Foam Core Hull

[captainstubbie]

I've read several threads on foam cored hulls, but still have questions and doubts... I will be looking at a Southern Cross 39' in the next couple weeks...but am a bit hesitant...is a solid hull that much better?

[Polux]

Originally Posted by captainstubbie

I've read several threads on foam cored hulls, but still have questions and doubts... I will be looking at a Southern Cross 39' in the next couple weeks...but am a bit hesitant...is a solid hull that much better?

Now you get me confused Why do you think that the best and more expensive sailboats use a sandwich hull with some kind of foam core inside? Because it is worst?

Regarding older boats a sandwich hull can pose some problems due to possible ingress of water to the core. All you have to do is to pay a surveyor to check carefully if the boat has humidity on the core.

[a64pilot]

Nothing at all wrong with cores, deck or hull.
Until they get wet.
My opinion only, but I prefer something that cannot get wet, but still maybe blisters?

[Mike OReilly]

My Rafiki 37 has a airex foam cored hull. It extends below the waterline, to above where the keel structure begins. I have never heard of any problems with foam cored hulls. Even boats with balsa cored hulls like the C&C Landfall haven’t produced a systematic problems (at least not that I’ve heard of).

[captainstubbie]

Part of my concern is damage from a minor collision with something harder or sharper...are they as tough to ding and easy to repair?

[daletournier]

This has been spoken about a number of times. All boat building mediums have their potential problems. My last boat was fully balsa glass composite. It had many advantages but also potential (wet core ) problems. Fortunately I only experienced the positives.
There are different types of foams used, some better than other's.
The best thing to do is education ones self on the potential problems so you can identify them if there is any and also do what's required to prevent future problems.



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[Polux]

Originally Posted by captainstubbie

.....is a solid hull that much better?

Here a good answer by a surveyor:

"Designers and builders of boats know that cored composite fiberglass structures have better characteristics than solid fiberglass structures. The general boating public does not. We tend to believe that solid fiberglass is stronger and less likely to suffer damage from water saturation, and the latter is true. Virtually every high performance racing sail or powerboat is cored....

The boating public became aware of the problem and many builders started advertising “solid fiberglass hulls”, likely beginning the boating public’s opinion that this was a better way to build a boat. It’s not. It is however a way to eliminate concerns about water intrusion into core...."
Cored vs Solid Fiberglass Structures

and a more technical information:
Getting To The Core Of Composite Laminates : CompositesWorld

[Jim Cate]

If a foam cored hull has not been involved with collisions or other severe trauma, and the POs have not foolishly drilled holes into the core, one should expect to enjoy all the benefits of the construction and none of the hypothetical issues internet pundits are so fond of.

Our previous boat, built by Palmer Johnson, is now 42 years old. According to her current owner, the core is still dry and no issues have arisen due to the coring.

Jim

[Mike OReilly]

Originally Posted by captainstubbie

Part of my concern is damage from a minor collision with something harder or sharper...are they as tough to ding and easy to repair?

I think this is more a factor of build quality than cores. Poorly built or designed boats will be more problematic in collisions than well built/designed. Southern Cross’ have good reputations as solid sea boats. Apparently some were sold as unfinished kits, but all the hulls would have been done by the factory.

Airex doesn’t have any wicking or rotting issues like balsa. To my mind, this makes it a better below-water core material. But like I say, I’ve never heard of any cored hull boats have systematic problems.

I can tell you my 1977 Rafiki has had her share of dings and bumps. No problems (so far).

[captainstubbie]

Great article

[cortezsailor]

On my Corbin their Airex cored on the hull above the waterline. I have never had a problem with the coring, the plywood on the deck I have

[daletournier]

Originally Posted by cortezsailor

On my Corbin their Airex cored on the hull above the waterline. I have never had a problem with the coring, the plywood on the deck I have

I thought the corbins were airex above and below? From what ive read they are an extremely strong yacht.

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[cortezsailor]

Correct above and below !

[captainstubbie]

Below the waterline too, correct?

[CarlF]

A foam core hull is superior to a non-cored hull - unless water gets into the core.

It's lighter for the same strength so the boat sails better

The foam is great insulation making the boat more comfortable in hot and cold climates. Also less dampness from condensation below decks

Is safer after a collision as the inner fiberglass layer is less likely to leak because the foam absorbs the impact (of course the outer laminate cracks but that won't sink the boat)

Collision damage to a core hull is no harder (and often easier) than collision damage to a solid hull where the collision caused delamination.

Most boats with a solid hull have cored decks - and a deck has many, many penetrations for the hardware. A hull has very few penetrations. As a result, most core water problems are in the deck not the hull and strike solid hulls as well as cored hulls..

The use of Airex as a foam core (like in the Southern Cross) has been mostly replaced by Core Cell that is a better foam - but a well built boat like the Southern Cross that passes survey is not likely to suddenly develop a problem after all these years.