Epoxy
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 drift boats 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!)Clear Marine Epoxy:
Epoxy as a wood finish is best used primarily on the plywood parts of the boat. Plywood, even marine plywood, is subject to "checking". Checking in plywood reveals itself as a series of hairline cracks running along the grain of the wood, with the grain fibers pulling apart from each other. This is particularly common when the boat is left out in the weather on a daily basis. Epoxy has the ability to soak farther into the grain than any other finish and inhibit checking. Epoxy should be used on bare wood, which means you should not use a stain underneath it (for color). Epoxy is also an excellent primer under paint. You'll need 2 gallons to coat all the plywood.
West Systems per gallon kit........ $125.00
West Systems per quart kit........ $50.00
System Three no-blush per 3 gallon kit........ $300.00
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) ....... $5.00 Roller Handle........ $8.00
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.To order call (541)221-5201 or e-mail at: tatmanboats@gmail.com
