Welded vs Riveted

[Ivan Cloherty]

Trying to see what colour knickers the girls had on Ivan.,?? Hoping to find a liberated one. JS

probably!

[John Arton]

When two steel plates are welded together correctly they can then be considered to be one plate with the weld having the same metallurgical strength and properties of the individual plates. The problems can occur if one of those plates has a flaw in its manufacture and should a crack appear in it then the crack can travel very rapidly along that plate, through the weld and into the adjacent plate.
With regard to the Liberty ships the root cause was the steel used in their construction, which was fine when the ships were in temperate waters but the moment they went into colder Artic waters the steel became "brittle" which considerable reduced its strength. That, along with square instead of rounded hatch corners together with there inbuilt hog, caused cracks to appear at hatch corners (aft end of no.3 if my memory serves me correctly). This cracks rapidly propagated and caused the vessels to break in two.
This discovery of steel weakening in cold waters led to a greater understanding of "brittle fractures" and after the war years an improvement in the manufacture and testing of steel used in ships construction . However even in the 70's there was a case of a U.K. registered and built tanker splitting in half in, I think, the Straits of Canso, due to brittle fractures developing in its hull.
With most modern ships being built in block sections in controlled environments and then being welded together in dry docks there is a far greater emphasis on quality control from start to finish of the building process and the use of advanced inspection techniques to ensure that the welds are of correct strength etc. The welds that join the sections together are most often done using robot welders which can produce welds of superior consistency and strength than most manual welders, so the need to stagger strakes is eliminated.
rgds
JA
p.s. As I write this the Red Arrows are screaming overhead doing the closing display at the Sunderland Air Show that around 1000000 visitors have watched over the weekend. Weather throughout from Friday has been almost perfect, light winds, no rain and broken clouds. Temp. a bit down on the average but you cant have everything, even in gods own country.