Some additional information: The Ferro-cement sheathing is almost a
1/2 inch thick, and strong. A couple of years ago I had a small
accident with a boat made from steal, he had to go to a reparation
dock. The deck and it's timbers are 15 years ago renewed. But its made
from pine, and it's not watertight. The water comes through the deck,
so it is fresh water , when we sail there is coming some salt water as
well but it's not the majority. The wood under the deck is old, there
has always been water in the bilge, there is a lot of rot wood, the
ventilation is difficult, I live in a humid country. Anyway the wood
is soaked.
But the boat as it is, still is strong. The old wooden hull in its
total functions as a part of the bone structure for the ship. The mast
rigging is still good, the shaft and propeller etc are renewed last
year(the old shaft was leaking water, we are trying to improve), the
steering system we are checking at the moment. Basically with the rest
we can live.
To keep it that way I have to do something with the rotten wood. I
think when I can stop the process of rot, I can try to get the boat
dryer and then I can try to improve the old wood structure with an
impregnating epoxy or polyurethane product.
Salt bags under the deck sounds like a smart thing.

Gerdjan van der Lugt

(Gerdjan) writes:

To keep it that way I have to do something with the rotten wood. I
think when I can stop the process of rot, I can try to get the boat
dryer and then I can try to improve the old wood structure with an
impregnating epoxy or polyurethane product.

It doesn't go that way, and here is the place you are getting the whole
process wrong. A chemical approach is not an answer to exessive rot. The
key is to stop the leaks. Stop the leaks by fixing the deck, changing
wood, patching the cracks in concrete etc. After _that_ you might be able
to use a chemical product or another, but if you don't stop the leaks
nothing will change by pouring some glycol, epoxy or other goop to the
bilge and hoping for the best.

If you had only a small spot of rot here and there you might survive with
just slopping on some epoxy, but now you are risking the whole structural
strength of the hull.

The only long-term solution is to change the rotten wood. There are no
miracle products which would stop the rot and make the wood new. There are
only products which may slow the rot down and restore some of the
strength, but that's not enough.

And fix the leaks. What you are doing now is just like having a house with
a leaky roof. Fussing around with chemicals without fixing the leaks is
just as stupid as trying to fix the damages of a leaky roof by putting on
new wallpapers to the walls.

Think about that for a while.

Pekka

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