Initial work on the backbone
Posted By Tom Daniels on April 28, 2010
By November 2009, the lofting floor had been set up, and everyone was working on the backbone. The backbone of Coronet is made up of a series of substantial parts that lie along the boat’s midline: the stem, keel, and transom. There are other parts that tie these all together, like the gripe, sternpost and transom knee, but for now we’ll stick with the basic parts. As the name implies, the backbone is the part that ties everything together. Break the backbone, lose the boat.
Eric and Chris have been up on the lofting floor, working on the stem sections. They use information from the lofting to determine everything about the shape of these parts. They use the lofting to get the general curves of the parts, the location of the rabbet (the groove that the planks land in), the changing taper along the stem… everything.
Here’s one section of the stem, laid on its side.
Another view, with the top of the stem to the right. You can see how the leading edge gets wider as it sweeps down.
It was getting dark early in the day back then, and the guys used halogen work lights carried to the areas they were working. Besides providing good, bright light, they give off some heat. Not a bad thing on a cold November afternoon.
Here, Eric is using a plywood template that he made from the lofting to lay out the exact location, depth, and angles of the rabbet at a particular location on the stem.
He’ll chop and chisel a pocket in the oak that matches the shape of this template exactly, and then move down the stem to another location with another template, and chop a pocket there. After a while, he’ll have a series of pockets that can be connected into one long groove.
Chris has been working on tapering one face of a massive chunk of oak.
He uses information from the lofting to draw in the edges of the taper on each side of the part, but then, how do you quickly connect those lines to produce your taper when you can’t see both sides at the same time?
Simple, use a jig.
Here’s a simple sled that guides a router with a straight-cutting bit and a guide bearing. On one end, the jig has a board with slots that you set your bit depth with. Line those slots up with your taper line on that side of the log, and you know that your router will begin cutting at exactly that depth.
You can see the taper depth line just to the left of the jig. Note the screws coming out of the jig… you really want to fasten this puppy to the work. An identical board with cut-outs for the router bit depth is attached to the underside of the jig on the other side of the log to lock in the taper depth on the other side of the log.
The rest is a piece of cake. Run your router down the jig, and you’ll create a slot that’s the exact taper you want. Move the jig down your piece a little ways, set up the same way, rout, repeat. This gives you a series of perfectly tapered channels along the length of your part. Connecting them is now easy. You just run a power planer across the part until you get close to the depth of your slots, and take off the final bits with light passes of a hand plane.
Down on the shop floor, Claes and Leo have been chopping the rabbet into the keel in exactly the same manner.
They also have templates that they use to check the location, depth, and angles of the rabbet as they go along.
You can see in this next photo that the rabbet is still a little shallow. It’s right when the template just touches the face of the keel along its entire length.
This is work that goes along inch by inch, day by day. There’s no machine that will carve out your curving rabbet for you. It’s all chopping and planing by hand.
It helps to have a good radio and get along with the guy you work with.
board is used to raise the jig to On the other end, If you set your bit depth to plane down
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