WWII Tech Pubs Feature

Written by
James Davies

Table of Contents

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Introduction

Background

It is said of the armed services that amateurs study tactics, whilst professionals study logistics.  This truism highlights the fact that wars can only be won if the fighting services receive the supplies they need at the time that they need them.  For many of the nations involved in the Second World War these supplies had to travel across the seas at least once, and often twice or more, before they reached their ultimate destination.  These supplies were carried in the merchant ships of nearly all countries of the world, even those who were 'neutral' in the war.

Island nations (such as Great Britain and Japan) relied heavily on imports to sustain their manufacturing industry and to provide food for the population, as well as on coastal traffic to move materials around the country.  Many other nations were also dependant to a greater or lesser extent on the sea.  Germany required oil, iron ore and small quantities of other key materials for use in manufacturing, as well as luxuries for the population (coffee, for example).  The United States of America relied heavily on oil and coal shipments around the coast, as well as benefiting greatly from international trade in the completed products.  The Australian and New Zealand economies were built around food exports (predominantly to Britain), and Canada too had significant trade passing through her ports.

In those days before widespread 'flags of convenience', ships usually flew the flag of the nation where the owners of the vessel were based.  Ships could expect treatment at sea or in port to be directly influenced by the flag flown, and could expect as a right the assistance of the navy of the nation to which they belonged.  In return for this protection nations had the right to requisition ships flying their flag in time of war.

The relative sizes of the merchant navies on the outbreak of war in Europe are shown below.  The relative importance of sea trade to a nation is approximately in proportion to the size of its merchant fleet.  (Over 90% of the ‘British Empire’ ships were registered in the UK).

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The Tonnage War

The hopes for German victory at sea were founded on winning a tonnage war.  The concept of a tonnage war is to sink more ships than the enemy can build.  Every ship lost is important not because the cargo carried in that ship does not reach its destination, but because all future cargoes that might have been carried by that ship also do not reach their destination.  This can only be important if the target of the tonnage war is restricted by the number of available ships, and if more ships are lost than can be built to replace them.

At the start of the war the British and Commonwealth shipyards were filled to capacity with warships, and there was little remaining capacity for building merchant shipping.  Some ships were acquired from other nations, however as much of the world’s fleet was already trading with the British Empire there was only limited opportunity to gain ships from elsewhere.  In this environment the tonnage war was hugely successful.  In 1940, for every 2,000 tons of Allied and neutral ships built, 9,000 tons were sunk.  In 1941 the ratio was significantly better, at 4,000 tons built for every 9,000 tons sunk, but still clearly unsustainable (see Figure 2).

During 1942-1943 the tonnage war faltered, then finally failed.  There was no single reason for this, however the improvement in the number and experience of escorts and the widespread adoption of technological breakthroughs were important factors, as was the secret war fought by the code breakers.  Also of great importance was the massive increase in the shipbuilding capacity of America, of which the Liberty Ship formed the foundation.

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The Liberty Ship Programme

In 1936, well over 90% of the American merchant fleet was more than 20 years old.  In order to ensure that America possessed a fleet that was adequate to meet the future anticipated needs a decision was made to greatly expand America's merchant fleet.  The fleet was to be owned and operated by American companies, and in order to ensure their success the American government decided to subsidise the building costs and operating expenses of the ships.  As yet there was little urgency in the programme, run by the US Maritime Commission.

In 1941, faced with war already underway in Europe and an expectation of war with Japan, there was seen to be a need to expand the pre-war programme with a ship that could be built rapidly.  The Liberty Ship design was chosen to meet this immediate need.  Eighteen new shipyards were built to meet the demand, and a workforce was trained to handle the construction.  It was a project on a massive scale, undertaken with great speed and efficiency.  The first Liberty Ship (the Patrick Henry) was launched on 27 September 1941 (and completed on 30 December 1941), which was an incredible feat considering that just seven months previously neither shipyard nor workforce existed to build her.

