Seaworthy Magazine: Inspecting Your Boat's Mast and Rigging
Surveying Your Rig:
What to Look For and WhyWhenever a mast tumbles overboard, the two seemingly obvious offenders are the mast itself—the aluminum extrusion—and the wire stays and shrouds that support the mast. In practice however, these are rarely the culprits. The offenders, in most cases, are the tangs, turnbuckles, and chainplates and the smaller, but no less significant, screws, bolts, terminal fittings, clevis and cotter pins that hold everything together. These can be inspected in a couple hours or less. All you need for an inspection is a magnifying lens, a mirror, some toilet paper, your fingernails, a boatswain’s chair, and a pair of reasonably good eyes. Click here to download the Rigging Checklist in PDF format.
FittingsWhenever you inspect a fitting, look for obvious problems like rust and distortion and use the magnifying glass to find smaller cracks. Rust, especially rust that you can feel, and even slight distortions or cracks should be considered serious, and the component replaced. Use your fingernails to feel for cracks and check the thinnest part of the fittings extra carefully, as this is where failure is most likely to occur. If a fitting has been painted (a bad idea), strip off the paint.
ChainplatesTurnbuckles and chainplates must be angled so that loads are in a direct line with stays and shrouds. Toggles, which act like universal joints to allow movement in all directions, should be used with turnbuckles but they cannot be relied on to compensate for a misaligned chainplate. A chainplate that is not aligned has a tendency to work until it eventually breaks. Besides eyeballing the shroud/chainplate alignment, misalignment is sometimes indicated by damage to the surrounding gelcoat.
If chainplates are bolted to a bulkhead, as is often the case, inspect the bulkhead for signs of weakness—discoloration, delamination, and rot. Chainplates are highly stressed, and will work and cause leaks where they come through the deck. Water can then enter the bulkhead and eventually cause it to rot (see Anatomy of a Dismasting). Probably the best, although maybe not the prettiest, place to secure a chainplate is to the outside of the hull. Chainplates that are only bolted to flanges under the deck, and are not secured to a structural member down below, are the least desirable installation.
TurnbucklesOpen turnbuckles are easier to inspect and don't retain moisture, which encourages corrosion. Closed turnbuckles retain moisture in the barrel and have of a tendency to freeze up, but they also are better at retaining lubricant.
Turnbuckles should be wiped clean and lubricated at least once a year; more often if they are open or are adjusted frequently.
Teflon is better for lubricating turnbuckles than oil or grease because it doesn't hold grit that abrades the threads. Oil or grease, however, are certainly better than nothing.
Most turnbuckles are tightened by turning the shank or barrel clockwise. Incidentally, you should never stress your rig by over-tightening the turnbuckles. If the turnbuckle squeaks stop tightening—this is a sign of over-tightening and poor lubrication.
If you boat has open turnbuckles, be sure to leave at least 3/4" of thread visible in the barrel and replace the old cotter pins. A cotter pin should be large enough to fit snugly into the hole and long enough to be bent half way back around. Rigging tape should then be wrapped around the pin to protect your sails, fingers, toes, etc.
Many closed turnbuckles can't be cottered and rely instead on locknuts. Experts warn that over-tightening the locknuts places too much stress on the threads.
Terminal FittingsMost sailboats rely on swage fittings at the terminals, but these fittings are not necessarily the most reliable, especially in warmer climates where they have a history of failure. Swage fittings are made by compressing a tube onto the wire under great pressure, a process that must be done exactly right to assure a strong bond. If the swage has to be pressed several times (a bad practice) before the wire is secure, there is an increased chance that the swage has been weakened and could crack.
There are other types of terminal fittings, such as Noresman and Sta-Lok, which are more expensive and less common than swage fittings but are highly touted by many sailors for their durability. Norseman and Sta-Lok fittings can be installed or repaired by the boat owner—an obvious advantage, especially for making emergency repairs on long cruises.
Careful inspection of all terminal fittings is a must. Cracks are usually microscopic when they begin, so use your magnifying glass. Also, you can sometimes feel a crack with a fingernail that cannot be seen.
