The Wreck of DKM Bismarck − A Marine Forensics Analysis 1 The ...

The Wreck of DKM Bismarck − A Marine Forensics Analysis
battleship. Minor flooding resulted, as the belt armor displaced inboard and damage control
packing in way of the shell hit in way of Compartments XIII and XIV was loosened.
Overnight, Bismarck broke contact with her British pursuers and headed for shelter and
major repair facilities at the Penhoet-Loire Shipyard in St. Nazaire, France. The heavy cruiser
Prinz Eugen was detached to continue the originally-planned commerce-raiding mission into the
Atlantic. After an interval of 31 hours, the German battleship was spotted by a British Catalina
aircraft, piloted by an American naval aviator, ENS Leonard B. (“Tuck”) Smith. 14
This sighting permitted aircraft from HMS Ark Royal to attack the German ship during
the evening of 26 May. If the Germans were not diverted from their course to France in the next
few hours, they would soon be within range of friendly shore-based aircraft and likely out of
danger, despite the best efforts of the men and ships of the Royal Navy.
At this time, the light cruiser Sheffield was shadowing the German ship. Fortunately, as
matters turned out, the Royal Navy aviators, unaware of the presence of the friendly cruiser,
attacked one of their own ships! This near-tragic incident was of enormous importance, since the
men on the cruiser reported that those torpedoes directed at their ship detonated prematurely. It
was judged that the magnetic-fused detonators fitted to the torpedoes were defective.
When a last-gasp attempt by Swordfish torpedo bombers to stop Bismarck was launched
later on the afternoon of the 26 th of May, more reliable contact fuses were installed. The
torpedoes were also set for a relatively shallow running depth, about three meters. This attach
was successful, scoring three torpedo hits. Two hits amidships caused relatively inconsequential
damage ─ minor inboard flooding was caused by a hit on the port side, in way of Compartment
VII. The detonation severed the degaussing system cable in the vicinity. The damaged cable
can be seen adjacent to the torpedo hole. A second hit on the starboard side in way of
Compartment VII caused some flooding, which was confined to the side protective system.
Unfortunately for the Germans, the third torpedo detonated in the stern near the starboard
rudder. This damage caused the instantaneous and devastating loss of steering control.
THE MORTAL TORPEDO HIT
Identification of torpedo hits was extremely difficult except for the mortal torpedo hit in
way of the rudders. It is very important to remember that water was frequently forced out by the
phenomenon of hydraulic outburst, discussed later in this paper, even where there were no preexisting
holes. We believe this phenomenon accounts for the majority of the damage to the
lower hull. Jim Cameron’s team clearly imaged an area on the port side where the lower hull
shell was detached from the main side belt and the plating forced outward, but the separation
attenuated to zero both forward and aft, and there was absolutely no evidence of torpedo or shell
damage in the vicinity, thus indicating the start of the hydraulic outburst process which was
stopped before the lower hull section completely detached. The forensic evidence at the wreck
site strongly supports the conclusion that any pre-existing torpedo or shell damage acted to stop
the propagation of cracks running along the joint between main side belt armor and the lower
hull shell, probably by acting as a relief valve to vent the overpressure. When a crack is running
in a piece of plexi-glass, for example, a hole is drilled ahead of the crack and that measure halts
the crack propagation at the hole. We believe what is seen on Bismarck is a similar mechanism
on a much larger scale. Almost all the damage that the team has seen from the May 2002 survey
14 As related by CAPT Leonard Smith (USN, Ret.) in correspondence with author William Garzke.
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