Action

1. Lateral rigging adjusted incorrectly. The most common fault is that the rigging is not tight enough. 2. Excessive mast bend. It must not exceed 2% of the height of the fore-triangle. For in-mast furling, the limit is 1.5%.3. Sailing or motoring in high seas. The mast is subject to acceleration and deceleration forces in the fore- and-aft direction, “pitching”.4. Reefing the mainsail until the head-board is considerably below the fore-stay fitting. There is a risk that the mast will take on a negative bend. 5. Pressure from the spinnaker pole on a broad reach (the spinnaker pole is close to the forestay).6. Pressure from the spinnaker pole if it hits the water during heavy rolling when running. 7. Fractional rig: Runners in combination with aft-swept spreaders. When a runner is tightened, it pulls the mast aft and to windward. Forestay tension increases, and it stretches accordingly. Lateral rigging tension and tuning will be affected. This increases the risk of the mast buckling aft (inverting).8. Hull not stiff enough. The rigging wire itself has negli-gible permanent deformation after loading. If, however, the hull gives too much under the rigging loads, tuning will be altered. All hulls, irrespective of construction material, will have more or less elastic deformations under load. GRP hulls take on a permanent deforma-tion after a certain time under load. Adjust the lateral rigging in accordance with the instructions before leaving the dockside, and then check under sail.Reduce bend by easing off the backstay and/or tension checkstays. Pre-bend is adjusted by the interplay between the baby stay and the aft lower shroud or the forward/aft lower shrouds. On keel-stepped masts, the fore-and-aft location of the mast heel can be adjusted.These forces are caused by the weight and movement of the mast. Damage is avoided if the rigging is adjusted to prevent movement of the mast. This reduces dynamic stresses on the whole rig. Give the mast a positive pre-bend by adjusting the backstay, baby stay/forward lower stay and any inner forestay. The mast pre-bend is important. Adjust the fore lower shroud or baby stay so that these counteract the aft- acting pressure from the spinnaker pole.• Alter the lead of the spinnaker sheet using a barber hauler to prevent the spinnaker oscillating. • Tighten the spinnaker pole lift. • Take in the spinnaker. Adjust the lateral rigging in accordance with the instruc-tions before leaving the dockside, tension the backstay, and then check under sail.There is not much you can do about it, other than be aware that it happens and check the tuning regularly.

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