Liberty ship cracks and lifetime

[Geoffrey Sinclair]

This is a carry over from the WWII aviation RAF B-17s thread, moved at moderator insistence.  So anyone from other discussion group is arriving with the party well in swing, and many guests already at least "merry".  Basically about Liberty ship and combat aircraft (expected) lifetimes, near zero modelling content.

 

I do not have access to the book, "Liberty's Provenance", by John Henshaw, Which has the blurb, "The battle of the Atlantic, fought by the Allies to maintain lines of communication and vital trade routes for armaments, men, and basic sustenance, could not have been won without the 2,710 Liberty ships that were designed and built for those critical one-way voyages to Europe—more than one voyage was considered a bonus"  So essentially the North Atlantic shipping system was expected to take regular 50% or more casualties.  Where at any time of the war, except for PQ-17 did that happen?  Or even planned as going to happen.  Or to use Clay Blair, Hitler's U-Boat War, 3,253 ships arrived in Britain in convoy January to August 1942, after losing 30 merchant ships and 3 escorts.  There were 2,285 ships in westbound convoys, 47 lost plus 3 escorts.  So on the one voyage rule the ship is lost either on the way in or out, 5,500 sailings, 2,750 losses, 350 ships a month to 700 per month.

 

The amount of allied ships being sunk was higher than new builds for much of the first half of WWII.  The tanker losses mostly off the US in 1942 took until the end of 1943 to be replaced.

 

The rest is taken from the book Liberty by Peter Elphick, the chapter entitled "close to calamity" which deals with the emergence of structural failures in US built WWII merchant ships and the investigations undertaken to solve the problem.

 

As of 1 September 1944 some 558 ships had reported a total of 785 incidents of cracking, and this is known to be an underestimate of the total.

 

The US "Final Report", containing data to 1 April 1946 noted of some 5,000 Maritime Commission built ships some 972 had reported a total of 1,442 incidents.  Top of the list were a tanker and two non liberty ships which had suffered 8 incidents, the "top" two liberty ships had suffered 6 incidents.

 

One of the first incidents was when building the ship Ocean Justice, a welder was amazed to watch cracks propagating, on a cold morning in February 1942, the damage was classified as serious and the ship was not launched for another two months.  Of the 60 Ocean class some 9 would suffer some sort of failure.

 

The next major incident reported was on 10 November 1942 and the third on the 11th.  By 12 January 1943 another 10 ships had reported major cracking problems.  The US assigned the category class I to these, with class II being bad with the potential to become class I and class III for other reports.  There were 18 class II and III incidents between November and January.

The Germans were well aware of the problem, even publishing an account in the journal Nauticus in 1944.  The US allowed the New York Times to carry an article on the topic in April 1944.  There is little doubt a problem in sorting out what was going on were the rumours, some of which were axis fuelled, as you would expect.

 

By the end of 1942 the cracking defects were clearly recognised as a problem and on 16 January 1943 the new tanker Schenectady nearly broke in half while being fitted out on the Columbia River. The break sounded like an explosion.  Air temperature was 26 degrees Fahrenheit.  The cracking had occurred so quickly the raised sections of the hull had almost no chance to ship water. (The ship broke into an inverted letter V as the bow and stern were carrying ballast).

 

It was clear the crack did not follow the welds but went through the steel plates.  The initial reaction was to blame the welds but that was not sustainable.  The steel was taken for experiments and passed all the standard tests.  The key observation was the steel had behaved as if it were brittle, with the pieces able to be reassembled into their original shape, whereas it should have been ductile, with some ability to "bend and stretch" before breaking and the distortions before breaking would mean the pieces could not be reassembled so neatly.

Since a majority of the early incidents came from Kaiser yards it was easy to assume it was a problem for that builder alone but as the incidents continued from February 1943 onwards it was clear there was a more systematic problem.  It was across all yards and all types of ships.

 

The next 11 class I failures resulted in the loss of two ships at sea.  Then the Esso Manhattan, a tanker, effectively split in two off New York on 29 March 1943, with its two escorting ASW blimps granted ringside seats to take lots of photographs.  In this case the crack had started at a defective weld.  The ship made harbour and was put back together.

 

The US started an official inquiry on 20 April 1943 with an "utmost urgency" brief, to find out what was going on.  At about the same time the British initiated a similar investigation, both countries gave the investigations considerable authority and resources, and exchange visits were organised to keep each investigation up to date with the other.

