Figure 23
Canoe formed (a) by crimping sides, showing rockered bottom line, and (b) by simple gores in sides. The same effects are obtained by making bark cover of three pieces: sides and bottom.
Birch bark gave much more freedom in the selection of form simply because it could be joined together in small odd-sized sheets to shape a hull, and because it was elastic enough to allow some "moulding" by pressure of the framework employed. Birch bark could be gored, or slashed, and rejoined without resort to folding or crimping; thus it permitted a smooth exterior surface to be achieved. The toughness of the bark was sufficient to allow some sewing in line with the grain, to add to the width of a sheet, if the proper technique were employed (this was also true to a lesser extent of spruce bark).
Figure 24
Canoe Formed by use of gores and panels.
The framework of most bark canoes depended upon the gunwale structure to give longitudinal strength to the hull; for this reason the structure was made sufficiently large in cross-section to be rather stiff, or was formed of more than one member. An inner and outer gunwale construction was employed in many bark canoes. The inner member was the strength member and was sometimes square, or nearly so, in cross-section. In some canoes bark was brought up on the outside of this gunwale member, lapped over the top, and lashed over it; in others the bark was lashed to both inner and outer gunwales. The outer gunwale, a rectangular-sectioned batten bent narrow-edge up, was applied like a guard, outside the bark, and was secured by pegs, by the lashings of the bark cover, or by widely spaced lashings. On top of the large inner gunwale and usually extending outward over the outer gunwale, a thin cap, pegged or lashed in the same manner as the outer gunwale, was sometimes added; this was intended to protect the lashing of the bark to the gunwale rather than to add longitudinal strength.
The corners of the inner gunwale, or of the single gunwale, were all rounded off to prevent them from cutting the sewing and lashings. The bottom outboard corner was sometimes rounded off more than the other, or beveled, in order to form between the outboard face of the gunwale and the bark a slot into which the heads of the ribs could be forced. An alternate method of accomplishing this was to notch or drill holes in the gunwales for the heads of the ribs.