SSPA Model Tests 3 April 2008


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SSPA Model Tests 3 April 2008 (DN 20080404)

"In the big basin of the SSPA test laboratory that can simulate wind and where the model of the Estonia can head into wind and waves to simulate the weather of the night of the disaster until the bow ramp opens and allows water to be loaded on the car deck: 

- It produces a heeling that causes the ship to turn, so it rests at 90 degrees against the waves. The engines stop and the heeling increases. When windows come under water, they are pushed in and water flows down into the hull via ventilation trunks and others. Then the ship turns upside down and sinks, explains SSPA research boss Claes Källström.

In reality it took almost an hour for the Estonia to sink. In the scale used in the SSPA basin it takes about eight minutes until the stern sinks, the bow rises up a short moment, while the last air bubbles out through the open bow.

- We have done this test several times with various assumptions about the interior of the Estonia. First using computer and then with the model in the basin. The results are stable and the sequence of events we get is in agreement with the total picture provided by survivors, says Claes Källström."

It is one thing to show model tests for an uncritical audience. Now the computer simulations and the model tests shall be described, recorded and explained, e.g. speed, course, displacement, floatability (draughts), angle of heel, trim, weights loaded due to inflow into deck house, superstructure and hull, their locations at every second (time t) during the complete sequence, i.e. from t = 0 (when the incident begins) until t = when the Estonia is lying on the bottom.

Photo: Bertil Calamnius, April 2008

Of great interest is how fast the heeling between 0° and 45° develops, due to water loaded on the car deck and what happens then. How fast is the deck house, now under water, flooded? The amount of water inside the deck house at various times is of vital importance to know!

During the test the model suddenly turns upside down with the keel up ... and floats. After this dramatic event no more water can flow into the hull - the air in the hull can only be compressed and it takes place instantaneously.

Either the model floats for ever or sinks immediately! If the model floats upside down ... and later the stern starts sinking, there is something strange going on. How is the air in the stern released?

Heiwa Co will analyse the SSPA report when available.

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