Back to the Backbone...

The rabbet is the boat.

That was what Bertram had told me, when I visited his shop in Port Townsend last summer, and while slightly exaggerated, I knew that, fundamentally, it was true. No other single component of the ship is as long, or needs to be as perfect as the groove that runs the length of the backbone from stemhead to sternpost. The rabbet is the joint into which every single plank of the hull will interface at least twice. Backbone timbers being large and irreplaceable, cutting the rabbet is something that must be done right the first time. Mess up badly, and your proverbial goose is cooked.

And so, as the weather grew warm again in springtime, I put my ambition to get started cutting out frames on hold, and returned to the backbone that lay waiting for me in the yard behind my house's back deck. There was no point in delaying the inevitable - if I were to proceed, this had to happen. Having spent the past two years working up to this point, however, I was just a little bit nervous.

As is usual when critical events in the construction are about to happen, I asked Dad if he would be willing to drive down and supervise. I find that having an extra set of eyes around is helpful in the "recognizing stupid mistakes before they happen" department, and with a cut as important as this one, I wasn't about to leave anything to chance. The fact that March 27 was Easter Sunday was entirely lost on me until he arrived and started cracking jokes about "the Easter rabbet". Good old Dad!

The plan was simple. I would cut into the backbone with a circular saw set 1/4" shallower than the final rabbet depth, and 1/4" inside the actual line. Since the backbone had already been shaped to the outside shape of the hull, that cut would provide a guiding surface that was always perpendicular to the hull's shape, from which one could excavate the remainder of the groove. I spent most of that morning triple-checking the marks I'd drawn against my lofting. Finally, after lunch, with dad standing by ready to unplug the saw if he saw me straying too close to my pencil line, I took a deep breath, and began cutting. Several minutes of intense concentration and steady hands later, I'd done it:

Over the next few weeks, I proceeded to dig out the remaining wood using hand tools, always making sure to leave an extra quarter inch, just to be safe. This excess will only be removed when the planks are actually fitted:

Some of the last remaining chainsaw marks from when I sawed out the keel timber are visible at right, about to get planed off.

Essentially, I was shaping the rabbet as if my planking were only one inch thick instead of 5/4". On the wider sections of the forefoot, I even made small plywood patterns to that effect, just to be sure I got the correct shape.

This portion is near the mast step, and will be subjected to some of the most intense forces while sailing, so a tight seam that fits well against the planking is essential.

At the bow, following Larry's advice in his book on the process, chiseled the rabbet by hand. On the extremely broad face of the stern knee, however, I defined the surface by drilling holes with a 2" diameter carbide Forstner bit and a stop collar set to 1" deep:

In addition to defining the surface, it removed a lot of material, making chiseling easier.

...then chiseled and sanded the surface down until it was smooth and uniform, with just the faintest ghosts of the drill holes remaining:

As with all operations involving the backbone, I then had to flip the entire assembly over, and do it all again. Needless to say, I'm getting kind of tired of flipping the backbone. Thankfully, once I finish shaping the rabbet on the port side, I'll only have to do that one more time: when I lift it vertically to the position where it will stay for the duration of the project. 

Sounds like a good excuse for a party.