: Hi,
: I am new to building and have what is probably a very elementary question.
: But, it sure would enlighten me if anyone could take the time to respond.
: I am making an older type traditional kayak ( strongback, frames,
: stringers, etc). I would like to keep a wood finish on the boat. I will be
: using ten inch or so strips of Oekume plywood to sheate the boat. When I
: put the fiberglass and epoxy on, do you see the cloth? And therefore have
: to paint the boat? Or, can I keep it natural wood?
: thanks, Joe

Are you planning to over the entire outside of the boat with fiberglass, or just the seams?

When you build with marine plywood over stringers (or chines as they are sometimes called) the stringers serve as both a fastening bed for the nails or screws used for holding the panels on, and they serve as seals or gaskets along the long edge seams. Or, sometimes you would put a gasket of paint-soaked canvas between the plywood panel and the stringer and let the action of the wood screws clamp everything tightly together.

Epoxy makes things a bit different, and maybe simpler. By using epoxy as a glue on the stringers (perhaps you would want to thicken this a bit) you can eliminate the screws (use gentle clamping pressure so you don't force out all the epoxy) and have a perfectly watertight seal between the plywood and the stringer. And, you don't really need marine plywood. You can use exterior glued plywood and encapsulate it by painting all sides with two coats of epoxy resin before the parts are assembled.

Or, for the "belt and suspenders" approach, you can cover the outside of the seams with a strip of fiberglass cloth which has been saturated with epoxy resin. A 2 inch wide strip of glass cloth gives you about 3/4 of an inch to 1 inch on each side of the seam, which is more than enough to keep out water, although some plans all for using wider tapes.

by the way, fiberglass "tape" is woven to the width you want, and the thick edge is a bit more difficult to make invisible. You'll probably want to sand doen that thick edge after the epoxy has hardened. If you buy fiberglass cloth by the yard you can cut it into strips yourself with a strong scissors or an inexpensive rotary cutting tool.

Making your own strips is not only cheaper than buying the prewoven tapes but it gives you the option of selecting any width you want, there is no stiff edge --so feathering this into the wood panels is easier, you have a wider choice of weights, or thicknesses of the glass fabric, and finally, you can cut your strips perpendicular to the weave of the fabric, or at a 45 degree angle to the weave. These "bias cut" strips can be deformed by gentle stretching (finger pressure) so they fit around curves more easily than the square-woven tapes or strips. You can use the bias strips on straight areas equally as well.

If you want to sheathe the entire outside of your kayak with fiberglass you'll get a little more protection from dings and dents, but this is not needed for strength. The frame inside the kayak takes care of that, and the plywood itself is much stronger than it would need to be for sheathing the boat. Remember that a lot of kayaks use a frame, and then cover it with simple cotton canvas or polyester fabric and a few coats of paint or varnish.

Thomas Hill, in his book "Ultralight Boatbuilding" suggests putting fiberglass only on the bottom of the hull, and sealing the plywood on the rest of the boat by painting on eopxy. This gives his boats more resistance to rocky shore landings, without increasing the weight.

PGJ