In the sheer plan (see Plate XXXVII.) the vertical positions for timbers are placed one foot apart. No. 1 is one foot from vertical of fore side of stem. The heights are measured from the load water-line to the upper side of the deck at gunwale ; and the depths are measured from the load water line to the lower edge of the rabbet on the keel. The back rabbet, or inside position, of keel will be seen in the longitudinal section plan.
The rocker or upward curve of the keel above the straight edge is at the sternpost lin., and at the fore end (at 6in. in from perpendicular of stem) the rocker is 44in. ; at No. 1 station it is 3M., at No. 2 it is 1 iin., at No. 3 it is sin. ; fore edge of stem at load water-line is 1 iin. in from perpendicular of stem ; sternpost at L.W.L. from aft perpendicular is 1 tin.
The keel, from No. 3 to No. 7 sections—i.e., in the wake of the centre-board slot—is sided at rabbet line 2in., and is 1 4in. at lower edge; the siding—i.e., thickness—at rabbet line forward and aft of this should not be less than liin. The cutwater of stem should be reduced on the fore edge to about fin.
Selecting the wood for the keel will be a matter of choice. For hard work teak is recommended ; for great strength and weight greenheart ; but red pine (not pitch) has been found quite strong enough for all ordinary work.
The next point of importance is the skin, or plank, and the mode of putting it on. Except for the roughest coast-bumping or for home lake sailing, oak is uselessly strong and heavy. A combination of mahogany and cedar, well seasoned and properly fastened, forms for a sailing canoe as strong and light a build as can be desired—that is to say, the canoe should be built with the three lower strakes, mahogany (the garboard very wide), and the three upper strakes of cedar, ranging from about a quarter to three-eighths of an inch thickness.
Various modes of planking have been tried with the object of ob taining a smooth outer surface, and a light but strong skin; of these the most successful are the " clincher," the " ribband carvel," and the " double skin." The ordinary carvel build requires sufficient thickness of plank to allow of caulking, but this increases the weight beyond what is advisable for a canoe. The " double akin" plan is as follows : When the stem and stern posts have been set up and fastened off, and the building moulds—say one foot apart—carefully and strongly fixed in position, and firmly battened round at their heads by a kind of temporary gunwale, and the centre-board case or cases fitted and fixed, this frame work is turned upside down, and again fixed in position. Thin, well
steamed planks of cedar, about "wager boat" thickness, are tacked in position edge to edge, over the moulds, as if for carvel-planking ; over this is then laid, plank by plank, a somewhat thicker skin of steamed cedar, the edges of which come over the centres of the planks of the inner skin. The two skins are then fastened off as if one, along the rabbet line, with brass screws; the edges of the outer skin are then pierced along and copper nailed as in ordinary building. The craft is then turned up and the nails are clenched off on the inside. It will also be found necessary on some strakes to nail along the inner skin edges also. In such case the holes will be bored from inside and nails driven from outside. Very few timbers will be needed, and the double skin will be found to possess great strength. A good coat of varnish or strips of varnished calico between the skins would no doubt add greatly to the strength and watertightness of the structure.
In the ribband-carvel build (see Fig. 121), the planks of, say fin. to sin. stuff, are tacked on to the building moulds edge to edge. Ribbands of clean-grained oak, about llin. wide and fin. or sin. thick, are laid along on the inside of the joints of the plank between the timbers which are placed in the vertical positions shown in the sheer plan; the edges of the planks are then pierced and nailed through the ribbands, and clenched on the inside, or they may be screwed into the ribbands. A stronger plan is to work a fin. ribband in whole lengths, cutting out notches in the backs of the timbers and moulds to take each ribband. In all cases a strip of varnished linen should be laid over the joints of the plank before the batten is fitted, and the linen should be continuous from end to end. The timbers are about sin. sided by sin. moulded. No doubt this mode, and that of the double skin, give a very fine outer surface ; but the number of nails required is nearly doable that employed in a clincher-built boat, and with neat workmanship a clincher boat can be built with next to no " lands " showing on the outside, and yet be of sufficient strength.