| Gelcoat repair
Repairing gelcoat
is not a difficult process, although it is usually time-consuming. The
first and most important job is to ensure the area in and around the
damage is free of any loose material, such as flakes of gelcoat or bits
of loose fibreglass. It must also be very clean and completely dry.
Wipe the area with acetone to remove any grease, oil, wax, etc. When
the acetone has dried, mask the area with masking tape to ensure any
spill-over can be easily cleaned up.
If the vessel is more than
a year old, the exposed fibreglass laminate should be wiped over with
styrene to soften the surface and assist the bonding process between
the new gelcoat and laminate. Styrene should make the surface slightly
sticky to the touch.
After the styrene has been
applied and left for a short time, the area is ready for the new gelcoat
to be applied. Mix the gelcoat with the catalyst (often known as MEPK)
at two per cent by volume or mass. Always read the mixing instructions
on the container. Be careful to thoroughly mix the gelcoat and MEKP
as it is very easy to miss some of the gelcoat, resulting in ‘dead spots’.
When mixing very small quantities, as is usually the case with gelcoat
repairs, it is particularly important to mix thoroughly.
Using a small brush – an
artist’s brush for very small repairs – carefully paint the gelcoat
into the damaged area. Keep adding gelcoat until it is a little higher
than the surrounding surface.
Leave the gelcoat to harden for at least 24 hours before attempting
the next step. The repaired area should be covered with masking tape
or plastic to prevent exposure to moisture overnight. When the gelcoat
has thoroughly hardened, use 400-grit wet and dry with fresh water and
very carefully sand the area down until it is flush with the surrounding
surface.
Next, use 600-grit wet and dry (again with fresh water)
to remove the scratches left by the 400 wet and dry paper. For a really
professional finish, complete the process by using 1000- or 1200-grit
paper. When using wet and dry paper, always use a sanding block employing
a circular motion (small circles) rather than a back and forth movement.
The circular motion will reduce the amount of harsh scratching and produces
a better finish. Do not be tempted to use a mechanical sander, as it
will quickly spoil the job. Also, electricity and water are a very dangerous
mix.
After sanding, you
may find that there are still some small hollow areas in the repaired
section. After the gelcoat is thoroughly dry and clean, wipe the surface
over with acetone, then paint in more gelcoat and once hardened, sand
again to a smooth, even finish.
When all gelcoat repairs
are complete, apply at least two coats of fibreglass polish. Automotive
wax is not recommended as it may damage or discolour the gelcoat.
The surrounding area needs
to be polished to blend in the repaired area with the rest of the surface.
The area being polished should extend out to an edge or a line where
the shape of the moulding changes rapidly to mask any slight colour
variations. Several coats of polish should be applied for best effect
and lasting protection. Most manufacturers advise that gelcoat polish
should never be applied on a hot day or in direct bright sunlight as
the solvents in the wax will evaporate too quickly, making it hard to
work the polish up to a glossy finish.
When using a lambs wool buff
on an electric polisher, it is important to always keep the polisher
moving. If the polisher is held in one position for any length of time
there is a risk of overheating the polish and producing a burn mark.
Burn marks can usually be removed by carefully applying a very small
amount of styrene with a rag and then thoroughly wiping the area with
acetone. The styrene should remove the burn marks and all of the wax.
Leave the area to dry thoroughly before applying several coats of polish.
Gelcoat manufacturers
usually recommend that a coat of polish should be applied to a fibreglass
vessel every six months, although I rarely see this happening. However,
vessels that are polished every six months certainly stand out from
the crowd.
For gelcoat that has too many blisters or cracks, the
only method of repair is to prepare the surface and paint it.
Before proceeding, it is important to first establish
the cause of any gelcoat cracks and investigate if the crack extends
into the laminate. The laminate may need to be strengthened to prevent
further damage to the structural integrity of the vessel. This may require
professional advice.
All of the blisters should be thoroughly cleaned out,
with any loose material removed. The crater should then be filled with
an epoxy filler. Next, the entire area should be heavily sanded to ‘break’
the surface. Sanding will also ensure all gloss, wax, dirt etc. is removed
from the surface. It should then be spray painted with a two-pot polyurethane
or epoxy undercoat, before applying a final gloss coat. Some paint manufacturers
recommend applying an etch primer before undercoating. Either way, consult
a reputable paint manufacturer before proceeding. |
