Building a Northumbrian Coble in Clinker Ply
Moving the shipyard, working on interior bits
Home!
Luckily my calculations and simulations all proved to be correct, and the hull did end up fitting out the door of my basement. The boat was trailered home on a rented trailer, and nothing exciting happened, despite the large bolt that somehow got lodged in one of the trailer tyres.
I did quite a bit of work without taking many pictures. I laminated the centerboard from 3 layers of plywood, and to make more efficient use of the wood I made the "handle" out of seperate pieces from the main part of the board. The middle layer of the blade is the full rectangular size, but the outer two have rectangles cut out so that the outer layers of the handle have some area to be glued to. The inner layer of the handle just butts up against the top/trailing edge of the blade, but because of the outer layers the whole thing is very strong. I glued a length of copper pipe into the pivot hole as a bearing.
CB trunk
Making the centerboard trunk took longer than I expected, but was not overly complicated. I made the spacers at the ends of the trunk and the bedlogs out of purpleheart. The bits at the top of the trunk are some rather nice douglas fir I found hiding in a really rough grey board that was lying around. It is amazing what a difference a little planeing can make. I didn't want to have to shape the bedlogs to the curve of the keelson, so I decided to screw and glue them to the keelson and then glue the centerboard trunk between them. I ended up putting rather a lot of screws in them, plus they are epoxied, so the whole thing is very solid even before any other support. To make sure the sides of the trunk were tight against the bed logs I put a bit of wood into the trunk and clamped it up so that it was twisted and forcing the sides apart and towards the bedlogs.
some cleanup needed
One of my main annoyances while building this hull was the massive fillets required in some of the laps. The turn of the bilge is very sharp, and I opted to keep the same 40mm bevel as everywhere else. Unfortunately I could only get about 8mm of that out of the plywood since the angle was so sharp, so I ended up gluing in a whole bunch of plywood strips and using excessive amounts of thickened epoxy. I doesn't look too bad for the most part, but it sure was a waste of epoxy. This is another thing that seems to point to the plans not really being worked through too well for clinker ply, since this wouldn't be a problem at all with stitch and glue.
The thwarts attach to the sides of the boats at little lengths of wood called "cleats". Making these was quite fun. First I ripped some 1.5 inch wide lengths of sapele, and then I cut them to length. I then put a bit of a radius in the ends using a holesaw. Unfortunately my holesaw was only 0.75 inch deep, so I had to drill through from both sides and meet in the middle. The cleats for the beam for the side benches and the sternsheets are notched for the beams, and cutting these notches was quite fun. For the sternsheets beam I used a bit of an old bit of honduran mahogany I found washed up on the beach a while ago. It's got a few little holes, but is quite stiff and very light.
I've still got quite a bit of scraping to do, and the gunwales will need a lot of cleaning up.
Once the cleats for the thwarts were screwed in place I decided to work on the keel and outer stem. The keel is basically a covering board for the keelson and the lower edges of the garboard planks. In this case it is designed to be sacrificial so that when it gets excessively worn from running up a beach or whatever, it can be removed and replaced. For this reason it's just screwed on rather than epoxied into place. I decided to make the keel out of purpleheart since it is very abrasion resistant and, as a bonus, is relatively cheap (I paid $7.50/board foot). To make the best use of wood I made the keel out of 4 pieces. From the bottom of the outer stem to the forward end of the CB trunk is one piece, there is one piece at each side of the CB slot, and then from the after end of the trunk to the stern is the fourth piece. While the keel doesn't contribute much to the structure, for the sake of good worksmanship I had to scarf each piece to the next. Unlike the scarfs in the planking, these ones are not glued, and also have a slightly different shape. I'm pretty sure there are special names for various types of scarfs, but I can't remember them all and google seems unwilling to reveal the answers for once. Since I didn't have any suitable wood for making the outer stem when I made the inner stem, I had to make it now. Unfortunately the jig I used for gluing up the inner stem was long gone, so I had to make a pattern from the stem and then make a new jig for gluing up the outer stem. I decided to use plywood for it since it was available and easy, although I had to try a number of strips before I found enough that would make the bend without exploding.
I flipped the boat back over and continued with the interior. I bought some lovely local vertical grain douglas fir for the thwarts and floorboards, and this time it cost me $5/board foot, and in significantly larger dimensions than the ridiculous windsor plywood stuff (these were real (non-nominal) 2x8" and 2x6", 8 and 10 foot long respectively). I sawed these boards into 3/8 inch boards to use for floorboards and thwarts, with one 1" thick board for the main thwart. I did this on the giant bandsaw at salts which went through the 8 inches of fir like it was nothing at all. Since I was dealing with such thin pieces I decided not to run them through the planer and will instead just use a scraper to get them smooth, since that wastes much less wood. As it turned out the floorboards were a bit too thin to span the gaps between the floors without bending uncomfortably, so I decided to add additional floors between the ones I'd already made. I used some leftover 1" fir from the main thwart and with my bandsaw I quickly had them shaped up. Now the bottom of the boat is supremely stiff, and there is barely any flex in the floorboards, so I'm very pleased.
This plan got scrapped for the much superior solution of chapter 6
The thwart the mast is stepped through is mounted on a pair of cleats that are screwed to the gunwales. Thanks to my bandsaw I was able to quickly cut the slight curves on the ends of the thwart and it now rests against boat gunwales just nicely. Eventually the ends will be rounded off so they look pretty.
Instead of oarlocks I'm going to use "kabes", which are small posts against which the oar rests to transfer the force. A little line holds the oar in place during the return stroke, and the kabes just slot into the gunwale so they can be removed and not be in the way.