Sides sides

(Plane off all corners to obtain 32 sides.)

figure 18-3a

Marking gauge for lining 8 and 16 sides on a tapered spar stave

The next move is to mark for the cuts that will make this stick 8- and then 16-sided. Figure 18-2 shows the process clearly: You draw a circle the exact diameter of your square stick (preferably on the side of the stick itself), and confine it with lines tangent to it and square across the timber. Then mark tangents at 45 degrees, to intersect those 90-degree tangents, as shown in the drawing. The final operation in this exercise is to draw yet another tangent, this time at 67 !/2 degrees, to locate the line for the 16-side cuts. If, now, you repeat this entire process at convenient intervals along your tapering spar, you will have a series of points to be joined by batten-faired lines, which you will duplicate on each side of the other three sides of the stick. Cut off the four big corners to make the stick 8-sided, with a powrer saw, drawknife, or hand plane, whichever best suits the size of the job. Freshen the marks and cut the 16 flats on it, then 32 (by eye, this time)—and it's ready for final finishing, which will be done with the aid of an inside-out power-driven sander belt, to be described later.

In the meantime, let's make a simple tool that will do automatically all the marking de scribed in the above paragraph. Figure 18-3 shows it all, better than I can describe it: the notched board, with an opening slightly larger than the greatest diameter of the spar-to-be; the beveled ends of the notch, to maintain a center-line bearing against the side of the square timber; finally, the sharpened markers, threaded through the board's backbone. The only tricky bit is to get these markers located at exactly the right spots. If you are a lot smarter than I am, you can do this spacing by percentages. As for me, I lay the tool across that circle, with beveled ends snug against the sides of the timber, and note where the 8-side and 16-side lines cross the centerline of the underside of the board's backbone. Drill for the markers, which may well be Vi6-inch screws, ground to a point and threaded through a V'32-inch hole. If the scratches they make are too dim, run a soft pencil along the groove afterwards.

As for the wonderful finishing tool: a rubber-covered drum (Figure 18-4), spun by a slow-speed electric drill, nestles in the bight of a sander belt that has been hung, inside out, over the 32-sided spar. Hang the spar up evebrow-high. Start the drill, walk the length of the spar, turn it over, and do the other half; go over it once again with a fine-grit belt. Don't expect this marvelous machine to correct gross inequalities. Remember always that this tool is but a poor thing to save some labor. It can't do your thinking for you.

So what more do we need to say about solid, one-piece spars? Mostly praise. They made possible the exploration of the world and all overseas commerce for a thousand years, and for lack of them, empires tottered. But that perfect tree is not always easy to come by, nor even a sawn timber of the right size and quality. And the solid mast is heavier than it needs to be, and it will develop checks. So

The hollow spar

We discovered good glue back in the 1930s and very quickly learned that it's easy, quick, and (usually) less expensive to build a mast out of several small pieces. No more need to agonize over imperfections in the one big piece, no need to pickle it in the salt pond, or dry it for a year before it's fit to use. In the 1930s, the jib-headed rig was fast displacing the gaff-headers, permitting (and requiring) the more elaborate staying after the style of Marconi's radio masts. The four-board, box-section mast suddenly became beautiful. The great breakthrough had come.

Plank or plywood gauge is laid on the spar stave at its greatest girth. Gaps are made equal on both sides.

Intersections of flats are ticked upon the gauge.

Boxed circle drawn on the stave

Centers squared from bottom to top

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