Page 313 - The Complete Rigger’s Apprentice

from a combination of sources, including salt, heat, Choosing a Foundry
loading, and from internal, literally built-in stresses
like bad tempering or uneven cold-working. Have bronze castings done by a foundry specializ-
Sometimes the cracks are vertical, or radiate ing in bronze; they’ll know which type of bronze is
out from a single point. These are usually caused by best suited to your application, and will be pickier
about ingredients and proportions than a gener-
simple overloading. Vertical cracks on swages are a al-purpose foundry.
common example of this; wire rope inside the swage
expands with corrosion from moisture, pressing out-
wards on the walls of the swage until it cracks. Some Minimizing Halyard Fatigue
sailors try to prevent this problem by pouring oil or
hot wax down their lower swages. It doesn’t seem to To avoid accelerated wire fatigue, never let a
make any difference, since water will migrate past splice, Nicopress sleeve, or other terminal get
anything but an adhesive put in under pressure, as within two inches of a sheave or fairlead.
one gets with Sta-Lok-type terminals. But at least
the attempt at pouring something in makes more Rigs with swaged terminals are among the most
sense than another fix I’ve seen: tightening a hose susceptible to failures; frequent inspections are nec-
clamp around a cracked swage, to hold it together. essary to ensure their integrity. If the strands of a
Obviously it pays to invest in high-quality stain- wire rope do not lead fairly into a swaged termi-
less and to make it plenty heavy, to delay the onset nal; if there is evidence of corrosion, especially at
of fatigue. Bronze is nearly impervious to fatigue, the top of the terminal; or if the terminal is cracked
which is why it is so often used in toggles, turnbuck- or warped, no matter how slightly, it is of uncertain
les, tangs, and chainplates. Galvanized steel is like- integrity and should be replaced at once. Swages
wise relatively fatigue-resistant, so if you can keep it are the overwhelmingly favorite choice for sailboat
from rusting, it will outlast stainless. the size of the terminals because of their low cost, neat, compact
stainless wire, but this will also involve increasing appearance, and high initial tensile strength. But
the sheave size. Can of worms. they are not to be trusted.
When rigging wire fatigues, its strands will begin When swages fatigue, they’ll crack, too. Again,
breaking. Note that a single broken yarn in 1 x 19 this can also be caused by internal corrosion—the
wire reduces strength by more than 5 percent. Wires corroded wire expands, trying to split the swage
will usually break first at the lower ends of standing apart (Figure 7-28). Cracked swages can survive for
rigging, where corrosion and fatigue work together. years or days. Replace any wire that has a cracked
But check both ends and all the wire between, just swage on it immediately, unless you enjoy that sort
in case. Fatigue can be reduced by increasing wire of gamble. A horizontal crack is always more dan-
size, but again this is not always practicable, espe- gerous than a vertical one. Use a magnifying glass
cially for racers, as it increases weight aloft. It’s usu- or dye penetrant to spot fine cracks. Check the eye
ally better to use an appropriately sized wire (see as well as the barrel of the fitting. Some swages are
“Selecting Wire,” Chapter 5) and to employ other made by a rotary swager, which hammers the fitting
fatigue-reducing strategies. The easiest one is the rapidly from all angles, making a smooth-finished
addition of toggles. Put one at either end of each surface. If you see a lengthwise ridge on the barrel of
turnbuckle or buy turnbuckles with built-in toggles. the swage, it was formed by passing it between the
Add another toggle at the wire’s upper end, particu- dies of a Kearney swager. Kearney swages are far
larly on stays with sails hanked to them, as these are more likely to crack, and frequently end up with a
most heavily worked. And keep your rigging snugly disquieting banana shape. Don’t use them.
tuned so that sailing motions won’t cause your mast Hayn and Sta-Lok fittings are the best mechan-
to bang around, shock-loading your wires. ical terminals—right up there with splices in terms

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