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Old 21-12-2013, 12:54   #16
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Re: Power boat capsize?

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Originally Posted by mcm View Post
I was one told that for power boats use the following guide.

In a fully developed sea state, when the waves reach the same as 2/3 of the water line length, then the vessel is in danger of capzize.

i.e..a boat with 30 ft w/l is in danger at 20 ft sea state seems it would be in danger before that, but, thats what an experienced delivery skipper posted.

I don't think a 20ft wave is the problem, its a 20ft breaking wave when suddenly hundreds of tonnes of water accelerates down the face of a wave that causes the problem. This is the best video I can think of to demonstate the point. Both yacht and powerboat deal with the large swell fine, but the breaking wave does the damage.

Powerboat Training UK ~ Yacht capsize plus rescue - YouTube

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Old 21-12-2013, 13:07   #17
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Re: Power boat capsize?

I suspect much of it is just exposure. In terms of percentages, long distance offshore runs where you are more likely to have the weather turn on you are dominated by sailing vessels.

The other issue is most power boats don't have large objects affected by the wind 30-40' above deck.

But it does happen a couple years ago an aft cabin cruiser went over due to a wake as boats head out after fire works.
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Old 21-12-2013, 13:07   #18
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Re: Power boat capsize?

Oh yeah, another cat flipped on its back.
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Old 21-12-2013, 13:59   #19
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Re: Power boat capsize?

BBC News - Cool box saves Australian fishermen
todays news
enough said........
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Old 21-12-2013, 14:52   #20
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Re: Power boat capsize?

^^

Maybe now some legislator is going to want to pass a law that we all carry Eskies for life saving.

Those guys in the training video were fortunate to escape. The attempted rescue of the first one was different from how I've seen such things practiced, maybe that's why it is a training film. There appeared to be little wind, so it must have been staged after a storm. You get to pick what mistakes were made.

Here's a few:

1, the chap in the sailboat had not cleared the lines after striking his heads'l and before starting his engine. Otherwise he would not have been beam-to.

2, approaching the breaking wave is usually done on an angle off the perpendicular, not straight.

3, The usual procedure is to lower a person on the cable from the helicopter to assist in the rescue of the person on the victim boats, no man-ropes or any real help from the Wales Sea Rescue people.

A comment and question: all the rescuees were young, fit males. In similar conditions, how would middle aged and older people fair? Would such victims be approached differently?
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Old 21-12-2013, 14:56   #21
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Re: Power boat capsize?

There was a semi planing trawler style boat (about 48 ft I think) sunk in the N.A. River system within the last year or so. In a shallow area a large tow sucked enough water out from the edge of the river that the small boat grounded, leaned over far enough that the boat foundered before it could refloat. Lawyers are still involved so we haven't heard the whole story yet. Maybe not applicable to this question but interesting.
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Old 21-12-2013, 16:00   #22
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Re: Power Boat Capsize?

Lots of power boats get in trouble broaching near shore in inlets and rapids. On the New Jersey coat and in Northwest it is a common danger.
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Old 21-12-2013, 16:16   #23
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Re: Power Boat Capsize?

Having spent many years commercial fishing and towboating as well as working deliveries, I'm of the opinon that there are a number of contributing factors that put a vessel in peril besides wave height. Wave moment, wave direction relative to boat travel and countervening sea states can all make an otherwise accepable sea, a killer.
One of the more tragic events occurred on the crab fleet out of Dutch Harbor many years ago when one family lost about 5 members in rollovers in moderate sea conditions. An exhaustive CG investigation finally narrowed down the cause of both vessels turning over to the incorrect painting of the plimsol line on both boats from the same yard in Seattle. The painter had come in on a Sunday to finish the job in order to have them splashed the following day so they could make it to opening day in Alaska. They travelled light to Dutch Harbor where they loaded their traps and kept loading until the Load Master and skipper said they where down to their lines. Unfortunately, the line was painted about 4-5 feet above where it should have been which added more weight above decks than was safe resulting in a very unstable vessel. Both boats were brand new and suffered the same fate. I was a green horn at the time working trollers and it took the whole community down. I'll never forget it... Be careful out there! Phil
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Old 24-12-2013, 00:35   #24
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Re: Power boat capsize?

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Originally Posted by valhalla360 View Post
I suspect much of it is just exposure. In terms of percentages, long distance offshore runs where you are more likely to have the weather turn on you are dominated by sailing vessels .

