Shocked by hull material catamaran

[Cotemar]

Lagoon 570 do have Mini Keels.

This was a major grounding that this boat went through to grind off a few feet of mini keel before biting into the hull.

[a64pilot]

One thing that has not been brought up, but maybe should, is that even with a huge hole in her hull the size of which would easily overwhelm any bilge pump, she was floating well enough to be salvaged.

[skipmac]

Originally Posted by daletournier

And you'll find tons of people that do buy, them, this is not new, balsa boats have been cruising the world oceans for years, there are 1,000s out there.

This is a subject that has been discussed over and over, often with no agreeing at the end. Ive read most of what there is to read and previously owned a balsa build, I have drilled through it, hit stuff in it and sailed many 1,000s of miles, most that (not all) make big statements regarding there longevity haven't any first hand experience with them.

When you smash a reef, and do that sort of damage its unlikely to make any difference what hull medium is used.

Anyway, everyones entitled to their opinion.

Cheers.

Sent from my vivo Y35 using Cruisers Sailing Forum mobile app

This is also my experience and opinion. Currently own a 30 year old boat with a balsa core hull below the water line. Did a peel and seal that allowed me to see the core once the bottom paint and gell coat layer was shaved. Amazing how clear even several layers of glass and resin can be. The core was perfect. Not a single spot of wetness or delamination visible.

Yes a couple of spots on the deck where fittings weren't maintained or properly bedded I had mostly very small areas of wet and rot. All fixed without too much fuss and muss.

[SV DestinyAscen]

I'm not sure what's the problem.

Sacrificial keel? In the pics I see the hull as intact and the keel as being gone.

Yah there's wood in the hull, but it is encased in resin. Ideally you don't want wood below waterline unless it is epoxy, but is there osmosis occurring? If not there's nothing wrong with it.

[iliohale]

Be sure to read my post of my factory tours at Nautitech and FP here:
http://www.cruisersforum.com/forums/...ch-172776.html

Here are my notes regarding Hull Core:

Core Material – FP uses Divinycell in the deck and balsa in the hulls. Nautitech uses Divenycell in both the hull and deck. The representative at FP indicated that they only use Divinycell in the deck because it is required for CE certification. I asked about the concern of having balsa core in the hull in terms of potential water absorption and the response is that the core material is never exposed to pentation from a fitting or fastening as these areas of the hull and deck are solid fiberglass. Further with the resin infusion used by FP it was very clear that resin fully penetrates the gaps between the small blocks and that water would not be able to migrate easily. It would be interesting to know the pros and cons between balsa and Divinycell and the associated weight differences between them in full section with infused resin. Also if there is any difference between adhesion to the fiberglass layers. The actual resin infusion process is pretty basic and I didn’t see any difference between the companies. Both companies use very controlled core placements and fiberglass schedule. All the glass is pre-cut and labeled for placement. At Nautitech I noticed very careful smoothing of the fiberglass layers and the infused parts looked really good and clean. On the FP I did see a few wrinkles here and there on the infused parts. Please do not take this as indicative of anything since my sample and time to inspect was so limited. Further, a wrinkle here or there in the cloth has no bearing on the overall quality of the boat and would be entirely expected. Further, I didn’t see the process of laying out the cloth while at FP.

[thinwater]

I dunnow. My cat (8500-pound PDQ) is solid below the water line and about 6 inches above that (I've installed through hulls).

Yes, weight is important, but the weight difference, only below the water line, can't be that great. Cats don't have deep bilges.

A delaminated (soft deck) is troubling, a laminated bilge is typically "game over."

All that said, my last cat was cored below the water line (Nomex honeycomb); it was damaged once in the yard and was easily repaired. Of course, honeycomb does not wick.

[smj]

Here's a quote from the FP website.
The foam used in the core sections is closed-cell, eliminating the balsa core deck issues found in many other brands. This technique also provides the buoyancy to comply with the stringent EC rules regarding unsinkable certification through CE. Fountaine Pajot also places foam buoyancy well above the bridge deck so a catamaran will float high out of the water in the unlikely event of a capsize.
It appears the use of Divinycell isn't required for CE certification, just the ability to provide flotation so the boat doesn't sink. I'm sure balsa would also be suitable enough to pass the CE certification as Lagoons and other CE certified cats use balsa as a deck core.

[44'cruisingcat]

If you smash the hull water can get into the core. Shocking.




Not.

[PaulinOz]

"One thing that has not been brought up, but maybe should, is that even with a huge hole in her hull the size of which would easily overwhelm any bilge pump, she was floating well enough to be salvaged."

I also find it totaly shocking that a 9 to 17 year old boat, designed last century, ran aground on a reef on Union Island, completely grinding away totally one of its mini keels. (from memory did the L570 not use its keels as tanks) and parts of its hull and here it some 120 plus miles away on the hard being inspected, photographed, complained about and possibly repaired.

Shocking should have had the decency like a lot of others to just become another artificial reef.

[neilpride]

I dont found the salvage details in the net, but im sure they Patched the holes with Plywood , lots of small holes around the damaged section.

[yeloya]

Originally Posted by barnakiel

One thing is I am not 100% sure it is legal to take images of somebody else's boat and post them on the forum without explicit or implicit indication of obtaining the owner's permit to do so.

