Some months ago we looked at the three-piece bark canoes of the Yahgan and Alacaluf people of southern Chile. Prior to European contact, these boats were prevalent all across the Strait of Magellan and several hundred miles up the west coast of Chile, to about the Taitao Peninsula. For another 200 miles or so north of that point, the common pre-conquest boat was the dalca.
In terms of design and even construction, the dalca was quite similar to its southern bark-built cousin, consisting of three planks. A "keel" plank, wide amidships and tapered equally toward the ends to points, was bent to impart a great deal of rocker, particularly toward the ends, so that the bottom curved up to form stem- and sternposts, after a fashion. Side planks were sewn on, with their ends curving inward sharply so that their ends met the outboard edges of the endposts. The sides leaned slightly outward at the top.
I believe the indigenous people of the Chilean coast had no metals pre-conquest, and hence no saws. The boards, therefore, must have been gotten out by splitting with wedges.
Reports differ on the caulking material used to seal the seams, with mentions of various materials including crushed herbs and clay or mud, a tree- or other plant-based resin, and moss. Likewise, the material for the stitches was variously reported as being of bark fibers, baleen, split cane or some unnamed cordage. There are mentions of floor timbers and thwarts. Other than the fact that the thwarts were narrow and structural, apparently not intended as comfortable seats, I've come across no other descriptions of these members, nor their numbers in the boats that existed at the time of European contact.
One of the earliest reports cited a length of 30-40 feet and a beam of 3 feet, which seems far too narrow. Even if three feet is taken as the width of the bottom and one assumes a width at the gunwale as 5 feet amidships, this would have been rather narrow boat at 30 feet LOA, and an outrageously narrow one at 40 feet LOA. I think it probable that at least one, if not both, of the dimensions in that early report were in error.
Propulsion was originally by paddle. One early observer saw the use of a rudimentary sailing rig, consisting of a single mast and yard to which a leather square sail was lashed. The clews (bottom corners) of the sail were held in the mariners' hands. According to Clinton R. Edwards in Aboriginal Watercraft on the Pacific Coast of South America, this was probably an adoption made soon after first contact; Edwards believes no sails were used pre-contact.
Early Europeans in the area often used dalcas for local travel, even commissioning their construction in large numbers, but making provisions for the use of oars instead of paddles. In some cases, they were disassembled for long portages and reassembled at the end of the carry. This was easily done, given their simple stitched or sewn construction.
Soon after European contact began, the dalca began to displace the bark canoe to its south, probably because access to metal tools made the more durable wooden boat that much more attractive and accessible to the Yahgan and Alacaluf people. Dalcas remained in use into the early 20th century, when they were displaced by small craft of European design.
The photo, of a dalca reconstruction at the the Museum of the Dalca in Chiloe, Chile, differs somewhat from the descriptions in Edwards, and may reflect post-contact modifications of an unknown (to me) date. The bottom board does not narrow to points at the ends, and the strakes or side boards butt against the inboard surface of the bottom board – not against its outboard edges. There is a batten on the outside, and possibly on the inside, of the main construction seam, held in place by the bottom-to-sides lashings. There are no floor timbers or frames, but there are seven thwarts, round and still not used as seats, lashed to the upper surface of the strakes.
(Photo is Creative Commons via Wikipedia. Most information is from Edwards, cited above.)