How to Build a Kevlar Canoe - Solo

"Gunwales (and cutting ribs)"

I trued up the hotwire setup (board, rails, mounts) and shortened the hotwire to 40 inches or so (cut is 36”- width of ribs).  I then cut a dozen or so ribs – worked pretty good. Note the enhanced ventilation setup (melted polystyrene is nasty stuff).  I also started “teaching the ribs", setting up for the curve when they’re installed. There’s kind of a skin on the hotwired polystyrene that can crack if you’re not careful.  Back to (paid) work tomorrow, so progress will slow down significantly. The finish coat should be cured by then, so I can start working on the gunwales.

I used the gunwales for the Tripper from last year that hasn’t been built yet (see http://www.myrabo.com/k-canoe/Kevlar%202006/8-gunwales.htm for the details). They are 3/8” wide for the inwale and 5/8” for the outwale – both by ~1” tall. The bottom outside edge has already been rounded off with a router (difficult to do after it’s mounted).

Temporarily clamp the inwales at approximately the right height. Place a temporary stick the width of the canoe, simulating a portage yoke width (it should be the same width as your form!).  Using a flexible tape (not a standard tape measure), establish a reference point on the sides measuring x inches from the centerline and mark it somewhere close to where the gunwale will be. Do this in at least five places (center, ends, and in between).

 

Trim one end of your inwales to fit into the “V” of the bow. Trim the other one with a similar “V”, so it nests up against the first one (follow the gunwale line, and fine tune with a Surform or belt sander (I used the latter).

 

Trim the stern end of the inwales in the same manner, using the reference marks as a guide to proper placement. Be careful not to trim the inwales too much, as you may need it if you have a curve back on the bow or stern. It doesn’t have to be exact placement yet, but pretty close, and the same height on both port and starboard!

Now place a straight stick of the right length in the center of the canoe, bridging the inwales, and measure the depth from the inwale topside to the keel line.

 

This is the starting point for your gunwale lines. Adjust the inwales to get the depth you have chosen. I ended up a little over 14”, so I’ll lower all of my marks ½“, as I’ve got a little bit of ripple at the center gunwale edge I’d like to trim off. Now do the same for the bow and stern, and temporarily clamp them in place. For a solo canoe, the bow and stern should not exceed 2” above the center depth to avoid side wind resistance problems.

"Eyeball" the gunwale line and adjust the midpoints until you like the way it looks on one side. Verify the two midpoint heights (between bow and center or stern and center) are the same on both port and starboard sides, and clamp them too.

 

I'm ready for the outwales now. I just clamped the outwales in about the right place, then trimmed the Kevlar down to the gunwale line so it’s easier to work with (took about 10 minutes with a fine toothed coping saw). I need to lower the gunwale line about 1 inch in the center, and ½“ in the bow/stern.

Trim the outwales and line them up with the inwales. I re-checked the keel-line to inwale distance at seven points, and measured the depth at center, bow and stern.I also used a 2x2 with a sawcut in the middle to assure inwales and outwales were lined up – hard to tell with the excess Kevlar sticking up.

I shaved the bow outwales so it matched the shape of the hull (a little bulge at the tip to adjust for).

Remeasured (one more time – found one line off ½“ on the starboard side), and placed sticks on top of the gunwales at three points for a final eyeball check.

Measure off 16” from stern to bow and drill the pilot holes for the screws and countersink. I used ¾“ #6 phillips head flathead brass screws. When installing, I set the clutch for the cordless drill pretty low to make sure I didn’t strip them. Clamp the gunwales around the screw being placed to assure tight contact.

I trim the outwale ends so that the outwale just reaches the end of the canoe, and taper it back. A Surform® or beltsander works fine to accomplish the taper. At the very end, I used 1” #8 screws, from the outwale through the stem reinforcement into the inwale.

 

Now trim the excess Kevlar/’glass above the gunwales flush with the top (fine blade coping saw again).

Take some time to cut it closely, since the Kevlar is so tough to sand. Sand the gunwale top with a belt sander (along the length of the gunwale), and follow-up with a random orbital sander.

The canoe now weighs 29 lbs.

 

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