Cleaning the fitting with metal polish helps brighten the fitting to make inspection easier and using one of the three-part spray products on the market also helps you see cracks. The latter are highly touted by their manufacturers but they are not infallible. The first part cleans the fitting; the second part is a dye that penetrates the crack; and the third part is a developer. The dye, incidentally, can stain gelcoat, so be careful.
Terminal fittings, especially swage fittings at the deck, are prone to rust where the wire enters the swage. Rust indicates a serious problem and the swage and possibly the wire should be replaced. Some skippers like to use gel or wax to prevent water from entering the swage. While this may be effective for a while, it probably won't keep water out for long and could very well trap water inside, encouraging corrosion.
The Mast and Boom:
Welds and RivetsAluminum welds on the mast and boom should be inspected, especially where there may be a lot of stress. Look at the ends of the welds first, as aluminum welds fail from the ends of the weld inward. Welds that are not done correctly have sharp edges and crevices which encourage corrosion. Any welds that are cracked or badly rusted should be rewelded immediately.
Rivets should be examined, and any that are loose or missing should be drilled out and replaced with the next-larger size. Also, if one or two rivets holding a cleat or gooseneck are loose, it is a good idea to replace all of the rivets with the next-larger size, not just the ones that are missing.
Galvanic CorrosionGalvanic corrosion occurs when stainless steel or bronze fittings—cleats, tangs, winches—are installed metal-to-metal on an aluminum mast.
Every few years, mast fittings should be rebedded with zinc chromate paste, polysulfide, teflon, nylon, or tufnol (plastic) to protect the mast from galvanic corrosion. Silicone does a good job of protecting the mast, but the fittings may be difficult to get off later. And in a pinch, Rolf Bjelke aboard the steel ketch Northern Light in the Antarctic, used a plastic coffee can lid to bed a halyard winch.
If a mast is painted, look for bubbles near fittings, which indicate corrosion. On an unpainted mast, look for white powder and pockmarks around fittings. Some powder, which is oxidized aluminum, is normal on an aluminum mast and is usually not significant. But heavy concentrations of powder, bubbles and/or pockmarks, especially deep pockmarks, indicates a serious problem that threatens the integrity of the rig. Contact a rigger or surveyor if you suspect a problem.
MaststepsWhether it is stepped on deck or on the keel, the base of a mast—a maststep—should be the same material as the mast. Because water that is outside the boat usually finds its way into the bilge, a mast that is stepped on the keel is especially prone to corrosion when the boat is used in saltwater. A rigger in Maryland likes to tell the story about an owner who complained that the stays and shrouds that couldn’t be tightened. He thought they had stretched. It turns out that the maststep had corroded so badly that the mast was "sinking" into the bilge.
A mast that is stepped on deck can cause problems if the load isn't supported properly down below. This is sometimes a design problem, but most often it is because a bulkhead or support stanchion has failed—shifted, rotted, delaminated, etc. Look down below for indications of movement, including jammed doors, broken bonds, and splitting wood. A sagging cabin top is a strong indication that adequate support isn't being provided.
Besides corrosion, maststeps can be damaged when the mast is cocked to one side and the heavy compression load is not evenly distributed. Indications of uneven compression load include cracking and/or crushing of the mast's base. The problem can be avoided by keeping your rig tuned—adjusting the stays and shrouds to make the mast straight. If the base of the mast has already been damaged, don't despair, it can either be cut down slightly and restepped or, if the problem is more serious, the damaged portion can be cut down and an extrusion added. Either way, the boat should not be sailed until a rigger is contacted and the problem has been corrected.
Wood MastsWood masts have a lot of eye appeal but require more upkeep than aluminum masts. Wood masts are usually made of spruce, a material that is light and flexible, but prone to rot.
Rot is easier to detect when a mast is varnished. Painted masts hide rot, but only for awhile. Any areas that are badly discolored on a varnished mast, or won't hold paint on a painted mast, are suspect and should be sounded with a hammer for indications of soft wood. Rot is most likely to appear around fittings, the masthead, mastboot, spreaders, and especially at the maststep. These areas should be inspected twice a season and treated or caulked as necessary. Weep holes, used to drain water at the base of a box mast, can become plugged with debris, leaving water to fester inside the mast. Weep holes should be checked periodically with a coat hanger to prevent blockage.
