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  #16  
Old 05-06-2009, 03:59 AM
lacage lacage is offline
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Using my Method of boat building the home builder can build a yacht that is unsinkable, build in half the time and half the cost, you are not locked into an exspensive marine system. Cheers from down under, Peter Bourne
www.bourneboats.com.au
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  #17  
Old 05-06-2009, 08:15 PM
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Richard Woods Richard Woods is offline
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The price of motion is not friction, it is accidents

Having said that, I have never been convinced that wearing a lifejacket automatically saves lives. Rather it is hypothermia that is the real risk.

Cold kills

As tens of thousands lifejacket wearing seamen found during WW2

When we were developing the ISO stability and buoyancy standards we wanted to ensure that open boats (in particular) could support the weight of the crew and the boat. We felt that there was no point in having only enough buoyancy to keep the boat afloat and not the crew. Furthermore the boat should float reasonably level so that the crew could still hold on.

Before that work the US Coastguard approved open boats that would float, but not support the crew (for example they could float stern down with just the bow above water - not very helpful to a swimming crew). Good for the insurance company (the boat survived) but of course death to the crew.

I remember a huge argument at one meeting (the US representative walked out) after I showed photos I had taken trying to stay aboard such a boat - I was wearing a drysuit. Fortunately reason did in the end prevail and we got a much more sensible - ie safer - standard than the old US Coastguard one.

Sorry, a bit off topic

Richard Woods of Woods Designs

www.sailingcatamarans.com
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  #18  
Old 05-06-2009, 08:33 PM
Ad Hoc Ad Hoc is offline
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"...Having said that, I have never been convinced that wearing a lifejacket automatically saves lives. Rather it is hypothermia..."

But without the lifejacket, one would ahve drowned, regardless of the sea temperature.
So what this does is just shift the mortality rate to another 'risk' area. But in doing so, bit by bit risk is mitigated. It shall never be totally removed, but, with sufficient information lives can be saved that would otherwise not have done so.

I presented a paper many years ago now,at a RINA conf, and one of the topics i addressed was/is demonstrating the stupidity of the HSC rules for evacuation. The method and philospohpy behind it is flawed. It spawned a major debate (in the field) but little progress. However, a death several years ago on an evacuation trial refocused the issue that is still being debated endlessly today.

Identifying the cause is often not enough...
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  #19  
Old 05-06-2009, 10:43 PM
Boston Boston is offline
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85% on boats less than 26'
80% on boats were the pilot had not taken a boating course
50% on open cockpit motor boats

were some pretty key figures
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  #20  
Old 05-06-2009, 10:58 PM
Ad Hoc Ad Hoc is offline
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indeed there were.
But some like to think of their "feelings" rather than understand what the stats show..since stats have no emotions!!
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  #21  
Old 05-06-2009, 11:20 PM
Boston Boston is offline
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my condolences to the lost of course thats not the question.
As someone who grew up on the water I have lost my share of friends to the sea, and have spent my share of moments watching the waves rolling in.

but its the lessons learned that at some point need to be quantified rather than just assumed. Frankly having grown up on the water its a miracle any of us cape kids survived, we did the dumbest things and if it werent for the fact that we generally did stupid **** in front of our friends who might pluck us from the water or tell us we were headed in the wrong direction, Im not sure any of us would have survived.

this thread's got some great info in it as to what to watch out for. That bit about 80% in boats with untrained pilots. There's one simple thing we could all do to be safer on the water.

of course we regret the loss of life involved, but to loose those lives and not ask how to avoid the same circumstances in the future is a greater disservice to the lost by far than a review of how many were lost and why

learning from the past is a great way to survive the future

best
B
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  #22  
Old 05-07-2009, 12:38 AM
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PAR PAR is offline
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Unfortunately, some will always find a way to eliminate themselves from the gene pool, literally. It's a fact of life. Looking at statistics can be quite deceiving. If we took them to heart, then Americans would live to 100+, just so long as they stayed out of the bathroom or garage, statically speaking.

Just the sheer volume of boating use in the country insures boneheads, their drunken friends and a few bystanders will be lost. It's much like a dog with 8 tits and 10 puppies. Someone is going to lose out. In nature it's an acceptable consequence of reality. In humanity, it's an over blown inability of acceptance, from well wishing folks who don't want to grasp the true nature of things.

We invite this, actually go looking for it in fact. An example: we swim along shallow coastal areas, preferably in warm water. We do so between sun up and sun down. Sharks feed in shallow, coastal areas and are most active at sun up and sun down. We know this, yet we still venture into their food bowl and bitch about it. Boating isn't any different.

Life's hard and made harder by those unwilling to prepare for the eventualities of reality. Boating places humans in an unnatural environment. Any time this happens, **** will hit the fan every so often. Having an elevator take you up to the 30th floor of a building, is placing humans in an unnatural environment. Flying at 30,000 feet in an aircraft does the same. Being in a boat farther from shore then you can swim back to or traveling at speeds you and/or the boat couldn't recover from, if you strike something is an unnatural environment for a human, so there will be eventualities of reality to accept or ignore.
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  #23  
Old 05-07-2009, 08:40 AM
Autodafe Autodafe is offline
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Nice posts Richard.

