Sailboat masts and rigging

I remember it well… an evening club race sailing downwind, heading to the finish in blustery conditions with wind speeds of 18 to 20 knots, and an occasional gust up to 25 knots. The following seas were 4' to 5' high and did not significantly affect the control or handling of our vessel. Our main competitor (read arch enemy) and friends were ahead and leading our class by 10 – 12 boat lengths after turning the upwind mark. After rounding the mark ourselves, we immediately raised the heavy spinnaker, dropped the genoa and got the spinnaker trimmed, when we noticed that our competitors ahead of us had not yet set their spinnaker. Knowing that they may have been a bit intimidated by the wind and wave conditions, we were pleased to see that we were closing the distance between us quickly when all of a sudden, one of our crew members yelled, “They just set their chute.” The next minute, the same crew member yelled, “They just lost their chute, and their mast.” As we went flying by them, we saw that the mast had broken just above the deck, with the top section of the mast hanging over the side of the boat in the bow. After making sure there were no injuries aboard their boat, we continued on to finish the race, first place in our class.

When we approached our dock, we saw our competitor had already secured their vessel in their slip – however, the top section of the mast was no longer aboard their vessel. After securing our vessel in its slip, we walked over to our competitor’s boat and were advised that they had cut the mast, rigging and attached mainsail from the boat, and had let it sink to prevent the mast from damaging and or sinking their vessel. They had marked the location of the mast and thought they could easily retrieve it from the lake bottom at a later date.

I then learned from the owner of the boat that he thought the backstay had failed, as after raising and filling the spinnaker, the mast had slowly fallen forward and to one side of the boat before breaking just above the deck. As most of the mast rigging had been cut away from the boat following the mast collapse, there was no evidence left aboard to dispute his theory that the backstay had somehow failed and caused the mast to collapse.

After handling and investigating marine related insurance claims for the past 20+ years, rarely have I seen a failure of the wire or rod rigging itself. Most often, the rigging failure is caused at rigging terminals, fittings, chainplates or other fittings. Unfortunately, my competitor was unable to locate and retrieve his sunken mast and he was unable to prove the exact cause of the failure.

Following this mast failure incident, I wondered if the failure could have been prevented by a visual inspection of the mast and rigging components. Here in the Great Lakes area of the country, we have a limited boating season. Most sailboats are hauled out of the water and are stored ashore for the winter months and at least half of those sailboats have their masts unstepped. With the mast removed from the vessel, we have the perfect opportunity to inspect our masts, rigging and all fittings to perform any maintenance related tasks.

When inspecting the mast, I first check the mast step mounted on the deck or at the top of the keel. The two common types of mast steps are the welded collar type that encircle the outer circumference of the mast and a step with internal structures (cross plates) that sit inside the mast as shown.

I prefer the collar type step as it captures the butt of the mast. However, it also captures moisture if good drainage is not provided. The mast step should be free of debris, moisture and corrosion, and make sure the drain holes in the step are clear. As the common mast and mast step materials are dissimilar metals (aluminum and stainless steel) and are not completely compatible, if they are kept dry there is seldom a problem of corrosion in fresh water. I then check the mast butt for any evidence of corrosion or deformation that could lead to problems. The corrosion can be hidden on the inside of the mast tube and appears as a lifting of the coating on painted spars or a powdering, pitting or bubbling of the surface of the tube on anodized or bare mast tubes. If minor corrosion is found on a painted mast, sand and touch up the painted finish. If minor corrosion is found on a bare or anodized mast, clean the affected area and apply a coat of zinc chromate to seal and protect the surface.

Working along the length of the mast from the butt to the top, next inspect the mast collar, wedges and boot. Water leaks are common in this area and you should check the mast collar bolts as loads upon the mast are transmitted to the collar bolts causing leaks. When installed, the mast wedges should be secure to prevent the mast from contact with the collar. Hard rubber gaskets or cut rubber wedges work best for this application. The mast boot should be free of holes and should fit securely against the mast at the top and bottom of the boot. Canvas covers with shock cord at the top and bottom work well, as do sections of rubber inner tubes secured by large hose clamps at the top and bottom of the boot.

There are several problem areas above the deck that should be inspected. These include corrosion of fittings and fasteners, terminal ends of rigging, evidence of cracking or bending of the mast tube, wear on halyards and halyard sheaves at the masthead. Inspect the gooseneck where the boom attaches to the mast for wear and signs of movement or cracking. Check all externally mounted hardware, such as cleats, stoppers, spinnaker pole tracks, mainsail tracks, winches, etc., to make sure they are securely fastened and free of any sharp edges that could cut or tear halyards or sails. Make sure the spreader bases are secured, and spreader tips are covered to protect sails from chafe. The masthead should then be checked for evidence of wear, stress cracking or elongation of holes at mounted brackets. Sheave boxes should be checked for fair leads of the halyards, edges rounded to prevent chafing of the halyard, and make sure the sheaves turn freely and are not worn. Then check all lights and electronics mounted to the mast for chafe and proper operation, and clean electrical connectors.

I then inspect the standing rigging from end to end, paying particular attention to the terminations for cracks and bends or kinks in rod, or broken or damaged strands in wire rigging. Swaged terminals, where the end fitting is bent under pressure to cold flow around and grip the wire, and mechanically attached end fittings, where a conical shaped wedge is inserted in the center of the wire and an external body covers the end of the wire, are the common termination ends for wire rigging. Discontinuous rod rigging utilizes a cold headed head or end to secure the rod to the termination fitting. Most termination failures are a result of stress corrosion and resultant cracking of the fitting that can be seen on the exterior surface of the fitting. Corrosion and cracking is caused by moisture between the wire and/or rod and the termination fitting as shown in the photograph.

When stress corrosion causes the fitting to crack, it is necessary for the fitting to be replaced to prevent a failure of the rigging. All turnbuckles at the deck should operate freely and should be lubricated to prevent corrosion. All locking pins should be installed and covered to prevent chafing of sails and trimming sheets. If you have any doubts about the condition and reliability of the mast or any of the mast components, a professional rigger should be consulted.

After your full and thorough inspection of the mast step, mast, rigging and fittings is completed, you will want to install and tune your mast. You need to make sure that the top of the mast is centered in the boat side to side. This can be accomplished on a standard in-line spreader designed mast by raising a metal tape measure to the top of the mast utilizing the mainsail halyard and measuring the distance to the vessel’s toe rail or similar fitting adjacent to the mast on each side of the boat. After adjusting the upper or main side stays to get equal distance readings on each side, you know the mast is now centered. By tightening each turnbuckle at the side stays equally, tension the rig so there is no play or movement in the rigging. All sailboats like to have a little weather helm. To achieve this, the mast must be raked aft or bent aft at the top of the mast. By adjusting the headstay and backstay, you will be able to bend the mast to achieve weather helm. If you experience too much weather helm, (boat continually wants to round up into the wind and requires excessive steering force to stay on course upwind), decrease the bend. If there is no weather helm, increase the mast bend while keeping the rig taut with no slack.

Hopefully these mast and rigging maintenance and tuning tips will lead to years of enjoyable sailing.

John Trost is an Accredited Marine Surveyor member of SAMS (Society of Accredited Marine Surveyors) who has been involved in the marine industry for over 20 years. He presently handles insurance claims for various pleasure and commercial vessel insurers including Markel American Insurance Company. Mr. Trost is a lifelong racing sailor, having competed in 38 (and counting) Port Huron to Mackinac Island races, and winning his class numerous times aboard his vessel PENDRAGON, a Contessa 43. Mr. Trost is married with four children and resides in Grosse Pointe Woods, MI.

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