Hogging (Naval)

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Diagram of ship hull (1) Sagging and (2) Hogging under loads. Bending is exaggerated for demonstration purposes.

Hogging is the stress a ship's hull or keel experiences that causes the center of the keel to bend upward.

A cause of dynamic hogging is when a wave is the same length as the ship and the crest of the wave is amidships. This causes the middle of the ship to bend up slightly, and depending of the level of bend, may cause the hull to snap or crack. This may have been what sank the Prestige off Spain on 19 November 2002.

Hogging, or hog, also refers to the semi permanent bend in the keel, especially in wooden hulled ships, caused over time by the center of the ship being more buoyant than the bow or stern. At the beginning of her 1992 refit, USS Constitution had over 13 inches (33 cm) of hog^[1]. The keel blocks in the drydock were set up especially to support this curve. During her three years in drydock, the center keel blocks were gradually shortened allowing the hog to settle out. Additionally, the diagonal risers specified in her original design to resist hogging, which were removed in an earlier refit, were restored. By contrast, the 1854 USS Constellation had 36 inches (91 cm) of hog when she was closed as unsafe in 1994^[2].

[edit] External links

• Constellation's 1994 restoration article has several photos showing the hogging.
• Diagram showing hogging stress and the diagonal risers.

[edit] See also

• Glossary of nautical terms
• Sagging
• Strength of ships

[edit] References

This article includes text from the public domain Dictionary of American Naval Fighting Ships.

1. ^ Otton, Patrick (1997-08-11). USS Constitution Rehabilitation And Restoration. Retrieved on July 2, 2006.
2. ^ Constellation. Dictionay of American Naval Fighting Ships. Retrieved on July 2, 2006.