Construction of a forepeak tank.

• The forepeak tank is the tank formed between the collision bulkhead and the bow (stem) of the ship, extending from the keel up to the freeboard deck or the tank top.
• It is bounded aft by the collision bulkhead, forward by the stem and bow plating, and at the sides by the shell plating.
• It is used for fresh water, ballast or occasionally for oil, and is fitted with a deep tank arrangement.
• The tank is fitted with a suction pipe, an air pipe and a sounding pipe. The suction is arranged so that the tank can be completely emptied.
• A manhole is provided for access, and the tank is fitted with a vent.
• The plating is stiffened by vertical and horizontal stiffeners. Because the tank is at the bow, the stiffening must resist panting and pounding.
• The collision bulkhead forms the after boundary and is a watertight bulkhead with no openings below the freeboard deck.
• The tank top (if a double bottom is present) or the bottom shell forms the lower boundary.

How the effects of panting and pounding are taken care of:

Panting:

• Panting is the in-and-out flexing (breathing) of the bow shell plating caused by the variation of water pressure as the ship pitches and the bow alternately rises and falls in waves.
• To resist panting, the bow region is stiffened with:
• Panting stringers: horizontal girders fitted on the inside of the shell plating at intervals, running longitudinally.
• Panting beams: transverse beams fitted at intervals.
• Additional vertical stiffeners and increased plate thickness in the bow region.
• The collision bulkhead itself acts as a major stiffener.
• Deep floors and increased frame spacing reduction in the forepeak.

Pounding (slamming):

• Pounding is the impact of the bow on the water surface when the ship pitches and the bow emerges and then slams down onto the water, causing severe impact loads on the bottom and bow structure.
• To resist pounding, the following are provided:
• Increased plate thickness in the bottom and bow region.
• Closer spacing of frames and floors in the forepeak.
• Deep floors (solid floors) fitted at every frame in the forepeak region.
• Additional longitudinal stiffening and stringers.
• The collision bulkhead and the forepeak structure are made stronger to absorb the impact loads.
• In some ships, the forepeak is kept empty or partially filled to reduce the impact, and the structure is designed to withstand the slamming pressures.

The combination of panting stringers, deep floors, closer frame spacing and increased plate thickness in the forepeak region effectively resists both panting and pounding.