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The Sinking of MS Estonia: Case Re-opened Part II

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Captain_Swoop said:
It's not a term I am familiar with.
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Oh dear, oh dear, oh dear. The atlantic lock was what the bow visor was hanging by as it was banging on the hull like a chimpanzee.

It's the huge lock at the bottom. Amazing that it, the two side locks AND the two hydraulic arms all fell off 'due to a few strong waves'! In a wavy sea. My, my.
 
Why the term 'atlantic lock' though?

And once again, it was not just 'a few strong waves' It was fifteen years of strong waves' and poor maintenance.

Even on a warship designed to move fast through strong waves you can feel the ship vibrate and flex as it is hammered.
 
Vixen said:
Oh dear, oh dear, oh dear. The atlantic lock was what the bow visor was hanging by as it was banging on the hull like a chimpanzee.

It's the huge lock at the bottom. Amazing that it, the two side locks AND the two hydraulic arms all fell off 'due to a few strong waves'! In a wavy sea. My, my.
Click to expand...

What's special about an "Atlantic lock"? Why is it called that? I just went back and yes, in the earlier of the 10+ times you have mentioned it, you said was the big lock at the bottom, and that anecdotally the crew were used to having to hammer on it to get it closed. What access was there to it? With the car ramp raised and closed there would be no access to it from the car deck, presumably.

What part of it was allegedly recovered and discarded? Part from the hull or part from the visor?
 
Captain_Swoop said:
Why the term 'atlantic lock' though?

And once again, it was not just 'a few strong waves' It was fifteen years of strong waves' and poor maintenance.

Even on a warship designed to move fast through strong waves you can feel the ship vibrate and flex as it is hammered.
Click to expand...

From what I remember it is just a term to designate the lowest and strongest lock. It prevents the hydraulic arms from lifting upwards inadvertently. AIUI these locks are noted as being stronger, heavier and bigger than other locks. I get the impression the Estonia's atlantic lock is some kind of bolt mechanism, from the descriptions of crew having to use a hammer to get it to lock, due to misaligned lugs on the sides.

No ship ever sunk because it was pounded by waves. Boats sink because the trim is wrong or it is too top heavy (cf: Sweden's greatest maritime embarrassment, the Vasa which went bottoms up almost immediately after having cost a fortune to construct and the demolition of 300 oak trees)

IMV even if it were so the bow visor fell off in a storm, I am sceptical it would have sunk in a matter of minutes, without anyone have a chance to evacuate.
 
I just had a look to see if I could find why "Atlantic Lock" and not just "large lock at the bottom".

The only two results I could find are from...Heiwa (Anders jorkman the lunatic again) and estoniaferrydisaster.com.

Wow.
 
The JAIC describes the Estonia atlantic lock as follows:

The bolt was moved in the bolt housing between the retracted position and the extended position by means of a hydraulic actuator, operated from the visor and ramp control panel as described in 3.3.5. A spring-loaded mechanical plunger, movable perpendicularly to the bolt, engaged grooves in the bolt in the open and closed positions respectively, thereby securing the bolt mechanically in its extreme positions regardless of hydraulic pressure. The bolt was also locked hydraulically at any time because the hydraulic fluid was trapped in the system, regardless of whether the system was under pressure or not.

Two magnetic position sensors were installed, actuated by a magnet attached to a bracket on the bolt. The sensors were actuated when the bolt was fully retracted or fully extended. The hydraulic control system as well as the arrangement and functioning of the sensors and the position indication and alarm system are covered separately in 3.3.5. The original mechanical switches were replaced by the magnetic sensors in the mid-1980s.
The mating lug in the bottom structure of the visor consisted of a single steel lug, welded to a transverse beam of the visor bottom structure and supported by a bracket as shown in Figure 3.8. The diameter of the bolt was 80 mm in the original von Tell drawing. The lug had a hole for the locking bolt with an original diameter of 85 mm.
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Presumably it is operated from the inside for the crew to be able to lock or release it.
 

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Vixen said:
Here is a picture of Estonia's atlantic lock.

