9th Maritime Heritage Conference - Historic Ships and Preservation
The Submarine Alliance
Wyn Davies BSc MSc CEng MRINA RCNC
Bob Mealings BA
This paper will describe the detailed planning that has been undertaken by the staff and consultants of the Royal Navy Submarine Museum in Gosport, Hampshire, to restore HMS Alliance, the last surviving Royal Navy Second World War submarine. It covers the preparatory work, surveys and the options study carried out in conjunction with experts from Frazer-Nash Consultancy Ltd, leading to a preferred solution for the repair and restoration of the submarine's steelwork. This work forms part of a larger project, which includes improving access for the public and for maintenance and improving the air flows internally, and as such this paper makes reference to the allied civil engineering and funding raising work necessary to complete the project.
To quote from the Conservation Management Plan,
"HMS Alliance is a diesel-electric, A Class patrol submarine, built for the Royal Navy Submarine Service by Vickers-Armstrong Ltd at their Barrow-in-Furness yard in 1945. The vessel was designed for operations against enemy shipping, particularly in the Pacific and the Far East, in order to aid the allies' war effort. Her innovative design and construction, intended to give her greater range and increased surface speed than her predecessors, benefited from over forty years experience in Royal Navy submarine construction; lessons learned during two world wars; and the latest available technology."
She was one of forty-six vessels of her class proposed by the Admiralty, although only sixteen of these were built, ten at the Barrow shipyard, and the other six at Scotts', Cammell's and one at Chatham Dockyard but none of these sixteen were completed in time to see active service during the Second World War.
Alliance, launched in 1945 from Barrow, was powered by twin diesel engines while on the surface, and by electric motors when submerged. She originally had ten torpedo tubes, a 4-inch deck gun, an anti-aircraft cannon, and three machine guns. She was completed at Chatham Dockyard and commissioned on the 11th March 1947 but, like many submarines, little is known of her early operational history. It is however know that In October 1947 she as involved in testing a 'snorkel' tube which, when adopted, allowed a vessel to stay submerged for long periods of time.
Figure 2 An A Class Submarine as built
The vessel underwent a modest refit in 1953 and then, as part of a modernisation programme for two classes of submarine (the A's and T's), Alliance underwent a major refit in 1958-1960, both intended to streamline and reduce the weight of the vessel, and thus make her faster underwater. External torpedo tubes were removed; the open bridge was replaced by an aluminium 'fin' which completely enclosed the masts and periscope; and the steel casing over the pressure hull was replaced using aluminium. As a result, Alliance has the features of a 'classic' patrol submarine of the Second World War, as well as elements associated with the radical change in the role of submarines which occurred in the immediate post-war period, but immediately prior to the advent of nuclear powered vessels.
Figure 3 HMS Aeneas after streamlining
Alliance had a long and varied career, with deployments all over the world and as far as Hong Kong and Singapore.
In 1973 Alliance was taken out of service and moved to the Royal Navy Submarine Service's base at HMS Dolphin, Gosport, for employment as a static training vessel.
In February 1978 she was transferred on permanent loan to the Royal Navy Submarine Museum at Haslar, Gosport, which had been founded in 1963, for public display and as a memorial to submariners who lost their lives whilst on active service in peacetime and at war.
In August 1979, Alliance was taken to Vosper Ship Repairs Ltd yard, at Southampton, for repair, strengthening. Upon her return to the Royal Navy Submarine Museum in 1981 she has been displayed out of the water, supported on concrete pillars and cradles, a very innovative means of display, maximising the limited space available at the site. She has full visitor access, as the centrepiece of one of the nation's several Defence Heritage Museums, which also includes the Royal Navy's first submarine - Holland I, built in 1901.
Whilst this form of display had the advantage of being very impressive visually, it unintentionally prevented unaided access to the external hull and maintenance has suffered as a result.
Figure 4 Alliance viewed from the sea side showing the forward concrete plinth
Over the years, exposure to the elements combined with difficult access has resulted in a breakdown of the original coatings, reactivation of chloride corrosion and the inception of electrolytic corrosion around the many examples of mixed metals, all of which would have been taken care of by the day to day maintenance that was carried out by a submarine's crew or depot ship. This decay has continued to the point that parts of the structure are verging on unsafe, but more importantly the original structure was in danger of being lost to future generations. To this has also to be added the deleterious effect of housing, for several years, the largest colony of feral pigeons on the UK's south coast!
