Simple mast maintenance

From Ocean Navigator #128
March/April 2003
Voyaging sailors who frequently venture offshore invariably look up at the mast – particularly when it starts to blow – and wonder just how fit the rig is. Eventually, unstepping the mast with the plan to go over the rig becomes a yard project. The rig includes stays, shrouds, halyards, winches and electrics. How often a mast should be unstepped and the rig inspected depends on several things: amount of offshore strenuous sailing, the climate where the boat usually resides, and the age of the rig.

The author’s Tartan 34 Endeavour in the slings after being hauled in Florida. After seven years of service, they unstepped the mast and performed some basic maintenance on the rig.
   Image Credit: Dick de Grasse

Our mast was last unstepped seven years ago. At the time, the boat had the original 20-year-old rig. The rig looked fine when we unstepped the mast, but in the meantime, just to be safe, we fabricated our own rig: one shroud/stay at a time, using 9/32-inch, 1-by-19 stainless wire and Sta-Lok fittings. We finally eliminated all swage fittings except on the staysail stay. In most instances, there is nothing wrong with swage fittings. I simply like the idea of fabricating our own standing rigging and carrying spare fittings.

We replaced the lower shrouds and cap shrouds, and installed a baby (staysail) stay, all with the mast in the boat. Given our attention to the rig during the past seven years, while the mast was in the boat, we didn’t experience any problems. But since some of the electrical devices were beginning to fail – the apparent-wind indicator, VHF antenna, masthead strobe and spreader lights – it was time to do some preventive maintenance.

Unstepping the mast

Sailors soon learn that unstepping the mast is much easier and quicker than stepping it, particularly when the mast is stepped on the keelson. Once we prepared the mast, the crane took less than 15 minutes to lift it out of the boat. It took nearly and hour to step it, not including the time necessary to retune the rig. The sails were stowed below, and the boom was removed. In preparation for unstepping the mast, we loosened the shroud and stay turnbuckles, and removed the 6/32 bolts securing the turnbuckles. To prevent the turnbuckles from turning, we use 6/32 bolts and nylock nuts, rather than cotter pins. Since there are no cotter pins to catch on sails, the turnbuckles are not taped. The staysail stay was brought back at the mast. The headsail halyard, spinnaker halyard, pole-lift halyards and signal halyards were tied with a separate line around the mast. The headstay/roller furling was tied off to keep it from swinging into one of the ports as the mast was lifted out of the boat. In addition, a guideline was attached to the heel of the mast to guide it down to the sawhorses on the ground.

Two people can handle a 50-foot mast, but it is easier with a couple extra hands to help guide the mast up and out of the boat and keep the roller furling under control. The crane sling is best slid up the mast inside the lower shrouds to the spreaders. The crane should be positioned well above and slightly aft so the sling lifts from behind the mast. Most keelson-stepped masts are likely to be heel heavy with the sling under the spreaders. It’s possible deck-stepped masts could be top heavy and tip over with the sling under the spreaders. A guideline on the mast heel is essential. The backstay is guided forward and tied to the mast as the mast emerges from the partners.

Belowdecks, the wires are unplugged and trim removed. Mast wedges should be removed if possible; otherwise, they will fall out as the mast is lifted out through the partners. One hand should be belowdecks to direct the crane and guide the mast up and out of the boat. Careful attention must be paid to keep the wires from catching on the partners as the mast is lifted. Aluminum masts stepped on stainless-steel keelson plates may need some extra work to separate the two metals. It’s not unusual for an aluminum mast to be corroded to the dissimilar stainless-steel keelson plate. Our keelson plate was aluminum.

Inspection and maintenance

With the mast on the sawhorses, the heel plug should be removed and any debris cleaned out. In a tropical climate, mud wasps tend to build nests inside the mast, and muddy debris collects inside the heel.

Image Credit: Dick de Grasse

The owners did a thorough check of electrical items and replaced various elements. For example, the masthead Tri-Color/Anchor/Strobe light needed new bulbs.

