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Old 19-07-2008, 21:10   #76
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exfishnz
I have read through this thread a few times and I have yet to figure out what if anything your posts bring to the subject of this thread.

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Really??? What if you cut ten holes in each hull?
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No worries mate. When are you bringing your sailing cat into the southern ocean to test its self-righting abilities?
Since you seem to be fond of schoolyard taunts and challenges how about we combine these two. We each drill a two inch hole in our main hulls and have a short race. It only needs to be a few miles. We could even do it in the Southern Ocean. No patching allowed.

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On a recent documentary I watched, the Titanic sunk due to poor quality of some rivets[1]. The collision on the side on the hull forced the rivets to pop & the steel plating to come unjoined.

Btw, I've yet to see a multi one of these (possibly because they don't upright themselves):
Attachment 4365

[1] Rivets were sourced from many locations in the same period for the building of the Titanic & her sister ships.
I don't know what the Titanic has in common with a thread on positive floatation in multihulls. Seems like it has more in common with your steel full keel whatever.

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I think that's a fair comment & just to be clear here mate, next time you ask us a silly question then I'll ensure that you receive the same type of comment with a referenced link to your post
Hoisted on your own halyard.......eh.

Back to the subject of the thread. This is a photo of a Searunner 31 with all three hulls holed below the waterline. There is no additional floatation just the buoyancy of the building materials. It does not matter how many holes you cut in the hull. With only the main hull holed it will float substantially higher and can even be sailed in a limited fashion. Multihulls with their narrow hull form always have some space, especially in the ends that can be used for floatation. There should be no excuse for a multi that sinks.
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Old 20-07-2008, 01:19   #77
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Steve Rust, Strygaldwir, & BigCat have restored my faith in cruisers, and the potential of this thread for further enlightenment.
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Old 21-07-2008, 04:47   #78
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It is easy enough to ask any yacht manufacturer how much positive floatation is present in the yacht , both in cubic metreage and in weight and you can draw your own conclusions from this info.
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Old 21-07-2008, 05:33   #79
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come on guys hes probably just (polite vernacular) taking the wind out of you sails, a bir like we do when we talk about floating moorings, half boats and leaners, each to their own with full marks given to the most witty read funny put down of the others sailing habits
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Old 16-08-2008, 09:34   #80
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I think that asuming that a sealed compartment or group of them will keep your boat afloat is not the best idea, the Titanic used that idea.
No, you have your facts wrong. Titanic was designed with watertight compartments, but they were open at the top. She was designed to float with a certain number of these flooded. Unfortunately the sideways swipe on the iceberg opened up too many compartments, therefore she fooded down by the bow so far that the water poured over the top of a pierced compartment into the next which wasnt pierced, and this cascaded onwards until she sank.

If the watertight compartments had been sealed at the top, she may well have stayed afloat, and we all would have been spared a succession of mediocre movies.
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Old 16-08-2008, 17:33   #81
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Here is a newby ?

If your multi hull is floating upside down, and not likely to sink, how do you you get it back "right side up"? Or do you just float it upside down till you run out of food & water?

Shawn
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Old 16-08-2008, 17:47   #82
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If "it" happens you should consider the boat to be a large liferaft at that point. There has been some discussion on self righting but I don't think it practical without outside help. Check the archives if you are interested, no need to rehash that subject here.
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Old 16-08-2008, 19:58   #83
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Here is a newby ?

If your multi hull is floating upside down, and not likely to sink, how do you you get it back "right side up"? Or do you just float it upside down till you run out of food & water?

Shawn
If you don't have any means of signalling then that might be what it comes down to.

But you'll have access to many more supplies as well as clothing than if you were in a liferaft. Your dinghy could possibly still be available to you as well, in case land is nearby.

But the majority of people will be carrying an EPIRB. They are becoming mandatory virtually everywhere now.
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Old 16-08-2008, 20:09   #84
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But if your on it, and obviously the sails are in the water, there is no danger of it flipping over "right side up"? If you had really large waves, but, then you probable wouldn't be hanging on anyways!

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Old 16-08-2008, 20:17   #85
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The idea isn't to hang on to the outside. The idea is to get back inside if rescue is going to take a while, or if the weather is bad.

It doesn't take much to set up an area that can be habitable if the boat is inverted. Simple one-way valves in the water tank breathers will stop your water emptying out.

I've only read one report of a multi being flipped back upright in a storm.
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Old 16-08-2008, 20:21   #86
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Ok, Thanx!

I told you I was a newbie! I have only been out sailing a few times, and a bunch of times out on a charter fishing boat or tourist trap site seeing cruise (both power)

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Old 16-08-2008, 20:46   #87
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No worries. It does sound weird at first, but the crew of the Rose Noelle survived for several months in an upturned trimaran. They were in such good condition at the end that it was thought to be a hoax! There's a book about it.

There's also a book by Steven Callahan who (barely) survived for months in a liferaft. Reading the two leaves little doubt which is the better option, if available.

Also, these days it shouldn't be neccessary to wait as long as that for rescue.
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Old 17-08-2008, 08:29   #88
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cored vs uncored hulls

I'm following this thread with some interest. The Admiral of this household is very concerned about the chances that a given sailboat might actually sink while in a storm on passage. Catamarans have been deemed "unsinkable" by some, and this is a major selling point. It's clear that holed lead-ballasted monohulls will sink. She's not enthusiastic about them for this reason and because she does not like heeling. We plan a cicumnavigation in the remote future, and currently have a 42' monohull we're selling.
I had a discussion with a catamaran broker regarding various cats. The Outremers came up in the discussion. I think I'd like the higher speeds these boats are said to attain. But he made an interesting point: Outremers have solid glass hulls, not cored as most others. He suggested that an Outremer is capable of sinking because the hull material does not have enough positive buoyancy. Cored hulls have been suggested to be less apt to sink because of their intrinsic positive buoyancy. For the moment, I'm setting aside the issue of watertight airfilled flotation compartments. any comments?

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Old 17-08-2008, 08:35   #89
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lot of discussion in a number of threads here about speed versus lightness. Outremmer is not in my opinion, a contender as a liveaboard, as it cannot really carry much weight.

I would much prefer a solid hull as it is more resistant to point impact than conventional cored boats - obviously, you can use exotic materials and make it almost bulletproof, but that costs. The downside is that the boat is heavier. regardless, most of these have sufficient watertight compartments to allow them to float, and their decks and hulls above the waterline are frequently cored as well.
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Old 17-08-2008, 08:46   #90
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Thanks for the comments, Talbot. The issue about load sensitivity in a liveaboard is of course very important. The Admiral has rejected Outremers as candidates for the above reasons as well as the very narrow hulls and resultant small interior volume.

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