Building a Northumbrian Coble in Clinker Ply

First week

Since I'm stuck working in a coal mine in Campbell River for 4 months I decided that I should build myself a new boat. I decided on a 12'6" sailing dinghy of a design called a "coble" which was a traditional type of fishing boat on the east coast of Scotland.

Here is what I did during the first week

Immediately after I bought the nice wood I planed most of it to a nice surface and then ripped the strips to laminate the stem. I also cut the planks for the transom and jointed those. I should have done those a bit more carefully since although they are very square the edges of the planks arenít quite straight, and so the ends touch but the middle of the sides are a tiny bit apart. I think I will probably end up just leaving them since itís so close and I donít want to ruin the nice squareness of the edge (the corners need to be 90 degrees so that when the planks are glued together they form a flat panel).

The next step was to loft out the shapes of the moulds (lofting is the full scale drawing of the bits of the boat, so basically drafting a boat life sized).

The moulds are wooden forms that are used to bend the planking around and so it is fairly important to get them the right shape, otherwise the whole boat isnít shaped right. To start with I drew the moulds out full size on a sheet of plywood. I then drew out how I was going to fit them onto a 1x8 board, which required me to split each half of each mould into two bits.

The first mould took quite a while to draw out properly but the next day I got a combination square and a big 250mm drafting square both of which speeded things up a lot. After Iíd figured out where to cut the boards I had to actually cut them.

To keep things symmetric I first screwed two boards together and I will only unscrew them once all the shaping is done. Since the cuts were on an angle they were mostly about 10 inches long and 2 inches deep. I had to make sure that the cut was at the right angle in two axis, as well as making sure the cut was as straight as possible. Oh, and by the way I had to do all this cutting with my trust little Japanese handsaw. The first one, done freehand with the board set across an armchair, went pretty well and was quite straight although not quite square to the face of the board.

For the next cut I decided to hold it in a vice and that just went horribly wrong. Plus, it turned out I measured it wrong so on top of my lines being 5mm off (I was reading the tape measure upside downÖ) I hadnít even followed the lines properly so the result was a nasty 5mm gap between two of the boards. The next one I went back to my armchair and by being careful and alternating the side that I was cutting from I managed to get it nearly perfect. By changing sides I could more easily correct the cut since you have very little control over the blade on the opposite side of the board. The other 3 went similarly well. My main problem in fitting those together was the screw heads that werenít totally flush with the boards putting the alignment off a bit when I set them on the original drawing/plywood.

I had to walk for an hour to get some more wood for the last mould since Iíd managed to miscalculate somehow. I think I might have actually only calculated for half the boat and then just bought lots of extra just in case.

After the moulds were all screwed together I had to transfer the curves from the drawing to the actual mould. I did this by putting nails back through the holes Iíd used to draw the curves originally and then pressed the mould down over them to get an imprint. I then hammered nails into the holes in the mould and bent a batten (in this case a bit of plastic moulding) around them and then traced the line that made. Once Iíd figured out how much I needed to remove I had to plane them down to shape. I screwed a bunch of the 2x4s that Iíll later use for the strongback (the base that holds all the moulds during construction) together in a grid.

This gave me something solid to clamp the moulds to while I was working on them. The blade on my brand new welfare brand plane was so horribly sharpened out of the box that it was basically useless and there were large grooves in it from the grinder (ideally it should be mirror-smooth). Luckily the day before I needed it I managed to find a suitable plastic container for my waterstones (sharpening stones that you keep wet) and so I set about sharpening the blade.

First I had to flatten the back of the blade, which took some time since it was pretty wonky. I was impressed with how easy it was to get a nice finish, and soon I went to work on the bevel side. This was a bit more challenging since you need to make sure you hold the blade at a very constant angle; if the bevel gets rounded it just sucks. Once Iíd gotten most of the grooves out of it and it was all shiny I decided to give it a go.

I was totally amazed and how much better it worked. Lovely curls of wood were flying everywhere and all was well. The first mould I tried had a giant knot in the way on one plank and that was troublesome to plane so I shaped the rest of it and left the knot for later. The second one went even better (mostly due to no big knots) and when I tested it against the original layout it was within a mm or two. At the time of writing I have only one more to go, and it's the easiest by far. Not only is it the smallest, it's also the one I used thinner boards for, and it only has one knot which so far doesn't seem to be a problem.

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