The seriousness of the situation was recognised by the Museum and in 2001 a restoration project was set in motion to try and recover the situation. It should be noted however that the internal structure and fittings were generally in very good condition and weren't to be included in the current programme of works.
Surveys and Planning
Acting on advice from fellow museums, the Submarine Museum engaged an engineering consultant to look at the problem. Unfortunately, the existence of consultants specialising in marine heritage was not widely known within the museum fraternity at this time and the consultants recommended had a mainly built heritage and infrastructure background which did not readily fit them for the whole challenge. Surveys were carried out on the structure and proposals made for restoring the structure, improving the ventilation and other systems and the access.
Whilst the mechanical and electrical proposals were generally acceptable, the restoration proposals were not. The initial proposal was to remove the free flood ends of the boat and replicate these in fibre reinforced plastic (FRP) around a steel tube mandrel. This strangely enough ignored the heritage imperative to retain as much of the original structure as possible, or to replace it with a similar structure assembled in the original fashion.
Figure 5 Steel tube mandrel as proposed
Shortly thereafter the Museum obtained a Project Planning Grant (PPG) from the UK's National Lottery Fund (HLF) and they asked Frazer-Nash for assistance in assembling a bid to the HLF for the monies to carry out the external restoration. During the course of this work, which included the preparation of the Conservation Management Plan, repair options study and risk assessments, further surveys were carried out as the HLF had by then indicated they were not satisfied with the proposed FRP solution.
It transpired that the original consultants had declined to enter the free flood areas of the submarine in view of the deposits of pigeon guano that liberally coated them. Whilst ship surveyors are made of sterner stuff, the pigeon infestation would remain a problem and continue to affect the structure unless they were completely removed. After seeking appropriate advice the Museum employed a specialist company to remove the birds and as much of the fouling as possible, covering the boat with fine mesh netting to prevent re-entry. This then allowed safer access to the crawl space below the casing and to the free flood areas at bow and stern.
The Frazer-Nash survey then revealed that, whilst much of the outer plating resembled Belgian Lace, much of the internal structure was probably re-usable. The biggest problem would come from the heavy weights still attached to the fraying steelwork, including the large bow sonar dome and the outer shell torpedo doors. These latter items had a very interesting operating mechanism which allowed the shell doors to be opened by the outer tube doors. Unfortunately there was a large amount of brass or bronze involved in this mechanism which was clearly encouraging electrolytic corrosion at the inboard end whilst the shell door was hinged at the forward end where the shell plating was most corroded. The connection between the tube and shell doors was by a slider which did not retain the shell door in any way. Had the hinge failed the door would have plunged into the harbour and been destroyed.
Figure 6 A typical view of the bow free flood space
The other area of concern was the former conning tower and fittings now covered by the Aluminium Alloy Fin. The fin and casing were part of the major refit to streamline the boat, in USN parlance producing a Guppy, but being al alloy these were now suffering an electrolytic corrosion where the insulation had long since broken down. Within the fin were the various periscopes and masts and the additional pressure vessel forming the Commanding Officer's (CO) cabin. This is attached above the main pressure hull and was also used as the access to the fin's conning position. Within this area, apart from guano pollution, the mixture of metals included a large bronze casting attached to one end of the steel pressure vessel of the CO's cabin. Not a good mix, particularly where any chloride compounds remaining in the steel could easily be re-energised by the exposure to rain, but even without, electrolytic corrosion clearly was still happening.
In parallel to the hands on planning, work was also being carried out to source information on the original design of the boat's structure and fittings, her refits and her preparation for preservation. Whilst there was a paucity of actual Alliance drawings, there were some class drawings that helped, but the major sources of information held by the museum was the Class Book. (It is an interesting fact of life that once work starts on a project like this, and no matter how thorough the search, new information will always turn up, usually from an unexpected source and often just after it was really needed!)
A major part of the planning process was the option study, a no holds barred piece of work that had to demonstrate to potential funders not only that the final option selected for the restoration had been thoroughly researched, but that those options discarded had been debated and rejected for solid reasons, i.e. a good audit trail would be available behind the decision making process.
