There are a number of labour and
materials saving techniques that are applicable when using
epoxy. Contents of this section
- Filleting and Gluing using
“Snap Lock” Plastic Bags
- Snap Lock Bags - Method 2
- Precoating Plywood Panels before
- Wet-on-Wet Coating and Dewaxing
- Building strong lightweight boats
- a note on the use of epoxy
- One Hit coating and gluing
and Gluing using “Snap Lock” Plastic Bags
Most supermarkets have varieties of “snap lock”
They have a seal across the opening of the bag that can be
pressed together with finger pressure. They make it
easier to keep epoxy glue away from areas on the boat where you don't
want to put it. And also areas on yourself where you don't
to put it!
Make up some epoxy, thicken it to the
consistency of peanut
butter. Put a "snap lock" Glad plastic bag into a tin and
the top of bag over lip of tin (like a garbage bag in a garbage bin -
trashcan). Scrape epoxy into the bag.
Take bag out of tin, seal opening and cut one corner out of bag to make
a hole a few mm (approx 1/4") across - size will need to vary with
consistency of mix.
By gently squeezing the bag a
bead of epoxy will ooze out of
hole in controlled way from the hole.
Pipe a bead of epoxy down the right angle between the two plywood
Use a filleting stick of a radius three
times the lesser ply
to smooth down the fillet. Practice getting it smooth and
even. Sometimes I use a flat edged stick which gives the
an even visual width and can also be useful where a radiused fillet is
getting too thin over the join in the plywood.
excess from either side of fillet with a stirring
stick that has
been sharpened to a chisel point. It is possible to lay
tape down either side of the join in the first place so that the excess
can be removed with the tape.
you find the supermarket bags are too weak find a
manufacturer of plastic bags on the net or in the phone
directory. Their prices are usually very reasonable.
Lock Bags - Method 2
This method is used by Duck Flat and has the advantage that very little
of the powders that are added to the epoxy for filleting or gluing can
end up in the air. Much better for health.
the mix in the bag from the start. Pump the
quantities of resin and hardener into the bag and mix very carefully by
massaging the bag.
Add the powder filler and massage
Don't be tempted to try and mix resin
and hardener and powder
in one step. It won't work very well.
Plywood Panels before Assembly.
I find this the best method, where possible. It saves the
of sanding between coats of epoxy and prevents any waxing problems
between the wet-on-wet coats.
Mask off all areas that you don't
areas you are going to glue to later - not strictly necessary with the
Lay surface flat where possible.
Mix resin and hardener.
You don't need to add any
powder when you
are coating - they are only used when gluing one piece to
another. Apply first coat.
NOTE - If doing
large areas the epoxy
will go off too quickly if left in the mixing tin. You will
much more working time if you pour most of it out over the surface
first and roughly spread with a squeegee, before going back with a
roller to spread properly.
When it is spread hold roller so
it cannot rotate and pull
surface of epoxy. It slicks the surface smooth and pop any
When first coat has become quite
tacky, roll on second
coat. Slick the surface.
When second coat is tacky roll on third (if required) and slick it down.
IMPORTANT - Remove masking tape
when third coat is still tacky. You don't want to glue it
down - forever.
When epoxy is fully cured turn
the panels over, sand off any
have come from the other side and repeat process if required.
When the epoxy has cured sand the
panels smooth using a
sander (these tools are a very worthwhile investment but hand is fine
too). 180 grit paper is about right. Sand enough to remove
If you have problems getting a good finish speak to your epoxy dealer.
Coating and Dewaxing Cured Epoxy.
As epoxy cures some of the unreacted components migrate to the surface,
leaving a waxy residue.
This can reduce the adhesion of following coats, whether epoxy or paint
and make them go "fish-eyed" (the surface finishes pitted).
Great improvements have been made to Bote Cote
(Australia) brand epoxy in regards to this problem. It is
unlikely to occur at all. All the preparation you need for
process is to sand the hardened epoxy surface. The wet-on-wet
application method is still the best so you don't have to sand between
the epoxy coats.