This is what they call property release in some countries. Lack of, in OP's case.


Cheers,
b.

If it's legal, it for sure isn't ethical..

I have seen in our yards 5-6 boats grounded over the last 7-8 years. The best one was a Dufour 40 limited edition with a lead keel, almost intact..
The worst one was a Lagoon 421 ,that sank. Another Lagoon could barely made to the marina with the keel damaged and taking water. I hit an underwater rock with my FP (sacrificial keel) and continued to sail another week. The repair was very simple and not expensive at all..
None of us here is as knowlegeable as VPLP to challenge him but I really don't understand why Lagoon is insisting on rigid keels. Maybe he knows something that we all don't..

The discussion of balsa, glass, etc is useless; there is no boat that can be designed to survive a grounding or hitting something at a speed of 7-8 kts, The attempt to achieve this will result in excessive cost or weight or both...

Cheers

Yeloya

[PaulinOz]

"they Patched the holes with Plywood , lots of small holes around the damaged section."
Well spotted Neil, when you zoom in screw holes very evident, along with the amount of grinding on the hull, as is evident by the worn through layers of Anti-foul, barrier coat, gelcoat and cloth lay up. Looks like she was washed around on an abrasive surface for quiet a while.

[SVTwilight]

Originally Posted by neilpride

Monohulls fair better on reefs or rocks, sometimes the isue with this condocats are that when they get stuck in a reef any towing or salvage operation result in hulls and keel ripped in pieces,, they need to keep it light as posible then those thin laminates make sense as far they dont touch noting hard...


https://youtu.be/EXSx4brt4E8

Nice outcome!

[Stumble]

Originally Posted by smj

Here's a quote from the FP website.
The foam used in the core sections is closed-cell, eliminating the balsa core deck issues found in many other brands. This technique also provides the buoyancy to comply with the stringent EC rules regarding unsinkable certification through CE. Fountaine Pajot also places foam buoyancy well above the bridge deck so a catamaran will float high out of the water in the unlikely event of a capsize.
It appears the use of Divinycell isn't required for CE certification, just the ability to provide flotation so the boat doesn't sink. I'm sure balsa would also be suitable enough to pass the CE certification as Lagoons and other CE certified cats use balsa as a deck core.

To get the Class A certification these boats rely on proving they are unsinkable (it's one possible route). In order to get the amount of foam they need to do that they could build a boat with solid laminate hulls then add enough foam to provide the necessary flotation. But the better option is to use the foam as a core. Because foam in the core not only adds flotation, it also dramatically to stiffness.

In most conversations about cored hulls/decks to engineering goal is to provide a minimum stiffness at minimum weight. Cores are ideal for this, and balsa is actually better than foam is because its stiffness is much higher.

But for the unsinkable boats as a class the core thickness is not designed for minimum weight, but for minimum flotation. They just keep adding core thickness until the boat becomes unsinkable, even if the laminate I see far stiffer than it needs to be.

For this way of thinking foams are far preferable to balsa because it it lighter than balsa per unit volume. Even if a balsa core is far stiffer, the foam is stiff enough but weighs half what balsa does. This means you don't need as much volume to float the weight of the core itself. (I am not explaining it well...).

The following numbers are purely illustrative, foams vary in density (from ~3lb/ft^3 to 6.9lb/ft^3) as does balsa (7-9lb/ft^3)

To try a different way of explaining it. Let's assume you start with a boat that weighs 1,000kg. And the volume of the boats structure as designed is 750L. It will absolutly sink if it floods, so you need to add 250L of volume to float the structure. To do that you decide to add a core to the laminate stack. The volume has to be there, and it's free stiffness, which is never a bad thing.

So you add 250L of foam. Great you can now float the boat. But you need a little bit extra to float the foam. The foam weighs in at .1kg/L, we added 250L so now we need to add an additional 25L of foam, to float that new portion of foam we need 2.5L of foam... and let's jus take stop there. So to float the original 250kg of weight we need to add ~275L of foam with a weight of 27.5kg

If you do the same thing with balsa... you need the same 250L of balsa, and it is far stiffer, so the boat is now even stiffer than it was with foam (which was already stiffer than we needed it to be). But where foam weighs in at .1kg/L, balsa is closer to .3kg/L. So to float the 250L of balsa we need 75L additional of balsa, to float that we need 22.5L and so on... so to float the originals 250kg of structure we need ~350L of balsa. With a weight of 105kg.

So even though balsa is a 'better' core I need a lot of ways it's density is a killer when the goal isn't to hit a minimum stiffness number, but to ensure a given about of flotation.

Core selection obviously gets much more complicated than this and most boats today's will use some mix of foams, both in type and thickness to get to the number size they want (stiffness, flirtation, insulation, weight, etc). So you very well might find a boat with a balsa core under the mast, light weight foam in the hull, denser foam near the chainplates, etc...

[44'cruisingcat]

Originally Posted by neilpride

Monohulls fair better on reefs or rocks, sometimes the isue with this condocats are that when they get stuck in a reef any towing or salvage operation result in hulls and keel ripped in pieces,, they need to keep it light as posible then those thin laminates make sense as far they dont touch noting hard...


https://youtu.be/EXSx4brt4E8

There were no reefs or rocks in the video.