Lagoon 400 Bulkhead an issue?

[smj]

Originally Posted by arsenelupiga

Great insight !

It does confirm that is metal used.

And wood has no structural relevance - thanks good for this one - i could not sleep with wood being structural and rot that one cant control like all other cats

weight / sail area is actually slightly better in L400 than L42.

my entry for upwind is 5 kn in 10 kn true at 55 true in similar conditions. This seem better than what stated for L42. Reaching, lagging for a knot or so with gennaker due to better geomerty of L42 for such conditions.

I see nowhere where it states that the bulkheads aren't a structural part of the boat. Yes they used a metal beam as a mast step rather than the main bulkhead, just like they did on my old 1973 Cherokee 35 catamaran. One of the problems with the metal beams in the old Sailcraft boats was rust! There is no perfect solution.
And by the way, your entire boat relies on wood as a structural member, that would be the balsa cored hulls and deck.


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[tuskie]

Originally Posted by smj

I see nowhere where it states that the bulkheads aren't a structural part of the boat. Yes they used a metal beam as a mast step rather than the main bulkhead, just like they did on my old 1973 Cherokee 35 catamaran. One of the problems with the metal beams in the old Sailcraft boats was rust! There is no perfect solution.
And by the way, your entire boat relies on wood as a structural member, that would be the balsa cored hulls and deck.


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Unfortunately the article is a bit "salesy" but it does give an insight to reasoning behind design. Thanks Peter. The mast geometry and support structure is quite different between L400 and the new 42, as the rig has been moved aft.

I've not yet seen a L42, but have crawled over a neighbour's L39, which has a similar rig. There is a stainless support structure and mast compression post, but it seems that this is supported by fiberglass structures below deck level.

SMJ is quite right about timber. From Peter's article it seems that the new L42 has followed the lead of FP's Helia and have used balsa core below the waterline. Whilst this undoubtedly saves weight, in my opinion this is a huge compromise for longevity. No timber, no rot, no buts.

[tp12]

Hmmm .. no holes, no moisture ingress, no rot.

Plenty of balsa cored boats out there that don't have issues.

[robert sailor]

Salesy eh! The whole article is an infomercial written by Lagoon, no matter the author.

[smj]

Yet with all the weight saving techniques it still weighs almost 50% more than the comparable Seawind or Catana and has equal or less sail area.


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[BigBeakie]

Originally Posted by tp12

Hmmm .. no holes, no moisture ingress, no rot.

Plenty of balsa cored boats out there that don't have issues.

And plenty that do. Balsa is very "water unfriendly".

I visited a shipyard in the US that pretty much makes it's living fixing up rotting balsa boats. It's not just that someone hasn't properly sealed a hole into the core. There is the issue of longer term osmosis & hydrolysis.

Sea Ray and Balsa Core Bottoms - by David Pascoe, Marine Surveyor and related articles.

It is used to keep costs down. Pure & simple. Ironically, cruisers who buy a production boat because they feel it is a lower risk option (risk averse) run significant risks if the boat is a balsa core boat. Foam is far superior and if you poke a hole in your foam boat at least you will have more time to get to a repair facility.

It may seem paradoxical with balsa being so soft, but it has high values in some mechanicals, such as compression. That would seem to be a good thing at first glance, but because the balsa core does not absorb impacts, it transmits them to the inner skin which can lead to delamination of the inner skin. Any moisture in the core then gets "pumped" by the repeated impacts, i.e. waves, and the balsa turns to mush.

There are foams such as Divinycell HM and Corecell M which absorb impact energy & are much better suited to quality boatbuilding.

But, if you just sail around in relatively benign conditions, as most people do, AND you never bump into anything below the waterline, AND extreme care has been taken in the construction (and of course production builders are known for taking extreme care in QA with EVERY boat they churn out), then balsa boats may be worth the risk for you.

But not for me.

[smj]

Originally Posted by BigBeakie

And plenty that do. Balsa is very "water unfriendly".



I visited a shipyard in the US that pretty much makes it's living fixing up rotting balsa boats. It's not just that someone hasn't properly sealed a hole into the core. There is the issue of longer term osmosis & hydrolysis.



Sea Ray and Balsa Core Bottoms - by David Pascoe, Marine Surveyor and related articles.



It is used to keep costs down. Pure & simple. Ironically, cruisers who buy a production boat because they feel it is a lower risk option (risk averse) run significant risks if the boat is a balsa core boat. Foam is far superior and if you poke a hole in your foam boat at least you will have more time to get to a repair facility.



It may seem paradoxical with balsa being so soft, but it has high values in some mechanicals, such as compression. That would seem to be a good thing at first glance, but because the balsa core does not absorb impacts, it transmits them to the inner skin which can lead to delamination of the inner skin. Any moisture in the core then gets "pumped" by the repeated impacts, i.e. waves, and the balsa turns to mush.



There are foams such as Divinycell HM and Corecell M which absorb impact energy & are much better suited to quality boatbuilding.



