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Old 01-10-2016, 19:16   #1
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Positively buoyant catamarans

I am interested in Leopards and Lagoons. Is there any way to look up if they are supposed to be positively buoyant?

Specifically:
Leopard 40
Lagoon 400
Leopard 43
Lagoon 410 S2
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Old 01-10-2016, 19:24   #2
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Re: Positively buoyant catamarans

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Originally Posted by lindabarzini View Post
I am interested in Leopards and Lagoons. Is there any way to look up if they are supposed to be positively buoyant?

Specifically:
Leopard 40
Lagoon 400
Leopard 43
Lagoon 410 S2
Can't answer your specifics regarding these particular vessels but the heavy production cats will not be as good as many of the custom foam and balsa core by the well known designers such as M & M, Suttleworth, Chris White and the Australian and NZ designers such as Schonning, Grainger, Hill, Oram, Stanton etc.
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Old 01-10-2016, 19:34   #3
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Re: Positively buoyant catamarans

Lagoon has fought more than one lawsuit over their claim in their brochures of being "unsinkable" after of course one would sink. Most cats will remain afloat from air pockets in the bows etc. Many found a year or two later with bows pointing upward, or even inverted, both leopards and lagoons. I know of one leopard 38 that had a fishing boat hole it mid ships and it did not sink and another that was holed on a reef , flooded an engine compartment and didnt sink either. Our Athena has 4 buoyancy compartments, and flotation foam in all 4 corners. Not sure what would happen if she were holed.
As for for core material the Leopards have a very thick balsa core. I have seen one large shuttleworth sunk that was listed here for sale at one point. I love the story article about the PDQ 36 the CG tried to scuttle w machine gun fire and it would just not sink.

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Old 02-10-2016, 01:40   #4
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Re: Positively buoyant catamarans

I've seen a Lagoon 410 floating upside down in Simpson Bay Lagoon, Sint Maarten. Got turned over at anchor during Hurricane Omar in 2008. That probably means it is buoyant but if the mast was still in place that may have been digging into the mud which would help!
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Old 02-10-2016, 04:03   #5
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Re: Positively buoyant catamarans

Nearly all modern production cats have sandwich construction in the decks and hull sides from above the waterline. This means they will not sink and hence can survive (unless very heavily loaded) but generally they will float with deck awash without other measures, so its a salvage job requiring external assistance.
Again, nearly all productions cats also have usually partial watertight "crash" bulkheads in the forepeaks and the aft ends. There may be 2 compartments in the aft end one for the stern itself and then the engine bay. If you crunch either bow or stern, these compartments can flood but there should be sufficient reserve buoyancy in the remaining hulls to limit the flooding to the affected compartment. Of course, the conditions may be such that flood water can surge over a partial bulkhead and pumping will be required to maintain that status. Generally, you will still be able to move and control the vessel in some way.
If you crunch the midships section of a hull, maybe by punching a hole by grounding, its not quite so clear cut because the centre section is so much larger and flooding has a much greater effect. Only the designer or proper calculation can tell you where the still waterline will end up and whether it will be close to or above the internal bridge deck level and allow unconstrained cross flooding into the other hull or across the partial bulkheads and flooding some of the watertight compartments changing the situation from possibly retrievable organically unaided by others (damage control and pumping) to just survival and salvage relying on the locked in buoyancy built into the hull and deck structure.
The good news, is that even in the worse case, you are still very much better off regarding sinking compared to nearly all monohulls.
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Old 02-10-2016, 04:07   #6
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Re: Positively buoyant catamarans

I have my doubts any of these floats, except if air is trapped inside.
Maybe the Lagoon 410 will still float as its relatively light compared to the others but even that one I have my doubts (and I have owned one of these a few years back).

I am quite sure some Fountaine Pajot models do float:
In addition to using light foam core they add a few cubic meters of foam floatation in specific areas.

Our Mahe had the lower half of bow compartment, under the aft cabin bed, under the saloon setteee all filled with foam. I would guess worth at least 2-3 tons (at 5 ton empty displacement).
Plus it has no penetrations from the engine bays to the main hull section so flooding the engine doesn't sink the boat.

