Connecting the shrouds to the mast at more efficient angles
Although we use the term spreaders nowadays for the two pieces of wood or metal that spread apart a sailboat’s shrouds, they were referred to as crosstrees in the days of commercial sail. Their purpose is to obtain a large and efficient angle between the shroud and the mast at the point of attachment.Obviously, the longer the spreaders and the larger the angle, the better from a mechanical point of view, but the lengths are always a compromise because extralong spreaders interfere with the set of headsails when you’re sailing on the wind.Spreaders should exactly bisect the angle formed by the shrouds where they run over their tips. In other words, the outside ends of the spreaders should be slightly higher than the ends next to the mast. This not only looks more pleasing, but is also structurally stronger as it ensures that the force exerted on the spreader is purely a compression load. A horizontal spreader experiences a bending load under compression, which can lead to flexing and sudden failure.Short, gaff-rigged masts on sailboats with reasonable beam do not need spreaders, but tall Bermuda-rigged masts are more difficult to keep upright—and need one, two, or more sets of spreaders to keep them in column.Single spreaders should be located between 50 and 52 percent of the mast height, measured upward from the deck. If you have double spreaders, the lower set should be located between 37 and 39 percent of the mast height upward from the deck, and the upper set should be between 68 and 70 percent.
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| A spreader should exactly bisect the angle formed by the shroud at its top. |
Wooden spreaders are usually painted white or a light color on top to protect them from the sun and weather; however, they are usually varnished underneath so that rot may be spotted before it gains too great a hold. It’s important to check the state of your spreaders regularly because the loss of one could easily result in a dismasting.See also
Shrouds and Stays. |
| Single-spreader masts have the largest diameter and are the stiffest spars. Double-spreader masts are about as far as a hard-core cruiser should go. Cruiser-racers can benefit from a triple-spreader mast, and extreme racers will make their sails marginally more efficient with a four-or five-spreader rig. |
