Home      MULBERRY HARBOUR & COTUG

MULBERRY HARBOUR

AND COTUG

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Page last updated 11-4-2013
 
 
Photo RGR Colln
 
It became apparent in 1943 that in order to supply an invasion of the continent an artificial harbour would have to be constructed. There are many existing websites which can be viewed giving details of the planning of this operation, and construction of the  harbour, therefore I will concentrate only on the delivery of this harbour to the enemy coast by tugs. It may however help to understand the logistics of the operation  by briefly summarizing the various components involved in the Mulberry Harbour.

MULBERRY
This was the official name for the complete harbour installation. There were to be two complete harbours, Mulberry A for US forces and Mulberry B for British use.

PHOENIX

These were concrete caissons of six different sizes, the largest of which were 200’x60’x60’ and each unit weighed between 6044 tons and 1672 tons They were airtight floating cases open at the bottom with air-cocks to lower them to the sea-bed in a controlled fashion. Around 2 million tons of steel and concrete were used in their construction. They would form a breakwater to protect the harbour.  146  were constructed  by well known civil engineering contractors in 28 different locations  mostly in the south of England, including East India Dock [which had been drained for the purpose], South Dock, Millwall, Red Lion Wharf, Northfleet, Southampton Docks, Portsmouth Dockyard and Beaulieu River. When completed they were towed to locations off Selsey Bill and Dungeness and partially sunk on the sea bed to help avoid detection. An early trial  showed that a 750ihp tug could tow the largest units at 3 knots in ideal conditions. Problems arose later due to under estimation of the time and equipment needed to pump out each unit and raise it from the sea bed ready for towing. Some units never floated again at all owing to a phenomenon known as 'sucking down'. a problem know to Thames lightermen and Thames sailing barge crews.
 
TYPES OF PHOENIX UNITS
 
TYPE 
HEIGHT 
LENGTH 
BEAM 
 TONNNAGE 
DRAUGHT 
 
A1 
 60'
204' 
56'3" 
6044  Disp
20'3" 
 
A2 
50' 
204' 
56'3" 
4773 Disp
16'4" 
 
B1 
40' 
203'6" 
44' 
3275 Disp
14' 
 
B2 
35' 
203'6" 
44' 
2861 Disp
12'3" 
 
C1 
30' 
203'6" 
32' 
2420 Disp
14'3" 
 
C2 
25' 
174'3" 
27'9" 
1672 Disp
13' 
 
 
THAMES BUILT PHOENIX UNITS
 
 TYPE
NUMBER
 SITE
BUILT BY 
 A1
 9
TILBURY GRAVING DOCK 
BALFOUR BEATTY 
 A1
10 
EAST INDIA DOCK 
McALPINE 
A1 
ERITH BASIN 
 NUTTALL
A1 
ERITH BASIN 
COSTAIN 
A1 
PORT OF LONDON AUTHORITY BASIN 
DEMOLITION AND CONSTRUCTION CO 
A2 
BARKING CREEK BASIN 
COCHRANE 
A2 
BARKING CREEK BASIN 
TAYLOR WOODROW 
B1 
SURREY COMMERCIAL SOUTH DOCK 
MOWLEM 
B1 
RUSSIA DOCK BASIN 
MOWLEM 
B1 
RUSSIA DOCK BASIN 
MELVILLE DUNDAS AND WHITSON 
B1 
GRAYS BASIN 
GEE WALKER AND SLATER 
B1 
BARKING EAST BASIN 
A MONK AND COMPANY 
C1 
TILBURY GRAVING DOCK 
HOLLAND HANNEN AND CUBITT 
C1 
COLD HARBOUR POINT BASIN 
TRUSSED CONCRETE COMPANY 
 
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GOOSEBERRY

A harbour of refuge for small craft  formed by sinking obsolete merchant and naval vessels on the 2 fathom contour.  70 obsolete merchant vessels and naval vessels  were amassed at Methil and at Oban on the west coast of Scotland, stripped down, ballasted and primed with explosive scuttling charges. Some proceeded to the Channel under their own power, others were towed. They were concentrated at Poole Bay until required. This was known as Operation Corncob. 

TUGS ALLOCATED TO ACCOMPANY THE GROUPS OF BLOCKSHIPS
 
GROUP 
TUGS 
EMPIRE JOHN; EMPIRE WINNIE. 
 2
EMPIRE AID; EMPIRE DORIS. 
EMPIRE HENCHMAN; EMPIRE VINCENT 
 4
EMPIRE LARCH; EMPIRE RUPERT 
EMPIRE JONATHAN; EMPIRE SOPHIE 
 
 
 
 
BOMBARDONS
A floating breakwater comprising a steel cruciform structure which was used where the water was too deep to use either Gooseberry or Phoenix breakwaters. Each unit was 200’ in length. They  were the outermost barrier and therefore the first line of defence against rough seas. 115 of these units were 'parked' at Portland ready to go over to France.

LOBNITZ PIERHEADS
Constructed by the well known Clyde based shipbuilders and engineers in a special facility at Leith. These were complete pier head units, secured to the seabed by a ‘spud’ at each corner which could be mechanically adjusted to compensate for the rise and fall of the tide.
After the war two of these units were salvaged and towed back to the Thames, where along with some beetle and whale units they became a new floating landing stage for the Phoenix Timber Company at Frog Island, Rainham Essex. Similar salvaged units were used to construct a new RoRo landing stage at the port of Preston for berthing the ex-LCT's that ran a ferry service to Larne.