Source: https://www.estoniaferrydisaster.net/estonia final report/enclosures HTM/2.6.2.70.htm
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Okay, that's clearer. It's like a shoot bolt. There's a pin driven by a hydraulic ram which slides across, through a pair of lugs, and between them it also goes through a lug that's attached to the visor. So that pins the visor shut.

What part of that was supposedly brought to the surface? Was it just lying around loose or did it have to be cut away from either the ship or the visor?
 
Jack by the hedge said:
Okay, that's clearer. It's like a shoot bolt. There's a pin driven by a hydraulic ram which slides across, through a pair of lugs, and between them it also goes through a lug that's attached to the visor. So that pins the visor shut.

What part of that was supposedly brought to the surface? Was it just lying around loose or did it have to be cut away from either the ship or the visor?
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The JAIC skips over that bit.

8.6.1 The visor bottom lock
All three attachment lugs for the bottom lock installation had failed (Figures 8.13 and 8.14). The locking bolt (Figure 8.15) remained attached to the actuating cylinder piston rod, which was bent (Figure 8.13). The remains of the attachment lugs and the locking bolt were removed from the wreck during the diving operation for close investigation.

It was noted that the weld beads between the lugs and the bolt housing and the support bushing respectively had failed partly in the bead itself and partly in the fusion zones. The steel plate of the lugs had failed in their thinnest sections, generally in a forward-upward direction. The two lugs for the bolt housing were twisted towards the port side.

When the locking bolt was removed from the actuator piston rod, the actuator was in fully extended, i.e. locked, position. The piston rod was bent upwards, away from the forepeak deck. The hydraulic hoses were connected. The bolt was checked for wear and deformation. The bolt was straight. The general diameter of the bolt was about 78 mm. Only a slight variation in diameter was measured at the contact area between the bolt and the visor lug. No other damage to the bolt was noted.

The mating lug in the visor was attached to the structure but was bent about ten degrees to starboard and the adjacent structure was deformed and cracked (Figure 8.10). The hole in the lug for the locking bolt had an original diameter of 85 mm while after the accident the hole was oval with dimensions at mid-thickness about 83 x 95 mm. The visor lug was removed from the visor after it had been brought ashore.
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AUIU the inspection was undertaken by divers at the scene and the atlantic lock itself simply thrown back onto the seabed. So the mating lugs were brought up but it is not said in the JAIC what happened to the bolt.
 
MarkCorrigan said:
I just had a look to see if I could find why "Atlantic Lock" and not just "large lock at the bottom".

The only two results I could find are from...Heiwa (Anders jorkman the lunatic again) and estoniaferrydisaster.com.

Wow.
Click to expand...
It does seem to be a term used exclusively by those embracing alternative theories.
 
Vixen said:
From what I remember it is just a term to designate the lowest and strongest lock. It prevents the hydraulic arms from lifting upwards inadvertently. AIUI these locks are noted as being stronger, heavier and bigger than other locks. I get the impression the Estonia's atlantic lock is some kind of bolt mechanism, from the descriptions of crew having to use a hammer to get it to lock, due to misaligned lugs on the sides.

No ship ever sunk because it was pounded by waves. Boats sink because the trim is wrong or it is too top heavy (cf: Sweden's greatest maritime embarrassment, the Vasa which went bottoms up almost immediately after having cost a fortune to construct and the demolition of 300 oak trees)

IMV even if it were so the bow visor fell off in a storm, I am sceptical it would have sunk in a matter of minutes, without anyone have a chance to evacuate.
Click to expand...

Yes ships do sink from being pounded by waves.

Don't you think that having to hammer the mechanism closed was an indication of a serious problem?

What stress and damage would hammering it closed do?
 
These two links say the lugs on the bottom lock failed through overload though it's not quite clear to me whether the pin was ripped out of the lugs or the lugs were torn off their welds. Either way the lug on the visor was able to slip off the pin while remaining attached to the visor, though that lug was both stretched and somewhat bent:
https://web.archive.org/web/2004081...nettomuustutkinta.fi/estonia/chapt12_3.html#1
https://web.archive.org/web/2004081...nettomuustutkinta.fi/estonia/chapt13_2.html#3

It does say the likely sequence of the progressive failure had the locks fail before the hinges, so the visor was not dangling on its bottom lock as Vixen suggested.
 
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