tied into the surrounding structure to give continuity of strength.

SOLAS requires a collision bulkhead to be fitted at the forward end, positioned at a distance from the forward perpendicular of not less than 5% and not more than 8% of the length (or 10 m, whichever is less) for ships, so that it is effective in limiting flooding. It must be watertight up to the freeboard deck, and no doors, manholes, ventilation ducts or other openings are permitted in it below the freeboard deck (except for a single watertight door in certain cases). The bulkhead must be of adequate strength and is subject to classification survey. The position and construction are governed by the SOLAS Convention and the classification society rules.

Pounding (slamming) is the repeated impact of the bottom of the bow on the water as the ship pitches in a seaway, when the bow emerges and then slams down on the water. It produces severe local impact loads on the bottom and forefoot plating. To resist pounding, the fore end bottom plating is made thicker, the frames are more closely spaced, and additional stiffening (intercostal floors, stringers, and a strong forepeak structure) is provided in the region of the bow; the bottom is strengthened over the forward 10-15% of the length, and the stem and forefoot are heavily constructed. The arrangement (sketch) shows the thickened bottom shell, closely spaced frames and the strong forepeak framing that resist the pounding loads.