Quark: A Digression on Glue
digression on glue for boatbuilding
resistant, one-part, nontoxic, water cleanup, and wood
flour added at the factory to make it stay put in use
-- Elmer's glue.
pull-stroke saw makes short work of plastic water bottles.
I cut right under the label to make a cup for mixing
epoxy. The ripples in the bottle are my measuring marks.
The method works. When I want to slow down the epoxy
on a hot day, I use plastic tubs sold as storage for
leftovers, but I mix the epoxy in the cut-down bottles.
I would like to be able to use epoxy for all uses in boatbuilding,
but there are several factors that push me in the direction
of finding additional options:
which is a few minutes from my house, on the Niagara River,
costs $55 per gallon plus tax. I like the convenience of
getting this specialty in gallon size without having to
pay shipping charges that could be as much as $10, and I
like the one-to-one mix ratio of resin and catalyst (I use
plastic water bottles that I cut with my Japanese
draw-cut saw to leave a cup-size container
with regular ripples in the sides that I use for measuring).
has no equal for gap filling and strength; it also has no
equal for toxicity and
messiness, and the possibility of sensitization is always
there. Sometimes I just want to glue two things together
without donning surgical gloves, face mask, long sleeves,
hat, and safety glasses,
then mix and use in a hurry to avoid waste. And then there
is the question of when to stop monitoring for drips and
dribbles and curtains and runs. Often I epoxy at the end
of a long session of work to prepare for gluing, and I go
inside and clean up, only to find the next time I'm in the
shop that the epoxy has made a runny, rockhard mess on surfaces
I will have to sand and sand and sand.
jobs such as filling a few but crucial screw holes in the
hull of a boat that I'm building require the donning of
all the safety gear and some attention to the amount to
mix and what to do with the excess, if any.
alternatives to epoxy in my mind include poly glues that
call for wetting one of the surfaces to be bonded and glues
such as Titebond II that have water resistance but not gap-filling
qualities. I have used resorcinal, many years ago, and my
father before me used this glue exclusively in prewar and
postwar years of backyard boatbuilding. Resorcinal leaves
a purplish-reddish line at each glue joint, and it kicks
off slowly depending on the temperature. It stains wood
in ways that reduce the beauty of varnished surfaces. It
demands tight joints and heavy clamping. Epoxy, by contrast,
is stronger when there are gaps and bridges gaps effortlessly;
clamping is accomplished with a box or two of self-tapping
deck screws in sizes of3/4 inch or 1 inch.
White, a frequent contributor to Messing
About in Boats, wrote an article about epoxy
a few years ago. He says that epoxy will penetrate joints
if there is enough heat. He assembles pieces and then ups
the heat in his shop or uses a heat source such as a handheld
hair dryer to encourage the epoxy to penetrate joints. Mind
you, I am relating this from memory, and any lapses or distortions
of Robb's approach are mine, not his. I used this approach
in the building of my Harmonica
canalboat mainly due to entropy: When the time came to seal
the edges of the plywood I used for the foredeck, I covered
the edges with moulding without any prior coating with epoxy.
When I was finished installing the L-moulding that I used
to edge the deck and provide a toe-rail effect, I brushed
on epoxy on a hot day and made sure that I sealed the joint
between the deck and the moulding, hoping that there had
also been penetration to the plywood edge. I figured that
a fillet-type seal on the moulding would do the job fairly
well, but I also was uneasy about my choice.
I understand that strip-built boats can be joined with fasteners
and cheap yellow glue such as Carpenter's Glue or Titebond
II. These glues clean up with water and don't stain wood,
though they will mar a surface if allowed to lay and cure
in drips and rings, because of the differences in penetration
of varnish, and stain (though why you would ever want to
stain wood on a boat is too many for me to figure out).
Epoxy makes fasteners almost redundant after the stuff has
cured. The epoxy is stronger at the glue line that the surrounding
wood is by nature, and the addition of fasteners is necessary
to keep the pieces in proximity after applying the epoxy
and waiting for curing to finish. I use bronze ringed boat
nails for most of my fastening needs, and after buying some
stainless steel screws, and using zinc-coated when I didn't
have the stainless sort on hand, I have been trying to avoid
screws as much as possible. I do like the way they look,
but I have a growing confidence in epoxy alone to hold most
boat parts in place. Mind you, I mess about in protected
waters, usually the Erie Canal.