The ships suffered from some initial structural problems, particularly related to the lack of understanding of the influence of welding on the strength of some key elements (such as hatch corners), however once the problems were understood they were soon fixed.  Less easy to fix was the 'stiffness' of the ships - they had a rapid roll motion which was uncomfortable for the crew and could lead to damage to cargo.  This could be partially offset by putting solid ballast in the 'tween decks, thereby raising the centre of gravity and reducing the 'stiffness'.  Unfortunately, if not stowed properly (and sometimes even when stowed properly) this ballast could shift in a storm and put the ship in grave danger of foundering.

A total of 2,710 Liberty Ships were completed (with one more being burnt out on the slipway and never completed).  This huge total almost defies the imagination when considering the resources that must be employed to produce this number.  Putting it in perspective, 1,088 Curtis Hawk fighters were produced (all variants), and approximately 2,900 M16 half-tracks.  During the peak building period (March 1943 to December 1943) over 100 were completed per month.

Despite being initially labelled an 'ugly duckling' by the newspapers, and intended to be expendable if necessary, the ships eventually caught the imagination of the public.  They proved to be easy to build, reliable and versatile, exceeding even the most optimistic expectations for their overall contribution to the war effort.

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Impact of Liberty Ships on the War

The impact of the Liberty Ship on the Tonnage War can be clearly seen in the graph below (Figure 3).  This graph shows the ratio of losses to new buildings if the Liberty Ships had not been built.  This graph can be directly compared to Figure 2 above.

As can be seen, without the Liberty Ship 1942 would have been a worse year (for the Allies) than 1941, largely due to the losses off the American East coast in the first half of the year.  The Liberty Ship programme began to tail off in 1944, with Victory ships replacing Liberty Ships as the new-build of choice.  Even without this new tonnage, however, the Allies would have been showing a positive balance sheet at all times from 1943 onwards.

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Development

Britain Builds ‘Emergency’ Ships

Having filled her large shipyards with warships, Britain had a pressing need to find new merchant tonnage to offset the losses of those being sunk.  Ships were built wherever there was space in British territories, with those built in Britain bearing the prefix ‘Empire’ and known as ‘Empire’ ships, whilst those built in Canada bore the prefix ‘Fort’ and ‘Park’.  Many different designs for those ships existed, however one devised by the J L Thompson & Sons yard had been specifically modified for mass production.  This was based on a pre-war design for the Dorington Court, and resulted in a general cargo ship of around 10,000 tons deadweight and a speed of 11 knots.  The first wartime ship of this type was the Empire Liberty (launched on the 28^th August 1941), and these were known as the ‘North Sands’ type.

Desperate for new tonnage, in late 1940 British representatives (including one from the Thompson yard) took the Empire Liberty plans to America to try to persuade the American government to let Britain place orders for 60 new ships.  The Americans agreed, however no space existed in shipyards to allow them to be built and it was decided to build two new shipyards to meet the British need.  These ships bore the prefix ‘Ocean’, with the first ship (the Ocean Vanguard) being launched on 15^th October 1941.

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The American ‘Emergency’ Programme is Born

Simultaneous with the decision to build ships for the British was a decision to rapidly expand the US merchant fleet, however the choice of a design appropriate for mass production was a difficult one.  The previous ships built by the US Maritime Commission were of a very high quality (but not suited to mass production), in stark contrast to the British wartime designs (which deliberately emphasised speed of construction), and there was considerable resistance to the idea of lowering standards to build ships rapidly.  Faced, however, with an urgent need, little time and a sound and readily available design a common-sense decision was taken to adopt the basic British concept for the American emergency fleet.  This design was modified somewhat to further aid mass production and to suit American building techniques and other US preferences, and orders were placed for the first 200 of these ships in early 1941.

As with the ‘Ocean’ ships, no shipyards existed to build these vessels and a total of nine new shipyards were announced (including the two required to build the British vessels).  Later expansions resulted in even more shipyards, and a total completed fleet of 2,710 ships.

Liberty Ships are famous for their all-welded construction, extensive use of prefabrication and the application of production-line techniques to shipbuilding.  Contrary to legend, these were not the first ships to make use of mass-production techniques as the Hog Island type had also applied similar principles during the First World War.  Nevertheless, the techniques used when building Liberty Ships resulted in a production rate far in advance of what was thought possible before the Second World War, with some ships being launched just days after the keel had been laid (the Robert E Peary being launched just four days after the keel was laid, and being completed only three days later).