I think but I'm not sure the Lipari is the same
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Old 02-10-2016, 04:24   #7
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Re: Positively buoyant catamarans

Not sure about the machine gun .but I know that a 36 went on a reef,took out one of the bottoms and floated of on the next tide. Water did not make it to the saloon floor. Except below the WL every panel is cored, the bulkheads are plywood. It took a big stack of foam to build the boat. Not helping the Op but interesting (at least to me)
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Old 02-10-2016, 09:11   #8
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Re: Positively buoyant catamarans

Linda I have. Some pictures of a leopard 44(sad case) that once inverted travelled upside down from almost Australia back to Cape Town over a full year with only. With human intervention. Sadly it ripped. Apart and sank.

So for Mcel it's clear that they are positively buoyant


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Old 02-10-2016, 09:32   #9
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Re: Positively buoyant catamarans

We have an 07 Leopard 40 owners version. There are indeed watertight bulkheads for and aft. In addition under each berth there are very large completely sealed storage areas. These areas are thigh deep almost 4 feet wide and 3 feet long. We Keep our boat very light and balanced so I do believe she would float even if completely flooded. {{{{{{{shivers at the thought}}}}}}}!


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Old 02-10-2016, 10:03   #10
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Re: Positively buoyant catamarans

I thought you had your heart set on an Amel because you liked the steering wheel? Now I'm trying to picture your Leopard or Lagoon with three composting heads, that's a lot to process.
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Old 02-10-2016, 11:35   #11
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Re: Positively buoyant catamarans

The nice thing with multi's, especially cats, is that it's easy to find the space to add lots of buoyancy to them. And to add it where you want it. As well as building sealed compartments via partial bulkheads. These things will ensure that the boat will float at a reasonable level, with the desired attitude (angle) if holed.
Also, fortunately, foam & glass are cheap. And for the most part, the foam needn't be the pricey, structural type used for constructing hulls & decks. Nor nearly so dense. Just ensure that any additions made to the boat are up to the hydrostatic pressure of water surging into & out of the hull at several knots. Ditto on any factory built structures that they're tied to.
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Old 02-10-2016, 11:47   #12
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Re: Positively buoyant catamarans

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Originally Posted by Dulcesuenos View Post
... I love the story article about the PDQ 36 the CG tried to scuttle w machine gun fire and it would just not sink.

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PDQs have multiple large crash tanks and bulkheads for and aft. Not all boats do. Pitty.

I had a through hull fail (speed sensor mis-assymbled after sea trial) during a delivery trip. It was in a bulkheaded compartment, so we simply ignored it for 3 days until we reach harbor. 5-minute fix, and no risk of flooding.

I would not foam a crash tank in a cat. A real mess if it gradually gets wet. It is simply unnecessary, since even holed it controls flooding. The important thing is to divide the tanks and to make them long enough (restrict the floor length).
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Old 02-10-2016, 12:33   #13
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Re: Positively buoyant catamarans

Personally I'm very skeptical of the unsinkable safety claim. Murphy has its way - say for example you're flying at 10 knots under spinnaker on port tack - clip a container on starboard and it gashes from front bulkhead to center of hull. Boat tips starboard and leans over from inertia and spinnaker. Starboard floods, boat slowly leans over so little air is trapped in cabin or saloon. Full water and fuel tanks, blackwater through hulls open as you're five miles out.

Only reserve bounyacy would be port collision and foam core. It might float - but it'll sort of useless as it'll be at sea level and imbalanced.
Only you can tell your risk tolerance is - but I wouldn't count on it advert total disaster. The safest cats have bow collision bulkheads and rudder assemblys bulkheads that mitigate rudder axe damage. But the wrong impact and one hull floods it's gonna be a bad situation.

It's like ppl in monohulls focusing on righting ability but perhaps rig is completely gone after bad knockdown. Seaworthy is one thing - imperveous to Murphy is another.
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Old 02-10-2016, 14:23   #14
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Re: Positively buoyant catamarans

The above post does bring up the other problem in cats, if holed. Which is that the boat may retain it's unsinkability after a holing, but the buoyancy imbalance as one hull fills may cause her to flip. Either right away, or later on with the assistance of a few waves.