It is worth noting that the options study examined the total impact of the project, the steelwork restoration being just one aspect of this larger overall project.
The options considered are listed in the annex, but to demonstrate that nothing was sacrosanct one of the options considered was that of removing the submarine either within the museum site or to somewhere else within the Portsmouth area.
In a bit more detail, the process for the down selection was as follows:
The final option selected was that of retaining the boat in situ, but in order to access the hull at all times for corrective maintenance, an island would be formed beneath it from piling and aggregate to form a solid base from which to work. The other aspects of the project, the improved gangways and a better ventilation system would then follow in the civil engineering planning.
The actual steelwork restoration would require steel work replacement, removal of some of the mixed metals causing electrolytic corrosion and improved visitor access and will be described below.
Grant Funding Procedures
It is worth a diversion at this point to review the procedures for obtaining heritage grants from the HLF here in the UK.
As a source of funds for restoration the HLF has been in business since 1994. The HLF is the body established by the UK Gov to distribute all proceeds raised from the National Lottery. By now it has become the prime source of such funding and has of course been keeping its policies and processes under review. This review has resulted in the introduction of Strategic Plan 3 (SP3) in March 2009 which probably introduced the first really fundamental change in the way it does business (This replaced strategic Plan 2 (SP2)).
Previously an applicant could apply for a PPG up to £50,000 to ensure they had all the necessary documentation in place and had a reasonable idea of the way ahead. The main application would then follow, based on this documentation and a sound business plan and, if successful, the grant would be ring fenced against a further refinement of the programme plans and costs. There were always some complications as the HLF process was built around its major area of business, that of built heritage, which didn't - and indeed still doesn't - map well onto marine industry methodologies.
SP3 however did away with PPGs, but lowered the standard for what has become known as a Round 1 application. It also incidentally removed any requirement for monitoring and assessing this stage by specialist monitors! A Round 1 pass now only permits the applicant to spend some development money to gain a Round 2 pass which has been made competitive, i.e. the money is no longer ring fenced.
This is important in the case of Alliance as the timescale of the work so far has taken her from the SP2 process into that of SP3. Whilst having had, and used, a PPG to obtain a fairly high level of understanding of the project requirements (under SP2) and obtained a Round 1 pass (under SP3) the next stage has to be a Round 2 application, with no guarantee that the funds will be available.
The Museum has used its Round 1 development funds to recruit a civil engineering consultant and to re-appoint Frazer-Nash as engineering consultants and to fund the development of works specifications for the project completion.
It is worth noting that the appointment of support and works contractors, to meet HLF requirements has to be undertaken on a competitive basis. Whilst this does ensure that the best prices are achieved for the work, it does introduce additional time into the overall project programmes and add to the resourcing requirements of the grant body.
As already seen, the current plans include the provision of the reclaimed "island" beneath the submarine to allow access, not only for assisting long term repair and maintenance, but also to improve the visitor experience. However, it is only once this has been completed that the repairs and restoration of the submarine proper can commence, over dry land.
Drawing on the findings of the first survey Frazer-Nash carried out an engineering study to determine how much of the original steelwork could be retained. An estimate of the level of replacement was made and a structural analysis was carried out to determine the load bearing strength and thus the factors of safety in the resulting structure.
Figure 7 Fraser-Nash proposal using existing material where possible, and original techniques throughout
The solution proposed for the forward end is shown in Figure 6. Where the main vertical backbone or spine plate has been retained (in yellow), an extension piece added to stiffen the upper hull (in orange) and new, extended frames added or repaired (in purple) to further assist in taking the weight of the sonar dome. This proposal had the desired result of retaining as much of the original structure as possible whilst using original materials and techniques to reconstruct or repair the rest of the structure.
Although not illustrated, an identical proposal was evolved for the smaller stern free flood area. In both cases salvaged or replicated plating would be put in place to complete the work, but at the bow the heavy torpedo outer shell doors would be replicated in lighter steel plate fixed in place. The original doors and their intriguing mechanism would be retained ashore, for display purposes.
