"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?
