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Old 25-10-2019, 07:31   #31
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Re: I watched a guy nearly capsize right in front of us

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Attachment 201702

The estimated 35 degree angle may have been “Apparent Heel Angle” (AHA), assuming the swell was large enough. This would explain the speed with which it happened (just swell passing from under the windward hull).

Not really a dangerous situation. Falling 10 degrees off does suggest entering the “death zone” though... so I might be wrong
Thank you very much for the graphic. As a cat newbie and visual learner, I was struggling to understand what was being described.
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Old 25-10-2019, 08:52   #32
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Re: I watched a guy nearly capsize right in front of us

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Attachment 201702

The estimated 35 degree angle may have been “Apparent Heel Angle” (AHA), assuming the swell was large enough. This would explain the speed with which it happened (just swell passing from under the windward hull).

Not really a dangerous situation. Falling 10 degrees off does suggest entering the “death zone” though... so I might be wrong

Very helpful. My question though is to shift that cat in the starboard direction 1/4 of a wavelength - then the port hull is up on the peak of the wave and the starboard hull is down in the trough. Then, I presume you would say the AHA is nil (or very small). But the boat is at greater risk of entering the death zone (or in it already), is it not? I have had to sail in that direction and while conditions were not that bad, and I was plenty reefed, but I really, really did not like it. And I wished I was in a monohull.
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Old 25-10-2019, 09:07   #33
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Re: I watched a guy nearly capsize right in front of us

Swell against tide produces elephants, steep slab sided waves. Beam on waves are NEVER FUN in a cat from powerboat swell on up. I imagine the other skipper puckered a bit there and learned to quarter the waves after that. And took some sail down.

I don’t think any other PDQ owner wants to spend any time on one hull. I teach the deck crew about the line to release when things start to go upside down shaped.

It can go so wrong so fast
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Old 25-10-2019, 09:54   #34
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Re: I watched a guy nearly capsize right in front of us

Maybe he was having a flashing back to when he was a baby and sailing a Hobi? Real question is after the got his shorts cleaned, did he pass you?
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Old 25-10-2019, 10:03   #35
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Re: I watched a guy nearly capsize right in front of us

Has anyone asked the question "what are these cruising catamrans doing rounding marks?" Sounds like racing to me.
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Old 25-10-2019, 10:10   #36
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Re: I watched a guy nearly capsize right in front of us

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Didn't Donald Crowhurst come up with something like this? Back in the 'Golden Age' (late 1960's) of sailing?
No idea.. but after Tristan Jones lost a leg and switched from mono's to multi's in the early '80s, he & Leo Surtees invented and patented a water-ballast stability device they called 'cooltubes' to help prevent multihull capsizes.


I once looked up the patent (US-4541356) out of curiosity. Quite interesting.. I know one was fitted to Tristan's trimaran "Outward Leg", but I've never seen any other references to it, or how effective it may have been.
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Old 25-10-2019, 11:50   #37
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I watched a guy nearly capsize right in front of us

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Originally Posted by lestersails View Post
But the boat is at greater risk of entering the death zone.

To clarify, the death zone I was referring to is when you are reaching at about 60 AWA, canvassed at the limit, and a gust hits. Then you are at a local minimum for the heeling moment and any heading change makes it worse:

1. If you bear off the mainsail gets more perpendicular to the wind

2. If you head up into the wind your AWS increases and the centrifugal force adds to the heeling.

(FWIW my preferred solution is to ease the main and head up, but sometimes there is no time and I bear off because it temporarily feels better due to lower AWS).

I have no idea if my “swell moving from under the windward hull” theory is correct. Because OP said there was a 10 degree heading change as it happened I suspect it may have been a death zone situation as described above and the heeling was real.

As to the swell pushing the windward hull over, this is mythical southern ocean or “rogue wave” kind of stuff... I don’t know. Just don’t have the lee board down I guess. And always chuck the first shot of rhum overboard to appease Neptune...
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Old 25-10-2019, 12:40   #38
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Re: I watched a guy nearly capsize right in front of us

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Just an observation, no comment on type of boat.