With the mast on the sawhorses, it’s a good time to wash, but not scour, the aluminum mast. Most sailors decide to inspect the rig before repairing the electrics. With a magnifying glass in hand, each shroud tang, spreader tang and all wire terminal fittings are inspected carefully. Look for any cracks or unusual corrosion. Pay particularly attention to backstay insulators; failures are rare, but they can happen. Crack-detection dye can be used to supplement a magnifying glass. Run a hand up and down each stay and shroud. There should be no “meat hooks” (broken wires). A few rust streaks in the standing-rigging wire are not unusual. Inspect all halyards for worn or frayed strands. Now is the time to replace them. The boom-topping lift should be replaced or turned end for end if the line has no worn spots. The turnbuckles, turnbuckle threads, toggles and fittings should be coated with lanolin to inhibit corrosion. A Dacron topping lift is used rather than a wire topping lift grounded at the masthead, since a grounded wire topping lift running parallel with the single-sideband backstay antenna can cause radio frequency interference.

Masthead sheaves are built into the masthead casting. Sheaves should turn freely and not wobble. Sheaves will likely be grooved from wear but need not be replaced unless the groove is very deep or the sheave is wobbly. Most halyard jams result from the halyard riding off the sheave and jamming between the sheave and masthead casting. Check that the clearance between sheave and casting is too small to allow a halyard override. On most masthead castings, the pin holding the sheaves in place can be removed and the sheave replaced. Replacement sheaves can be had from a rigging supplier. The spreader boots need to be retaped with self-vulcanizing tape.

With the mast out of the boat, now is a good time to inspect the chain plates on the hull or belowdecks and reseal the deck chain-plate covers. With the mast on the sawhorses, the mast winches can be greased. The mainsail track should have no burrs or exposed rivets, and the sliders should move freely.

Stepping the mast

This is the time to install a new mast boot. Guidelines are attached to the mast above the partners and to the headstay/roller furling to prevent it from smashing into the boat. If none of the standing rigging has been re-led, it should all fall in place as the mast is raised above the deck. The belowdecks helper should order the crane and guide the mast through the deck partners onto the step. It’s not unusual to make several attempts to step the mast on the keelson plate. With the mast upright in the boat and the sling in place, reattach the standing rigging. Headstay first, then backstay, followed by shrouds. With the standing rigging loosely attached and toggle clevis pins in place, the sling can be removed and the rig tuned. To replace the forward mast wedge, the mast will likely have to be moved aft in the partners, using a winch line looped around the mast just above the partners. With the forward mast wedge in place, releasing the winch line will move the mast forward enough to allow placement of the aft and side wedges.

Tuning the rig takes an hour or so. Follow the manufacturer’s rig-tension guidelines, if available. The turnbuckles will likely have marks on the threads where they were previously adjusted. The lower shrouds are adjusted first and are tensioned using the main halyard as a ruler. The distance from masthead to port and starboard shroud toggles should be within 1/8 inch. Sight up the mast track; it should be straight. The shrouds should be tight – not harp-string tight but enough so that when a shroud is pushed out at shoulder height, it flexes an inch or so. The cap (upper) shrouds are adjusted using the previous turnbuckle settings, the main halyard ruler and sighting up the mast track. Riggers likely have a more precise means of tensioning standing rigging. One inch or so of flex at shoulder height seems to work well.

The backstay turnbuckle is tensioned to the previous setting. Generally, this results in a slight rake in the mast as recommended by the manufacturer. There should be no sag in the roller-furling headstay; otherwise, the furling gear will not work smoothly. The headstays on many boats are not adjustable. The backstay turnbuckle is used to tension the rig fore and aft, rake the mast and take the sag out of the roller-furling headstay. Once the rig is tuned, the turnbuckles can be pinned with cotter pins or 6/32 bolts and nylock nuts.

Dick de Grasse and first mate Kathy live on Islesboro, Maine, when not voyaging on their sloop Endeavour. He is a former member of the Coast Guard and holds a USCG masters license.


By Ocean Navigator