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#11
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![]() "You don't have to worry"??? Last summer in the entrance to Laguna di Marano, northern Italy, a returning professional fishing boat was slewed and rolled by an extra large breaking wave and dropped on the bottom while inverted, smashing in the wheelhouse and killing two men. A third, who was on deck, was thrown in the sea and survived.- Hide quoted text - Oh, Id let you talk to a friend of mine who took a 36' somthing in to a snug little harbor on the south Oregon coast. But he is dead. Oh, thats right................ while entering the channel between the two jetties he hit bottom, next wave hit an pivoted his boat on the keel, kicked him beam-to, the next one rolled him over a few times. Cause of both fatalities: shallow water with big rollers make for dead sailors. Ups, guess they should have measured water depth, wave height, and draft. |
#12
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![]() "BrianH" wrote in message ... Matt O'Toole wrote: On Fri, 02 Mar 2007 08:05:53 -0500, Roger Long wrote: Shaun Van Poecke wrote: If the waves are big enough to worry about this, the real issue is breaking waves. Any time you are in water less than about twice the depth of the average size waves going by, there is the possibility of one of the few largest waves of the day breaking on that spot. If you think a wave twice the size of the average breaking hard on your boat would create more excitement than you care to deal with, you should keep at least twice the average wave height under your keel and a little more when passing over isolated ledges. Shallow water may cause steep waves, but prevents them from building beyond a certain point. So you don't have to worry about the occasional huge wave in shallow water like you do in the open ocean. "You don't have to worry"??? Last summer in the entrance to Laguna di Marano, northern Italy, a returning professional fishing boat was slewed and rolled by an extra large breaking wave and dropped on the bottom while inverted, smashing in the wheelhouse and killing two men. A third, who was on deck, was thrown in the sea and survived. This sounds like a case where deep-water swells ran onto a shallow bar or entrance. In this case, when the swells start to feel the bottom they slow down, getting closer together and steeper, and taller -- not a good place to be, of course. On the other hand, when you are surrounded by shallow water, any large deep-water waves will quickly lose their energy (often by breaking) and become smaller. And as Roger said, wind-driven waves can not build beyond a certain height in shallow water. -Paul |
#13
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Paul wrote:
"BrianH" wrote in message ... Matt O'Toole wrote: On Fri, 02 Mar 2007 08:05:53 -0500, Roger Long wrote: Shaun Van Poecke wrote: If the waves are big enough to worry about this, the real issue is breaking waves. Any time you are in water less than about twice the depth of the average size waves going by, there is the possibility of one of the few largest waves of the day breaking on that spot. If you think a wave twice the size of the average breaking hard on your boat would create more excitement than you care to deal with, you should keep at least twice the average wave height under your keel and a little more when passing over isolated ledges. Shallow water may cause steep waves, but prevents them from building beyond a certain point. So you don't have to worry about the occasional huge wave in shallow water like you do in the open ocean. "You don't have to worry"??? Last summer in the entrance to Laguna di Marano, northern Italy, a returning professional fishing boat was slewed and rolled by an extra large breaking wave and dropped on the bottom while inverted, smashing in the wheelhouse and killing two men. A third, who was on deck, was thrown in the sea and survived. This sounds like a case where deep-water swells ran onto a shallow bar or entrance. In this case, when the swells start to feel the bottom they slow down, getting closer together and steeper, and taller -- not a good place to be, of course. On the other hand, when you are surrounded by shallow water, any large deep-water waves will quickly lose their energy (often by breaking) and become smaller. And as Roger said, wind-driven waves can not build beyond a certain height in shallow water. This whole area is shallow, around 3-6 metres out to at least 2nm off-shore. The channel is dredged to about 5 metres, on average. The fishing boat was slightly out of the channel, converging on it and well off from the entrance, in about 3 metres depth. The wind was fresh and directly on-shore. It sure shocked us sitting in harbour wondering if we should be going out. |
#14
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This sounds like a case where deep-water swells ran onto a shallow bar or entrance. -Paul- Hide quoted text - Yes. Good call. Add to that missing the high tide and trying to cross with the tide running out. swells got steep, even steeper with outgoing tide, troughs really brought the depth down, bump thud Wut ?!......................... the rest is history. Excellent assumption on your part. |
#15
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On Mon, 05 Mar 2007 07:20:39 +0100, BrianH wrote:
Matt O'Toole wrote: On Fri, 02 Mar 2007 08:05:53 -0500, Roger Long wrote: Shaun Van Poecke wrote: If the waves are big enough to worry about this, the real issue is breaking waves. Any time you are in water less than about twice the depth of the average size waves going by, there is the possibility of one of the few largest waves of the day breaking on that spot. If you think a wave twice the size of the average breaking hard on your boat would create more excitement than you care to deal with, you should keep at least twice the average wave height under your keel and a little more when passing over isolated ledges. Shallow water may cause steep waves, but prevents them from building beyond a certain point. So you don't have to worry about the occasional huge wave in shallow water like you do in the open ocean. "You don't have to worry"??? Last summer in the entrance to Laguna di Marano, northern Italy, a returning professional fishing boat was slewed and rolled by an extra large breaking wave and dropped on the bottom while inverted, smashing in the wheelhouse and killing two men. A third, who was on deck, was thrown in the sea and survived. Well of course waves breaking as they hit shallow water, such as when they hit a bar, is a big problem! But then the energy dissipates, and large expanses of shallow water cannot carry big waves. Matt O. |