Block ship
A block ship is an old decommissioned ship that is sunk alone or together with others in a fairway or in front of a port entrance to prevent passage.
When sinking block ships, several things must be observed so that the best possible locking effect is achieved:
- It is ensured (e.g. by using tugs) that the block ship comes to rest across the direction of traffic and is not subsequently turned out of its position by the action of the tides . Possibly. anchors are deployed.
- The ship used must be large enough that even at spring tide it is only flooded so far that no passage is possible.
- If a body of water is so wide that it can only be blocked with several block ships, the largest of them is sunk in the middle at the deepest point of the passage. Further block ships, which are to prevent bypassing, are sunk in an overlapping manner with the smallest possible lateral distance to the others.
Block ships are almost always used in conjunction with other locking devices such as submarine safety nets, beam locks and sea mines . Their disadvantage is that they are only effective against larger vehicles, while combat swimmers and certain small weapons are not affected by them.
commitment
In 1918, the Royal Navy tried to block the German bases in Ostend and Zeebrugge in Flanders with block ships and thus prevent the torpedo boats and submarines from leaving for their missions. However, the operation failed because the schedule was not adhered to and the extremely strong ebb current in this area had already set in when the sinking was initiated. As a result, the ships, which were already partially flooded, drifted to the edge of the fairway, where they were almost unable to develop any blocking effect and practically did not impede the arrival and departure of German boats.
During the Second World War, the British natural harbor Scapa Flow was initially secured on the east side only with block ships, after the sinking of the HMS Royal Oak these were replaced by four dams, the Churchill Barriers .