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Old 07-24-2010, 06:27 PM   #1
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I am supposed to be fixing things on the boat, instead I'm distracted by more interesting pursuits. I just watched this video of a Coast Guard helicopter rescue of 3 people on an overturned PDQ 32 sailing catamaran. Talk about risk to life and limb, these rescuers are heroic!

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Old 07-25-2010, 11:29 AM   #2
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The Coast Guard are to commended on a fine job.

However, the skipper of the catamaran is said be very experienced - yet he risked the lives of many people by taking the boat out in conditions that were clearly understood to be hazardous at the time.
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Old 07-25-2010, 10:15 PM   #3
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The myth of "an unflippable cat". Someone on the boat design forum has recently offered USD 10 000 to anyone who can flip his cat.

If I knew how to survive the situation, I would surely take the challenge.
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Old 07-26-2010, 12:19 AM   #4
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Quote:
Originally Posted by magwas' date='26 July 2010 - 05:09 AM View Post

The myth of "an unflippable cat". Someone on the boat design forum has recently offered USD 10 000 to anyone who can flip his cat.

If I knew how to survive the situation, I would surely take the challenge.
Assuming you would survive! How would you flip it?
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Old 07-26-2010, 11:49 AM   #5
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Originally Posted by MMNETSEA' date='26 July 2010 - 03:13 AM View Post

Assuming you would survive! How would you flip it?
Look for a big fat hurricane, and aim for a spot where wind is against current. So I would get nice big breaking waves. Keels down I would go for a broad reach. As a preparatory task I would move stuff to the leeward hull. I would gradually raise more and more sails and use spare running rigging to complement windward standing rigging. I would try to go fast, and bury the leeward hull in runnig down from a wave.

I hope I have summarized all the mistakes which can be done to flip a multi
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Old 07-27-2010, 03:01 AM   #6
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Originally Posted by magwas' date='26 July 2010 - 06:43 PM View Post

Look for a big fat hurricane, and aim for a spot where wind is against current. So I would get nice big breaking waves. Keels down I would go for a broad reach. As a preparatory task I would move stuff to the leeward hull. I would gradually raise more and more sails and use spare running rigging to complement windward standing rigging. I would try to go fast, and bury the leeward hull in runnig down from a wave.

I hope I have summarized all the mistakes which can be done to flip a multi
Maybe better to summarize the above as a number of steps required to Flip a specially designed catamaran, rather than a list of mistakes.

Whatever!

The exercise was quite useful in reminding us cruisers of the realty of storms when these are encountered on the high seas. The idea that one is able to carry out any normal sailing task is highly problematical.

-----------

Questioning each step in turn gives an idea of the complexity of Hurricanes when considering their use to solve a challenge.

Step #1 "Look for a big fat hurricane"

Question : How?

Question : "BIG FAT" means what ? Category 4 = sustained wind 114 <> 136 kts

Category 5 = sustained wind >155 kts

Step #2 "Aim for spot where wind is against the current"

Question : In a Hurricane is there such a condition ? The normal current to be found will have no effect in the seas developed by the Hurricane's forces.

Step #3 "Get nice big breaking waves"

Question : How big ? Category 2 Hurricane Danielle on the 1st September 1998 in the North Atlantic recorded significant wave heights of 51 ft with peak waves of 87ft.

Step #4 " Keels Down"

Question : Presume this means the Dagger boards are both lowered ? Keels (if any) are fixed on catamarans.

Step #5 "Go for a broad reach"

Question : How will one know where the wind is coming from ? During a Hurricane, trying to face the wind and open your eyes is not likely to tell you how to bring the boat into a broad reach.

Step #6 " Gradually raise more and more sails"

Question : How? Even trying to raise sails quickly in 30kts of winds while steering the boat at the same time will be a task that requires the boat to be turned directly into the wind. With a minimum of 2 able-bodied crew..

Step #7 " Use spare running rigging to complement windward standing rigging"

Question : If available, what will it be attached to?

Step #8 " Try to go fast, and bury the leeward hull "

Question : How to go fast ? Imagine trying to swim upstream in a river which is in full flood. The speed of the boat will be determined by the Hurricane's wind and waves.
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Old 07-27-2010, 11:17 AM   #7
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Originally Posted by MMNETSEA' date='27 July 2010 - 05:55 AM View Post

Maybe better to summarize the above as a number of steps required to Flip a specially designed catamaran, rather than a list of mistakes.

