I left off my tale of building a lapstrake canoe at the point where the scarf joints needed to turn the half planks into full length planks had been cut. Now all I needed to do was glue those joints. This was another scary stage as the planks are all curved and that curve needs to run smoothly and regularly through the glued joint. The canoe plans provided offsets from a line drawn between the end of the planks and the edge of the plank at the point where the joint should be made. However ensuring that the planks actually end up being glued in that position looked problematical at first.
The first thing I did was to buy three sheets of cheap composite board that looks like it is made from wood shavings. The ones I ended up with were narrow but had tongues and grooves along their edges making it simple to join them into a continuous strip. I nailed the joints to hold the sheets in register as I wanted to be able to draw a continuous line down their length. I was not going to rely upon this line but it helped get the planks roughly in position – I then re-checked that positioning using a line of string. I placed the first pair of half planks from one of the sets into position with the scarfs carefully overlapped and (after double checking all of the measurements) then drove pins into the board tightly alongside the ends and in a couple of positions along the top edge of each plank. This gave me a jig for setting up the second plank. After checking that the fit still worked for the second plank I mixed up a batch of epoxy resin – my first.
Mixing the resin was a new experience but the resin pumps supplied along with the West resin and hardener ensured that the mix was correctly proportioned. I had to thicken the mix using some colloidal silica – another first that needed some experimentation to get the thickness right. The book said to make the mix the same consistence as “jam” but I have met a lot of different jams in my time. In the end I went with apricot conserve.
I applied the epoxy to both surfaces of the joints of both planks. The planks were set in position within my mini jig with pieces of polythene sheet under and between the sheets. The joints were clamped using a short section of timber screwed into the boarding just outside the edges of the plank joints again separated with a strip of polythene.
With plenty of epoxy left over I then glued up two of the oak lengths destined to form inwales or outwales. These I clamped using plastic spring clamps as these would not stick to the epoxy and clearly had sufficient clamping strength to hold the scarf joint tightly closed. Three clamps per joint seemed optimal.
I had pre-heated the gluing area to about 16C (roughly 60F in old money) and ensured that the epoxy and hardener were also warmed through so they flowed properly – it was a bit chillier outside so a small fan heater did the trick. Now all I had to do was wait for the epoxy to cure.
The first canoe plank clamped in my gluing jig plus two oak lengths made from three 2 metre lengths clamped and curing.
Next come the other four plank sets and two more oak lengths. I also have to play around with the router to determine if I should use that or a rebate plane to cut the plank rebates – but that is getting ahead of myself.
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