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a.) no mention is made of a "breaking" wave, and
b.) it an amateur's recollection of an accident. but nice try. stew ped, but nice try anyway. From: (Bryan Glover) Date: 2/8/2005 12:45 A.M. Eastern Standard Time Message-id: Following is from www.seriesdrogue.com and I scoff and mock all you scared weard little guys,like Jax, who will no doubt cry foul, because someone with a commercial interest in this subject dares make a post. Worst Case Breaking Wave Strike I have chosen the case of the Winston Churchill in the 1998 Sydney Hobart race as an example of a worst case breaking wave. The Churchill was a classic wooden sloop of 25 tons displacement and 55 ft. LOA. Of the experienced crew of 9, two perished in the accident. From "Fatal Storm' by Mundle. "A sea came out of nowhere", said Stanley, " I could feel it from where I was in the aft coach house. It picked the boat up and rolled it down its face - 25 tons of boat- into the trough at a 45 degree angle. It was like hitting a brick wall when we hit the bottom". A crewman below reports that a sudden motion of the ship picked him up and threw him 7 ft. He observed that 8 ft of the heavy timber bulwark and planking had been torn off near the leeward shrouds, and the ribs were exposed. . The boat filled rapidly and sank in a matter of minutes. This is an unusual type of accident. Although there are records of many storm casualties, I am aware of no documented instance of a well found yacht of the size and reputation of the Churchill and crewed by an ample group of expert sailors, suffering such catastrophic structural damage that it sank in a matter of minutes. How could this possibly happen? The severity or the storm was extreme but by no means unprecedented. There are numerous reports of large sailing yachts surviving hurricanes of the same general magnitude. Although yachts have been lost in such storms I have been able to find no record of comparable structural damage. History shows that the probability of a yacht being capsized and damaged by a large breaking wave is strongly influenced by the displacement of the vessel. Yachts under 35 ft. have a poor history while yachts over 50 ft are rarely capsized and damaged. The nature and extent of the damage incurred by the Churchill is also most unusual. The vessel was designed by Sparkman and Stevens and was maintained to the highest standard. Yet the heavy timber bulwark was shattered, the planking gone and the ribs exposed. There is no question of the fact that the leeward bow of the boat was driven into solid green water at an extremely high velocity, far higher than would be expected in a simple contact with a breaking wave. We now have a technical understanding of how such a destructive force can be generated. Observations from many experienced sailors on a number of the SH yachts provide data which permit a sound engineering analysis of the performance of the waves and the boats in the race. Water forces are applied to the hull of a yacht by two means, buoyancy forces and dynamic forces. Buoyancy forces are the familiar pressure forces which keep the boat afloat. They never reach sufficient magnitude to damage a well found yacht. Dynamic forces result from the motion of the boat relative to the water, either as a result of the boat velocity or the water velocity due to wave motion. A speeding power boat can be destroyed by striking solid water. Similarly, a sailing yacht can be destroyed if it is accelerated up to a high speed by a breaking wave strike and then impacts solid green water in the preceding trough. This is the fate that befell the Churchill. To understand this phenomenon we must consider the concept of energy. A moving car or boat has energy. This form of energy is called kinetic energy. Kinetic energy is measured in foot-pounds. Kinetic energy can be calculated by the formula KE=1/2 (w/g) times (v squared). Where w is the weight of the car or boat, g is the acceleration of gravity (32.2 ft/sec) and v is the velocity in ft./sec. Thus a 3,000 lb. weight traveling at 30 m |
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