Many people I talk to are enthusiastic about my catamaran building project until I mention that I am planning to do some high latitude cruising, when horror sets in. There is a common assumption that cats (however fun for tropical cruising) will inevitably capsize, and so must only be sailed in reach of rapid search and rescue facilities.

Without taking a poll, it appears to me that the majority of monohulled boats in open ocean are neither self righting nor positively buoyant. For boats without sails it is considered normal and safe. A sailing cat reefed conservatively is considerably more stable than these "safe" craft of comparable size so I am puzzled by why so many otherwise rational boaters are frightened of multis.

There are a number of people (a small minority I would say ) that report excessive sea sickness on multis, and that can certainly pose a fatigue and safety issue but I haven't heard any other arguments against ocean going multis that bear close examination.


Ad Hoc, on the issue of lifejackets, averagely fit (and sober?) people can (given enough incentive!) tread water and/or swim for over 24 hours. Unless the water is over 27C (80F) hypothermia and death is likely after less than 12 hours in the water (around 4 hours with the water temperatures around my neck of the woods). So the life jacket only helps if both a) you can't swim and b) you're rescued very quickly.
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  #24  
Old 05-07-2009, 09:54 AM
bad dog bad dog is offline
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To take this wonderful discussion in a slightly different direction, since the weight and logic of Richard's original argument is clearly in favour of things that float whichever way the mast is pointing, is there any value in discussing how to get the mast skywards again?

There have been a couple of attempts I am aware of to create practical 'after the event' righting mechanisms for larger multis. This is not 'self-righting' since some (al lot) of work is required of the now-swimming crew.

One method for tris involved folding one float (ama to you N hemispherians) in to the main hull, and rolling the whole back over that now partially submerged hull.

For cats there was a bow-over method, using a long long (very long) large sea anchor rowed out from the boat, with partial flooding of the stern, then massively fast winching somehow.

Both methods required winching up (down) the sails, a general tidy up, and waiting for calm weather, all of which should be possible from the safety of the upturned hull/cabin.

I also wondered about having a bladder hidden at the masthead, which could be pumped up over a period from inside the hull, to bring the mast back level-ish with the surface, from where any other method would become easier.

I had a Catpult cat (5m, inflatable, see http://www.catapultcats.com/the.boat.html) which has a canting rig, which has serious sailing advantages (for another thread perhaps) and also massive aid in righting quickly after capsize.

Anyone got any more details on this?
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  #25  
Old 05-07-2009, 10:08 AM
bad dog bad dog is offline
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ps - it occurs to me that you could winch a deflated bladder down to the masthead on the main halyard, with a long hose attached, and pump it up then. The more you pump, the higher it floats, the easier it is to pump, etc etc. Of course things get really uncomfortable when the boat is on its side... a big incentive to have a fast reliable system.
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  #26  
Old 05-07-2009, 10:20 AM
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marshmat marshmat is offline
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Autodafe,
I'm afraid I can't agree with you on the lifejackets issue. Yes, a well-rested, sober, reasonably fit adult can keep their nose above water for quite a long time. But a kid can't. A non-swimmer or weak swimmer can't. Someone who hit their head, arm or leg on the gunwale when they fell out of the boat certainly can't. Someone who's exhausted from spending the last two days fighting the helm and sails in a storm will have a hard time, too. And if the water's cold and you have nothing to climb onto, the best way to keep warm is to huddle together with other survivors- which is only possible if you are buoyant.

As a former lifeguard and swimming/survival instructor, I know I can swim hard for several kilometres if need be, even towing someone else. But in my boat, PFDs are mandatory, for everyone, including me, at all times. If major trouble hits in a five-metre craft, you have three or four seconds at best to react. That's simply not enough time. So we stand prepared for emergency at all times.

And nobody, in this boat, has ever complained about having to wear a PFD. Ours do not interfere with movement, and are so comfortable that we sometimes forget to take them off when we go ashore.


bad dog,
It would be nice to have some kind of self righting ability in a multi. The techniques you describe sound like they could work in some cases.

There are a few more problems, other than insane initial stability, that could pose a problem in trying to self-right a cat or tri:

- Rig damage. Quite often, when a mono goes over, the rig is heavily damaged or lost. I suppose the worst case would be if the rig is toppled but several stays keep the remains of the mast close enough to the boat to serve as a battering ram. When a multi capsizes, there's a good chance it's going a lot faster than the mono, with potentially much higher stresses on the rig. I wonder if it's possible to build a rig strong enough to survive a capsize without making it excessively heavy.

- Downflooding. I can't help but think, when I see a lot of the charter/cruiser cats at the boat show, that many of them would lose windows, hatches, etc. in a capsize. Those big sliding patio doors are, IMHO, among the worst offenders. The boat may stay afloat by the air trapped in the hulls and beams, but what happens when you try to right it? How much water will rush in? If we are to make multis that can survive breaking waves and capsizes, the topsides will have to be pretty close to watertight.
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  #27  
Old 05-07-2009, 10:56 AM
Boston Boston is offline
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I gotta admit multi's do make me nervous and I hate life Jackets

thats not to say I cant see the value in em now that Im a few years older its just that if there as uncomfortable as I remember them to be Im probably going to be guilty of not wearing it again

course Im talking about a ~60' motor cruiser with positive buoyancy and self righting ( hopefully ) capabilities.

