I've tried it and it does some nice things, but I've also found several ways
to screw up.

It is mandatory that all air bubbles be gotten out before the epoxy sets up.

If the plastic is folded by the salesperson, it will remember and you'll
have creases (long narrow bubbles). Mutter and fuss until they find a
cardboard tube to roll it on and carry it carefully so it doesn't fold.
(Easier said than done.) Store the plastic carefully.

If there's any outgassing from the wood, it will create a bubble. Best to
first seal the wood with a thin coat of epoxy and sand out the bubbles, but
sometimes the outgassing pinhole acts as if you've tapped a geyser. Hot to
cold works best.

Then there's the frustration of trying to chase each bubble that you notice
to the edge of the plastic.

The epoxy seems to like the sheet plastic better than the fiberglass. If
you miss a bubble, you'll have a crater with the fiberglass at the bottom.
(Small bubbles don't seem to pull the fiberglass away from the wood.) If
you don't get back to it within the three day window for chemical bonding,
then you have to sand the inside of the crater (or drill it out) so the
patch will adhere.

I like it best for fillets. Cut the plastic sheet shorter than the length
of the corner. Roll the fillet with something spherical, or maybe the end
of your roller. You can chase the bubbles the short distance up the side of
the fillet easily. The result is a well faired join.

Between folding and cutting down to size I only get a limited number of
reuses for the plastic.

Roger

http://home.insightbb.com/~derbyrm

"Brian D" wrote in message
. ..

Some guy posted an article at http://www.duckworksmagazine.com about using
slightly-heavy clear plastic sheeting to fair a boat. If I recall, he put
the glass on the boat, then rolled the sheeting onto it, let it cure and
pulled the sheeting off. The pictures that I saw were marvelous ...glossy
smooth with no imperfections, no boundary marks or lines near edges of
overlapped cloth or at scarfs or anything. Never did give it a try myself
though, but it looked like it worked for him.

I did recently cut off the curved top of a transom to make it flat so I
could run a tuna handline behind the boat (tied to a handline cleat)
without the line rubbing on the transom. It's impossible to get a
perfectly straight cut and all I did to tune it up was to put a thin layer
of microballoon mix + epoxy on it, lay plastic wrap over it, then used a
piece of aluminum angle stock to press the top flat. Came out beautiful.
Ready to fair it in and paint....

Brian D



"DSK" wrote in message
...
Brian D wrote:
I don't think that I've ever gotten a drip of epoxy falling off a
pre-wetted chunk of fiberglass tape. Of course, by the time I started
using that method, I'd gained enough glassing experience to know how
much resin to put into it, but really ...the glass holds the epoxy quite
well. Try it sometime 'cuz I think you'll like it.


Another good way to pre-wet-out pieces of cloth is to use PVC sheet. It's
commonly sold in varying thickness as painter's dropcloth. The .5 mil
stuff is kinda flimsy but can be molded around 3-D shapes pretty well,
the 3 mil stuff is pretty strong and I use it for wetting out pre-cut
pieces on a flat bench or floor. It can be re-used almost infinitely too.
Cured epoxy will not stick to it, makes a great barrier film.

My method is to get a piece of the plastic sheeting that's at least twice
as big as the fiberglass cloth I'm laminating, lay the cloth into one
half of it, then add some mixed resin. Fold the other half of the sheet
over, then roller it so that the resin gets spread eavenly thru the cloth
and you don't get ick all over your hands or the roller. You can really
get a great resin-glass ratio and handle the piece without fear of runs
or drips.


And isn't the concern over a drip here and there a bit like being
concerned about getting wet when you go fishing? Be careful, but don't
sweat the occasional drips and runs. Buy a 3" wide carbide scraper
(with handle, and a knob above the business end) and the SurForm tool
with the short handle and 2" by 1-1/2" (approx) curved cheese-grater on
the end and you'll no longer sweat the little accidents ...they come off
easily after curing and it's easy to leave a smooooth finish behind.
Home Despot has these things for cheap and no epoxy user should be
without them. Forget sandpaper for fixing drips and runs ...bad idea.
Relax and enjoy the build.


Or get a plastic putty knife and scrape up the dripping / running resin,
take it over to your wet-out work area, and re-use it on the next piece
of cloth. Economical and saves clean-up time.

I've seen a heck of a lot of people working in fiberglass who seem to
bring an unshakeable woodworker's mentality to the process.... make it
thick, then cut it or sand it... then add some more and sand it off...
etc etc. Shucks, the beauty of molding composites is that you can make it
any shape you want, in less time, and make it *strong*. Get the material
to work for you, not against you.

Not that I'm an expert or anything, but I've made a lot of stuff out of
epoxy resin added to various other materials... including carbon fiber...
over the years.

Fresh Breezes- Doug King