Answer to Wim and Allan


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Posted by Bengt Blomberg on May 24, 2000 at 15:25:58:

Sorry, but it seems to be something wrong with the
follow up system. I cant see the answers I posted
earlier so I repeat:
Drying of a polyester laminate which is going back into
water is sheer nonsens! The laminate is an absorbing
material and so is all epoxies or vinyl esters which
cures in temperatures below 80 degrees C. The water will
be back a few months after launching.
It is not the water that causes the damages even if a
very small amount is needed for the hydrolysis. It is
the acid, formed in the process, which creates an
endless chain reaction if not removed. The reason for
the higher moisture readings in an "osmosis" laminate
is that the hydrolysis creates a lot of cavities which
allow the laminate to absorb more than normal. Drying
with or without coating does not prevent the cavities
from being filled again. And it absolutely can not
remove the not water soluble pthtallic acid!
Now the hydrolysis creates a certain amount of heat,
which is needed for the process to proceed. If the
water is allowed to pass freely in and out of the damaged
laminate it has a cooling effect which substantially
slows down the hydrolysis. An epoxy coating instead
accelerates the damages often without any telltale
blisters.
Since a few years when the problem has got its proper
description, many inventors try to find solutions for
removal of the acid but so far only the HYAB Osmocure
is available. That, due to the complicated training
needed for the operators, still only in a few parts of
the world.
Awaiting any suitable technique to arrive in your area,
I recommend to sand the blisters and eventually even
them out with as little epoxy filler as possible and
apply antifouling only. Still better to remove all of
the gelcoat. There is a wide spread believe, that the
gelcoat is there to "prevent" the laminate. In reality
it has no such function. It is only a fast and cheap way
to give the top sides a nice and durable finish. It is
really absolutely not needed on the underwater parts.
Don't let anyone scare you into worthless dry and
shield treatments. They just want your money.
Another 5 years won't make a proper repair more
expensive.
Please e-mail me the wereabouts of your respective boats
so I can advise when and where you can find the proper
treatment.
Regards Bengt


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