 

The US started by circulating to masters of US ships a survey form requesting reports on cracking problems, accepting the inevitable rumours that fuelled.  The available data collected revealed by 30 April 1943 there had been 28 class I events and over 100 events in total.  Later the British circulated a similar survey.  These surveys were continued throughout the war but they inevitably missed some incidents.  It seems the reporting system stayed in use until the late 1960's.

 

Looking at the official US final report, which was data collected to 17 March 1946, there had been 132 class I failures.  Peak class I failure month had been January 1944, with 20, worst month for all types of failures was March 1944 with 138.

 

It would appear it was not until November 1943 that a failure resulted in US lives being lost, and that was from a lifeboat going missing.

 

Some 8 US and 6 British ships were used as tests, taking ships out of commission as required.

 

The British tests were more elaborate than the US ones, using still water trials of sister ships, one welded and one riveted, and ocean trials with a ship whose master was instructed to go through storms as much as was safely possible.  Incidentally these full size trials run in the 1944 to 1947 period were published by the Admiralty and remain to this day the most modern set of data on the stresses full size merchant ships encounter.  Elphick hints that maybe it is time for another set of trials.  It took the sea trials to finally convince the die hards that it was not a case of riveting being superior as a joining technique.

 

The first obstacle any investigation had to overcome was the fact ship building rules were not codified, they were a collection of rules of thumb developed over the years.  So no one knew what sort of stresses a "normal", that is riveted, merchant ship would see. This enabled those who preferred riveted construction to hold the view it was welding causing the problem, ideas like faulty welds or because riveting made the ship overall less rigid and so able to absorb stresses better.  It took the full size trials to disprove the claimed superiority of riveting when it came to handling stress. In simple terms the difference between riveting and welding was minor.  The crack resistance superiority came from the fact the welds created one metal sheet, riveting kept the sheets separate.

 

As another example of the time needed it took about a year, that is until sometime in 1944, before any researcher reproduced the cracking in a laboratory experiment.

One of the actions first approved was the fitting of crack arresters, 4 long slots were cut in the ship's plating and covered by a strap that was riveted into place, it was easy to do this for new ships but expensive for ships already built, about 1,000 already built Liberty ships received the modifications.  Apart from structural failures the crack arresters helped limit damage from bomb etc. hits. Ships meant as troop transports were given additional strengthening.

 

The first sets of data showed as expected cracks started from parts of the ship under high stress and strengthening was ordered for key areas.  Welding remained a favourite candidate for the ultimate cause and more care was taken to ensure welding was to proper standards and the crack down did uncover problems, where welds were simply done incorrectly.  A practice of poor welding was wide spread enough to have its own word, slugging, to describe one technique.  Yet tests on slugged welds showed if anything they were superior to the "correct" welds, as opposed to other cases where the weld was simply faulty.

 

Another clue was British built welded ships were not suffering the same defect rate.

 

It was also clear from the incident reports the cracks did not normally follow the welds, indeed they often seemed to quickly move away from them.  Extensive US tests showed welds did not create "locked up" or residual tensions which then created failure points.

 

The way the plates were cracking suggested the steel was the problem and like welding more effort was put in to ensure quality control was improved.  As expected some quality problems were found in the steel supply but again standard testing on cracked plates kept coming up with pass marks.  The Bethlehem Fairfield yard used part riveting in its ships and they suffered a much lower rate of cracking, which was another point in favour of the riveting was better belief.  There was also the suspicion Bethlehem was managing to make sure its best steel went to its own ship yard.

 

The original April 1943 survey was also clearly pointing out low temperatures were a problem.  As an aside whoever produced the survey questions managed to do a very good job, covering almost all the information needed to solve the problem.

 

As the incident numbers built it became clear that ships built in lower temperature environments were more at risk.  It also seemed to be ships in ballast were at more risk, and ballasting instructions were changed

 

Another complicating factor was ships in US service had a higher risk of seeing structural problems, ships in UK or Norwegian service a lower risk, but in Soviet service the risk was higher than for the US.  While the Soviets were operating in lower temperature environments Elphick points to the average US merchant marine officer had much less sea experience than the British and Norwegians and this may have lead to the US ships being subjected to greater storm stresses as seamanship is more experience than theory.

