TECH TIPS PAGE TWENTY NINE A
Building Tip - More on Miniatures by Ted Behne You can view Ted's work here.
News and Stuff
Setting the Sheerline
This article continues the assembly process by setting the sheerline of the canoe. The sheerline is the height of the gunwale above the baseline of a canoe. It is lowest at the center of the canoe and gradually rises toward the ends, sometimes rising sharply between the end thwarts and the stems. Properly setting the sheerline is one of the most important steps in the assembly process because it determines not only the final look of the canoe, but also its structural integrity. The sheerline is formed by the inwales and outwales, with the bark locked in place between them by both hardwood pegs and spruce-root lashings.
Assembly constitutes about 50 percent of the work in making a canoe, so at this point you are about half way home. Previous articles outlined other basic steps. These include: Selecting a canoe to model; making a quarter-scale "blueprint"; constructing a reusable building platform; making a gunwale frame; making and installing thwarts; making ribs; splitting cedar; splitting spruce roots for lashings; making sheathing to line the interior of the hull; and unrolling and raising the bark. To review previous articles, go to www.barkcanoe.com/home.htm. Then select "Tips," then "Building Miniature Canoes."
Carefully remove the gunwale frame from the bark enclosure. Insert the two halves of the plywood building frame into the rough canoe shape, being careful to center each half and not to disturb the position of the bark.
Next, attach sheering posts under each thwart of the inwale frame. Sheering posts determine the amount of gunwale rise from the canoe center to each end. Sheering posts can best be held in place by running a small screw through one of the lashing holes at the ends of each thwart and into a pre-drilled hole in the top of each sheering post below. Check the blueprint for the size, number and placement of lashing holes in each thwart. Each sheering post will need to be reduced in height by the thickness of the building frame, i.e., 1/8" if the building frame is made of 1/8" plywood.
Reposition the inwale frame, with sheering posts attached, inside the bark enclosure, being careful to center the frame both widthwise and lengthwise. Cover the inwale frame with plywood planks to support the brick weights and to protect the inwale frame while the sheerline is being set.
Trim the excess height of the bark, using scissors or a razor knife, to an inch above the gunwale frame between the end thwarts, but not beyond the end thwarts.
Next, add the outwales to form the inwale/bark/outwale sandwich that constitutes the gunwales of the canoe. Center the outwales on the centerline of the center thwart and line them up at the same height as the inwale. Clamp them in place at regular intervals with clothespins.
Beginning at the center of the canoe and working outward toward each end pull the gores upward to form a smooth surface, with no bulges or gaps in the hull. Where the gores overlap, one side will be vertical and the other angled. With a pencil, transfer the vertical line of each gore onto the angled side and then carefully trim away the excess angled side so that both sides join in a vertical seam. These seams will later be sealed with spruce gum to waterproof them.
With all the sheering posts in place, replace the plywood support sections and then replace the weights to hold the now-sheered inwale frame in its permanent position. The inwale frame is now held at the proper height to begin pegging and lashing.
In the next newsletter, we will lock the inwales, bark and outwales together with hardwood pegs and begin lashing together the entire gunwale assembly with split spruce roots.
If you have questions about any of the above, just send an email to email@example.com.
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