Posted by Darrell Nicholson at 12:00AM - Comments: (6)
As we tune the shrouds and stays for another summer of sailing, I’m reminded of how easy it is to overlook the warning signs of an impending rig failure. Fishing around in the wayback machine, I found the below gem on inspecting your mast, rigging, chainplates, and turnbuckles. It's as pertinent today as it was then, back in the black-and-white, courier-font days.
How frequently do you bother removing spreader boots and taping to check the condition of the spreaders and rigging? No matter how well the spreader ends are protected, and whether you use ready-made vinyl spreader boots or conventional rigging tape, water will get through to the fittings inside. On a boat used in saltwater, the atmosphere's corrosive nature can cause rapid disintegration of aluminum fittings (nevermind the fact that the spreaders might be 25 feet or more off the water). The thorough taping job you did on the spreader ends may actually accelerate the problem by holding in water.
The problem can be just as bad on a boat with wooden spreaders. Wooden spreaders are usually spruce, a wood with very low resistance to rot. Water trapped by spreader boots, or taping at the inboard ends of the spreaders at the mast fittings, can rot a spruce spreader in a single season. Keeping wood spreaders varnished can help, but it is no guarantee of protection. Wooden spreaders are almost always fitted with metal ends, both at the mast and at the spreader’s outboard end. If these fittings were not thoroughly bedded with compound when the spreader was assembled, all the varnish in the world won’t keep water out of the joint between the spreader and the metal end fitting.
And water sitting in this joint will eventually cause the spreader to rot. If the boat is decommissioned some time during the year, that’s the time to make a careful inspection of the rig and rigging. Every component must be gone over thoroughly.
First, check the mast tube for problems. Do the masthead sheaves turn freely? Are the edges of the sheaves worn, so that a halyard might jump the sheave and wedge itself between the sheave and its box? Is the mast dimpled, or bent? Worn sheaves should be replaced.
Stainless-steel wire tends to chew aluminum sheaves over time, particularly those used for spinnaker halyards. Sheaves that show only slight wear or burrs should be dressed smooth with a file. There should be no sideways play in halyard sheaves. Space between the sheave and the sheave box can be eliminated with micarta shims, which will also help prevent the sheaves from seizing. Seized shims can usually be freed with liberal applications of a solvent and heat applied with a propane torch. Finding a replacement sheave for an older boat like John Foster's Nonsuch 22 can open up a can of worms.
Physical damage to the mast tube in the form of dimpling, wrinkling, or bending requires professional analysis by a sparmaker. This type of damage rarely happens when the mast is in the boat. It is more likely to result from a shipping accident, or from stepping or unstepping the mast. A mast can become permanently bent through improper blocking during storage, however. Look for grooves in the mast extrusion where internal halyards exit the mast. Check the mast heel for corrosion. Corrosion at the heel of the mast is probably the most common problem with keel-stepped aluminum spars. The cure is to keep the area of the mast step in the bilge bone dry, and provide drain holes in the mast heel and mast step.
Deck-stepped spars are not immune to heel corrosion, and also require drain holes in both the heel and the step. Examine all mast fittings, winches, and cleats for signs of corrosion between the fitting and the mast. Unless the fittings are bedded, there’s a good chance of serious pitting here. The first clue is likely to be a powdery white deposit around the edge of the fitting. All fittings on the mast should be bedded in an elastometric marine sealant that will galvanically isolate the hardware, as well as protect damaged finish. (Rigger’s preferences for this job range from 3M’s 101 polysulfide to 3M UV4000 or Sikaflex 291—the latter two have the advantage of faster curing. See our article on marine sealants for more on this topic.) Other options include using either zinc chromate paste or plastic shims—neither of which have adhesive properties but do isolate the dissimilar metals. Check all the rigging tangs on the mast. Look particularly for elongated clevis pinholes or cracks radiating from clevis pin holes or points of attachment to the mast tube.
Any damage to tangs is unacceptable. Elongation or cracking means the metal of the tang is too thin for the load, or there is simply not enough metal between the clevis hole and the edges or end of the fitting. Brownish discoloration on tangs should be polished out using a stainless steel cleaner or buffing pad to make examination easier. Don’t use sandpaper or a harsh abrasive. You may destroy the surface polish of the stainless steel, which is its major source of discoloration protection. Badly discolored wire or fittings should probably be discarded. Any wire having a sharp kink in it should be replaced. Any swage fitting that is cracked should be replaced, although the lack of cracking is not necessarily an indication of health.