After marring the finish of one boat with microballoon-augmented
epoxy, I no longer use microballoon additives. I couldn't
tell any difference anyway when using the micorballoons.
I also don't use Cabosil anymore, though it is higher in
my estimation than microballoons. I use wood flour if I
want to thicken epoxy, and nothing else. I like its cost
and the way it works, and it doesn't alarm me as much as
Cabosil does when it gets airborne while my dusk mask is
hanging on the wall instead of in place on my face.
I built The
Weekend Skiff, I was determined, based on
promotional materials, to which I am highly susceptible, to
use the two-coat epoxy sealing approach on all surfaces. Since
then, I have read about boatbuilders who say that the inside
of the boat should be allowed to breathe some and allow moisture
to escape; builders such as my
wife's brother-in-law who even use interior
plywood on boats that they store in the garage between outings;
builders who swear by an interior coating of equal parts of
linseed oil and turpentine (smells wonderful!) applied once
a day for a week, once a week for a month, and once a month
for a year. Another of my brothers-in- law, a builder of fine
homes in California, swears by the principle that both sides
of wood used in construction must be treated in the same manner.
All this is a prelude to my decision
on my latest boat project, the
Quark, to try something new. I am at the
point of putting the hull together and have decided to use a
one-part glue such as Titebond II to glue the parts together
with the aid of ringed boat nails and perhaps deck screws on
such parts as the gunwales and external chines. I will be aiming
for a reasonably close fit but not resorting to clamps. Some
gaps are fine, because I will fill them with thickened epoxy
as a second step, then use epoxy to tape the chine joints and
to seal the outside of the boat.
I have been wanting to test further the idea that the outside
of a boat can be sealed with epoxy, to give abrasion protection,
a good base for paint or varnish, and as a seal against the
penetration of water through the joints; on the inside of the
boat, I want to test the effectiveness of epoxy as a fillet
sealer on joints such as chines and around centerboard cases
and other joints at or below the waterline, with varnish or
paint on the other surfaces, but without a base coat of epoxy.
I like the idea that the boat can breathe and expel moisture
rather than encasing moisture with epoxy on both sides. I am
partly influenced by those who assert that fiberglass boats
are heavier at the end of a season in the water than they are
at the beginning of the season when they are put back into the
water. That tells me that epoxy-saturated fiberglass does not
exclude all moisture, so it may not be necessary, and perhaps
not wise, to use the epoxy encapsulation method that the epoxy
manufacturers swear by.
The overriding consideration for me is the fact that I store
my boats inside when not in use, and that the storage is reasonably
dry and weathertight, but not heated. I also am aware that I
live in the northern tier of the country on the Great Lakes,
where there is seldom a prolonged problem with high humidity
and high temperature of the sort that Robb White, say, encounters
Update: When I went to the home store to get
some glue, I chose Elmer's Carpenter's Wood Glue (Exterior),
which has wood flour added to slow down runs and ripples, got
my vote over the poly glues, because Elmer's doesn't expand
as it dries; the poly glues foam up and expand while drying;
and because Elmer's was half the price of poly glue. Elmer's
is at least half as expensive as epoxy; poly glues appear to
be as expensive. Elmer's cleans up with water; poly glue cleans
up with mineral spirits. Elmer's is not toxic; poly glue is
a bummer if it stays on the skin.
from 3-21-03: I loved using the Elmer's instead of
epoxy for putting the hull together on the Quark.
This new kind has wood flour, which makes for zero (!!!!) runs.
The glue stays where you put it, and even when there is some
squeeze-out, the squeezed-out glue stays in place instead of
running and rippling. Set-up time at 60 degrees F. or so was
generous. The hull is doing fine with Elmer's and bronze boat
nails. Unlike the case with epoxy, the boat nails are necessary
for a backup to the Elmer's.