Choosing a deck core

Discussion in 'Materials' started by Charly, Nov 23, 2010.

  1. Fanie
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    Fanie Fanie

    I have considered using a PolyEthilene foam as a core for my cat's floor. It is available in a veriety of densities, closed cell marine, thicknesses and bonds very well to resins. Drilling holes is not a problem since the foam does not absorb water.
     
  2. War Whoop
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    War Whoop Senior Member

    Polyethylene?? It is a member of the olefin family, I do not see this bonding well as it is waxy ,We had a bunch of it and could find no use for it.
     
  3. mark775

    mark775 Guest

    "...has no idea what type of foam he is talking about" - Did I say I had no idea what foam?
    "...every single problem i have ever seen can be traced to the builder making the wrong choice..." - Indeed, sometimes choosing foam is the wrong choice.

    "...more difficult to engineer a foam cored panel than a balsa panel..."
    "(balsa is) not at all tolerant of bad or even average building procedures"
    - What is your point with these two sentences? Well, I guess there is a difference in semantics between "engineering" and "building procedures" but shouldn't one insure that the builder and the engineer have conversed? Is balsa harder...or easier, in your view?
    We are all inflenced by our experiences and you may have heard about early experiments with sawn balsa lumber used in boat construction. It didn't work out well. Also, sure enough, people have let it get wet, for whatever reason, with bad results. For every instance you may find of balsa not being ideal, I guarantee I can find five for foam - I have seen more foam-cored hulls where the inner and outer skins are independantly searching for the best path than you can shake a limp core at. I have drained water out of dozens of foam boats and even had adjusters total them when the shells completely came apart.
    Steve, I realize that you are just sticking up for your material of choice but I just didn't want to leave the implied slight of balsa hanging out there. With your shoulder in here, the slight is no longer implied and you also drug my credibility through soggy foam.
    Now then, cut a three foot panel of what you consider to be the right choice of epoxy/foam for a deck. Now cut one side of it down the middle through to foam. Stand on half of it and bury the claw of a hammer on the edge of the other half and lift (zzzzip!). Now try it with a balsa or plywood core. When you are finished picking your gones up, let us know how it went. This did not address freeze/thaw, which I consider to be the root problem with wet core of any type but I seriously don't want to hear this "closed cell" crap - It is only closed-cell when it has not been compromised and why does that delamination we just made have a 1 bubble thick layer of foam on it?. I didn't say that foam was no good, I simply stated that balsa or plywood is better for this application. Foam is great for keeping coffee hot, beer cold, raceboats light, stuff like that. You look like you know what you are talking about. Do you want to leave it alone now with the attacks? "But, but...Bu..." No buts. I don't have a problem with foam. Balsa or plywood are better for this application. There can be no argument. Let the guy get on with his boat.
    Nice lookin' paint on the speedboat...and nice shape from this vantage.
     
  4. Fanie
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    Fanie Fanie

    On the contrary, it bonds extremel well. It sheers the foam instead of delaminating. PE in sheet form is a totally different thing, I agree nothing bonds to it.
    The only disadvantage this foam has is it's price. Everything else lends itself to a perfect marine product.
    http://www.sondor.co.za/index.php
    Have a look at the XPS range of foams - and it has nothing to do with polistirene.
     
  5. War Whoop
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    War Whoop Senior Member

    I have been building with foam for a long time,Have YOU? Corecell DOES NOT absorb water, where in the HELL did you ever get a crazy Idea like that?
    Wood is a natural water pump on the other hand and part of natures recycling system,Just add water LOL,That is why I would never use it.
     
  6. War Whoop
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    War Whoop Senior Member

    I went through the link and did not see any Lloyd's ratings!
     
  7. Herman
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    Herman Senior Member

    I did not find XPS, but did find SPX foam. Is that what you are using in SA?

    No Lloyds (but that would not bother me too much, Core-Cell started without as well) but also no shear modulus, and a statement that it is primarily a packing foam. Or did I pick the wrong one?

    I must admit we have PE foam for stringers, just as a quick shape to laminate over. And PE foam panels with glass rovings stitched through, for RTM light purposes.
     
  8. CatBuilder

    CatBuilder Previous Member

    Hey Charly,

    Cool that you're fast approaching the deck stage. I drove by the rte 95 exit to your area in GA yesterday and was wondering how you were making out.

    Foam wise, I have done a ton of research. Corecell, while very good, will be a bit expensive... although you only need small pieces around the perimeter. Another alternative (though not as thought of as highly by many) is Divinycell.

    To see how PSI compares to foam density, take a look at this link. You'll find a chart in the PDF that details Corecell A foam (their original recipe) and compares the PSI and other physical characteristics.

    http://www.gurit.com/core/core_picker/download.asp?id=957

    I have ordered nearly all of my materials from Jamestown and would highly recommend them. They know what they're doing. Not only that, they work very closely with many of the top people in the area up there in RI. They always know what the latest and greatest materials are. They also are pretty good at helping you select the appropriate materials for the job because they are always visiting the world class local builders (like TPI, Goetz, etc... etc...)

    FWIW: My entire boat is being built with a Corecell core this time. I'm using 1" as well in 5lb and 6lb densities for the hulls, as Kurt's foam/glass plans call for.
     
    Last edited: Nov 25, 2010
  9. War Whoop
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    War Whoop Senior Member

    I did a lot of work with it 20 years ago but never got any trust worthy bonding. Corecell was started by a group with HUGE background in core material.
     
  10. CatBuilder

    CatBuilder Previous Member

    Regarding Corecell being able to be "ripped" by pulling on the outer laminate with a hammer:

    "Corecell A-Foam can elongate up to 65% in shear
    before failure, making core shear failure in a laminate almost impossible. Tests and experience show that Corecell
    A-Foam is the most reliable core material for dynamic loading situations where PVC and balsa may fail due to poor
    shear elongation properties. "

    That foam that was ripped by pulling on it probably wasn't Corecell.
     
  11. War Whoop
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    War Whoop Senior Member

    Post #15 there is impact testing,follow the link.
     
  12. War Whoop
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    War Whoop Senior Member

    Pro Balsa is from Diab, Baltek started selling Foam years back so the Divinycell people started selling Balsa.
     
  13. Herman
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    Herman Senior Member

    Couple of loose comments:

    -Next to Core-Cell A foam (the original) also take a look at M foam.

    -on PE foam: all applications that I am aware of are just for holding shape while laminating / processing. No structural properties after curing.
     
  14. War Whoop
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    War Whoop Senior Member

    Yes there is a very light cross linked foam we used for that exact application.
     

  15. mark775

    mark775 Guest

    "Corecell DOES... absorb water" - please note where I stated this.
    I have not destructively tested Corecell, you are correct. Many panels of scraps (Airex R63, C-70 and others) from this builder have died at my hands however:
    http://www.slothboats.com/vesselfabrication.htm
    Is he doing it wrong?
    Corecell is apparently the latest in a long chain of foams, all previous with a colored past. Is this the Holy Grail? All other materials will now fall by the wayside? I have heard of it but haven't had the pleasure of taking a piece apart... but I will!
    Well, It does appear that the thread has devolved into a conversation of various foam products and is really no place for me. When you get done telling your stories, make sure to leave space to admit that Balsa makes a better deck for this application, is stronger, has better compression, shear, and more localized crush. Plywood, too.
     
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