To U boat Net.

SubjectXI hull instability-welding problems

I cant comment on the instability problems but the welding aspect is right up my
street.I asked a related question on steels and welding technique of which i have hopes of a suitable answer.

To cut to the chase,you only end up with serious instability problems if the hull is defective in some of the following areas-

1.Hull segments progressively out of alignment to the left or the right as the hull sections are assembled.
2.Drive machinery is not bedded correctly,prop shaft is off centre to centre line of engine.
3.Ballast tank venting sequences,pump fill/empty sequences are out of phase,wrong capacity pumps are fitted on any of the fill/emty lines,wrong diameter pipeing is fitted,etc,etc
4.Weld sequences i suspect are to DIN pressure vessel standards,in which case if your root run weld is started and the pre heat temperature is right,the welders work on clock sequence ie 12 -6,3-9 oclock etc.It is customary for a welder to complete the root run come hail,rain,500 lb bombs,whatever.We hate having to rework a root run!.If the root is correctly lapped,ie one segment of weld deposited ,the next is started 10mm back from the previous welds end run.The process is very slow as each pass has to be ground and the end feathered to accept new welds.Visual inspection of each run is vital and if there is a slag inclusion,it has to be ground out and reworked.
The net result of all this is the welds are sound and ultrasound or x ray inspection is only required when there are doubts as to the quality of the weld.

I hope this may help.

Cheer John Martin