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82 | Seacock service 86 | Ask the experts 90 | Seaworthy
coat is. Gelcoat is the first thing sprayed
into a female mold when a boat is built,
usually to a thickness of . 5 to 1 mm.
Depending on the method of construction, layers of chopped mat and fiberglass
cloth are then built up on top to form the
hull, deck, and other molded parts. When
the parts are taken out of the mold, it’s
the smooth, now outside layer of gelcoat
that you see. Gelcoat doesn’t fully cure
when it’s exposed to air, but because one
side is against the mold and the other
is covered by fiberglass and resin, air is
excluded, and the gelcoat cures to form
an impervious barrier between the water
White is the most popular color for
gelcoat, but there are other colors, too.
When doing repairs, see if you can buy
gelcoat from your boat’s manufacturer so
you’ll know the color will match. If not,
you’ll need to buy white or clear gelcoat
and tint it to match. Tinting kits are
available from gelcoat suppliers.
Gelcoat is thin, almost like paint, and
will run, especially on vertical surfaces.
Use several thin coats or use gelcoat paste
that is thicker with fewer tendencies to
sag. Which type you use will depend on
the repair and your method of application. For vertical surfaces, I prefer spray
application using several thin coats.
As mentioned, gelcoat has to be sealed
from the air for it to harden properly.
Otherwise it will stay tacky to the touch.
For this reason, you’ll often see “waxed”
Nonwaxed gelcoat can be used when
several coats are required, but that means
having two different kinds of gelcoat on
hand. The simpler way is to always use
the waxed kind, lightly wet-sanding the
cured surface between coats.
As with all repairs, preparation is
key. Just slapping on some gelcoat will
give disappointing results as well as look
unsightly, and the repair will probably
need to be redone within a year or two.
It’s better to do it right the first time.
If this is your first time repairing
gelcoat, start with a fairly small repair in
an inconspicuous place. Gain confidence
before moving on to more visible spots
on the boat.
Seaglass, my Grand Banks 32, had
a small crack in the top of the forward
cabin trunk that needed repairing. Here’s
how I did it.
1. Start by wiping
down the area to
be repaired with
acetone to remove
surface dirt, contaminants, and any
surface wax that
with the bond of
the new gelcoat.
2. Open up the
crack a bit to give
the repair the best
chance of seamlessly blending into the existing gelcoat. This
can be done using a sharp wood chisel or
scraper; I prefer to use a Dremel tool fitted with a burr bit. If you start cutting into
the laminates, you’re going too deep.
3. It took about five minutes to create this
V-shaped groove in the gelcoat. Vacuum
up the dust and then wipe down the area
to be repaired with an acetone-soaked rag.
Protect yourself, especially from dust
and fumes. Use common sense, and read
and understand all the safety instructions that come with your tools and
materials. Catalyst is especially noxious;
avoid breathing in the fumes. Wear a respirator, Tyvek suit, and disposable gloves.
If you get gelcoat on your skin, wash it
off right away with soap and water.
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