And there are collisions which total a boat so badly that your only option is to hop into another boat (AKA the life raft). Such as when a big Crowther struck a whale at speed (15kts), & she pretty much crumpled for most of her length. So that the crew had but seconds to take to the raft.
Rare yes, but possible.


thinwater I'm not entirely clear as to your view on it being unwise to build in some crash protection. Especially if you're adding foam floatation anyway. As it's quite easy to integrate them both into the same package. And to me it seems like common sense to do so, since it takes little more effort to do both vs. adding just one of these options.

I concur that poorly chosen foam, improperly installed could be quite a mess. But I don't think that doing this kind of work is at all rocket science. Besides which, if such added structure prevents a compartment from being breeched by the sea, then odds are it was a success.

That, & I agree too with the idea of dividing the boat up into enough compartments that breeching one or two of them won't drastically affect the boat's floatation & trim. Much as is (or was) dictated for the OPEN/IMOCA 60's & other boats of similar type. Even though all of them already had built in positive buoyancy prior to this dictum.

BTW, why sail around for several days with a hole in the boat when it was easy to fix it? As plugging a transducer into it's through hull is typically about as easy a fix as they come (in terms of below the WL stuff). Non?
And were any of those bulkheads surrounding the leak wooden, or cored? Thus being subject to possible moisture ingress.
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Old 02-10-2016, 15:40   #15
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Re: Positively buoyant catamarans

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Originally Posted by UNCIVILIZED View Post
The above post does bring up the other problem in cats, if holed. Which is that the boat may retain it's unsinkability after a holing, but the buoyancy imbalance as one hull fills may cause her to flip. Either right away, or later on with the assistance of a few waves.

And there are collisions which total a boat so badly that your only option is to hop into another boat (AKA the life raft). Such as when a big Crowther struck a whale at speed (15kts), & she pretty much crumpled for most of her length. So that the crew had but seconds to take to the raft.
Rare yes, but possible.


thinwater I'm not entirely clear as to your view on it being unwise to build in some crash protection. Especially if you're adding foam floatation anyway. As it's quite easy to integrate them both into the same package. And to me it seems like common sense to do so, since it takes little more effort to do both vs. adding just one of these options.

I concur that poorly chosen foam, improperly installed could be quite a mess. But I don't think that doing this kind of work is at all rocket science. Besides which, if such added structure prevents a compartment from being breeched by the sea, then odds are it was a success.

That, & I agree too with the idea of dividing the boat up into enough compartments that breeching one or two of them won't drastically affect the boat's floatation & trim. Much as is (or was) dictated for the OPEN/IMOCA 60's & other boats of similar type. Even though all of them already had built in positive buoyancy prior to this dictum.

BTW, why sail around for several days with a hole in the boat when it was easy to fix it? As plugging a transducer into it's through hull is typically about as easy a fix as they come (in terms of below the WL stuff). Non?
And were any of those bulkheads surrounding the leak wooden, or cored? Thus being subject to possible moisture ingress.
Very good questions.

Foam. Early Geminis filled the tanks with foam, and when they had a few top-side leaks, they were terrible to fix and very heavy. I know that my tanks occasionally get some water in them; if a compartment has an inspection hatch it will breath, pant under way, and occasionally sweat. In the case of a rudder tube compartment, I want to be able to inspect the tube after impact (bent one once) and perform internal repairs if need be. I would not want them foam-filled. Just an observation. It makes good sense for small bow compartments for racers, but maybe not for cruisers.

Why didn't I fix the leak? The water was 32F making work (while basically standing on your head in rough conditions--an ugly location in the compartment) quite unpleasant. We were in the Chesapeake Bay, not off-shore. I was able to pump it down periodically and determine that it was a very slow leak; it took over 8 hours to re-flood. I suspected the source. No, none of the bulkheads nor the gear in them was subject to water damage. All electrical components are WAY above the water line. Yes, I would have been more proactive off-shore.

Good questions.
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