Whatever!

The exercise was quite useful in reminding us cruisers of the realty of storms when these are encountered on the high seas. The idea that one is able to carry out any normal sailing task is highly problematical.

-----------

Questioning each step in turn gives an idea of the complexity of Hurricanes when considering their use to solve a challenge.
You are perfectly right that carrying out any normal sailing task is problematical in storm conditions. This makes it a challenge.

Doing anything in hurricane conditions is even life threatening, this is why I did not take the challenge.

Step #1 "Look for a big fat hurricane"

Question : How?

Question : "BIG FAT" means what ? Category 4 = sustained wind 114 <> 136 kts

Category 5 = sustained wind >155 kts

The bigger, the better If I would be serious to try it, I would try to find the smallest one which is enough to flip the cat, as I most probably would want to survive it after that And the size and parameters of the cat would be seriously considered to make an educated quess.

Step #2 "Aim for spot where wind is against the current"

Question : In a Hurricane is there such a condition ? The normal current to be found will have no effect in the seas developed by the Hurricane's forces.

There is the effect that waves go bigger and steeper when current is against wind. Not even a cat5 hurricane will stop the gulf stream. Maybe the flow direction in the surface will not be consistent with the normal direction, but the stream and associated energy is there nonetheless, and it will have its effect.



Step #3 "Get nice big breaking waves"

Question : How big ? Category 2 Hurricane Danielle on the 1st September 1998 in the North Atlantic recorded significant wave heights of 51 ft with peak waves of 87ft.

It depends on a lot of factors, and it is the most complicated part of planning if one would be serious about the attempt. The height of the wave is only significant when one tries to guess the speed of the boat in the through, e.g. would it have enough momentum to flip when one of the hulls dig? But in this respect wind force also plays a significant role. Also, steepness of the wave - which more depends on wind and current conditions than the height itself - is a significant factor. The third wave-related thing is the parameters of the crest. A nice breaking wave can flip a boat in itself is it is big enough, and without breaking waves it is very hard -some might argue it is impossible - to flip a multihull.

Step #4 " Keels Down"

Question : Presume this means the Dagger boards are both lowered ? Keels (if any) are fixed on catamarans.

Yep. Actually keels are important when the cat lays ahull. The leeward one will "hang on" to the water, so wind and wave forces can have a "fixed" point to turn the boat around.

Step #5 "Go for a broad reach"

Question : How will one know where the wind is coming from ? During a Hurricane, trying to face the wind and open your eyes is not likely to tell you how to bring the boat into a broad reach.

I would know where it is going to, by observing foam patterns. I would nearly run with the wind and waves, but still have a significant enough angle to their direction so I clearly put assymetric forces on them. The leeward one will be pushed down, and the point is to have enough wind and wave under the windward one so it will be pushed up.

Step #6 " Gradually raise more and more sails"

Question : How? Even trying to raise sails quickly in 30kts of winds while steering the boat at the same time will be a task that requires the boat to be turned directly into the wind. With a minimum of 2 able-bodied crew..

Gradually. Step by step. The point is to raise enough sails to give the wind enough area to hang on, while not breaking the mast if possible. I don't think too much canvas is needed for this, and of course it would be a very hard task.

Step #7 " Use spare running rigging to complement windward standing rigging"

Question : If available, what will it be attached to?

If there is good structural part in the right part of the boat, then there. Maybe at the bow of the windward hull.

Step #8 " Try to go fast, and bury the leeward hull "

Question : How to go fast ? Imagine trying to swim upstream in a river which is in full flood. The speed of the boat will be determined by the Hurricane's wind and waves.

I would go nearly with the wind and waves, so it would be relatively easy to go fast. See Jordan's analysis of the Fastnet disaster. He basically says that the speed in the through is actually determined by the height of the wave. And when a hull is buried in the trhrough, the boat slows, apparent wind will increase. The aft part of the boat will raise because the momentum, the buoyancy due to following wave and because the wind will push its sails and the back of the hull.
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