Page 155 - The Complete Rigger’s Apprentice

really, really short spreaders for that proverbial To solve, use the prescriptive diagram detailed
close sheeting angle, but they can end up with mast under “Slings and Compression,” earlier in the
compression and rig tension loads even higher than chapter. This matches spreader and wire strength,
what they’d get with a single set of moderate-length with the assumption that wire strength has been cal-
spreaders. culated previously to match the loads the hull and
As an exercise, let’s find the load on the upper sails will impose (see below).
spreaders in Figure 5-13. They’re 2 feet 3 inches As you can see, once you start playing with
(0.69 m) long, and the upper shroud is ⁄32-inch angles, you start playing with a lot of other things,
7
(6 mm) 1 x 19 stainless with a rated strength of too. And all must interrelate, or none will. Where,
6,300 pounds (2,864 kg). The angle of shroud to then, do you start? What factors do you consider
mast is 11 degrees. first? In sailing vessels rig forces relate directly to the
stability characteristics of the hull, but as we’ll see
The 29-foot 6-inch Lyle Hess cutter Syrinx. in a subsequent chapter, hull characteristics can be
largely determined by the design of the rig. Design
is a matter of gestalt, arrived at by attentiveness to
the interplay of forces. So the double-spreader rig
in Figure 5-13 isn’t just something to stick on a hull
to make it look “modern” (although that has, sadly,
happened more than once). Rather, it’s a reflection
of system awareness.

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