Stress corrosion cracking can be a serious problem with stainless steels on boats kept in salt water and warm climates. The greatest danger from stress corrosion is that a stressed fitting usually appears to be in perfect condition prior to failure. Many mysterious rigging failures are no doubt due to this little known and often misunderstood problem. There is evidence, however, that keeping rigging clean and polished with a product containing lanolin or silicone can decrease the possibility of a failure due to stress corrosion cracking.
Carefully examine each strand of rigging wire, including terminals, toggles, turnbuckles, clevis and cotter pins. Every season, a very expensive rig goes by the boards because a bolt is “temporarily” inserted in place of a missing clevis pin.
Any swage fittings having a “banana shank,” a curved shank that results from passing the fitting through the swaging machine without using the proper guide, should be replaced. Likewise, retire any cracked or bent turnbuckles or toggles. Seized turnbuckles should be freed using a penetrating oil such as WD-40, and heat from a propane torch. Brute force is almost guaranteed to ruin turnbuckles with screws under 3/8-inch.
Untape and examine inboard and outboard ends of spreaders. Check leading and trailing edges of spreaders carefully, particularly if the spreaders are airfoil-shaped, welded aluminum sections. Wire halyards can wear through them very quickly.
Halyards should be carefully examined. Wire halyards, in particular, should be checked for meathooks. Running the halyard through your palm is an accurate, but sometimes painful way to detect meathooks. A better way to find burrs and broken strands is to rub over the shrouds and halyards with a piece of cheese cloth or an old nylon stocking. This method, however, is not a substitute for a careful visual examination.
The most likely places for meat hooks to develop are wherever the halyard changes direction over a sheave. As a rule, any halyard with more than one broken strand per 10 feet of length should be replaced. A halyard with a broken strand where the halyard wraps around a thimble should be shortened or replaced.
Check wire-to-rope splices for fraying. If the splice spends much of its life wrapped around a winch drum, the part of the wire inside the cover of the rope can chafe through the rope’s cover. Chafe is also the enemy of all rope halyards, whether they are polyester, or more exotic materials like Spectra to Vectran. If you have switched from polyester halyards to one of these materials, you may also have to change sheaves. Halyard sheaves scored for both wire and rope are unsuitable for use with some other types of halyards.
Key wear spots for rope halyards are at the headboard shackle, over sheaves, and where the halyard is held by cam cleats or line stoppers. Rope halyards should be ordered overlength to allow yearly shortening to remove the work sections at the top of the mast. This advice applies only to rope materials and braids that are easily re-spliced after moderate use, or those ropes that happily take a knot. Remember knotting will reduce strength significantly, so know your loads, the strength reduction a knot will impart, inspect frequently, and use common sense. Splices are preferable; but a halyard hitch (or some variation) serves fine on smaller vessels. On these boats typical halyard diameters offer a large safety margin, even when you take into account the strength reduction introduced by a knot. On larger vessels the safety margins in halyards are achieved through high-strength, low-stretch fibers and braids that may not lend themselves to knotting or re-splicing. For a guide to halyards materials and breaking strengths see Practical Sailor’s Guide to Choosing Cost-Efficient Halyard Materials.
Although re-splicing old rope is difficult, it is not impossible. Rigger Brion Toss gives the following advice for sending in old rope for splicing:
"We prefer not to splice used rope, so if we agree to work on your used rope - we will ask you to first wash it with soap flakes. Put the coiled gasket of rope (see instructions in the Rigger's Apprentice) in the washing machine on gentle cycle. rinse well, and add fabric softener. Then undo the coil and loop it around the garage to dry in the air or take it outside and do the same. Now your rope will be soft and much nicer to handle."
We also described the best way to clean rope in June 2011.
Halyard shackles also deserve close attention, as I explored in my blog on “The Case of the Broken Snap Shackle.”
Another surprising trouble spot on the average keel-stepped aluminum mast is the mast boot. Water lying between the rubber mast boot and the mast tube can cause severe corrosion of the aluminum tube on boats used in salt water. This is particularly common in mast boots secured with stainless-steel hose clamps, and corrosion can occur even when no water reaches the interior of the boat. At least once a year, loosen the mast boot. Bedding the boot to the mast will alleviate but not necessarily completely prevent this type of damage. The area under the mast boot is probably second only to the mast heel as a potential trouble spot.
A once a year top-to-bottom inspection of the rig is a simple way to prevent minor problems from becoming major. With the exception of structurally marginal racing masts, most rig losses are caused by component failures that are largely detectable before problems occur.
While it is far easier to examine the rig with it removed from the boat, the same inspection can be conducted, less quickly and comfortably, from the bosun’s chair. Your time and effort will most certainly be rewarded, and if you’re lucky you’ll also enjoy the view.