Marine epoxy, led by the Gougeon Brothers WEST SYSTEM brand
marine epoxy products, has revolutionized the making of wooden
boats. Wood, as a material for boats has lost a lot of favor over
the years, as a result of the aging of the wooden boat "fleet" and
the advent of fiberglass and aluminum for use in boat construction.
Now the early boats built with glass are oxidizing and
de-laminating, and the shiny aluminum boats are now showing their
dents and loose rivets or welds. At the same time, epoxy has come of
age as a superior marine glue, a filler, and a coating which greatly
inhibits dry rot in wood. Now, wood boats can be built with a wide
variety of construction techniques using epoxy, making excellent
crafts on par or even better than boats made with glass or
aluminum.
We believe that epoxy works well in the construction of driftboats in
three ways. First, epoxy makes an excellent wood glue. When we make the
frames (ribs) for our kits, we use it to glue them together. We also
use it to do any scarfing (the joining together of wood into longer
lengths) and most other gluing applications. The advantage of epoxy is
that one needs no clamping pressure, all that is needed is contact with
the two surfaces being glued and the epoxy itself. This allows for
imperfect joints, especially if one adds some wood dust to the epoxy to
thicken it. (Excess epoxy works great for all those loose wooden chairs
floating around the house that have been unsuccessfully glued with
every hardware store glue that has ever been made!)
We sometimes use epoxy as a coating on the plywood sides and
bottom before the boat is assembled. We use marine grade Douglas fir
plywood as a standard plywood on all our kits. Fir plywood is an
excellent material to build boats. The long fiber structure and
lightness, as well as its relative resistance to dry rot makes for
beautiful, long lasting enjoyment. It holds a place in our hearts as
well because it is a wood that is native to Oregon. (There are few
things as pretty as a fir colored, naturally finished drift boat
floating in space over a crystal clear, but slightly green stretch
of the Mckenzie River on a hot July afternoon!) One characteristic
of fir plywood is that is can be subject to checking - small hairline
cracks along the grain - when boats (that have a natural finish)
aren't able to be stored inside. Coating with epoxy seems to greatly
inhibit this, as it is able to saturate deeply into the wood to help
"glue" the fibers together. In extreme use, boats (sides and bottoms
prior to assembly) can even be sheathed with a very light fiberglass
cloth in order to stabilize the grain. This amounts to a lot of
effort, extra expense and weight. Our opinion is that the addition
of cloth is worth it only in extreme cases.
Finally, we add
various fillers to epoxy to make a thicker, gap-filling mixture or to make a very durable wood
putty. We usually use wood dust as a filler. When mixed properly, this mixture looks just like peanut
butter. When one holds some out on a stick, it should not drip or
run. It is an excellent material for dents and repairs. If one desires to fill
screw holes with a natural colored, durable putty, this is the
stuff. We sometimes mix in less wood dust and use it to sink into
cracks in wood. This method is great for gluing cracked surfaces
together when no other gluing method will work.
What comes when you buy WEST SYSTEM brand epoxy? Your first
purchase of this material ought to include the pumps - to meter
the resin and hardener in proper proportions - and some
instructions about use, mixing, and safety. We decided to
include all these in an epoxy "kit" so you can get off on the
right foot. Since the pumps and instructions can last through
large quantities of epoxy, all subsequent purchases would be
simply resin and hardener, ten dollars cheaper than the "kit".
West System epoxies consist of a resin, designated 105, and a variety
of hardeners (205, 207, etc.) that can each be used with that same
resin to get different results. The ratio of hardener to resin is
fixed for each hardener (it cannot be varied by the user to alter the
properties of the epoxy - you wouldn't be happy with results!), and the
pumps that we provide with the kit ensure that that proper ratio is
maintained. One need only apply one stroke of the resin pump for every
one stoke of the hardener pump.
For gluing and other general use, we use and
recommend West System's fast hardener (205). This hardener works well
when one does not wish to wait a full day between application and final
cure. It is fine for coating surfaces but has a tendency to get a
milky appearance when overworked. Therefore, for places where the
finished surface will be visible (i.e., all of the plywood except for
the outside bottom of the boat) we suggest using West System's "Special
Coatings" hardener (207) instead. This hardener reduces the
chances of cloudiness and gives a very attractive clear finish to the
surface.
