My Backyard Boats:

The Quark: A Digression on Glue

A digression on glue for boatbuilding

Water resistant, one-part, nontoxic, water cleanup, and wood flour added at the factory to make it stay put in use -- Elmer's glue.

Japanese 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.

    20 March 03: 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:

  • Epoxy at ClarkCraft, 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).

  • Epoxy 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.

  • Small 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.

  • The 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.

  • Robb 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.

    When 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 in Georgia.

     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.

    Update 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.

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