Sunday, April 20, 2008

Carving the Ribs

While the gunwales waited to dry and set, I turned my attention to making other structural components for the canoe, beginning with the ribs. Most readings mention the ribs taking a while to prepare properly and the warning to make extra ribs to account for normal breakage during the bending process.

The half-image Adney plan for the 11'8" Attikamek hunting canoe illustrates 3 ribs between the stem piece and end-thwart; 6 between the end thwart & intermediate thwart; and another 6 between the intermediate thwarts & centre thwart. This means means that for the full canoe, there will be double this amount - a total of 30 ribs.

At quarter scale, the ribs would need to be ⅝" wide and 3/32" thick. Following Ted Behne's suggestion, I first tried to make a single rib as practice using a broken piece of cedar from my earlier frustating attempts at making the gunwales. This way at least the materials wouldn't be a waste. The actual ribs would be carved from a single, large chunk of cedar provided in the kit. The practice rib I carved was placed on the soaked cedar piece and lines were drawn at a little wider thatn ⅝" intervals to serve as guidelines for the splits. Luckily, this piece split rather evenly so I was left with 6 pieces around the perfect width for ribs.

Carving a rib from broken gunwale batten; Sample rib on soaked cedar stock; 6 split cedar battens

These split cedar battens were about ¼" thick so in theory they could be split a few more time to form neat and tidy ribstock...that's in theory of course. I'm no master splitter and while I tried to learn from mistakes in shaping the gunwales, the cedar would not split evenly along its thickness. For many of the battens I was only able to split the thickness once, some of them allowed for 2 splits, and one even allowed 3 splits. This was not without its consequences however - my crazy sharp Mora Canoe Knife sliced into my fingertips twice and the tip slightly punctured my thumb leading to more bloodletting and band-aids. But a rough pile of ribstock continued to grow. These were then thinned to 3/32 thickness with a blockplane - a non traditional tool in canoe making, but necessary in my case. I've got a new respect for those master builders who could split and shape cedar perfectly with just a crooked knife. Each of the ribs was checked for appropriate thickness - a time consuming process.

Pile of rough ribs; Shaping with blockplane; 3/32 thickness (the red spot is blood from my punctured thumb)

In the end, I separated my finished ribs based on whether they were of decent quality or low-grade (defects in my splittling). I was left with a total 26 decent ones and 6 not so good ribs. By this time, I was pretty much out of stock to make ribs and was really on the edge in terms of the necessary numbers. Then I realized I needed temporary ribs (not part of the normal ribstock) when preparing and laying the sheathing in the boat. Clearly I didn't have enough ribs. Another executive decision was made to slightly deviate from Adney's plan. Instead of spacing ribs & lashing every ½", I redrew the lashing spots at ⅝". This reduced the number of ribs between the thwarts to 5 each instead of 6, resulting in 26 ribs for the boat...the exact number of quality ribs I have on hand. Let's hope this compromise and the bending process works out well.

The last thing I did was lay out the ribs (on the plywood box packaging of the kit) and numbered them in pairs starting from the centre thwart towards the ends. They all have relatively random lengths now but will be cut down to size after the bending process.

Ribs layed out and numbered

Next up, prepping the stem pieces & headboards as well as carving permanent thwarts.

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