Sagging

Sagging is a nautical term and can best be translated as " sagging ".

It describes the bending stress acting on the structure of a vessel, when this is running in the longitudinal storm waves and corresponding to the wavelength as that of the vessel. When the stern and bow are in the wave crest at the same time, so there is increasing locally the buoyancy of the water, while in the center of the vessel, in the trough, the buoyancy force decreases significantly. This bending forces occur which result in the area of the keel to tensile forces and in the area of ​​the deck to compression forces. In riveted hulls may occur shearing of rivets to the ribs. As a result, a direct structural failure occurs, wherein the break usually in quick succession at the same time the deck and keel and the boat starts to decrease.

Of these, the distinction is hogging, which describes the opposite condition: the stern and bow are in the trough and the ship center on the wave crest.

Factors of this accident scenario are the coming together of relationship between wavelength and vessel length, wave height, fitting course in relation to the waveform direction, load distribution and design defects.