The fin area was not so clear cut. But the proposed solution is to remove as much of the bronze as possible, where necessary replicating the removed artefact in steel to reduce the potential for electrolytic corrosion.
The degraded tank plating identified by the original contractor still required repair or replacement as did the aluminium alloy casing and fin. As a precaution Frazer-Nash undertook a second survey of these areas. They included the saddle tanks and fairing plates, bilge and ballast keels, but also those tanks internal to the pressure hull which had not been checked by anyone for this project.
Somewhat surprisingly active chloride corrosion was found in two of the internal tanks with a further two having suffered a severe coatings breakdown. This result came as something of a surprise to all concerned as the internal atmosphere of the boat had been subject to forced ventilation from a shore side plant, but despite this condensation is the most likely culprit The saddle tanks were found to be a mixed bunch with, in some, a very active corrosion from either the ingress of rain or from seawater coming in from the free flooding holes at their bottoms at high tide. Others seemed to have their coatings almost totally intact. An initial conclusion was that it was the fuel tanks that had suffered the most. One other conclusion, based on experience from actually trying it, was that access to blast clean these tanks would be almost impossible without cutting a large hole in them.
Figure 8 Internal tank with active corrosion
Figure 9 External saddle tank showing corrosion
As a result the original Frazer-Nash survey proposals for the restoration of the steel work were then reviewed and refined with the addition of the findings of the second survey to bring them into line with the heritage imperative and then incorporated them into a detailed specification to allow appropriately qualified contractors to bid for the work.
As noted above the first proposals include the disassembly of the worst areas of corroded steel external to the pressure hull. As a result of the structural strength calculations carried out earlier, Frazer-Nash have derived a set of steel tolerances that will allow a contractor to replace only the very corroded steel and to match the replacement steel with the minimum acceptable thickness of existing steel, rather than trying to attach, for example, 20 mm plate to an original 20 mm plate that has corroded down to 10 mm., 10 mm replacement will be used. Not only does this retain as much of the existing material as possible, it has the incidental effect of reducing the tonnage of new steel needed and hence the cost of the restoration.
In addition, methods have been suggested for accessing the saddle tanks, both short term and long term, and the internal tanks without damaging heritage material too greatly, and without contaminating the boat's interior. This guidance included identifying original weld seams that could be cut open during refurbishment, an enlarged permanent lower access to the saddle tanks and opening up the saddle tank dividing bulkheads to form a continuous passage for internal inspections.
An additional task is to improve access for less than able visitors. A difficult task in something as compact as a submarine, but it is possible to use a wheel chair for example in the after torpedo compartment so it should be possible to increase the size of the existing side entry to allow access to this part of the boat.
The basis of the work then will involve removing extraneous fittings where they are invisible to the public, e.g. where hidden beneath the casing, or where they add weight to a structure that has been weakened by corrosion; only replace structure that has corroded beyond a minimum safe tolerance or where its original material is causing electrolytic corrosion or where, as in the case of the shell torpedo doors they would be better demonstrated ashore in the museum.
All the steel work is to be blast cleaned and given a modern, long life, coating which, with improved access for the minimal maintenance necessary, and should last as long as the boat has survived so far.
The aluminium alloy casing, refurbished and similarly coated will then be replaced with a long term insulant between the two metals, again with the intention of giving a long life, but low maintenance load.
In parallel to the steel work restoration specification, the Civil Engineering Consultants were producing detailed work specifications to allow for contractors to tender for the "island" and the ventilation improvement works. The island is the most crucial aspect of the whole programme as, as noted above, work cannot start on the boat itself until the selected contractor as a firm base from which to work.
At the time of this paper, the project is concentrating on the round 2 application and on fundraising strategies.
Figure 10 The future
It is intended to invite tenders for the civil engineering work in time to inform the HLF Round 2 application in January 2011. At the same time prospective steel work contractors will be asked to quote for their work, recognising that it will not start until the initial civil engineering works have been completed towards the end of 2011. This is necessary in order to ensure a high level of confidence in the overall cost prediction that goes into the Round 2 application. Funders tend to take a dim view of cost overruns!
Subject to winning the Round 2 HLF award, work is expected to start in about May 2011 and will continue for two years, completing in August 2012 or thereabouts.