Death roll
From Wikipedia, the free encyclopedia
In a keel boat, a Death Roll is the act of broaching to windward, putting the spinnaker pole into the water and causing a crash-gybe of the boom and mainsail, which sweep across the deck and plunge down into the water. The Death Roll often results in destruction of the spinnaker pole and sometimes even demasting of the boat. Serious injury to crew is possible due to the swift and uncontrolled action of the boom and associated gear sweeping across the boat and crashing to the (now) leeward side.
For dinghy sailors, a Death roll is a common type of oscillation while running downwind. It may, and often will, result in a capsize if the skipper does not take quick action to prevent one.
During a death roll, the boat rolls from side to side, becoming gradually more unstable until it either capsizes or the skipper reacts correctly to prevent it. While on the dead run, off the wind, the force exerted by the sail lies almost parallel to the center line of the boat. There is little or no force causing the boat to heel to leeward, like other tacks, and, if the sail is out past perpendicular to the center line, or the sail is incorrectly shaped, there may be a force causing the boat to heel to windward. Instabilities in the wind, and turbulence caused by the sail, which 'fouls' the wind on such a tack, may cause this force to change rapidly. Most sailors also retract the centerboards of their dinghies while on the run, to reduce drag and increase speed. The lack of resistance to the rolling motion can enhance it.
[edit] Dingy capsizing due to a Death Roll
In a dinghy, death rolling may ordinarily be associated with a motion of the craft that presages a capsize. Unlike many other capsizes, death rolling commonly results in a windward capsize. In this case, the boat capsizes in such a way that the mast falls on the windward side of the boat. The boat may right itself, normally only capsizing again with the mast on the leeward side, unless the crew is quick to react. If the boat does not right itself, the skipper or crew will have to attempt to right the boat, normally from the leeward side. Very experienced sailors have learned to perform an Eskimo roll after a windward capsize. They hang onto the centerboard which pulls them under the water as the mast swings in the breeze, surfacing again on the windward side of the boat and climbing aboard.
More commonly, in choppy waters and while sailing very fast, some sailors (usually in single handed boats) will literally get washed off the deck as the side they are sitting on is submerged in the water when a death roll becomes severe. Without the weight of the skipper, the boat usually capsizes, after drifting several meters.
[edit] Capsize Prevention
An experienced skipper will learn to diagnose a death roll quickly and take action to prevent a capsize. Capsizing is detrimental to racing and any and all measures possible should be taken to prevent it. Methods to cure a death roll include sheeting in the sail, so that it exerts a definite force to leeward and no force to windward, slamming the centerboard down to stabilize the boat, shifting the skipper and crew's weight to counter the roll and, if all else fails, luffing up slightly to sail on a broad reach instead of a dead run. It is always more efficient, and ultimately faster, to sail with the sail pulled in slightly than to risk a capsize.
[edit] Boats Prone to Death Rolls
High performance racing dinghies are most prone to Death Roll situations.
These include Skiff designs, such as the Musto Skiff, 29er, 49er and International 14. Sailors of these boats generally prefer to sail on the broad reach than on the dead run because the boat is more stable and actually faster. Additionally, as their speed increases on the broad reach, their apparent wind changes to allow them to point lower. Often they can point as low as the other boats, only faster.
More traditional racing dinghies such as the Laser and Laser Radial are also prone to death rolls.
