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 GRP Repairs
Racing yachts, motor cruisers, lifeboats and pilot cutters - all types of repair
undertaken. Our technical knowledge and practical experience encompass GRP, FRP,
foam and Balsa sandwich construction in both polyester and epoxy resins.
Osmosis
Treatment
The yard has considerable experience in the application of
epoxy coatings to the hull of vessels. Osmosis prevention
or Osmosis treatment is regularly undertaken with the yard
operating as an approved treatment and application centre
for Blakes Paints, International Paints, SP Systems and West
Resins.
What
is Osmosis
A
polyester laminate may look watertight at first sight, but
looks can
be
deceiving. In the molecular laminate of the polyester there
are
enough
crevices and holes through which moisture can diffuse in.
This
process doesn't happen over night, but stretches over a period
of many years. During this time, the individual layers of
the hull laminate will resist the penetrating moisture in
different ways. The gelcoat is the most watertight layer.
This coat should never be damaged, since it prevents water
and moisture from coming into direct contact with the laminate.
If the laminate were in perfect condition,i.e. hte hull had
been laminated without any air pockets or air bubbles, it
wouldn't be such a big problem if moisture slowly penetrated
the polyester. However, even the most perfectionist laminate
technician will not be able to guarantee laminate that is
completely bubble free. And now we come to the real problem,
these bubbles may contain residue of the unhardened resin,
curing agents, and binding agents made of glass matting. The
water (water molecules) which diffuses through the gelcoat
into the laminate dissolves these residues in the bubbles.
The concentration of these residues in the resultiing liquid
is higher than in the laminate environment. This is when the
osmosis starts, when the different concentration levels try
to balance each other out. However, since pure water molecules
are smaller than the molecules in the solution, these can
also permeate the laminate more quickly and easily. The bubbles
with the dissolved residues draw the moisture away from the
laminate in the surrounding area and gather it in the bubbles.
When the bubbles are full, they exert pressure and the osmosis
bubble typically seen in the gelcoat are created.
How
to identify osmosis
The
firswt visual signs will be the formation of blisters in the
gelcoat beneath the water line. If you pierce an osmotic blister
the liquid contents will have a sour smell similar to vinegar.
The problem may be discovered prior to its visual symptoms
appearing by checking the moisture content of the hull with
a moisture metre
Typical
Osmosis Treatment
- Peeling
Gel coat - To remove the defective Gel coat and Laminate
- Slurry
Blasting - To open up the profile of the surface
- Steam
Cleaning - To remove Glycol and Hygroscopic contaminants
- Drying
- Natural \ Infra Red
- Application
of coatings - In accordance with manufacturers recommendation.
ARRC Boats
 
Navy Vessel 'Gleaner'
Fishing Boats
   
Spray Painting
 
General Repairs
 
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