Assembling the Backbone

Today I took a glance at my blog and realized that I hadn't updated it for almost a year! I promise I have a good excuse, though -- boatbuilding! Despite the lack of updates here, quite a bit has been happening in the backyard shipyard. Following the roughing out of the keel timber last summer, work continued into the fall, with the assembly of the backbone timbers. This is more than just a simple matter of bolting the rough pieces together. Because the rabbet, the channel in he backbone that interfaces with the lowest course of hull planking (called the garboards) crosses the joints between these timbers, they all need to be watertight. That meant *lots* of sanding, in order to get the rough cut surfaces made by the Prazi down to a perfectly smooth finish. Following that, as Larry Pardey recommends, I created a *very* slight (1/64 inch) hollow in the pieces to allow for subsequent shrinkage of the wood.

Once the sanding was done, I clamped the pieces in place and drilled the holes for the bronze bolts that will hold the backbone together. While additional holes were drilled, the pieces were temporarily held together with half-inch threaded rod from Home Depot, which had the benefit of threading the insides of the bolt shafts, thus allowing the permanent fasteners to be easily spun in when chucked into a drill.

Drilling the bolt holes. The two framing squares and tape helped keep the bit straight on this long bore.

Prior to final assembly, I painted the joining surfaces with copper wood preservative, followed by red lead, to discourage any organisms who might think my boat would make a tasty meal. The properties of Angelique wood are supposed to address this problem anyway, but better safe than sorry! To fill any remaining gaps, I spread Dolfinite bedding compound onto each surface as well:

Preparing to join the forefoot (upside down, right) to the forward end of the keel (left).

Dolfinite used to be the quintessential fungicidal bedding compound, until its (very effective) active ingredient, pentachlorophenol, was ruled unsafe for consumer use. These days it has no such toxic properties. In an attempt to jury-rig them, I mixed a heaping portion of copper napthenate horse-hoof treatment into the can. In addition to being highly poisonous, this turned the goop a delicious green color.

Yum!

Once both pieces were thoroughly covered in toxic sludge, it was time to join them permanently with bronze bolts that I made using 1/2" bronze rod and a thread cutting die. I then repeated the above procedure six times, once for each component of the backbone - since most of the pieces were large and unwieldy, that took quite a bit of time!

Hoisting the stem into place. This was a tricky piece to fit, as it has to be snug to both the forefoot and stem knee. (October 2014).

The bolts that sandwich the keel (center) between the stern knee (left) and aft deadwood (right) are almost three feet long. Drilling from below was not an option for such long holes, so I laid the whole assembly on its side using my chain hoist. The drill bit was lengthened for this bore by welding a steel rod to its lower end. (December 2014).

Upright again, and drilling the holes that fasten the sternpost to the keel assembly. The apparatus of 2x4s exists to guide the drill bit so that it emerges directly on the centerline and (critically) does so without fouling on the vertical bolts that attach the stern knee to the keel and deadwood below. (March 2015).

For the assembly of the final piece, the sternpost, I threw a party at my house and invited several of my more nautically-inclined friends to help heave it into position. I promise that the resulting picture wasn't planned in any way, and any resemblance to other famous photographs is purely coincidental!

"Raising the sternpost on Astraea" (April 2015).

Mmmm! Guacamole! :P

The completed backbone, again on its side and ready for shaping, May 2015.