WHALE
The floating roadway which connected the line of Lobnitz units to the beach and were supported by floating pontoons called Beetles. These sections comprised 84 tows, each 480' long [six 80' sections coupled together] and were moored at Peel Bank near Ryde after being towed from assembly points at Marchwood and Richborough. These were to prove the most difficult and most vulnerable tows with losses under tow in the order of fifty percent, mostly due to unfavourable weather.
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It will be appreciated that with the exception of most of the Gooseberry vessels every component of the harbour would have to be towed from the manufacturing site to the operational area, either free floating or on barges or pontoons.  A pool of 158 tugs was estimated to be sufficient. Agonising decisions had to be taken in regard to this tug procuring process, not least of which was whether to re-deploy rescue tugs then currently engaged in convoy rescue duties. Throughout the operation the most acute  problem was the tug shortage, which was never satisfactorily remedied. The target date for completing Mulberry had, as a result, to be postponed.  [Even after VE day there was still an acute shortage of tugs and a directive was issued urging that now redundant A/S trawlers should be pressed into service for towing barges etc]
 In August 1943 it was stated that 50, 750hp and 40 ,1000hp tugs would be required. A tug census was taken by the Admiralty and MoWT and it was decided that 65 tugs could be provided for a limited period.  This could only be achieved by:-
 
1] Withdrawing 20% of tugs from commercial ports.
2] Suspending coastal towing operations.
3] Withdrawing 30% of rescue tugs.
4] Withdrawing 25% of Admiralty dockyard tugs.
 
It was hoped the shortfall would be made up by US tugs but by  December 1943 delays in deliveries of US tugs caused more anxiety and Churchill called for another tug census. Requirements for Mulberry towage had now risen to 154 tugs and for other work in connection with the invasion a further 36 tugs could be required.
 
The document below, part of an official report, illustrates the somewhat alarming situation regarding the towing of Mulberry Components that existed as of 30th April 1944, just over a month before the invasion took place!!
 
  
 
 
 

COTUG

 
At the Admiralty on 12th May 1944 a meeting to discuss the setting up of a special body, to be known as COTUG, was held.  The requirements of the new body would be;-
 
a] To assess priorities of tug requirements both before and after D-day and pass decisions to the tug operating authorities.
b] To operate the tugs in the area Dover to Lands End from now on, but would allocate tugs for other Overlord requirements outside this area.
c] To arrange maintenance of the tugs.
 
The only organization able to overide COTUG authority would be the Admiralty if they became anxious about tug requirements to tow damaged ships. COTUG HQ would be either at Fort Southwick or Southwick Park. It was agreed first priority would be arrangement of tows for Mulberry components and certain barges. The main Overlord tug assembly area would be Lee-on-Solent with a stores depot on Lee Pier and also accomodation on the SS Aorangi.  In charge of COTUG was Capt. J G Y Loveband RN. with Commander F H E Vaughan RNR as deputy.  A further meeting on 15th May 1944 confirmed that Mr J R Watkins would be in a position to exercise complete control over Red Ensign tugs involved and that the officer in charge of Army allocated TID tugs would be co-opted on to the committee.
 
On 19th May 1944 Capt E J Moran USNR [A member of the American tug owning family] was appointed Tug Controller. He was made responsible for the control of over 200 tugs involved in the assembly, assault and build up stages of Operation Overlord.
There were not enough tugs in the country, however, to satisfy all Commercial, Naval and Military demands for their services.
As late as 31st May 1944 only 48 out of 72 large, and only 4 out of 44 small tugs allocated for towage of Phoenix and Whale units were available. On that date Admiral Ramsay directed that "the principle, that Mulberry and construction constituted a vital part of the whole operation, must govern decisions as to the extent that tug assistance could be provided for other purposes". The operation finally commenced with a total of 132 tugs, 72 British, Dutch or French and 60 American. Out of this total 97 tugs were suitable for cross-channel tows and 35 were small handling tugs, only really suitable for use in sheltered waters.
 
  On 18-12-1944 COTUG was relocated from Lee-on-Solent to offices in Bryanston Square, London.

A statement to Parliament in March 1945 reported "One hundred and thirty-two tugs, including British, American, French and Dutch, were employed in towing the units of this harbour from sheltered anchorages in the United Kingdom to the Normandy coast. Nearly 1,000 tows were made for this purpose in June and July. Tugs were mobilised from far and wide to accomplish this mighty task, made the more daunting by the rough and unseasonable weather in the Channel. The moorings in the British area alone included 242 buoys, requiring the handling of 3,265 tons of mooring gear."
 
COTUG ceased to exist at 2359hrs 13 July 1945, and the pool of Overlord tugs ceased to exist with it. After that date all control of US tugs reverted to the US authorities, the Admiralty resumed control of all rescue tugs, and control of all other tugs reverted to MoWT or Naval Director of Sea Transport. This included foreign flagged vessels still on charter. The shortage of tugs had never been completely solved and commanders of captured continental ports were still fighting to hang on to their allocated vessels.
 
The following pages  list  British, Dutch, French and US tugs known to have been involved in the actual towage of the Mulberry components to Normandy. In the days immediately following the invasion there were many more tugs, not mentioned here, involved in salvage work, especially of damaged landing craft, and the towing of plant neccesary to reopen the captured continental ports..