[BITList] more Vibrations

[s!4engine]

Hugh

Swan Hunter’s was ‘up north’, sir charles geddes and assoc were not too far from one aldgate and fine dining!

your point about fine lines aft certainly applied to the “B’s” and I presume the hulls were all the same but also applied to some fine lines for’d too.

I was involved with a neptune orient lines [NOL] container ship built in finland whose for’d lines were so fine the entire bow with the for’d half of #1 hold [with cargo] was lost at sea!
The lines were so fine that there was only about 6 feet between the for’d corners of no. 1 hatch and the edge of the deck and coincidentally longitudinal framing changed to transverse and more coincidentally there was a deep tank at the aft end of #1 hold.  The double bottom at the for’d end of #1 hatch was extremely narrow contributing little to the strength. This abrupt change of section must have made for an exceptional shear force and bending moments diagrams – going from sublime to ridiculous.

The interesting thing is that the loss of the bow happened during the night, inclement weather prevented anyone going for’d so it was only discovered at dawn! About 0200 the engine room reported to the bridge that they heard a thump or clang – the bridge reported alles klare.

It was also interesting that the speed of the ship without the bow section did not reduce significantly enough for anyone to be concerned ..................................!! 

ct

From: HUGH 
Sent: Thursday, April 18, 2013 1:18 AM
To: BitList 
Subject: [BITList] Vibrations

Colin,

It surprises me that Swan Hunter couldn't do their own design around 1970, but there you are. There was a lot of fine lines aft stuff going on then - maybe the fashionistas had discovered ships. One Blue Flue ship I worked on while with Scotts in the 70s was so fine aft  that the gennie flat could barely take the 3 gennies. I recall measures taken after trials to rectify vibration issues. The last vessel I worked on before retiring was built by Kvaerner in the early 90s and "designed" by Norwegian "consultants", many of whom had read a book about ships after graduating.  It, too, had very fine lines aft, so much so that the after end at bottom plates level was empty of all but air and a couple of essential pipes. The lines aft were only the start of it - where it was physically possible, everything in my remit was comprehensively redesigned by me, but I could do nothing about the lines.

MV Bhamo, designed and built by Lithgow in 1957 for British Burmese, engined by Kincaid, scrapped 1979, had bizarre vibration problems. The instigator, or the easiest to blame, was the main engine, a 4-cyl B&W opposed piston - 4-cyl engines are prone to causing problems. Most vibration was felt in the accommodation, so a system was evolved of opening certain doors.  So a friend said - he sailed with her from Kincaids as a first tripper.

Hugh.


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