The Mulberry Harbour at Arromanches cont.2



These were redundant ships called "Gooseberries", and some sixty ships made their last voyage many under their own stream.
These old ships were filled with concrete and explosive charges and were sunk to provide even more protection on this exposed coast.
As the ships were put into position and the explosive charges fired, American and British troops thought that they had succumbed to enemy fire.
The Germans thought the same and that night German radio told of many Allied ships sunk with great loss of life.
Next to arrive were the Bombardons the Navy's contribution.
These barrages were made of steel 200 feet long and 60 feet high and were hollow with buoyancy tanks in the upper part.
Their design allowed the sea to pass through but dissipated the strength of the tide by up to 90%, and they were moored 45 feet apart.
Navy scientists had tested the design in the diving tank at Portsmouth.
Unfortunately, during the great storm, most of these broke from their moorings and did most of the damage to the floating harbours.
The elements of the outer concrete harbour, the only part visible today, are the Caissons, code named Phoenixes. In all, 147 of these were made in six different sizes.
This was necessary because of the different depths of water there were to be sunk in.
The Phoenix was in effect a large concrete box that was water tight but when filled with water would settle on the seabed and provide a safe anchorage for ships to unload supplies.
The Phoenixes started their journey to Normandy on D-day, and the first elements arrived on
D-day +1. They weighed between 1,500 tons and 6,000 tons each.
The towing operation required 132 ocean going tugs, which equated to 95% of the world's tugs, and the construction team numbered over 10,000 engineers.
The four pier heads, code named "Whales", were then put into position and these huge metal structures resembled a modern oil exploration platform.
Fitted with four legs they could be raised or lowered to compensate for the state of the tide. Each of these weighed 6,000 tons.