Scribing the length of a tapered spar stave
Marking gauge set for 8 faces at the stave's widest girth
Proportional narrowing of faces is maintained if the legs of the gauge hug the sides of the timbe
Twisting the gauge as the spar stave narrows retains the same proportional distance between the scribed edges and the sides.
The marvelous spar-finishing machine
Pipe nipple, or loosely bored wooden handle
Spar hung at eyebrow height
Sander belt turned inside-out
We made scarfing jigs and spar clamps, and convinced ourselves that the glued joints were the strongest parts of those assemblies. We decided that the making of hollow spars is probably the easiest part of boatbuilding. With enough dry spruce (or fir, or other light and tough wood) of any available size, we could add length to existing spars, mend broken booms, or build new light masts that would stay straight forevermore. We had taken yet another step toward controlling our destiny—and had lost the primitive joy of seeking out that perfect tree in the depths of the swamp.
Therefore, we'd better get to the business of gathering the few, simple bits of equipment you'll need.
Ground 6-sided for drill chuck
4//-diameter rubber-covered wooden drum
Make up half a dozen tall (36-inch) horses, and space them 6 feet apart down the middle of the shop (see Figure 18-5). Shim them to a tight string, tack them to the floor, and brace everything diagonally to withstand all the end-thrust you can put on it with your good right arm. Fit a 2- by 10-inch plank along one side, full length, to tie the horses together and to provide a solid base for scarfing, rabbeting, and edge-joining the staves that will make up the completed spar. Note that this spar bench can be disassembled, to sleep peacefully under the shop for 50 weeks of the year. It's slightly more elaborate than you'd need to shape and glue a solid boom, and it could be improved to handle all the possibilities in a full-time spar shop. Use your own ingenuity, but keep it true and uncluttered so that you can march up and down both sides, and around the ends, and spread glue at a dead run.
And on this bench you'll clamp a scarfing jig, which is a very simple device for marking and controlling chisel-like matching cuts. (See Figure 18-6.) Two identical wedges, with a slope of 1 inch in 12 inches, are screw--fastened to a short plank—exactly abreast of each other, separated only enough to accommodate the widest pieces you'll be joining. The wedges will, of course, be deeper than the work-piece you're about to slide between them and out to the jumping-off place. To fit an end, you'll clamp as shown, make cuts across, split off most of the wood between cuts, and finish with a long jointer, precisely to the slope of the wedges. You could, of course, cut. these slopes almost to size on a bandsaw, or do the whole job with a high-speed router and a special jig, or even work them down with repeated passes on a movable ramp in a surface planer. Just be sure that the ends match perfectly.
Unless you own or can borrow vast numbers of C-clamps, you'd best make up a set of special spar clamps, as shown in Figure 18-7—two pieces of hardwood, two continuous-threaded Va-inch steel rods, with nuts and washers above and below. You'll need one every foot for the longest spar you'll make. You can distribute the pressure (on staves less than an inch thick) by inserting a 6-inch pad above and below, as shown. You can even squeeze the staves together with giant hose-clamps, or rope and wedges, or spiral wrappings with strips of rubber or nylon line, but you won't have the good control of pressure that you get with these homemade clamps.
(And you may say at this point, "Who needs pressure? Doesn't the old...fossil realize that epoxy has changed all that? At last made wood a reasonable substitute for the more commonly
accepted materials for boat- and spar-making? Fills the gaps, seals against fungus forever-more, makes joints stronger than welded iron? No pressure needed?" —Sure enough. But I still prefer cold-water-mix Weldwood, which does not require controlled temperature or humidity, costs very little, and forgives my incompetence as a chemist. And anyway, we grew up together.)
One more bit of soul-searching. What about this caution to scatter scarfs, the weak spots, as widely as possible? If you hark to that implied doubt and accept it, you'd best stop right here. Glued wooden spars are not for you. But if you believe, as I do, that the glued-scarf sections are always the stiffest and strongest parts of the stave, then you'll be happy to see them all cheek-by-jowl, or howrever else chance and available lengths may dictate their spacing.
So here we are with a bench, a scarfing jig, some clamps, glue, and a pile of 18-and 20-foot spruce planks—2 by 6, which actually measure about 1 Vt by 5lA inches. We need a mast for a moderately powerful jib-headed cutter, which we'll sail in the track of the Spray to the Straits of Magellan. Nothing special, but it's to be as light as we dare make it. It must be strong enough to take a hundred knockdowns in a row with the spreaders in the water, and never the slightest doubt that it can take another hundred without a worry in the world. It must, of
course, be able (with once-a-year maintenance) to cope with the tropical sun and northern winters through the next 30 years. Nothing very special, as you can see—no controlled bending, or internal halyards, or engine exhaust up the hollow. Since time is not of the essence, we can afford to spend all of six days on this job. (Let's pray for cool and cloudy weather for gluing, hot and dry for the cure.) We'll make it round, for the natural look, and because we might decide to switch to a gaff-headed rig at the last moment. We'll need to scarf an 18-foot piece to a 20-foot one to make, comfortably, the 35-foot overall length of each stave, with some left over to trim back on the butt end of the finished spar. We'll do all the tapering in the upper section of each stave, before gluing the scarfs. And when wre clamp these scarfs together, with slippery glue on both faces, we'll be agonizingly aware of their desire to skid lengthwise and out of line when the clamps are tightened. So we'll squeeze them between perfectly straight cauls, a foot longer
Was this article helpful?
If you're wanting to learn about boating. Then this may be the most important letter you'll ever read! You Are Going To Get An In-Depth Look At One Of The Most Remarkable Boating Guides There Is Available On The Market Today. It doesn't matter if you are just for the first time looking into going boating, this boating guide will get you on the right track to a fun filled experience.