Gumming the Canoe's Hull

The last step before she's water-ready...gumming the hull! The whole experience of gumming the inside made for a really messy interior that was ultimately covered with sheathing. To make sure the exterior was neat and tidy looking, the gores and lap seams were first bordered with some conventional masking tape.


Masking tape on hull
There was some gum left over in the can from when I originally tempered the mixture a while back. It had hardened considerably (left outdoors) but with a quick re-heating the gum was syrupy again. To seal each gore, a large gob of gum was placed at the bottom end of the gore (positioned on top in the flipped over hull). Rather than smear it all over with a thin cedar stick (like in the interior), I wet my thumb and gently pressed it into the seam and stitching holes while dragging it down the side of hull. This left the majority of the gum below the waterline while leaving a thinner coat well above the waterline were the gum doesn't need to be as thick.

I had to work quickly as the gum would set and begin hardening after a few minutes. This meant only sealing about 3 or 4 gores before the gum would need to be reheated. To hasten the process, I left a candle burning out on the balcony and would simply reheat the can of gum by carefully suspending it over the flame and then run back inside to do the sealing. Going back and forth like this and sealing with my hands created quite sticky fingertips, so I didn't stop to take pictures along the way, but only after the job was finished.


Finished seams
Should mention that the ends received the most amount of gum which resulted in a very dark amber. In these areas, the gum was pressed into the cracks and sealed any other minor openings. Unfortunately, I noticed some new tiny hairline cracks in the bow where some eyes had opened up, probably after the hull dried after placing the ribs under tension. This meant a rather sloppy appearance at the bow end, but it was necessary to prevent any water seepage. After that was done, I let the gum sit for about an hour and then proceeded to take off the tape revealing some clean looking seams.


Removing the tape
With the hull still inverted, I gummed any remaining spots, including a tiny blemish on the bottom and the huge knothole on the port side. With the inside gumming and extra bark pressured with sheathing and ribs, some of the interior gum oozed out so I didn't need much to perfectly seal this area.


The gummed hull including knothole on the side
It was then time for the leakage test in the tub to see if I did a good job. After letting it sit empty, no leakage was seen, but when I pressed into the center of the boat (mimicking the weight of a paddler) small droplets were seen at the bow end. I also pressed down the stern but no problems there and even heeled the boat over onto each side to spot any gore leaks and there were none. The bow was sealed with another layer of gum over any suspicious spots and after a second test, she sealed up completely even when weighted down almost to the gunwales.


Testing for leaks in the tub

Even though the main project is done, I still have ideas for this model. I'll be carving some minature paddles to go with the design as well as making a background frame & wallmount to display the work at the cottage and inspire work on the "real one".


Gummed up and ready to rock!