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General Cargo Vessel Type EC2-S-C1

The Liberty Ship was 441 feet 6 inches long overall, with a maximum beam of 57 feet and a depth of 37 feet 4 inches.

Liberty Ships had five cargo holds, three forward of the accommodation and two aft, and the deck was designed with minimal obstructions to enable cargo to be carried on top of the holds.  In common with marine convention, holds are numbered from forward to aft, with number one hold being the most forward.  Three masts supported booms for cargo handling.  These had an initial lifting capacity of five tons, however this was increased to 50 tons for the number two hold and to 15 or 30 tons for the number four hold.

The single machinery space was located below the accommodation, although there was a slight overlap forward over the number three hold.  This space contained two boilers and a triple expansion steam turbine.  A single propeller was fitted (normal practice in merchant ships) which gave a speed of 11 knots (comparable with many general cargo vessels of the day).

Fuel oil was carried in the inner bottom tanks (just above the keel of the ship) and settling tanks to port and starboard of the machinery space (settling tanks are used to allow impurities in the fuel, such as water, to settle out before the fuel is used).  Oil (either cargo or fuel) could also be carried in deep tank number three, which was located just aft of the machinery space.  There were a total of three deep tanks, with number one and two located beneath hold one.  All deep tanks could carry dry cargo, with an option for water ballast in deep tanks one and two.

Weapons were provided for defence.  Previously, rules of war had required armament on merchant vessels to be restricted to 'abaft the beam' but in view of the German failure to follow agreed protocols for protecting merchant seamen armament was provided that could also fire ahead.  The armament provided varied considerably, and could include four inch and three inch guns, 20mm and 37mm cannon, as well as 0.3 and 0.5 inch machineguns.  The largest gun (generally a four inch) would typically be fitted at the stern, and would be flanked by two smaller guns.  There would usually be four guns on the superstructure, and these could be 20mm cannons, machineguns, or a mixture of both.  The forward mast would be provided with two guns, usually 20mm cannon or 0.5 inch machineguns.  On the bow would often be a single three inch gun.  Many variants on this typical arrangement existed, with additional guns being fitted in other areas (such as two or four guns added adjacent to the second mast), or the arrangements changed from those described above (such as replacing the single bow gun with two 37mm cannon).  As with all ships during the war, the armament tended to increase as the war progressed, especially if service with the advance elements in the Pacific campaign was expected.

Accommodation was provided for 81 people.  This was initially intended to be 45 crew and 36 gunners, however changes in this arrangement were not uncommon.  Four lifeboats were provided, two with capacity for 25 people and two with a capacity for 31 people.  At first one, then later both, of the 25-man boats were provided with a motor.  Motors are used in lifeboats only to get clear of a sinking ship, as insufficient fuel could be carried for a long voyage.  Motor lifeboats are expected to tow the other boats clear also.

This basic design was suitable for modification, with changes being made after launch (and often after completion) to produce troop ships, hospital ships and repair ships.  These modifications are discussed in the Major Modifications section.  In addition, two main variants were produced - the Liberty tanker and the Liberty collier.  These two vessels are discussed in the Variants section.

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Variants

There were two major variants of the Liberty Ship produced - the tanker and the collier.  These ships are treated as variants rather than modifications because the ships were built from the keel up for these specific roles.

Tanker Type Z-ET1-S-C3

The Liberty tanker was proposed in late 1942 as a response to the need to transport more oil (due to the US entry in to the war) and offset the large losses amongst the existing tanker fleet.  The initial intention was to both convert existing cargo ships and build specific new tonnage as tankers, however the conversion plan was soon abandoned.

The tanker was very similar to the standard cargo ship, with the same length, breadth and draft, as well as the same propulsion system.  It deliberately retained dummy or redundant deck equipment to prevent these ships from being identified as tankers (and so prevent them from being specifically targeted), with the necessary piping being concealed.  The deception was further aided by the ability of these ships to carry deck cargo.

