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post #11 of 28 Old 05-27-2012
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Re: Balsa cored hulls

From what I have seen and please correct me if my observations are wrong, but I have yet to see a production boat, other than pure race boats to be completely foam cored. What I have observed is the foam finishes at the waterline and the underwater part of the hull is solid glass. I do know that Ben, Dahl, Jano and Bov, did look at at some point look at totally foam cored and did make a few boats in all core, but went back to solid glass below the waterline. It may have to do with the fact they all use bolt on keels.

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post #12 of 28 Old 05-28-2012
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Re: Balsa cored hulls

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I would always chose epoxy resins, and pay the premium for them. If they can make the boats lighter using epoxy then they are saving weight somewhere else. ... Hanse is selling an epoxy version. It is heavier, not lighter. I don't know what the core material is. So the layup and core are identical with the trade off being heavier epoxy for greater strength--...
No, Hanse epoxy boats are lighter not heavier than the ones that use "normal" resins. Not only Hanse but on all builders I know that have an option with epoxy, the lighter boat is the one made with epoxy. I guess they will need less resin using epoxy for the same or even bigger strength.

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post #13 of 28 Old 05-28-2012
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Re: Balsa cored hulls

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From what I have seen and please correct me if my observations are wrong, but I have yet to see a production boat, other than pure race boats to be completely foam cored. What I have observed is the foam finishes at the waterline and the underwater part of the hull is solid glass. I do know that Ben, Dahl, Jano and Bov, did look at at some point look at totally foam cored and did make a few boats in all core, but went back to solid glass below the waterline. It may have to do with the fact they all use bolt on keels.
No, fast boats have also most of the hull cored. Only around the keel and in the areas near by they use monolitic.

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post #14 of 28 Old 05-28-2012
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Re: Balsa cored hulls

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No, Hanse epoxy boats are lighter not heavier than the ones that use "normal" resins. Not only Hanse but on all builders I know that have an option with epoxy, the lighter boat is the one made with epoxy. I guess they will need less resin using epoxy for the same or even bigger strength.

Regards

Paulo
My information is out of date.

It seems you are right in that less epoxy is needed, resulting in a lighter hull.

An interesting article on core, fibers, and bonding resins.

I learned a few things reading it.

Adrift at Sea Cored Laminates in GRP Boats

It seems these days less epoxy is used so would it be stronger? Perhaps not. Also there is the temperature issue.

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post #15 of 28 Old 05-28-2012
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Re: Balsa cored hulls

Yes, nice article.

Regarding weight many times when you use epoxy you use also more expensive infusion techniques, namely vacuum infusion and that can provide with less epoxy a stronger boat. You can add the epoxy you want if it is more than the one that is needed it will not make the boat stronger, only heavier

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post #16 of 28 Old 05-29-2012
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Re: Balsa cored hulls

PCP,

The primary reason to use foam as opposed to balsa is actually not it's mechanical properties on race boats. Balsa is nominally a much better material than foam across the board. The difference is that every since piece of foam is structurally identacle, with almost no variation until you put it under a microscope, and even then... Balsa on the other hand can have significant variation in density, sheer, and compression loads, on average they are better, but if you are the one that has a weak panel.

While it might suck on a J-24, if you happen to be on an Open 60 where the rig tension is running 60,000lbs or so. When it fails things don't fall over, they explode.
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post #17 of 28 Old 05-29-2012
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Re: Balsa cored hulls

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PCP,

The primary reason to use foam as opposed to balsa is actually not it's mechanical properties on race boats. Balsa is nominally a much better material than foam across the board. The difference is that every since piece of foam is structurally identacle, with almost no variation until you put it under a microscope, and even then... Balsa on the other hand can have significant variation in density, sheer, and compression loads, on average they are better, but if you are the one that has a weak panel.

While it might suck on a J-24, if you happen to be on an Open 60 where the rig tension is running 60,000lbs or so. When it fails things don't fall over, they explode.
You know the expression, "I drive it like I stole it"? That is how Open 60's skippers sail those boats. I seriously doubt rig tension would be the problem. Slamming the relatively flat hull on waves over and over again will IMHO more likely cause a delamination failure in one of those boats. There are lots of cheap Open 60's out there. The question is how much life is left in them?


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post #18 of 28 Old 05-29-2012
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Re: Balsa cored hulls

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You know the expression, "I drive it like I stole it"? That is how Open 60's skippers sail those boats. I seriously doubt rig tension would be the problem. Slamming the relatively flat hull on waves over and over again will IMHO more likely cause a delamination failure in one of those boats. There are lots of cheap Open 60's out there. The question is how much life is left in them?
A lot. There is a circumnavigation race for old Open 60 (Velus five Oceans). Some race with 20 year's old boats that had circumnavigated (racing) many times. Never heard about significant problems with delamination. but I have heard problems about delamination problems on the super hi-tech new Volvo Ocean Racers

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post #19 of 28 Old 05-29-2012
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Re: Balsa cored hulls

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A lot. There is a circumnavigation race for old Open 60 (Velus five Oceans). Some race with 20 year's old boats that had circumnavigated (racing) many times. Never heard about significant problems with delamination. but I have heard problems about delamination problems on the super hi-tech new Volvo Ocean Racers

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A 20 year old boat would weight twice as much, wouldn't it? As for newer boats--

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One must also wonder about keel failures and masts that snap. I suppose carbon fiber is more fragile, but the true nature of these failures is not discussed.


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post #20 of 28 Old 05-30-2012
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Re: Balsa cored hulls

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A 20 year old boat would weight twice as much, wouldn't it? ...
No, Operon racing a 1991 Finot designed boat, winner of the Vendee Globe and having changed of name Sponsor and skipper 10 times along its racing long live, weights 10.95T and it is a carbon boat.

JVM industries, a 2004 boat, a Marc Lombard design, that is going to be skipped by Sam Davies on the next Vendee Globe weights 9.5T.

Even on the best lighter and more modern boats the weight difference is far away from being the double or even near it. The more recent boats, made this year or last year weight around 8T.

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Last edited by PCP; 05-30-2012 at 06:25 AM.
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