 

In the end the metallurgists came up with the answer.  The Cambridge (UK) team was lead by Dr Constance Tipper.  The term notch brittleness is used to describe a plate having a higher stress area, a notch, and when it would break in a brittle manner at low temperatures. No tests were done for this at the time and it turned out US steels with their lower manganese to carbon ratios showed the problem more than UK steels.  In almost all cases it required temperatures so low that they were rarely encountered however some of the US steel batches were so sensitive they could crack in tropical waters.

 

It explained why welding was not a problem, why UK welded ships were not giving the same amount of problems, why it was worst in winter and why temperatures when under construction seemed to matter.

[Julien]

Yes it was moved at moderator instance as you insisted on posting it in a thread on B-17 where it was not wanted or relevant. 

[Dave Swindell]

6 hours ago, Geoffrey Sinclair said:

Incidentally these full size trials run in the 1944 to 1947 period were published by the Admiralty and remain to this day the most modern set of data on the stresses full size merchant ships encounter.

I'd assume that you're quoting from a source here, and that it's a pretty ancient source at that. Ship design is governed by classification society rules, these may well have started out empirical in nature, but this hasn't been the case for a long long time. Shipping is a cost sensitive business, and shipowners want minimum scantlings and maximum space in their ships to maximise carrying capacity. To achieve this, material and design stresses have to be understood, and testing is part of this. I was involved in fitting some 10 kilometres of cabling into one of our container ships to monitor stresses and strains throughout the ship for Germanisher Lloyd, this was 20 years ago and was by no means unique, and I'd suggest that the data collected was significantly greater and of better quality than that referred to above.

 

Brittle fracture or cold fracture of iron and steel in shipbuilding was known about pretty much since its introduction into shipbuilding in the 19th century. The loss of the Titanic was in part due to brittle fracture of the hull plates, which significantly increased the amount of damage to the hull. It's not confined to welded ships - Titanic was rivetted - but cracks developing in rivetted plates don't generally propagate into adjoining plates, which does happen with welded construction. Brittle fracture can lead to rapid crack propagation, which whilst damaging in a rivetted ship, could lead to catastrophic failure in a welded one. Like a lot of engineering problems, there is rarely one single fault, it's a combination of circumstances that lead to failure, and determining what all the factors are is necessary to find  a solution to the problem.

[Jamie @ Sovereign Hobbies]

@Dave Swindell such strain gauge data from all over ships would have engineers very excited. Finite element analysis is a wonderful technology not available to naval architects even 30 years ago as it is now - but you still have to be able to calibrate your models with codified parameters to get any sense out of them

[Dave Swindell]

16 minutes ago, Jamie @ Sovereign Hobbies said:

@Dave Swindell such strain gauge data from all over ships would have engineers very excited. Finite element analysis is a wonderful technology not available to naval architects even 30 years ago as it is now - but you still have to be able to calibrate your models with codified parameters to get any sense out of them

It wasn't just strain gauges  @Jamie @ Sovereign Hobbies, there were several accelerometers around the ship as well, and the data recorder was also linked into the ships data monitoring systems, so you got a record of all the met, nav and engineering data as well. The project was primarily to study the effects of parametric rolling on the ship to find out why boxes were falling overboard, but part of that involved modelling how the ship moved and flexed when under way. This is still a concern as ship size increases, we were an 8000 teu ship (pretty large in the late 90's) and lost 50 boxes in one roll, with another 100 or so damaged, Ships are now 20,000 teu plus and are loosing several hundred at a time - not very often, but the financial losses involved are significant.

[Army_Air_Force]

Interesting reading. My dad sailed on a number of Liberty ships in the 1950's for Ellerman Lines. They got cracking on the deck at one point and when they made port, they welded some steel railway rails across the cracks to reinforce the area until they got home to proper facilities. He survived 15 years of life at sea, including a fractured skull, when a hatch plank gave way under him. He spent three days on pain killers until they reached Calcutta where in his words, he also survived the hospital treatment there!

[noelh]

I've followed this over because it is most interesting. Definitely worthy of discussion. 

[Geoffrey Sinclair]

Thanks for the update on marine construction monitoring/testing.

With the rise of electronics and satellites plus the aviation industry monitoring programs I would assume modern practice would be to collect more (real time) monitoring data.  I do not know how much then how much is published, plus if anyone has deliberately moved into bad weather to run tests versus using modern systems to better avoid the bad stuff.

 

The book I was quoting from was published in 2001, so the manuscript would date a year or two before that, my original summary dates from 2008.  It would seem for WWII they thought they did not have the brittleness problem with "modern" steel which appears largely correct.