Internally, there were also few changes.  The major change was the addition of two pump rooms, forward and aft of the machinery space.  Pump rooms are used during cargo discharge, to pump the cargo up from the tanks to the shore facility.  This reduced the available space in what used to be the number three hold.  The two deep tanks under number one hold were removed (adding their volume to the available cargo space), and part of the number three deep tank was used in the forward pump room.

The remaining spaces were provided with additional subdivision.  Vertical oil-tight bulkheads were placed at the edges of what used to be the hatches, producing trunks down to the second deck, with bulk of the oil cargo being carried below the second deck.  In to the void spaces thus created (between the second deck and the weather deck) were placed all the pipework, manifolds and valves (hiding them from view).  The previous number one, two, four and five holds were subdivided transversely (ie across the ship) near to the centreline of the previous hatch covers, and all holds were divided longitudinally (forward and aft) down the centreline of the ship.

The resulting tanker had a total of eighteen tanks for carrying oil:  tanks number one, two, three, four and five (port and starboard) forward of the accommodation (a total of ten spaces) and tanks six, seven, eight and nine (port and starboard) aft of the accommodation (eight spaces).

Either light fuel oil (petrol) or heavy oil could be carried in the forward tanks, with heavy oil only in the aft tanks.  The piping arrangement allowed different cargo to be carried forward and aft, although it was also arranged to allow the aft cargo to be pumped via the forward pump room (and vice-versa) if necessary.

The vents for the tanks were at the top of the masts, and the forward tanks (the light oil tanks) were also provided with pressure relief valves and flame arrestors (to prevent an external flash fire from travelling back down to the tanks through the venting system).  Aft tanks did not require this as the heavy oil did not produce high levels of vapour.  All tanks had a steam smothering system (to put out fires in the tanks), heating coils (heavy oil does not flow without being heated) and a tank cleaning system (tanks are normally cleaned after discharging every cargo, both to prevent future cargo contamination and to free the vessel of potentially explosive residual gas).

All tankers are very difficult ships to sink.  They are designed to carry liquid with a very similar density to water (oil is approximately 98% of the density of water), and a hole in the side simply replaces one liquid with another.  Unladen tankers have such a reserve of buoyancy that they are almost impossible to sink unless structural failure occurs.  For laden tankers the major danger is from fire, as burning petrol leaking out from the side can quickly spread around the ship preventing the crew from escaping (modern lifeboats are now totally enclosed and fitted with a sprinkler system to enable tanker crews to escape if the worst does happen).  Heavy oil is difficult to set alight, and does not flow well, however ships carrying petrol were extremely vulnerable.

A total of 62 tankers were produced, although after the war was over most were converted to dry cargo vessels.  The tankers are listed in the Production Figures section.

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Collier Type EC2-S-AW1

In contrast to the Liberty tanker (which was produced with minimal changes to meet an urgent wartime need), the collier represented a major redesign to meet anticipated peacetime requirements.  The existing east coast collier fleet was old (only two were less than 20 years old) and new tonnage was needed to secure the supply of coal for the future.

The Liberty collier's outward appearance had little in common with the standard Liberty Ship.  The main change was the relocation of all machinery aft.  This was a much more efficient arrangement that reduced the space 'lost' to the propeller shaft and ensured that the cargo was carried in the parts of the ship where the hull was shaped least (this is generally more efficient for cargo stowage, and reduces the likelihood of damage when discharging cargo with grabs).

As far as possible, standard Liberty Ship components were used.  The ship was very slightly longer than the standard vessel, but with the same breadth and depth.  This meant that many of the standard Liberty plates and structural members could be used for the hull, although some new components were needed.

Despite the radically different appearance, in fact there were many similarities between the two vessels.  The aft machinery space was placed in what used to be the number five hold, retaining the dimensions of the original hold.  In to this space was fitted the same propulsion machinery as was installed as the standard vessel, with some relatively minor modifications to ensure that it could fit in the new space.