But, if you just sail around in relatively benign conditions, as most people do, AND you never bump into anything below the waterline, AND extreme care has been taken in the construction (and of course production builders are known for taking extreme care in QA with EVERY boat they churn out), then balsa boats may be worth the risk for you.



But not for me.

A well built balsa boat is much better than a badly built foam boat but then again a well built foam boat is much better than a badly built balsa boat, they each have properties that are advantageous. I believe balsa is superior in adhesion, and if you use epoxy and take care to build correctly it's a great product. Foam is also a great product as its rot resistant, so if care is taken when building to get good adhesion it's a great product.


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[robert sailor]

You pretty much have to core a deck or your boat will be a piglet, as to hulls, if the builder knows what he's doing cored hulls above the waterline are fine, I've owned both and had no issues.

[BigBeakie]

Originally Posted by smj

A well built balsa boat is much better than a badly built foam boat but then again a well built foam boat is much better than a badly built balsa boat, they each have properties that are advantageous. I believe balsa is superior in adhesion, and if you use epoxy and take care to build correctly it's a great product. Foam is also a great product as its rot resistant, so if care is taken when building to get good adhesion it's a great product.


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Yes, as I said, IF you do the right things like use epoxy (do they use epoxy in production boats ie Leopard, FP & Lagoon?? - I think not) and all the other ifs, then MAYBE it is suitable in order to save a few bucks.

But there is not much reason anymore to not use infusion, even for a home builder, and that fixes any adhesion issues regardless of core used, especially using perforated/channelled core and good vinylester resin with high solids.

So it seems to me the ONLY advantage for balsa now vs the HM/Corecell M is cost. It is the cheapest material to use. But the cost difference over the areas of hulls and underside bridgedeck is quite minimal.

My point is, why take the risk?

[BigBeakie]

Originally Posted by robert sailor

You pretty much have to core a deck or your boat will be a piglet, as to hulls, if the builder knows what he's doing cored hulls above the waterline are fine, I've owned both and had no issues.

Agreed, with respect to decks. IF the balsa is de-cored, filled back with epoxy bog, on EVERY single core penetration EVERY time, then sure. But, wouldn't the extra labour required to take such measures offset the slight savings of using balsa in the first place?

Impact delamination can and does happen above waterline, in fact it happened to a cat I was on at the time with a wave strike to the starboard bow area. A real hassle to repair as all the furniture bonded in that area had to removed which is easier said than done let me tell you.

IMHO, it is well worth getting a boat that is built with good materials and good, proven boatbuilding techniques in the first place. Yes, it might cost you 10 grand $ more. On a boat over half a million $, that seems like a good investment to me.

But the market is driving the "cost chase" so, that's what we get. This thread is a good example of folks that buy space, (sorry, I mean "comfort") instead of quality. Quality being light, strong, durable over the long haul, boats.

[Factor]

Yes - Balsa, or more particularly Duracore, and Epoxy built carefully is a wonderful strong stiff and reliable material, If you are building a custom cat its definitely worth considering. Closely followed by western red cedar and epoxy.

For production builders who don't use epoxy, well I have little time for the material.

An infused foam and glass with at least Vinylester Resin is the only reliable production method that keeps weight down and stiffness and strength up.

[BigBeakie]

Factor,

Spot on, mate!

[44'cruisingcat]

Originally Posted by BigBeakie

So it seems to me the ONLY advantage for balsa now vs the HM/Corecell M is cost. It is the cheapest material to use. But the cost difference over the areas of hulls and underside bridgedeck is quite minimal.

My point is, why take the risk?

No, balsa still has better properties in compression, tension and sheer.

If you get your hands on a sample of properly laminated balsa cored panel and foam panel, and try to peel the laminates off, the difference will surprise you.

[BigBeakie]

Originally Posted by 44'cruisingcat

No, balsa still has better properties in compression, tension and sheer.

If you get your hands on a sample of properly laminated balsa cored panel and foam panel, and try to peel the laminates off, the difference will surprise you.

The best materials testing information I could find was by the Swedish Navy which were doing meticulous panel testing for their upcoming high speed patrol boats. They tested all the core materials, e-glass vs s-glass, and the various resin formulations. They did it with both vacuum bagging wet layup and VIP.

Then they subjected the panels to various torture tests including maximum impact drop testing and repeated lower intensity cyclic loads simulating wave strikes.

The clear winner was Corecell M with epoxy resin infusion giving a 1:1 resin to glass weight ratio. The epoxy was, from memory, SP Systems which had a high "toughness" characteristic (no micro-cracking). We also tested West Systems vs SP and found the same thing.

Balsa core was down the list and had inner skin delamination, because it's compression modulus is so high. The force gets transmitted through the balsa to the inner skin, particularly where there are longitudinal members or bulkheads that restrict the panel being able to flex. So in this case, more is not better.

There is a big move in the high performance watercraft field to be using the Diab HM or Corecell M for this resistance to delamination, check it out yourself.

[robert sailor]

Cost conscious builders like Group Beneteau will not be looking for hi tech expensive solutions to weight and strength improvements for Lagoon yachts because their buyers prefer more space, not more speed.