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In-depth | DAMAGE STABILITY


Figure 1. The visor is connected to the hull at Gångjärn, Sidolås and Bottenlås (Hinge, Sidelock and Bottomlock). From JAIC final report, Swedish version.


hardly reassured. Notwithstanding, declarations that immediate capsizing follows an open cardeck, if anything confirmed by the runs in the HSVA model basin, they, nevertheless, deal with an open cardeck, because with the ramp only slightly open there will not be enough water for the given scenario to occur. And again computation of leak stability shows that for those large heel angles, leakage in the underwater body as cause of the accident is out of the question. All of which is in accordance with what the JAIC arrived at 12 years ago and for which it was so criticised. Yet the Estonian state prosecutor insists on the ramp being up, not down. Crewman Henrik Sillaste’s drawing


shows that the visor is gone, because if it had been in place the water should have seeped in at the top. But, as you can see for yourselves below, it spurts! Measured directly on the drawing, with scales from figure 3.13 in the JAIC-report (also reproduced below) it spurts into the cardeck with about 10m/s, which, incidentally corresponds to Estonia meeting the waves with full power (simply apply Bernoulli’s equation). However, before the visor has


separated completely it hangs on the starboard actuator arm. Te liſting device (consisting of a piston in a cylinder, filled with hydraulic oil, a medium which, when treated analytically, for extreme impulsive loads is not to be regarded as incompressible) is now loaded from the weight of the falling visor. When the last connection, the attachment to the deck, bursts, it recoils and the free end of the actuator arm smashes into the starboard front bulkhead, resulting in an oblong hole of at least one square metre, which in the absence of other plausible explanations was believed to have been caused by an explosion. Before this however the ramp, loosened


by the visor, has temporarily come to rest on the upper cross-bar inside the visor. It now falls forward with the visor, but is


38


immediately flushed back into an almost closed position by the encountering seas when the visor leaves, thus acting much like a return valve. According to Margus Treu, the third


engineer, the water influx was enormous, the camera was partly obscured….the ramp was not mentioned. (Did Mr Treu see the first big flush that could possibly have caused the sudden heel? Both he and HSVA are contradictory on this point, HSVA-report p12 and 14; and on p16 and 123 HSVA assumes that the ramp opens again.) The following influx in the gap at the ramp, now closed, was observed by motorman Henrik Sillaste and motorman Hannes Kadak and the camera was not obscured. (Compare with HSVA figure. 27 and comments on ingress through full opening.) The influx through the front bulkhead


has been seen by nobody, but could very well be of the same order as through the gap. The heel when the visor collides with the bulbous bow and falls to port is close to zero (a fact to be contained in any hypothesis) according to photos of the rescued visor. Not so, however, in the Seaman-


simulation in the SSPA final report. Note that Mr Sillaste looked into the monitor after the first heel (because he was worried), that is when the visor already had slipped over the ramp and fallen off. Thus the visor photos verifies Mr Sillaste’s drawing, ie. he drew what he saw. When the ship turns away from


the waves the ramp falls forward and smashes onto the forepeak deck. Not until then is the ramp deformed into its final shape, with the ramp-railings bent outwards. Successively and intermittent, water is accumulated on cardeck, which leads to the course of events described


Figure 3.13 (from JAIC-report): Crewman Henrik Sillastes drawing showing water flooding through the sides of the bow ramp.


by the witnesses. The ramp slowly falls back to its closed position when Estonia is lying on its side at a heel exceeding 90deg and trimming astern. Because of its heavy weight it then


easily snaps the much lighter railing, pieces of which were later found on the sea bottom lying some 250m aft of the ship’s stern, which indeed fits well to the drift of the hull due to the current of one or two knots. Some prefer more interesting explanations eg. it was cut off in a clandestine operation (in the aftermath of the cold war...). Now however, after the Kurm Report,


the pieces constitute ample evidence that the ramp never even passed its ordinary open position when the visor fell off. Instead, as suggested, it was flushed back into its nearly closed position together with an amount of water that was enough to dynamically tip the ship over to some 20–25deg, whereupon it rebounded to a temporary list of around 15degs (as stated by witnesses). According to the JAIC final report,


this amount of water is about 600tonnes. With an opening of 25 to 30m2


and


a relative speed of the water of some 6-12m/s it could very well enter the cardeck within a few seconds. The next stage, inflow of an additional 1400tonnes of water is a much slower process due to a much smaller opening, reduced speed and a change of direction. Before sinking the ship did turn


upside down, ie. capsized, which is documented by an extraordinary photo reproduced below (Öun, Scanpix). Contrary of the official investigations


The Naval Architect September 2010


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