These ships were VLCC-sized OBO's;
ships that can handle both oil and dry cargo.
They had a double hull structure
that is very similar to a double hull tankers.
The double bottom is for all purposes the same.
A Norwegian Master who had served on these ships told djw1
they did have cargo leaks into the double bottom.
Surveyors check for such leaks by shining a mirror down the ullage hole
into the double bottom when it has ballast in it.
If there is any oil on top of the ballast water,
a trained eye can see it in the beam of sunlight.
To fool the surveyors, the crew would put a large bucket
of water under the ullage hole.
The surveyor's mirror would see only the clean water in the bucket.
After the Vanga disappeared, Bergesen the owner
took all the sisterships out of the crude oil trade.
Henceforth, they traded only as dry bulk carrier.
A little monument to these two crews used to
stand in the entrance of the Bergesen office.
Don't know if it is still there.
These two casualties indicate the hazard
associated with cracks from double hull cargo tanks
to double hull ballast tanks is real.
Double hulls have already killed at least 80 people.
Woinin says Vanga was loaded with 108,000 tons iron ore
which is a little strange,
since the ship could load 180,000 tons or more.
Maybe a typo, but accepting this figure for now.
Need to confirm.