Agree plus as sailors desire windy conditions they are more likely to go out in them than power boaters. Thus leaving them more exposed when conditions are worse than forecast.
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Old 24-12-2013, 01:01   #25
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Re: Power boat capsize?

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A slightly different topic would be commercial fishing trawlers that have had weight added topsides after their initial design, making them much less stable. To bring this back to the original topic, I wonder if this has ever been an issue for recreational power trawlers or other recreational power boats. Power boats would also differ from sail perhaps in regard to what happens to stability and survivability when power is lost.

I read an article some time ago discussing recreational trawlers having weight deliberately added up high to give them a more sea kindly motion, as in a slower roll moment making them have a less snappy motion. The article pointed out that ultimate stability was decreased.
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Old 24-12-2013, 03:44   #26
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Re: Power Boat Capsize?

The capsized power boat that Valhalla referred to was grossly overloaded; 27 people on a 34' Silverton flybridge, with probably quite a few of them on the flybridge. There was no issue of rough seas... until the fireworks show was over and the spectator armada revved up its engines to leave like a cloud of bats out of hell.
A graphic...
http://www.nytimes.com/interactive/2...=nyregion&_r=0

Ages ago when I was a teen, I was standing on the exposed bow of a Coast Guard cutter for a "Blessing of the Fleet" for a large regional fishing tournament. I was holding a heavy object and there was no more than a bit of toe rail. It was the custom for all the boats to proceed to sea after the blessing, at a rather unrestrained rate in a slightly constrained channel. With eighty to a hundred power boats of all types and sizes revving their engines, some in semi-displacement mode, some transitioning to planing, and some planing, the sea state quickly ramped up from nearly calm to a two-foot or higher confused chop, with waves bouncing at all angles. It was rough going, for a professional crew in a hugely seaworthy boat.

Now imagine this sort of scenario, but with the confusion of darkness, with some intoxicated crews, and with a badly overloaded boat of almost all landlubbers who have limited understanding of boat trim and stability.

Now imagine that about 4400 lbs. of pax are on a boat of nominal displacement 12500 lbs., as a live load with a high center of gravity, and with the boat loaded down maybe as much as a foot below her normal displacement. Now imagine the effect of wakes hitting from all sorts of directions, and in the dark. Now imagine the suddenly wild and unexpected motion of the boat and the effect this might have on civilians on board. Plus un good.
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Old 24-12-2013, 04:08   #27
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Re: Power Boat Capsize?

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Originally Posted by rgscpat View Post
The capsized power boat that Valhalla referred to was grossly overloaded; 27 people on a 34' Silverton flybridge, with probably quite a few of them on the flybridge. There was no issue of rough seas... until the fireworks show was over and the spectator armada revved up its engines to leave like a cloud of bats out of hell.
.
I was just pointing out a well publicized example of a power boat rolling.

I think you will find the vast majority of boats that turn turtle are due to operator error (sail or power).

On a side note, we used to have a 31' silverton and one time we had 14 people on board. Never left the dock and I was getting nervous.
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Old 24-12-2013, 04:12   #28
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Re: Power Boat Capsize?

Of course, the 2009 boat capsize that cost the lives of two NFL football players (Marquis Cooper, Corey Smith) and a friend (Will Bleakley) was both notorious and unusual. Capsizes of very small powerboats are common, but much less so for bigger boats. The twenty-one-foot boat had been anchored well offshore, but in shoal water, for fishing, but difficulties arose when winds and waves got rough and there may have been difficulty in raising anchor, apparently causing the crew to move their end of the anchor rode to a point midway along the boat's port side and try to power the anchor loose... which appears to have contributed to the capsize. Lack of communications, exposure, and some crew giving up their pfds and trying to swim may have also contributed to the loss of life.
Bad anchoring caused football players' boat to flip - CNN.com
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Old 24-12-2013, 06:05   #29
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Re: Power Boat Capsize?

it's all about design
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Old 24-12-2013, 07:14   #30
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Quote:
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I was one told that for power boats use the following guide.

In a fully developed sea state, when the waves reach the same as 2/3 of the water line length, then the vessel is in danger of capzize.

i.e..a boat with 30 ft w/l is in danger at 20 ft sea state seems it would be in danger before that, but, thats what an experienced delivery skipper posted.

Think about this. What is the dircect physical relationship between sea height and LWL that would lead to capsize?

There is however a very direct physical relationship between the beam of a vessel, wave height, and capsize. This is why beam seas are so potentially dangerous.
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