Jim,
This could be a very serious problem. You need the entire hull surveyed with
ultrasound to determine plate thickness. You may very wll find this is the
tip of a large iceberg so to speak and the entire boat maybe unsafe. Please
take this seriously and pull it out of the water immediately.
Steve

wrote in message
...
Hi all,
No rush for answers on this one, but I'm sinking... I found a bit
of water in the bilges and put it down to something benign, but on
inspection, found a blister on the paint inside the hull, which when I
burst revealed a ~2mm square hole in the hull on the bottom of the
boat. I've plugged it with gaffer tape, rubber mats and bits of wood
for now, but has anyone got any neat ways of fixing this without
taking it out of the water (boat is a 20 tonne wrought iron/mild steel
dutch barge, and a proper repair job would be ~£700)?
I'm thinking a bolt with a big rubber washer on both sides and
liberal use of silicon sealant. I'm hoping the rot is very localised.

cheers

Jim
UK