Inspecting AloftMost people have a natural aversion to hanging from a rope at the top of a swaying mast. If possible, inspect your mast while it is unstepped. If you do go aloft, make sure there are experienced hands below to hoist you up. A snap shackle, if one is used on the halyard, can be made safer by taping the lanyard to prevent its accidentally opening. Also, if the boat is in the water, you'll want to moor it where it won't get tossed around by a passing boat wake.
Take tools: screwdrivers, pliers, a small hammer, lubricant, the mirror, extra cotter pins, and rigging tape. Put them all in a tool pouch or boatswain’s chair with tool pockets and Velcro flaps. Whenever possible, use lanyards on the tools. The only thing worse than making the crew haul you up and down the mast getting tools you forgot is to drop a tool on someone's head. (You can also help the grinder's morale by using your feet and hands to help hoist yourself up.)
First stop is the spreaders. (While you're working, have the tailer cleat-off the halyard.) Make sure the ends of the spreaders bisect the shrouds at equal angles and are secured properly to prevent slipping. Skewed spreaders have been responsible for many dismastings. Tape or spreader boots, used on the spreader ends to prevent damage to the sails, should be removed temporarily so that the spreader ends can be inspected and the connection tightened as necessary.
Some skippers paint the top of the spreaders, even aluminum spreaders, to reduce damage from sunlight. This is a necessity with wooden spreaders, unless you go aloft every month and add a coat of varnish. Remember, you can't see the tops of the spreaders from down below.
Like their counterparts the chainplates, fork tangs, used to secure the shrouds to the mast, should be angled so that loads are in a direct line with stays and shrouds. Cotter pins should be taped so that they don't shred flailing sails or snag a halyard. Shrouds that use "T" terminals should be examined for stress cracks where the bend occurs and for elongation of the slot. Either problem indicates the shroud or fitting should be replaced.
The last stop, before you begin your descent, is the masthead. If you are even slightly acrophobic, the masthead can be a very scary place. Avoid looking down.
The mirror (remember the mirror?) is especially useful for inspecting fittings at the masthead that would otherwise be inaccessible. Look at the halyard fittings, especially the sheaves, which wear over time and can be crushed or split by the strain of the genoa. Even if it's healthy, a squirt of two of lubricant can help whenever the sail is raised. Wind indicators and radio antennas should also be checked for loose mounts and connections.
On the way down check the rivets and/or screws used to secure the mast track. Replace any that are missing or suspect. While you're at it, you may as well lubricate the track (use teflon) to make raising and lowering the sail less of a chore.
Standing Rigging: Stays and Shrouds
Wire should be inspected for broken strands or "fishhooks" by wrapping some toilet paper around the wire and running it up and down. If the paper shreds, the wire is nearing the end of its useful life and should be replaced. Check the wire where it enters the swage fittings for rust, which also indicates weakened wires that should be replaced.
Replace Your Standings Rigging: $$$?Lets play "what if". What if a small voice inside you says your rig is living on borrowed time: you've found rust, cracks, failed welds, and fishhooks?
As a general cost guideline, replacing the standing rigging on a typical 30 footer with 1/4" wire rigging will cost about $1,200. That price includes turnbuckles but not unstepping the mast. The cost of replacing the standing rigging on a 40-foot cruising boat with 3/8” wire could be almost twice as much. Incidentally, it pays to get estimates, as prices can very significantly. Our estimates to replace the standing rigging on a 30-foot boat, for example, were as high as $2,800.
Professional InspectionsIf you're not confident in your ability to inspect your boat's rig, you can hire a professional—a rigger or surveyor—to do it for you. Riggers specialize in rigging, which is an advantage, but they could be biased since they also sell rigging. An inspection, including going aloft, should be under $100 for a 30' boat.
BoatUS Marine Insurance Group has 20 years experience dealing with surveyors and can provide you with a list of surveyors in your area. Call 800-283-2883 and ask for Policy Service. (Not all surveyors will survey a sailboat's rigging and many will not go aloft.)