To get back my main current interest , the book "Liberty's Provenance", by John Henshaw,  What does it say about British financing of the expansion of US commercial shipyards?  Also has the blurb writer done the reader a service by letting them know how hopelessly exaggerated the book is or done the author a major disservice?

[Phil Gollin]

12 hours ago, Dave Swindell said:

... The loss of the Titanic was in part due to brittle fracture of the hull plates, which significantly increased the amount of damage to the hull. ....

 

.

 

That is a poor quality finding from a TV documentary, I would be very careful quoting it as any sort of fact.

 

Full reports on the British testing of Liberty ship were published post war, with large summary papers being printed in various yearly Royal Institute of Naval Architects TRANSACTIONS.

 

.

 

 

[Graham Boak]

As requested, here's a summary of Henshaw's most interesting book. 

 

It starts with a brief history of the standard ships of WW1.  He then goes on to show the development from earlier Thompson designs, starting with the Embassage, with drawings of each stage.  It has been said elsewhere that the design taken to the US for study was the Embassage, or its close descendant the Dorrington Castle (a poor match), but these are smaller ships.  The later Empire Wave (ship 607) has also been suggested, but Henshaw argues that it was likelier to be the latest design available, Empire Liberty (ship 611), the first example of 13 standard ships.   The shipyards built to (initially) meet the British requirements were by Kaiser, in California and Portland, Maine.  The first ships built there were known as the Ocean class, for example Ocean Vanguard, and the design was very closely based on Thompson's Empire Liberty.  The Liberty ship design was a copy of the Oceans with some changes, not affecting hull shape or structure, down to the same position of the engine mountings. 

 

The book then proceeds to describe the Liberties and the Forts, Parks and Victorys, including their postwar use with a selection of interesting examples. 

[Geoffrey Sinclair]

The company managing the yard in Maine was owned 35% Todd, 35% Kaiser, 30% Bath, in California 65% Kaiser, 35% Todd.  Kaiser-Todd-Bath.  Now if I have the various name permutations correct.
Todd-Bath Portland (East) = New England Shipbuilding Yard East, 3 building basins, 2 holding 2 ships the third 3 ships, so 7 berths built for the British.

Todd-Bath Richmond California = Kaiser No.3 Richmond = Permanente Metals yard No.1, 7 slips built for British.

Is this the total number of ship building slips/berths financed by the British?  As noted the Maritime commission authorised 222 building berths in class I yards (large ocean going ships)

 

Contract estimated cost was 96 million pounds of which 9 million was for new shipyards.  30 ships each yard, completion months
Month    /    Portland    /    Richmond
Oct-41    /        /    1
Nov-41    /        /    2
Dec-41    /        /    2
Jan-42    /        /    3
Feb-42    /        /    2
Mar-42    /    1    /    3
Apr-42    /    3    /    5
May-42    /    3    /    3
Jun-42    /    3    /    3
Jul-42    /    4    /    6
Aug-42    /    4    /    
Sep-42    /    4    /    
Oct-42    /    5    /    
Nov-42    /    3    /    

 

Liberty by Peter Elphick had access to Cyril Thompson's Diary, which makes it clear, he arrived in the US on 3 October 1940 with the plans for Hull 607, Empire Wave, then on 16 November came word to change to Hull 611 Empire Tide.  Which became the 60 Ocean class.   In the US Gibbs & Cox did the detailed design work.  After the US contract was signed 26 North Sands type were ordered from Canada, the "Forts". Then came the Liberty ships "5 year" versus the "29 year" design the Maritime Commission was then involved with.  So oil burning, revised accommodation, etc.

 

Where does the last one voyage claim come from?

 

The US proceeded to build 2,580 EC2-S-C1, 24 EC2-S-AW1 colliers, 6 Z-EC2-S-C2 tank transporters and 36 Z-EC2-S-C5 aircraft transports

 

Henshaw's book is becoming less attractive.

[EwenS]

Details of the Oceans, Forts and Parks can be found here.

https://fortships.tripod.com

 

[Pig of the Week]

Very interesting topic and well worth discussion...when doing our welding tests / certificates many years ago, we had a lecture about the Liberty Ships as a good set of examples to illustrate these type of issues.   One thing that sticks in my mind was that a source of many of the faults was coming from the square cut corners of the deck hatches, which would be far less likely to occurr if the design used rounded corners for example.

Edited July 11, 2021 by Pig of the Week