Angle of Vanishing Stability - Page 2 - SailNet Community
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post #11 of 19 Old 12-06-2011
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Far more people leave their boats upright and floating than find themselves upside down.

Seems we tend to worry about our imagined worst cases and can't quite grasp that WE are the weak link in most cases.
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post #12 of 19 Old 12-06-2011 Thread Starter
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Quote:
Originally Posted by peterchech
I often wonder about what you do if you are in the cockpit when the boat rolls. If you are tied in (you should be), you may be held under for some time before the boat comes back up especially if sheets are not released in time or if wave/wind action coincidentally holds the boat inverted longer than would be expected. If you cut away from the tether to get to the other side of the boat, you risk being separated and lost at sea. Webb Chiles talks about being rolled twice in the southern ocean on one of the "furled sails" podcasts, but he was in the cabin both times and the boat came right back up. I think I would be tempted to throw out a sea anchor and hide below if the going got really rough, but that isn't always an option and often it is a rogue wave that breaks unexpectedly which rolls the boat
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That's exactly the situation I thought of when I raised the subject.
Many boats have AVS below 140 degrees which, according to the book, means that they would incline to stay up side down for several minutes once rolled over. In this time the boat might take water, something that would worsen the situation .
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post #13 of 19 Old 12-07-2011
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Quote:
Originally Posted by midlifesailor View Post
Far more people leave their boats upright and floating than find themselves upside down.

Seems we tend to worry about our imagined worst cases and can't quite grasp that WE are the weak link in most cases.
Agreed... in most cases I think even the 'crappy' boats will take more than most of us when push comes to shove....

Ron

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post #14 of 19 Old 12-07-2011
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Midlife:
I totally agree with you but that's a hard factor to graph.

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post #15 of 19 Old 12-07-2011
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Quote:
Originally Posted by bobperry View Post
Midlife:
I totally agree with you but that's a hard factor to graph.
Yeah, but there's a bunch of photographic evidence on this site of people risking life and limb abandoning boats that didn't appear to be in immediate danger of sinking.

Since the rigs are on those boat were intact, and these boats don't seem to be in danger of sinking, loss of steering could be a possible factor. If you can't control the boat, you have no ablity to get yourself out of the situation but from the threads I see, it seems folks headed to the briny blue worry more about getting upside down than how to steer the boat if the rudder snaps off.
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post #16 of 19 Old 12-08-2011 Thread Starter
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Quote:
Originally Posted by peterchech View Post
However the flush deck, and relatively low ballast to displacement ratio might make recovery from turtle much less likely, ...
Tying an inflatable boat on top of the coachroof or on the foredeck should lower the inverted stability of the boat, but is it significant ?

Anybody knows how to calculate it ?
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post #17 of 19 Old 12-08-2011
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Quote:
Originally Posted by shaile View Post
...We can take this idea a step further and install a balloon on deck. Such a balloon can be empty in normal sailing and automatically inflated when the boat is inverted. If this idea is right, I suppose I would have not been the first one to raise it. So why don't we see such systems on boats ?...
Among other reasons is the fact that roll-overs are quite rare and those that do occur, usually do so in conditions that are so violent that the yacht is quickly rolled up-right anyway. Moreover, it would be difficult to implement such a solution in a cost effective manner. Further, you have evidently not spent any time at sea in rough conditions. In such, it is not uncommon to have the entire deck all but submerged. A hydrostatic release might/likely would have a difficult time distinguishing between an immersion and an inversion, and all one needs at such times is an inflation device exploding open to add to the difficulties. (If you read/review Rousmaniere's "Fastnet Force 10" you will discover that more than one crew had to hack up/cut away their life-raft when it inadvertently inflated in the cockpit at the height of the storm, hazarding everyone in sight.)

As for an inflatable tied down on deck, it would be a foolish person indeed that would add such windage and such a target for a breaking sea on deck in all but relatively benign conditions.

FWIW...

"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
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post #18 of 19 Old 12-08-2011
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I liked the comment that came out of the Fastnet disaster "The safest way to enter your life raft is to step UP into it!"

I've always thought real blue water cruisers should have seat belts down below. So when you really want your mommy you could just buckle in and wait for everything to stop moving. The Fastnet proved that most of the people lost would have survived if they had seat belts!

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post #19 of 19 Old 12-08-2011
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Quote:
Originally Posted by GaryHLucas View Post
I liked the comment that came out of the Fastnet disaster "The safest way to enter your life raft is to step UP into it!"

I've always thought real blue water cruisers should have seat belts down below. So when you really want your mommy you could just buckle in and wait for everything to stop moving. The Fastnet proved that most of the people lost would have survived if they had seat belts!

Gary H. Lucas
As a matter of fact, we have a seat-belt at the navigation table that was salvaged from a 1963 Chevy. It works a treat to keep one in place in rough conditions albeit, sometimes rough on the mid-section, eh? (My wife wants me to add them to the heads!)

FWIW...

"It is not so much for its beauty that the sea makes a claim upon men's hearts, as for that subtle something, that quality of air, that emanation from the waves, that so wonderfully renews a weary spirit."
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