The Grindylow Build Diary: The Frame Construction - SoF Canoe

I decided that instead of floorboards, I would have half ribs and 3/4 ribs between the full ribs. This means feet and knees will not bulge through the skin and disrupt the waterflow, the weight will be lower than the traditional floorboards, and I could strategically choose what length of rib where, so I have an extra full rib under where the kneeling thwart will be, 3/4 ribs around the seats, and half ribs else where. All of these ribs did increase the lashing time though quite considerably...

The ribs look like they are of varying widths and species - because they are! I experimented with air dried and green sweet chestnut ribs (Lightweight, never rots, but the failure rate when steam bending was sky high - the rib starts off bending niely and then flops open at a growth line because the inter growth shear strength is too low in this species it seems. oh well, worth a go.  I also tried larch that I found that was largely knot free - It steam bent excellently, but I found that it was brittle when tapping the oak dowels that attach the rib to the outwale and would sometimes crack. I also have the old fallback of green oak which I bent the rest of the ribs from.

The thwarts have a little block glued with casein glue into a rabbet at the ends so that the thwart ends bear against the outwale, and the block is between the inwale and the thwart, so when it is lifted it pulls on the whole gunwale assembly. They are bolted in against a pad over the top of the gunwales, with the bolts passing through the scuppers. The bottom of the thwarts have a small larch strip glued to it, as I chose to make the thwarts are made from sweet chestnut which is prone to split. The casein glue dries very dark on high tannin woods, hence the staining around the glued in spacer block.

The last rib next to the stems of the canoe are too tight a radius to bend without using multiple thin laminations glued together, but for a craft like a canoe that won't be subjected to prolonged pounding in a chop, using normal rib stock, and strategically breaking it at the apex of the curve where it reaches the hog (keel stringer) is fine - the main thin is that the stringers to ether side are all lashed to it as then they share the load rather than acting independently.

USEFULL TOOLS (AND why japanese tools suit skin on frame construction)

I find that Japanese hand tools are excellent for boat building -  The Japanese woodworking tradition offers a superior designb philosphy for the "in-situ" demands of small craft construction. Unlike Western carpentry, which relies on the heavy, static workbench to provide mechanical advantage, Japanese masters traditionally worked at floor level. By eliminating the bench, the carpenter uses their own body—feet, knees, and weight—as the primary clamping and bracing system.

This means that the tools are lighter weight, often smaller, easier to use and smoother for your money. A modest budget can get you very good quality steel. The plane (Kanna) works on the pull stroke with much less pressure, with one hand. The saws are amazingly sharp with a thin kerf and silky smooth finish, and the spoke shave here is tiny, and gets into the smallest spaces.

This allows for precision when working in awkward positions where a Western push-stroke can cause the tool to slip or require two hands. This means I have the ability to refine a piece exactly where it sits, without the constant farting around between the hull and a workbench and clamp.

Finally, another recommendation - the countersink drill bit here is fantastic. it can be adjusted for any metric screw to give a perfect depth and diameter, and doesn't drill the pilot hole at the same time - a boon when working with the small scantlings of a skin on frame canadian canoe

In the UK, Canadian Western Red Cedar is very expensive, and British WRC is too knotty to get clear lengths. I forked out for the good stuff to make this build as lightweight and rot proof as possible. Unfortunately though any little dings damage the wood very easily which can cause stress risers, so it's always best to shave these down to smooth off any jagged edges. 

Finally you can also see I managed to crack the top of rib with sloppy drilling, and also split through into the top of the inwale slightly - never mind...chalk it up to experience and effect a minor repair next time I mix up some glue.

Oiling the Frame and Tensioning the Lashings

I chose to use Roslag Mahogonay (Pine tar - Linseed Oil - Gum turpentine) for this build rather than mixing up my own boat soup, purely to see how it is. I've got to say I love it. The smell is divine, like a sweet vinegery woodsmoke mixed with some sort of aromatherapy scent! It's a very old nordic recipe and has been used for centuries. It also brings out the grain of the sweet chestnut and oak beautifully.

The linseed and turpentine reduces the internal friction of the tarred marline, so once it's saturated in the oil, you can pull the lashings frapping turns really tight with the connecting diagonal standing runs, so theres no need to pre-stretch it even though it's natural fibre. 

Next post - Skinning the frame