Posted by B.Blomberg on April 01, 2000 at 14:06:01:
In Reply to: need held! posted by Jean Collard on March 21, 2000 at 07:04:10:
: I have a 38' sailboat "Henry Wauquiez (Hood 38) and
: most of the bottom is cover with tiny gelcoat blis-
: ters. From what I understrand the only way to cure
: indefinitely the osmosis problem is to use infrared
: lamp to heat up the hull between 70-80o Centigrade
: until the hull is completely dry and all the styrene
: and acid evaporate. I would like to know apromima-
: tely how many infrared lamp I need and how far from
: the hull do I have to install the lamp so I get the
: precise temperature I require to heat adequately.
: Furthermore, what is the wattage of each of these
: lamp should I use and also, how can I control and
: check the temperature of the hull? Is it advisable
: to cover the boat to keep the temperature during the
: heating process? Please somebody help me! Thanks!
I you are lucky and the hydrolysis is only superficial
(which it might be with this kind of blisters) IR can delay
the problem for 10 or more years IF YOU DOES NOT APPLY ANY
TYPE OF WATERSHIELD!!!! It is only the styrene and the
uncured polyester which cause the process. The little water
needed is always contained in the submerged parts of the laminate
wether shielded or not. The fact that "osmosis" hulls always gives
high moisture readings has caused the mistake to believe that water
entrance is the cause for instead of a consequence of the hydrolyse!
has for decades caused boat owners to waste enormous amounts on
Drying and watershielding just cover like a cosmetic so you does
not see it for some time. Like cosmetic the watershield mostly
accelerates the damages underneath!
The IR can extract practically all of the syrene which is inside the
uncured polyester enclosures and thus theoretically prevent hydrolysis.
However the phthallic acid, which is a by product from the hydrolysis,
can transform cured polyester molecules into further uncured polyester
and free styrene if left in the laminate. Now the acid is chrystallic
and not water soluble. The acid when formed is immediately dissolved in
the styrene which helps it spread deeper into the laminate. When heated
with IR the styrene evaporate but the acid crystalizes and stays in the
laminate and within short causes new hydrolysis if the hull is covered
with epoxy or or other watershield.
Opposite to common believe, water does not do any harm to a laminate more
than dissolving some of the fiberglass coating during the first years the
boat is launched. This creates capillaries along the strands which allowes
water to pass through the laminate at a very slow pace. Also boat owners and
even yard people have been made to believe that the gelcoat is some kind of
protection for the laminate. This is not the case! It is just a cheap, convinient
way to provide a nice long lasting surface of the hull. The reason for applying
it also on the underwater areas is mainly to prevent you from seeing right through
the otherwise crystal clear laminate.
Regarding the "osmosis" or more adequate hydrolysis, It has to produce some heat
in order to proceed. If sufficient water is allowed to pass through the laminate,
it will cool enough to slow down the process substantially. Damages like
delaminations, which often occurs within a couple of years under a watershield,
will instead take 10 years or more to form and then much less severe.
The so far only technique which can remove the acid without damages to the laminate
is the HYAB Osmocure which costs about double as much as now common treatments and can
only be performed by highly trained operators with the help of special tools and
environment equipment. Still very few boat owners understand the problem and most
prefer to believe in the big paint manufactures and present them with half of the cost
for noting. Therefore the establishment of Osmocure Centers proceeds very slow.
They can be found in Mallorca, Malta, Greece, Holland, Bodensee and quite a few in
New Zeeland and Australia. We are currently seeking financing for opening at least
ten in USA
Regarding IR you will need 500-1000 W / square meter under water surface. The technique
is dangerous if enough heat is applied to cause any post curing and it will still affect
only the outer 2-3 layers and this only if there is enough free styrene in the laminate.
The principle is the same as when water is boiled in a kettle: As long as any water is
left, the kettle will not get hotter than the boiling water. If it boils dry the kettle
As long as the laminate contains styrene and moisture the temperature will cause no damage
to the hull but it is of utmost importance to disconnect the heaters immediately as there
is no more smell of styrene. Most yards never heats the hull over 50 degrees Celcius in order
not to cause any damages to the laminate. To get any postcuring what so ever, a surface temp.
of 90 degrees is needed which indeed is risky.
With or without IR I recommend you just to sand the blister open or still better peel off the
gelcoat and then apply antifouling only. This way you can use the boat for at least five years
without problem when wating for Osmocure or eventual other proper to arrive in your neighbourhood.
Regards Bengt Blomberg
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