> I am planning on building a stich-and-glue kayak this winter, but have
> some questions about the epoxy. Everything I read refers to epoxy for
> filling the seams, but they don't say what kind.

The plans that you buy should be more specific. There are several brands of epoxy that are used for boat building. . Some are less expensive than others. The brand names mentioned in a previous post should work fine. Either buy what is available locally or go for the best price through mailorder.

> A friend of mine who used
> to do auto-body work recomended Dura-glass. Would this work for filling
> the seams, or do I need a special epoxy?

My question is this: Is Dura-glass a polyester or an epoxy based mix? Most auto work is done with polyester based materials. For that matter, most of the 'fiberglass' items you see are made with polyester based resin, including most 'fiberglass' boats. If you want epoxy, then get epoxy, and don't be confused by the other materials on the market. They may be great materials, but they aren't necessarily the best for this application.

> Also, what should I use to coat
> the outside of the plywood with to water-proof it? Fiberglass resin or
> maybe fiberglass gel-coat? Do I need to use fiberglass mesh on the entire
> hull to reinforce it or is just water-proofed plywood alright? This will
> be for lake fishing and will probably not see a river or rough water. Any
> advise will be greatly apreciated!

Check the plans again. Some boats are simply coated with varnish or paint, with paint being the most common coating for the outside of the hull. Historically this has been the case.

HOWEVER <-- a big however

Epoxy (not polyester) resin has the ability to soak into the wood and seal the surface. Epoxy is also better at resisting water vapor. As a result, many people use a process called epoxy encapsulation to completely seal all wood surfaces during the construction of their boats. This keeps the wood from rotting, and is a great idea for large boats that are kept in the water all the time. Small craft that are primarily stored out of the water (like most canoes, rowboats, and kayaks) may not need this level of protection. If you use epoxy in this fashion you must cover it with a coat of opaque paint, or a clear finish that can provide an UltraViolet barrier, if the boat will be left in the sun for a long period of time. If the designer calls for epoxy encapsulation, go for it! Otherwise, use a good grade of marine paint, enamel, polyurethane, or whatever is specified.

Fiberglass gel coat is a form of polyester resin designed as a final surface. Think of it as a finish coat for polyester based resins. You don't want to consider this.

Some boats are made from thin plywood panels and need to be reinforced with fiberglass cloth and plastic resin. In effect the designer is asking you to create composite material that resembles plywood with two outside layers of high strength glass and plastic. Again, if this is what is called for, do it. Other designers use slightly thicker plywood which does not require the additional strength (and cost) of those added fiberglass layers.

Some people put a layer of fiberglass cloth just on the bottom of their boats to provide resistance to scratching when the boat is dragged onto a beach. If you launch from a dock you might not even need this.

so, the answers to you questions are: Buy a boat building epoxy, not an auto motive one. You may or may not need the glass cloth (it is significantly denser than fiberglass mesh, which looks like window screening) and if the design does not require the hull to be covered with glass cloth, and the seams are well constructed, the painted wood will be just fine for many years of use.

Hope this helps.

Paul G. Jacobson