Ive seen the struggle people go through to get a multi's mast pointing the right way again and it looks like a whopping pain in the ass

its definitely there Achilles heel
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  #28  
Old 05-07-2009, 12:21 PM
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rayaldridge rayaldridge is offline
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Quote:
Originally Posted by marshmat View Post
- Downflooding. I can't help but think, when I see a lot of the charter/cruiser cats at the boat show, that many of them would lose windows, hatches, etc. in a capsize. Those big sliding patio doors are, IMHO, among the worst offenders. The boat may stay afloat by the air trapped in the hulls and beams, but what happens when you try to right it? How much water will rush in? If we are to make multis that can survive breaking waves and capsizes, the topsides will have to be pretty close to watertight.

There really is no excuse for building a multihull that does not float, even with the bottoms torn out of its hulls. In the early days, there were some solid fiberglass multis that could sink, but today I think a multihull that sank in any circumstances would probably involve its manufacturer in lawsuits. Most if not all multihull manufacturers now build cored hulls. They shouldn't sink, no matter how much water gets inside. Even if you own an ancient solid glass multi, it can be made unsinkable fairly easily, since you don't have to float a massive amount of lead when the boat floods.

However, I must admit that a few of the condo-cats in the bareboat trade in the Caribbean have in fact sunk despite their cored hulls. These were likely heavily overloaded; you can't make any boat completely foolproof. When you add gensets, reefers, big engines, scuba tanks and compressors, cruising gear, etc. you will eventually overcome the boat's natural buoyancy. I personally would not want to own a cat that didn't have a fairly large amount of reserve buoyancy, and these are easy to find. Almost all performance oriented cats have lots of reserve buoyancy.

As to rigs: multihull rigs must be much stronger than the rigs of similar-sized monohulls, because multihulls don't heel when hit by a gust. It's the old flagpole set in concrete problem. Because of this, I would guess that multihull rigs are far more likely to survive a violent capsize than monohull rigs.

Of course, when the mast is pointing straight down, it doesn't do you that much good.

But in the end, people should understand that the capsize of a large well-designed modern cruising multihull is such a rare event that worrying about it is like worrying that a meteorite is going to hit you on the head. Almost all multihull capsizes (aside from beach cats) occur as a result of racing. If you're not racing, and you sail your big cat or tri prudently, you're not in any significant danger of capsize.

In a lot of ways, figuring out a way to right a capsized multi is like trying to design a meteorite-proof hat.

In the real world, you're probably not going to ever need either of those things.
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  #29  
Old 05-07-2009, 01:18 PM
Boston Boston is offline
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Quote:
I would guess that multihull rigs are far more likely to survive a violent capsize than monohull rigs.
maybe I misunderstood something
multi's dont self right
mono's do
sooooooo
how is the multi more likely to survive
or at least its crew, I say you can sacrifice the continued usefulness of the boat as long as its floating and providing shelter for the crew,
its gravy if you can get it going again but its a dry place to hang out that maters

Ill put a fat lead shoe on mine if I have to, but that things coming back up no mater what hits it, and those companionways are going to be water tight bank vaults by the time Im done with em. Decent storm shutters might be a plus as well. but there are ways to be as survivable as possible while not sacrificing the function nor beauty of the build

in the event of an asteroid of course
( that was dam funny Ray )

although roage seas have been shown to generate up to 30 meter waves with unusual characteristics conducive to trashing anything that floats. A 10 meter wave is more than enough to demolish most pleasure craft and going beam on for whatever reason you could find your self upside down fast.

personally Ild like to be just hanging on hoping the Lou doesnt break loose and brain me, while the boat comes back around, rather than go swimming
on a cat your ass is swimming no two ways about it

as for the occurrence of capsize in a cat vs mono hull
anyone got the numbers
?
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  #30  
Old 05-07-2009, 01:35 PM
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marshmat marshmat is offline
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The nonlinear "rogue waves" are of course going to beat the stuffing out of anything short of a nuclear submarine. There are photos going around of 700' freighters that have been hit by such waves, ripping through steel plating like it was paper and taking out a few thousand square feet of structural bulkhead in the process. Dynamic loads on the order of fifty to a hundred tonnes per square metre, or so I've heard. Thankfully they're rare, and certain areas known to be prone to this phenomenon can be avoided.

With normal (linear) waves, I suspect that as long as they're not breaking, a well-balanced cat should be able to raft right over them. (Not necessarily with sails up, though.) Some reports of monos getting in trouble with such waves seem to indicate that everything's reasonably OK unless the boat goes beam-on to the seas, at which point the keel digs in and trips the boat as she surfs sideways. That's when the self-righting ability (and, B., some good strong bolts on the head ) comes into play.... Now, once breakers get involved, that's a whole new ball game.
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