You can substitute slow hardener (206) for extra working time on
those very hot days or extremely large surfaces. We have never
used the slow hardener at the shop, but we sell it
occasionally to customers who feel they need it.
West System Epoxy
Quart (A)
Gallon (B)
105/205/Pumps (Standard
Kit)
$55
$125
105/206/Pumps (Slow Hardener)
$55
$125
105/207/Pumps (UV
Protection)
$75
$150
105/205 (No Pumps)
$45
$115
105/206 (No Pumps)
$45
$115
105/207 (No Pumps)
$65
$140
Extra Set of Pumps
$12
$12
Rollers
In the twenty or so years that we have been working with
West System epoxy, we have found that the best way to apply it as a
finish to a large surface (such as the sides or the bottom of a
plywood boat) is to first mix a plastic margarine container nearly
full with the mixture. After stirring very thoroughly, pour it
out on a flat surface before it has a chance to heat up and set,
then spread it out with some sort of spreader (we use a 6" square
of 1/4" plywood). We always apply the epoxy before assembling the
boat so that there is less chance of runs. In any case, we then use
a special foam roller to roll it out smooth. The number of rollers
you need depends on how much of the boat you epoxy. For just the
bottom, two rollers will work (we cut them in half with a band saw
or hand saw to fit the roller handle). To do all the sides and
bottom, you may need six or eight. And, of course, a small roller
handle.
Foam rollers (packs of
two).........$4 Roller Handle...............................$8
Applying Epoxy
How is epoxy applied as a coating? We recommend applying it on the
plywood sides and the bottom prior to assembly of the boat. First we
mix it up in a flexible container, such as a margarine container. We
pump the container almost full, then mix it very thoroughly. We then
immediately pour it out on the surface, so that the heat it creates
while curing can dissipate, which gives it a much longer pot life. We
further spread it around with a board of some sort, then roll it smooth
with a foam roller, using slow strokes, minimizing bubbling. Do not
apply in the direct sun, as heated air will bubble out of the plywood,
causing bubbles and craters. Curing time depends on the temperature of
the workspace, but it is normal to cure overnight, then re-coat the
next day. Two coats usually does the trick. After curing, there is a
greasy film (a so-called "amine blush") on the surface of the epoxy.
This film must be removed by wetsanding with #220 sandpaper (do
it by hand and scrub like you're cleaning a dirty pan). Only then
can whatever is to go over the epoxy be applied. It is worth
noting, though, that if a second coat of epoxy is to be applied one can
forego the previous step by applying the second coat before the first
has fully cured: Apply the first coat, let it become firm, but before
it ceases to be tacky spread out the second coat. In any case,
the final cured coat will need to be sanded before the application of
any other coatings (e.g., varnish or paint).
A couple of tricks we use to ease application: First, we sand the plywood with a fine grit
(#220) right before coating with epoxy, in order to reduce the
raised grain and help minimize the sanding of the epoxy after it
hardens. We clean the surface with a vacuum cleaner with a brush
attachment before applying the epoxy. We also use a fairly generous
amount of epoxy so that it will flow out more easily and to help
minimize the roughness common on a first coat.
Epoxy should only be applied to bare wood. If a
stain is desired, use only a water-based dye stain and allow it to
fully dry before proceeding with the epoxy. The object is to
allow the epoxy to bond with the fibers of the wood unimpeded,
strengthening both the bond of the coating and the structure of the
wood. If you desire to use a more common oil based stain for the
sides and bottom - a very popular choice on Fir - you should use
only varnish over the stain, not coat with epoxy.
Epoxy has little to no ultra-violet protection built in to it.
When it is used as a coating, it needs to be protected by a coating
with a high quality UV protector, such as paint, or our Z-Spar
Flagship varnish. If you choose an epoxy/varnish system for your
boat, a typical quantity of epoxy and varnish to do a sixteen or
seventeen foot boat is two gallons of epoxy, and two gallons of
varnish. That should do two coats of epoxy on the main plywood
pieces and two coats of varnish on the plywood as well. All the rest
of the parts ought to have four to five coats of varnish, but no
epoxy.