Dismasting

Dismastings occur for many reasons. They tend to occur more prevalently for certain types of sailors, in particular areas, and particular types of sailing vessel. Having too much sail out for the weather conditions is perhaps the number one cause of dismastings. Novice and racing sailors in particular are more likely be flying more sail cloth area than more experienced, and non-racing sailors. Areas where sudden weather changes and wind shifts are frequent are more risky than areas where winds tend to be more consistent. For this reason sailing vessels in areas with consistently high winds may suffer fewer dismastings than vessels where winds are normally light but can suddenly change to very intense when a squall occurs.

Dismastings owing to rigging failures tend to occur either very soon after a vessel is launched or soon after the rigging has been modified from the original design. This is particularly true for custom designed vessels. Production vessels on the other hand benefit from all the experience of similar vessels that have the same mast and rigging. One particular problem identified has been changes in rigging cables from a smaller to a larger size. Larger diameter cables produce far more compression forces on the mast when they appear to be taunt. This in turn causes the mast to collapse in column owing to over compression. Older rigging is also the source of problems since the older the rigging is the more likely corrosion has damaged the integrity of metals. Stainless steel rigging in particular has been cited as being problematic since out strands of a wire rope might appear to be fine while at the same time inner strands are compromised. For this reason many insurance companies insist that rigging holding the mast upright, termed the standing rigging, must be replaced every 10 years.[5]

Heeling characteristics of the sailing vessel are also a contributing factor. Some vessels are more apt to lean away from the wind and "spill" a sudden wind gust harmlessly. The more likely a vessel tends to heel, the more a sudden strong wind gust is said to spill out of the sails because the vessel leans out of the way. A vessel that heels easily is termed as being tender whereas a vessel with a larger counter weight down low in the water, called the ballast, is termed as being stiffer. Racing vessels tend to be stiffer and spill the wind less and hence are at a greater risk of dismastings. However, it is also not good if a vessel is too tender. A very tender vessel can be easily rolled by a wave and flip completely upside down. Dismastings have occurred after a sailboat has been rolled. The extreme resistance of the water causes the failure to occur.

Multi-hull sailboats, namely catamarans and trimarans, are particularly prone to dismastings. These types of vessels don't readily spill a sudden wind gust for a different reason. It is their wide beam that causes their sails to remain closer to vertical in the face of strong wind. The wider the vessel's beam the more likely the extreme loads. Therefore, since trimarans tend to be wider than catamarans they also tend to be more prone to dismastings owing to extreme loads. It is not as if designers fail to recognize these facts. A multi-hull vessel will typically have a much stronger mast and stronger rigging than a mono-hull of the same size.

G-force loads is one of the less common reasons for a dismasting, however, it is still a real risk for both types of sailing vessels. Very stiff mono-hulls with a strong righting force tend to return to a near upright position much faster after being heeled by a strong gust of wind. This causes the motion to much more jerky. The mast will come to a sudden stop when the vessel returns to near upright when the wind fills the sails again. The problem is the mass of the mast still has momentum. Multi-hulls don't suffer g-forces caused by the wind to the same degree. Instead they are far more susceptible to g-force load owing to wave action. Waves coming abeam, i.e. striking the vessel sideways pick up and drop each hull of the vessels. If the amplitude of the wave and frequency of the waves corresponds to a factor similar to the distance between the hulls even relatively short waves can cause a dismasting. Trimarans in particular are prone to this type of dismasting since this type of vessel can rock back and forth between being supported on the center hull and one of the two ama at one second, and the center hull and the other ama the next. This violent rocking in turn translates to extreme g-force shocks on the rigging caused by the weight of the mast swinging back and force. Hence a trimaran can be dismasted even if no sails are up at all and waves are not extreme.

A particular travel direction of a sailing vessel is also more likely to lead to a dismasting. When a sailing vessel is traveling downwind, there is a chance the vessel may jibe. An accidental jibe in particular occurs when a sailing vessel is traveling downwind and the boom of the main sail suddenly swings from being on one side of the vessel to the other. The boom will come to a sudden halt when the rope controlling the boom's position becomes taunt again. At roughly the same moment the wind will fill the mainsail and a shock load will transfer into the mast and rigging and a dismasting might occur. To help prevent accidental jibes, sailors will frequently tie a line to the end of the boom to secure the boom to one side of the vessel. This line is typically called the jibe preventer.

In Herman Melville's seminal novel, "Moby Dick," Captain Ahab is said to have been, "...dismasted off Japan," alluding to Ahab's leg having been taken off by the white whale and replaced with a polished whale-bone peg-leg. "but like his dismasted craft, he shipped another mast without coming home for it. He has a quiver of 'em."

• Stars & Stripes (America's Cup syndicate)