RE: upside down canvasing
I don’t claim to be an expert but have helped canvas a few by the upside down method. This is how it has been done at the museum at Havre de Grace, MD, by the Upper Chesapeake chapter.
Make sure the hull is very smooth because every lump will show thru after the canvas is stretched. Run you hands all over the hull, checking for roughness and proud tack heads. Correct problems.
You can estimate the height of the ‘sawhorses’ from the photo (maybe 36”). These have wheels on the bottom so they can move as the canvas is stretched. The canvas is laid over the hull, and evened out with approx. 2’ extra front and rear, and 4-6” hanging over each inwale at the center.
Wood pinch clamps are attached at each end. These shown have a ‘tongue and groove’ down thru the center, and steel eyes near the center which accepts a heavy bolt, and rope or chain gets hooked to this bolt. Notice additional C-clamps.
Rope on one end gets tied down low to a solid object, in this case a tree. On the other, end rope goes to a come-along winch, which is secured down low to another solid object, in this case a truck. (Sometimes the winch is dispensed with and the vehicle is used to pull on the canvas.)
Carefully pull the canvas very tight against the hull, working out wrinkles. Hard to describe tight, but nearly enough to start ripping canvas.
Start at the center, grabbing the edge of the overhanging canvas and pulling it inward and upward, over the inwale, and when extremely tight, with canvas just starting to rip, place two stainless steel staples into the rib tip. A ‘ducksbill’ type vicegrip like a sheetmetal worker would use is good for this canvas stretching operation. Work evenly toward both ends and on both sides until you get to the deck plate and can go no further. You probably will need to cut away some of the excess canvas as you approach the ends, as it gets in the way of stretching and stapling to those last 3 or 4 rib tips.
Relieve tension of come-along, remove pinch clamps. Mark the centerline of the canvas and cut back to near the keel. See second photo. Apply a strip ~1/4”/ ½” wide of double sided carpet tape to the stem, then remove the paper.
Now you need to recruit 4 or 5 friends, a couple to hold the hull steady while the others grab an end of the canvas and pull it as hard as they can across the stem. Starting near the keel line pull down and across, working out wrinkles, and put several staples into the stem. Then grab another handful, pull, work out wrinkles, staple, and repeat all the way to the stem tip. Some excess canvas can be cut off. With this entire first section done, tap the staples with a hammer, and then apply another strip of double-sided carpet tape over the staples. Have your friends grab canvas, pull across, work out wrinkles, staple and repeat until done. Tap staples down, and trim off excess canvas at the stems, but leave excess hanging from the inwales, as that provides a bit of protection to the inwales and interior of the hull during painting.
Not entirely necessary, but makes for a smoother stem: mix fine sawdust into epoxy to create a thick paste and spread this over the stems to give a slightly rounded bead all along the edge. Then stretch saran wrap or stretch wrap plastic over this, which it is still unset, and use fingers to smooth out the epoxy mixture. Use masking tape to hold the saran wrap in place until the epoxy sets hard. Let set overnight.
With both ends done, and looking good - we hope - filler could be applied without moving the canoe from the horses.
Hard to put some of the process into words.
Like you I would be concerned about putting a lot of rope tension across fresh filler, but if it has to be moved, put something wide but flexible under the rope, like ethafoam, or building insulation foam, or pipe insulation foam. Good luck, Tom McCloud