As with the original vessel, the collier had five cargo holds, although the 'tween decks were necessarily removed and replaced with a simple structural member running along the side of the ship at the place where the 'tween deck would otherwise have met the hull.  The forward (number one) hold retained the two deep tanks at its base, and additional wing tanks were provided in holds two to five.  These wing tanks were triangular, being created by adding angled plate between the deck openings and the place where the 'tween deck used to meet the hull (this space would otherwise have been wasted, and in fact added significant structural strength).  These wing tanks were used to carry water ballast when the vessel was empty.

A third deep tank was provided aft of hold number two, on top of which sat the forward accommodation.  Double bottom tanks were retained under holds two, three, four and five.  Fuel oil was normally carried in the double bottoms beneath holds three, four and five, although it could also be carried in number three deep tank and number two double bottom.  Number three deep tank and number two double bottom were normally used for ballast.

Accommodation and lifesaving arrangements were different to the standard vessel.  The forward accommodation contained the deck officers, with the remainder of the crew being housed in the aft accommodation.  Two small (13 person) lifeboats were provided for the deck officers forward, with two 52 person boats (equipped with motors) provided aft.  Accommodation was designed for a crew of 46, although space was available for gunners should they be required.

A total of 24 colliers were produced, and these are listed in the Production Figures section.

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Operational Use

Overview

The operational history of the Liberty Ship is a microcosm of the histories of all Allied merchant ships during World War Two.  Their tasks mirrored those of the merchant service as a whole, in many respects an 'average' ship doing the normal tasks of merchant vessels in wartime.  Therein lies their greatness however, as when you examine these 'normal' tasks you find a rich history of brave deeds, carried out by civilians in an environment which is hazardous in peacetime and unimaginably more deadly in wartime.

The Liberty Ship saw service all over the world: they were present in the Atlantic and Russian convoys; they anchored off the beachheads in North Africa, Europe and in the Pacific islands; they carried food to civilians as well as supplies and equipment to the armed forces; as hospital ships they treated the wounded; they transported prisoners away from the fighting; they evacuated rescued Allied prisoners from Asia; in perhaps their most welcome role, they brought the troops home again after the fighting was over.

Of the 2,710 ships completed, 253 were lost during the war, a loss rate of 9%.  The wide cause of losses shows the wide range of hazards that these ships were exposed to.  Losses occurred due to kamikazes, torpedoes, surface raider guns, aircraft bombs, collisions (made more likely with blacked-out ships travelling close together in convoy) and to the weather (an ever-present hazard, even during wartime).

Even more striking is the loss rate for ships completed before the end of June 1942.  The battle of the Atlantic appeared to be in the balance until early 1943, when U-boat losses began to rise sharply, and ships completed up to mid-1942 underwent one year of service during this hazardous time.  Of the 153 ships completed before 1^st July 1942, a total of 34 were lost before the end of April 1943 (and 47 before the end of the war).  At 22% loss for this short period, and 31% before the end of the war, this was a loss rate significantly higher than the overall loss rate for the class.  Considering that these ships only served through part of one of the two U-boat ‘happy times’, it gives some indication of the carnage that the U-boats were causing to merchant shipping in the early years of the war.

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Gallant Ships

The US government recognises exceptional courage by a ship and her crew in the form of Gallant Ship Awards.  Seven Liberty Ships were given Gallant Ship Awards, the Stephen Hopkins, Adoniram Judson, Samuel Parker, William Moultrie, Marcus Daly, Virginia Dare and the Nathaniel Greene.  The citations for these awards are repeated below (Note:  Some errors exist in the citations):

Outside of these awards there remains many stories of interest.  One example is the Robert F Hoke, a ship that would not sink and went for three and a half years with an un-repaired torpedo hole in her side before being discarded.  Another is the Charles Willson Peale, who fought off the attack of U199.

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SAM Ships

Many Liberty Ships were transferred to other nations, the largest number being to the British.  All the British ships (except the Adolph S Ochs, named after a famous New York Times editor, who retained her original name after lobbying) were named with the prefix 'Sam', officially indicating that the ship had the 'superstructure aft of midships', however it is impossible to believe that the connection with 'Uncle Sam' was merely a coincidence.

The SAM ships were:

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Liberty Ship Fates

Wartime Liberty Ship Losses

Note 1: 5 ships were lost to mines post-war whilst 1 was lost to a mine on an unknown date, and these losses are not included in the above figures.

