Skin-on-frame boats are lightweight, delicate but very rugged anyway. They can be built in a resource-efficient manner and offer some interesting crafting steps such as steam bending or skinning and sewing the skin.
Traditional construction methods do not require glue, screws or nails, as the boats are held together with dowels and artificial sinew. A modern variation on traditional skin-on-frame construction is the fuselage frame construction, which uses frames sawn out of sheet material instead of steam-bent ribs. This construction method is based on techniques used in ancient aircraft construction.
In traditional skin-on-frame boat construction, the gunwales define the sheer and provide the main structural strength of a skin-on-frame boat. The transverse ribs, which are steam-bent from narrow strips of ash or oak, are attached to the gunwales. The ribs hold the stringers, which determine the shape of the outer skin and are responsible for the typical hard-chined shape. Everything is connected with artificial sinew or dowels. Nails, screws or adhesives are not necessary.
The gunwales and stringers are made of the lightest possible wood. Red Cedar is particularly suitable for this purpose, as it is very homogeneous, knot-free, light and easy to process. In addition, its high resistance to rot and fungus should also be pointed out. Other woods such as spruce, pine or douglas fir can of course also be used.
The ribs are made of ash or oak. Ash wood has the advantage that even kiln-dried wood is suitable for steam bending.
In a canoe, the gunwales are equivalent to the coaming; in a skin-on-frame kayak, the gunwales are located at the transition from the hull to the deck. They carry most of the forces acting in a skin-on-frame boat. In kayak construction, they are usually set at an angle of about 17° and thus naturally produce the typical sheer as well as the trapezoidal cross-section of the hull. In canoes, the gunwales are glued together from several strips to form the desired sheerline, since the shape of the hull requires vertically positioned gunwales. Placing the gunwales at an angle, as in the kayak, is not an option here.
The gunwales are provided with pockets on the underside, in which the ribs are attached.
Since the gunwales are important statically, a careful choice of wood is important. Red Cedar is the best choice, as the wood is very strong and resistant to rot in relation to its light weight. It is also very easy to work with hand tools and can usually be obtained knot-free. A board with lying annual rings results in gunwales with lying annual rings (see photo).