Boat Forum / Building / November 2005

Gelcoat can be thinned and sprayed, but it's more of a pain than
painting. Gelcoat can be rolled as-is, but thick coats will tend to run.
In either case, you need to use "finish" gelcoat, which contains a wax
that migrates to the surface to promote proper curing. Standard
"laminating" gelcoat will not cure in the presense of air. It must
either be covered with plastic or sprayed with PVA to seal it off from
air contact.

Gelcoat WILL adhere over fully cured epoxy repairs that are cleaned and
sanded. I do it all the time on kayak repairs.

Gelcoat is just poly resin.  I painted a rough dinghy made on an old
wooden plug with a recipe. One cup resin, I think 13 drops of MEK,
one pea sized blob of colour, a spoon of thickener. It was necessary
to experiment, considering the environmental conditions. As the day
warmed up, I think I reduced the MEK a little to get a little more
brushing time from the mix.

Gelcoat is usually sprayed inside a mould first, rather than painted
on the outside, last.

I used Continuous brush coats applied a cup at a time, for a few
hours work in a summer carport shade.  Beautiful,  hard, self
levelling finish 1/16 inch thick, on horizontal and vertical
surfaces. No breeze, no dust.

I don't think it would actually jump off if it were to be put over
epoxy, but maybe a primer would help?  On the 29 foot Tylercraft,
I've got epoxy scars in the antiskid portside, where the chunks of
top deck were dremelled off and replaced over plywood in lieu of
rotten balsa, using  epoxy and lots of silica gel, spongy, fizzy
even, and fast to cure, too. I levelled the replaced sections with
small adjusted screws under the recycled anti skid, wiping off most
of the excess with polyethylene plastic bag "towels."

I used a caulking gun and cobbled up elephant syringe to inject
epoxy in the areas not uncovered but where rotten core was scooped
out, jamming in new "core" pieces of plywood, rolling doobies of
toothpaste epoxy in saran wrap, squeezed into the syringe.

If epoxy sticks to polyester, how come polyester can't be said to
stick to epoxy?  Maybe it's all in the timing, which one cured
first? This epoxy argument smacks of rabid fundamentalism, to me.

As it is, Urethane deck paint seems to cover the flaws somewhat and
has not yet chipped off along the seam lines, but only on the peaks
of the anti skid, but then, I haven't been out there much with my
hobnailed boots. It's only a one coat of a slightly different shade
of blue, after all. Think of it as patina, character.

I don't spitshine my hobnail boots, either. Function trumps beauty
every time, me, nor I haven't fallen through the deck, neither, and
the leaks are gone, too, whoohoo!

Terry K