We were beating up wind, 25kn TWS, he was comming up behind us in a big cruising cat and lifted the hull often, occasionally it would hang up for 3 or 4 seconds then drop back down. There was wind against tide and the steep swell up to about 2.5m most around 2m.

We rounded a mark which took us off the wind about 10deg and bought the swell around to more side on. It lifted the windward hull like it did before then suddenly it shot up further to about 40° hung there for a moment like it was balancing on the edge and fell back down.

It was so fast, if the sheet is on a winch you would not have a hope of doing anything about it and I doubt the helm would shift the dynamics of the boat in time. The only chance you might have is if you were holding the sheet with a couple of wraps on the winch and just let it go.

I guess there are all types fast and slow but it was a real eye openner to see what might have happened.



I dunno, but sounds like fun to me.
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Old 25-10-2019, 12:58   #39
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Re: I watched a guy nearly capsize right in front of us

As I have said before, the most stable boat in the world is an inverted multihull. There was a time when a masthead float was popular.
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Old 25-10-2019, 16:08   #40
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Re: I watched a guy nearly capsize right in front of us

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As I have said before, the most stable boat in the world is an inverted multihull. There was a time when a masthead float was popular.
Like a lot of folklore, this is incorrect. It is reasonably easy to right a capsized multihull by towing bows over sterns. A relatively small power boat can pull a cat upright easily. If you do the same (tie a towline to the back) of an upright cat, it will just glide along.

The free surface effect makes water logged objects quite unstable. So the common saying that a inverted multi is more stable would only be correct if the cat had no water in it when inverted. Go play with a dinghy and tip it upside down. It is really easy to roll upright when filled with water. Much easier than the force required to capsize it in the first place.

I know of two capsized multihulls (St Therese and Incinerator) that rolled themselves back upright when lost (found upright after capsize). Tris with bouyant floats are probably the most stable inverted and cats least.

This is why many experienced cat sailors have been able to get their inverted cats back up and sailing quickly, because they use the lesser inverted stability to get the boats back up with a first responder. I have seen cranes used but this needs to be very carefully undertaken.

So be happy that your cat is at its MOST stable when upright. It is strange that many of the things we acknowledge as true are not correct when viewed critically.
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Old 25-10-2019, 16:44   #41
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Re: I watched a guy nearly capsize right in front of us

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Originally Posted by skenn_ie View Post
As I have said before, the most stable boat in the world is an inverted multihull. a monohull on the seabed. There was a time when a masthead float was popular.

There, FIFY
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Old 27-10-2019, 18:39   #42
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Re: I watched a guy nearly capsize right in front of us

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As I have said before, the most stable boat in the world is an inverted multihull. There was a time when a masthead float was popular.
Yeah - nah. For all the reasons above, Hard to capsize a decent multi, easy to flip it back
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Old 27-10-2019, 19:52   #43
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Re: I watched a guy nearly capsize right in front of us

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Originally Posted by earthbm View Post
Attachment 201702

The estimated 35 degree angle may have been “Apparent Heel Angle” (AHA), assuming the swell was large enough. This would explain the speed with which it happened (just swell passing from under the windward hull).

Not really a dangerous situation. Falling 10 degrees off does suggest entering the “death zone” though... so I might be wrong
Just re-read this one, the angles I mentioned where relative to the horizon.
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Old 28-10-2019, 04:32   #44
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Re: I watched a guy nearly capsize right in front of us

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As I have said before, the most stable boat in the world is an inverted multihull. There was a time when a masthead float was popular.
No you are wrong such a vessel is still rocked gently by the swell. The most stable craft is a holed monohull firmly sat on the seabed.
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Old 29-10-2019, 17:56   #45
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Re: I watched a guy nearly capsize right in front of us

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Not a Wharram. They bury the bow and trip over the flat foredeck when overpressed.


The hull never flies, the lee one just sinks.


Fortunately they have such small rigs you have to try really hard.
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