Building Spars

Most wood boatbuilding tasks begin with millwork and the spars are no exception. Our first step is to plane the wood to thickness then joint one edge. The sitka spruce piles are graded by dimension and quality as we work through them. The jointing and table saw work to follow are done with the aid of a power feeder shifted from tool to tool. This accessory helps produce even quality cuts as well as reducing the workload a little.

We are building a spar factory for this job and the more rote each task becomes the better we like it. The painstaking and really fun part is setting the routines up and seeing them work. In this factory the production run is relatively short so there is still some handwork and still the possibility of messing things up through human error. We have not yet brought on the automaton robot zombie boat builders or the next generation of software to replace them so we do have to be careful through each phase of this job.

All of the spars we are building in this run will be of eight-stave birds mouth construction. We begin by cutting the staves to their widest dimension on the table saw then joining them with a slash scarf joint to make up the required length for each spar. The joints are roughed on a band saw then finished in a router jig and glued together on a bench.
The staves are then clamped into a jig on the backboard of our spar bench. The taper is cut into them with a circular saw adapted to slide along that jig and smoothed with a router set up in a similar way. In this way each stave comes out exactly the same as the other seven that make up the spar. The position of the batten and its wedge clamps is changed for each spar. That position is determined by a little exercise in graphic geometry where we start with the diameter of each column and proceed to determine how wide each facet of an octagon must be to encompass that diameter. Remember how many times we protested the uselessness of geometry in high school? I loved geometry.
The finished staves are bundled and held in place with hose clamps so the fits can be checked and plugs for the ends fashioned. More geometry and handwork. Once this is done they can be glued. That is a bit of a gooey juggling act as the bundle of staves tends to fall apart until they are all together and at least one hose clamp is on. One of the basic tenets of boatbuilding is, Never ever cut a piece of wood to its exact length until you absolutely have to. I am sure Noah chiseled this into a tablet and it will be found someday. Because our staves are long we can tack them together with dry wall screws in the very ends. The drywall screw holes will be removed when it is essential that the spar be cut to length. Once the glue is set the spar can be 16 sided with a power plane and roughly rounded with a spar plane to prepare it for the lathe.
Send comments and questions to info@woodboatbuilder.com
Click here for a Quicktime movie of the spar lathe
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