Analysis of the German Navy Stability Standard BV 1030 With Respect to Operability in Heavy Weather

Abstract

The stability standard of the German Navy — the BV 1030 — was developed in the mid-sixties of the last century in close cooperation with the German Navy Authorities (now BAIINBw) and the University of Hamburg. Other than the stability standards used for commercial shipping, the BV 1030 is based on righting and heeling lever balances for each individual loading condition of each individual ship. Different types of heeling moments have to be assumed in several combinations and they have to be balanced against the righting levers of the ship. Not only the still water stability curve is subject to this lever balance, but also wave crest and wave trough situations are subject to the stability analysis. The BV 1030 stability standard further requires a minimum stability if the ship is on the wave crest. Since this stability standard is in force, the German Navy never experienced a stability accident. The development of new hull forms with the focus on fuel efficiency has widely brought up new problems in heavy weather, for example the vulnerability for parametric rolling. It was therefore of interest for the German Authorities (BAIIN) whether the existing stability standard has sufficient safety to cover also these phenomena connected to more modern hull forms. Therefore an analysis was carried out in close cooperation between BAIINBw, MARS and TUHH where the operability of several ships of the German Navy was analyzed with numerical sea keeping computations. The nonlinear sea keeping code E4ROLLS was used which allows the computation of time series of the ship motions in irregular, short crested seas. From these computations, operational limits could be derived, or, vice versa, the required stability to guarantee a certain operability. The results showed that the concept of the German BV 1030 stability standard provides a significantly higher safety level compared to IMO standard for commercial ships. The results did also show that for modern hull forms, some adjustments to the existing safety standard were found to be useful to better cope with righting arm fluctuations in longitudinal waves.