B2/1998M ms GABRIELLA, Bow Door Damage in the Gulf of Finland on 24.10.1998

The bow door of the Finnish passenger car ferry ms GABRIELLA was damaged on its scheduled voyage from Helsinki to Stockholm in the Gulf of Finland in the night of October 23rd to 24th 1998. GABRIELLA, owned by Viking Line, met high seas in the sea area south of Utö and the speed was slowed down after strong slamming at 00:05. The reduction was from an already slowed down speed of 13 knots to about 10 knots. Another, but lesser slamming occurred at about three o’clock. After arrival in Stockholm the starboard bow door could not be opened. In the subsequent inspection it was observed that the jamming of the bow door had been caused by apparently minor and restricted structural damage in one door support.

The immediate cause for the damage was structural weakness in the longitudinal support on the main deck. The weak structure had its origins in the design and building stage of the vessel. There were two different sets of drawings for the support - one set for the support for its position and its components by the consultants who had designed the bow door and one set by the shipyard for the strengthening required and exact positioning relative to the ship´s structural elements. However, these drawings differed from each other concerning the reference line indicating the transverse web in the tank below the support. The support had been built according to the consultants’ drawings. The assembly became deficient because the parts that had been dimen-sioned into every detail caused the assembled support not to fit right onto the underlying strengthened web, which - on the other hand - by itself may have been positioned incorrectly. The shipyard had not ensured the compatibility between the support components and their own design for the built reinforcement structure. The support was misplaced more than 60 mm forward from the underlying reinforced web compared to the shipyard´s design requirement, which specified positioning of the support directly on the reinforced web. The strength of the reinforcement designed by the shipyard would have been adequate but would have required a design change of the components of the support or change of the reinforced web to implement the yard’s design idea for the assembled support-web system.

The stamping of approval by the class of the drawings for building of the support components and the reinforcement was misleading since these were not mutually compatible. It is evident that the shipbuilders did not check the compatibility of the support with the web and reinforcement as they had been built.

Inadequacy of the supervision of the building of the bow door supports is manifested by the “As Carried Out” approval by the classification society of the shipyard drawings that did not correspond to the actual structure. The faulty structure of the bow door support, which deviated from the “As Carried Out” approved drawings, was difficult but not impossible to detect after it had been manufactured and assembled. The deficient structure passed all stages of inspection including those ordered for bow door structures of all ro-ro-passenger car ferries after the ESTONIA accident.

A decisive contributing factor to the failure can be found in the vagueness of the execution of responsibilities between the parties involved concerning the compatibility of the built design detail.