(Click on the pictures for a larger view)
There are several ways to make gunwales (or gunnels, or wales...), most of which are adequately described in the popular books. Some are solid, others scuppered, and I have seen some that are capped over the sheer. I like scuppered gunwales - they look nice, provide gear tie-down points, and water will easily drain out when the boat is tilted up. I know of one kit dealer (Newfound Woodworks) that supplies scuppered inwales cut from a solid piece of ash. These are ready to go, needing only fitting and mounting in the boat. Other kit dealers may also sell similar ones.
Gunwales are commonly made from a piece that is mounted along the sheer inside the boat (inwale), and a similarly mounted outer piece (the outwale). They can be made from just about any wood, but the harder woods, like ash or maple, are preferred for abrasion resistance. Some builders use a hardwood for the outwales, and a less dense wood, like cedar, for the inwales in the interest of weight reduction. Scuppered inwales may be cut from a single piece, or built up by gluing scupper blocks to a solid piece before mounting. The blocks may be the same wood as the base piece, or different for the sake of aesthetics. I like to make the inwales by gluing blocks of contrasting wood to a strip of ash or maple. I also like to round over the scuppers, which has the effect of softening the edges and giving the boat a soft look.
Here's a close-up:
The edges of the scuppers are rounded over. Shaping the concave ends on the blocks is described below.
For the inwales, I begin by cutting the main ash or maple strip 3/8" wide by about 7/8" high, which will be finished later to 3/4" high. The blocks are cut from a dark wood (red cedar in the pictures, but a harder wood would be better to hang seats from). The stock for the blocks is also 3/8" wide by about 7/8" high. This will make the assembly a little bit wider than the design height of 3/4" so that they can be cleaned up and planed flush to size later.
I use a 3/8" diameter Forstner bit in the drill press to cut the blocks, drilling down through the edge of the stock. This leaves a concave end on each block.
The blocks are then epoxied to the main strip...
...and planed flush to 3/4" high.
When you epoxy the blocks to the base strip, it is a good idea to presoak the strip with unthickened epoxy. Wipe off the excess after about ten minutes, then glue the blocks on with thickened epoxy.
The size and spacing of the scupper blocks is up to you. I use a "dashed line" type of accent stripe, so I size and space the scupper blocks to match the stripe. My scupper blocks are 31/4" long and spaced at the same distance, which is the same as the dashed line in the accent stripe. The contrasting wood plugs (described later) are centered at the scupper blocks; the whole assembly then looks good with everything aligned and centered.
If you don't have a planer, a table saw can be used to trim the glue-up. If you go with the table saw, set the blocks slightly shy of one edge when you glue them on. This edge is then clean and can be used as the reference edge against the table saw fence. Do a skim cut to clean up the opposite edge, then use that new edge as a reference against the fence to cut the inwales to correct size (height).
The inboard edges of the inwales may be rounded over at this point. Be sure to give some thought to how the inwales will connect with the decks - you may want to leave the ends of the inwales square until the decks are installed.
I mount the gunwales with epoxy using temporary screws in place of clamps, removing the screws after the epoxy cures. Some builders screw the gunwales together on to the hull dry. If that is your choice, be sure to at least seal coat the inside surface with epoxy.
Begin by positioning the inwales dry, holding them onto the hull with spring clamps. Then screw right through the hull into the scupper blocks, using #8 x 3/4" round washer head screws. Don't put the screws in the center of the scupper blocks; set them off to the side a little bit away from center. This cuts the screw threads for easy attachment when glued. Mount the inwale just a hair below the sheer so that later trimming will leave the sheer flush with the gunwale. Remove the screws, and coat the scupper block gluing surfaces with unthickened epoxy. It is a good idea to seal coat the insides of the scuppers with epoxy at this point as well. The inside of the hull must be sanded to provide a bonding surface for the epoxy glue. Coat the scupper blocks with thickened epoxy, and screw the inwales back in. Positioning is easy, since you already have the screw holes. Don't pull too tight on the screws - epoxy needs a slightly wider glue line than PVA glue. Let the epoxy cure for a day or two, and then remove the screws. The screw holes will be covered by the outwales. Clean up the top edge, making the top of the sheer strip flush with the top of the inwale.
The shape and dimensions of the outwales is a matter of personal preference, governed somewhat by the size of the boat. Obviously, a sixteen or seventeen foot canoe would benefit both structurally and aesthetically by gunwales larger than would be practical or pretty on a more delicate craft like the Wee Lassie.
The last few feet of the outwales are generally tapered in both thickness and width. If you are building a kit with the outwales already rounded over, the inside surface would get the taper cut into it. If making your own, taper the outside before rounding over the edges. This leaves the smooth inner surface for gluing to the hull, and a better joint results. To cut the taper, lay it out with pencil and cut it out with a portable jig saw or on the band saw. Clean up the cut with a block plane. Thinning the height of the outwale is done with a block plane on the bottom edge, leaving the top edge straight and able to be easily aligned with the sheer.
Attach the outwales in a fashion similar to mounting the inwales. Clamp the outwales on the hull and mark for drilling screw holes aligned with the center of the scupper blocks. Remove the outwales, drill a 3/8" diameter counterbore recess for plugs using a Forstner bit in a drill press, followed by clearance holes for #6 x 11/4" square drive face frame screws. If the outwales were tapered, there will not be enough thickness to drill a counterbore and still leave enough wood for screws near the ends. I drill the counter bore, but do not drill for mounting screws. The counterbores are simply plugged later for looks, and the ends of the outwales are glued on and held with clamps until the epoxy cures.
Screw the outwales on dry (again, to cut the screw threads), making sure of the exact alignment with the top surface of the inwales. Remove the screws and coat the outwale with unthickened epoxy, let it soak in, wipe off the excess, and glue it down with thickened epoxy. After curing and cleanup, the screws are removed and the holes plugged. I use contrasting wood tapered plugs for visual effect that I cut myself with a tapered plug cutter.
After the inwales and outwales are installed, I use a 1/8" round-over bit with a brass pilot to rout the edges of the scuppers. This softens them, and I like the look. The bit is from MLCS. The catalog number is #6600, and their phone number is 1-800-533-9298.