Sunday, April 6, 2008

Folding Up the Hull

With the building bed all prepared and the bark cleaned, the next step was to prepare the canoe's hull. I mentioned earlier the the bark panels provided with the kit were of insufficient length to form a 1-piece hull. This meant that the hull would have to be lapped - a technique described in Jim Millers's fantastic DVD.

The dilemma I had was that the two pieces of usable hull bark had large knotholes in perfectly akward places. Which ever way I oriented the panels, there would be a gaping hole right at the delicate bow/stern or right under the centre thwart..not acceptable. To get around this dilemma, I was forced to to cut one of the bark panels into pieces so as to remove the centered knothole and build a three piece hull.

Central Panel; Cutting out knothole; placement of panels below form

The bark was placed white-side-up under the form and starting from the stern, the panels placed on top of each other moving towards the bow, like laying shingles. The pieces are supposed to overlap 2" in a full scale model, so for my ¼-scale model that meant ½" lap. Effectively this means some overlap ridges on the bottom of the canoe, but these will be sewn and sealed with pitched to make a watertight seal. In also means that this canoe model will in fact have a distinct bow & stern, unlike may 1-piece hulls that are symmetrical at either end.

Overlap at bow; Overlap at stern

The bed was moved out to the balcony and boiling water was liberally poured onto the bark & the weighted down frame (weighed down with some heavy block planes). At intervals of 3", gores were cut into the bark ensuring that they were cut perpendicular to the frame edge - that's why they look like they are on an angle. The cutting was done with a utility blade angled towards the stern to get a thinned edge.

Softening the bark with boiling water; Cutting a gore

With the gores cut, the bark was carefully folded up and held into position with the ¼" dowels serving as stakes. To ensure even pressure along the sides, scrap pieces of cedar, serving as battens, were sandwiched between the bark and dowels. Once I finished these outer stakes, I placed square ¼" dowels (not included in the kit, purchased at Canadian Tire) with their bottoms shaved to a point on the inside of the hull. These were placed carefully to fit in the small space between the bark and edge of the plywood frame. Then the inner stave and outer stake were tied with scraps of leather lace to effectively shape the hull.

Folding up the bark; Tying the first inner stave & outer stake combination

After all the inner staves were tied off and done, the outer stakes were tensioned to vertical by tying additional lacing across each pair of dowels. Now the soaking bark needs to dryout for a few days to permanently form the hull shape. Starting to look like a canoe!

Inner staves positioned; Tensioned hull with cross lacing

Items up next include the most difficult part in my opinion...carving the gunwales - the real backbone of the canoe. Scaling them down to quarter scale means that these structures will be quite delicate. We'll see how it goes in another post.


Mungo said...

You know, if you run out of birchbark, you could always try chopsticks!
I have the Ray Mears episode of him and a fellow building a birchbark canoe, have you seen it? It really is fascinating to observe the process and how the natural materials are handled.


Murat said...

Great link! Amazing patience to glue 7000+ used chopsticks together to form a hull. I guess he'll be laminating used toothpicks together to make a paddle next!

I have seen the Ray Mears episode you're talking about. Another inspirational episode from Mr. Bushcraft himself. Great detail on the steps involved. I also liked the Canoe Journey episode where he carved a paddle from some dead cedar with an axe and crooked knife.

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