A couple of years ago I spent a fascinating few hours with three farming friends in the village of Kingston Seymour on the North Somerset coast. We were exploring the history of two Second World War era wrecks which had been deliberately sunk in Woodspring Bay by the so-called 'Wheezers and Dodgers', a group of scientists and Admiralty personnel based at Birnbeck Pier - which had been taken over by the Admralty from 1941 to 1945 and designated as HMS Birnbeck by the Department of Miscellaneous Weapons Developent (DMWD). I wrote about the history of the two ships - S.S. Staghound and S.S. Fernwood - on my blog at the time and made a number of observations about why the Navy might have taken the trouble to re-float these ships and bring them up into the Bristol Channel. The original post can be accessed on this link.
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| The Woodspring Bay Wrecks - Curme Collection |
Earlier this week I visited the National Archives in Kew and was pleased to find that the answers could be found within the meticulously kept DMWD files which sit within the ADM/277 papers deposited by the Admiralty in the 1970s. Amongst the papers one can find a report on what the DMWD scientists referred to as Project No. 86 - 'Wreck Dispersal'.
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| Birnbeck Pier - HMS Birnbeck (1941-45) - Curme Collection |
To understand what Project 86 was all about, a little bit of context is required. In January 1944, an approach was made to the DMWD by planners working on 'Overlord', a large scale attack aimed at liberating Nazi occupied France (D-Day and the 1944 Normandy Campaign). It had come to their notice that the enemy had prepared a number of blockships filled with concrete in order to obstruct progress when a landing in Europe is attempted. (The idea of using blockships to protect harbours and ports or force ships to take a circuitous route was not new, indeed there are examples going back as far as the Viking era - click here for my post about the blockships of Roskilde, Denmark). What the D-Day planners were getting at, was that in order to supply a large scale army after an amphibious landing, port facilities needed to be made available without delay. So, the blockships in the Cherbourg Harbour needed to be cleared!
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| Beehive hollow charges - National Archives |
The preferred solution that the 'boffins' at HMS Birnbeck came up with, was to break up the concrete using modified hollow charges - effectively bombs designed in such as a way to project the force of an explosion into concrete. At a meeting on the April 7th 1944, a decision was made to use two concrete filled blockships at Weston-super-Mare in order to test whether beehive charges could work as required. Subsequently, the two ships were towed to a coastal area north of the DMWD outpost at St Thomas's Head (now part of the National Trust owned Sandpoint scenic area), partially filled with concrete and weighted to the seabed. Like many other DMWD experiments run out of HMS Birnbeck, the nearby coastline was ideal because of the exceptionally high tidal range. The beehive mines could be ignited whilst the ships were under water and at low tide when the water receded the damage could be easily assessed without the need for diving equipment.
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| S.S. Staghound at Woodspring Bay - National Archives |
The first trials took place between May and June 1944. Both Staghound and Fernwood were fitted out as blockships by W.P.S. Cardiff. In order that the ships could be manoeuvred into position the concrete filling was not to exceed their usual carrying capacity. In the case of the former 630 tons of concrete were poured, forming a large block extending from the floor of the hold to the main deck. The mix was one part cement, two parts sand and four of aggregate and the concrte block was 34 ft long, 26ft wide and just under 12ft deep. In conducting the first trial the Staghound's deck plating was removed and 12 'beehives' each containing a 70lb hollow charge and modified for use underwater, were fitted vertically on top of the concrete. The beehives would be fired together from the shore using an electronic detonator.
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| Beehives in place on S.S. Staghound - National Archives |
The approach taken for the test involving S.S. Fernwood was deliberately different. The quality of concrete used by the German Kriegsmarine was unknown so it was decided to use a better quality mix for the S.S. Fernwood trial. in this case it was felt that the beehives would blow out cavities in the concrete and 'main charges' would need to be inserted to break up the block.
So, what happened in the tests? Well, the general effect in the case of Staghound was that the surface of the concrete was irregularly shattered and the structure was deeply cracked in places. The height was reduced in the centre by about eighteen inches and the ships sides were forced out by the force of the explosions.
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| The Fernwood explosion - National Archives |
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| The Staghound aftermath - National Archives |
Taking learnings from the Staghound trial, modifications were made in blowing up S.S. Fernwood on the 12th October. Fernwood was not a complete ship in that after it had been sunk by the Luftwaffe in September 1942, the damage was so extensive that the ship was cut in two. It was the mid-section and fore part of the vessel which was towed to Woodspring Bay via Cardiff Docks. Having said this, the fact that the Fernwood was not a complete ship did not effect the efficacy of the trials.
Prior to the trial, in order to make the demolition more effective, vertical cuts were made in the Fernwood's structure and line-charges were attached by magnets across the roots of the ship's frame outside of the hull-plating. The hull was also cut vertically. Two holds were filled with high-grade concrete and the number of Beehives attached was greater than had been the case with Staghound. Thirty were fixed onto the top face of the main concrete block and twenty four on the smaller one.
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| The Fernwood Trial - National Archives |
At high water with a minimum depth of 12ft of water above the tallest part of the ship, the initiating chargeswere fired. Examination at low water showed that the forward part of the concrete was entirely dispersed, almost to the keel of the vessel. The reinforced portion was found to be reduced in height by from two to six feet. The ship's sides were thrown outwards, but were not laid flat. They were, however, sufficiently weakened to become detached in the tideway.
The trials had been very successful and the 'beehive' method of wreck dispersal worked. In a final report published in 1946 (ADM 277/1), the DMWD reported that the Beehive wreck dispersal technique had proved successful when 'in service' during the Second World War and remained effective in clearing access to ports in the post conflict clean-up.
Note: Where indicated images are sourced from The National Archives (UK), ADM 277. Reproduced under the Open Government License.
For Part One of the Woodspring Wrecks (1944) story click here.
To view the wrecks in Woodspring Bay walk my Clevedon Military History Trail at low tide.