However other brands of epoxy may suffer from wax.
is why I always use a "wet-on-wet" epoxy application method (see
"epoxy coating" above). If the surface is allowed to cure it
to be dewaxed (not Bote-Cote) and sanded (Bote Cote too).
Dewaxing- When the two to three coats have cured I always de-wax the
surface using a plastic domestic scourer (Scotchbrite) and water with
some cloudy ammonia added. Scrub very thoroughly.
You can then sand the surface to key it for further painting, epoxying
glass over top dry and trim to approximate size
coat of resin using a squeegee made of scrap ply (sand the working edge
smooth and round off the corners so they won't catch the weave of the
cloth). Additional coats are applied with a roller as each
successive coat goes tacky.
Epoxy coats are
all cured the next day - glass can be trimmed with a stanley (carpet)
the surface smooth - be careful not to go through the glass - you will
start to see the pattern of the weave while sanding if you are about to
go too far. The centreboard on the right is already sanded to
remove the shine of the epoxy surface. I have done a little
of sanding in the middle of the rudder on left - see the difference in
fully sanded and ready for a thin sealing coat of epoxy - to protect
the fibreglass in any areas where the weave has been exposed.
for getting a good end result with the final sealing coat is to
get the surface sanded smooth to remove all the shiny epoxy surface (or
make 95% of it non-shiny).
2/ apply a thin coat of
epoxy with a roller - work the epoxy out over a large area.
finish off the surface by holding the roller so it can't spin and
sliding it lightly over the surface to pop bubbles and slick off the
texture left behind by the roller.
The end result should be
something like this...
Now they are ready
for a really light sand and to be varnished or painted to protect the
epoxy from UV deterioration.
strong lightweight boats - a note on the use of epoxy
Epoxy is expensive stuff, so when there is a bit left over from a
process there is a temptation to use it somewhere.
Don't do it! The boat
has been carefully designed
to be strong
enough already - all you will do is add weight and ruin the
Where you can use it for a legitimate step, do so - but think about it
Another time it is best to throw
out epoxy is if it is
starting to go
off in the bag or tin. If it is starting to get too hot to
comfortably hold it is going to be hard very shortly - you are unlikely
to have enough time to put it into place.
Furthermore, hot epoxy fillets slump badly, hot coatings wax and get
fish-eye pitting, and hot glue joins end up with lumps that stop
clamping. Make up a smaller mix next time and get it out on
surface earlier - straight after careful mixing in the tin or bag.
One Hit coating and gluing
extension of wet on wet epoxying is a method for coating areas that
are easy to get at now (plain plywood compenents) may be hard to get
at a bit later when other parts are attached. A couple of examples
are fitting the bottom, fitting the side decks and fitting framing to
example if gluing the bottom panel in place it is easy to coat the
inside of the bottom at the same time. For major gluing processes
like this it is important to make sure that everything will work
smoothly – do a DRY RUN without the epoxy to make sure that
have enough screws etc to hold the bottom on OK – you can use
the same holes again when you are putting the bottom on permanently.
is the method (put on your disposable gloves!!!).
get all the framing that the bottom will be attached to bevelled and
ready to accept glue
put three coats of epoxy “wet on wet” on the inside
the bottom as per the mehod in the appendix above.
immediately put glue (epoxy plus the gluing thickening powder
make up to a peanut paste thickness) on all the framing of the hull
that the inside of the bottom will be glued to – spread it
ready to take the bottom.
drop the bottom on with its wet face in contact with the glue in the
previous step and screw the bottom in place.
clean up any excess glue that has squeezed out of the joints about 20
minutes after the assembly. If you wait till tomorrow you will be
sanding forever. Use a flat piece of timber sharpened to a chisel
edge on the end with a sander.
same method can be used when putting the framing on the bulkheads. Coat
one side of the bulkhead immediately before gluing the framing
on that side.