Note 2: Marine losses relate to the normal hazards experienced by ships when going about their business.  They include grounding, collision, foundering, fires, cargo handling incidents and other non-wartime causes of loss.

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Overall Liberty Ship Fates

Note 1: Marine incidents relate to the normal hazards experienced by ships when going about their business.  They include grounding, collision, foundering, fires, cargo handling incidents and other non-wartime causes of loss.

Note 2: This table represents the status of ships in 1970.  It is expected that all ships in the reserve fleet will now have been disposed of (mostly scrapped).

Note 3: Includes vessels that were still operating in 1970.

Note 4: Includes one ship burnt out on slipway before launch.

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Specifications (As-Built)

Note 1: Draft quoted is maximum normal seagoing draft in peace conditions, and corresponds to the maximum displacement.  This draft may be exceeded in coastal or inland waterways, or by overloading during wartime.  Unladen ships will have a significantly lower draft.

Note 2: As well as cargo weight, deadweight also includes the weight of stores, fuel and other consumables, although on a cargo ship the 'deadweight' is dominated by cargo weight.

Note 3: Cargo volume is quoted in various measures depending on the type of vessel.  The 'grain' measurement is for general dry cargo vessels, and indicates the total volume of the holds, excluding any structural items or fittings (grain fills in all corners and around structural members).  The 'bale' measurement is again for general dry cargo vessels, however it measures volume up to the stiffeners on the inside of the hull, with space between stiffeners being lost (bales of cargo don't flow around beams).  The 'barrel' is quoted for oil carriers, although in the modern world oil is now normally measured by the ton.

Note 4: The armament provided varied considerably, and could include four inch and three inch guns, 20mm and 37mm cannon, as well as 0.3 and 0.5 inch machineguns.  The largest gun (generally a four inch) would typically be fitted at the stern, and would be flanked by two smaller guns (such as two single 20 mm cannon).  There would usually be four gun positions on the superstructure, and these could be 20mm cannons, machineguns, or a mixture of both.  The forward mast would be provided with two guns, usually 20mm cannon or 0.5 inch machineguns.  On the bow would often be a single three inch gun.  Many variants on this typical arrangement existed, with additional guns being fitted in other areas (such as two or four guns added adjacent to the second mast), or the arrangements changed from those described above (such as replacing the single bow gun with two 37mm cannon).

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Major Modifications

Modifications were made to many ship to fit them for special purposes, such as hospital ships, troop transportation and repair ships.  These ships are considered as modifications rather than variants as the ships were first launched (and often completed) as a standard Liberty Ship, before being refitted for these new roles.

Post-war many changes were made to the ships, besides the obvious removal of armament.  The major change generally involved the cargo handling arrangements, customising it to handle specific cargoes ranging from liquefied gas to modern cargo containers.  Several ships were lengthened, and others converted to barges.  There are even occasional examples of two halves of different ships being joined together to make a new vessel.

Passenger Transport

Large amounts of additional transportation were required at relatively short notice to carry prisoners from North Africa to prisoner of war camps in North America.  This transportation was to be provided by converting existing cargo vessels, with the original plan calling for the ships to carry 308 prisoners, however this was later raised to 504 (although about half the ships retained the lower 308 person capacity).

The conversion was relatively simple, with the vessels retaining their essential character as cargo ships, but with five-tier bunks being added, along with facilities to provide food, drinking water, environmental control and sanitation.  To provide an essential minimum of protection in the event of an emergency, additional lifeboats, liferafts and lifejackets were provided, people were generally not accommodated below the waterline and two emergency escapes were installed from each compartment.

The ships were retained for carrying American troops later in the war, although the accommodation was improved.  The reduction in bunk height from five to three reduced the capacity to 350 people, although this programme was not complete when the war in Europe was won.  Another re-think resulted in requirements for the capacity to be increased to 550 people, and this programme had nearly been completed when the war in the Pacific ended.  It should be noted that the nominal carrying capacity of the ships was often exceeded for special purposes, particularly for voyages over short distances.

The following ships were converted to carry up to 550 people.