foam cores and core materials

Discussion in 'Fiberglass and Composite Boat Building' started by Mark C. Schreiter, Jan 14, 2021.

  1. Mark C. Schreiter
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    Mark C. Schreiter Junior Member

    I've been reading some articles found on Yacht Survey Online: Buying, Owning, Maintaining a Boat or Yacht by David Pascoe, Marine Surveyor(Retired) https://www.yachtsurvey.com, specifically about foam cores. The author seems really down on them and at times most core materials in general. he does have some valid considerations but no real data or any supporting facts. which is sort of funny because those are the same reason he's opposed to foam, not a lot of data or facts.

    I'm curious if any of you have read this and if you have any thoughts?

    -Mark
     
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  2. gonzo
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    gonzo Senior Member

    The articles are opinionated but offer little or no data to support them. In fact, cores in fiberglass boats have been around since very early on. He admits the mass production of boats started about 65 years ago. Most of those boats had wood cores for stiffening and reinforcement. However, he refers to coring as a recent experiment.
     
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  3. Mark C. Schreiter
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    Mark C. Schreiter Junior Member

    I was at least hoping he had some data to back up he statements considering hes so opposed to them. maybe he owned a terrible example and got burned by it?
     
  4. TANSL
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    TANSL Senior Member

  5. Mark C. Schreiter
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    Mark C. Schreiter Junior Member

    Its opinionated from the perspective of a supposed 40 years of experience surveyor.
     
  6. TANSL
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    TANSL Senior Member

    Sometimes opinions are not based on specific data but on experiences, feelings, beliefs ...
     
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  7. Mark C. Schreiter
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    Mark C. Schreiter Junior Member

    Right, that would be the simple definition of an opinion.

    A fact would be if one could use those experiences as data points and therefore turn your opinions into facts.

    For example if 80% of the foam core boats he surveyed in 40 years had a core related failure then if would be safe for him to say that his experience shows an 80% fail rate among foam cores. But he sort just bashes them.

    I’m interested in those experiences because some of the other information although much speculation and opinion is good stiff.
     
  8. fallguy
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    fallguy Senior Member

    You are missing some of his points and the data is dated.

    First of all, foam and the esters are part of the issue. Any bond between the foam and the resin is a mechanical bond. The bond strength of esters is nowhere near that of epoxies.

    Secondly, there is another problem. Secondary bonding in any system can be a failure point. A core boat may be subject to more secondary bonding based on the build methods. Again, seondary bonding of the esters is not as good.

    To top that all off, cores require resin and early cores laid up without resin may have suffered from errors in the layup-think starvation.

    You have to understand Pascoe's comments in a detailed fashion before you call him cranky. Consider all the problems boats can and have had over the years and realize his dismay at poor build quality in an expensive item like a boat.

    someone here might know the typical bond strengths of polyester, vinylester, and epoxy-I have studied them, but cannot cite them. They are significant.

    In my build, we are bordering on the edge of dry and resin starvation, but all indications are that we are okay. When I cut into the matrix, sometimes it tears, a wetter layup would not. So, I might be a bit dry. Hope not. Quality matters and if I built a panel with 5% too little resin; it is sort of a pretty touchy science since I start at 100% and am ending at 65%. If 70% is the perfect amount; how do I get there? Less vacuum? More entrained air acceptance then?

    Use epoxy and be careful about amine blush (use good epoxy) and be careful about secondary bonding and be careful about meeting core resin needs and your boat will be fine.

    As a post script, I bought a beautiful old '74 Starfire in February years ago. Brought it home and it thawed in April and I realized the entire core was rotten balsa. Boat was junk because of the poor build methods and subsequent piercing of the hull for a ? wire clamp?. Seriously. A wire clamp ought not result in a core failure. The boat was landfilled. The money lost. I recovered maybe about $2000 in parts and was out about $1500 for a rotten core I did not understand in frozen weather. Got tricked, wasn't aware of balsa core rot.
     
  9. fallguy
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    fallguy Senior Member

  10. Mark C. Schreiter
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    Mark C. Schreiter Junior Member

    For sure, all good points.
    My take away from the articles admittedly could be biased based on a few statements that remain at the forefront for me. At times there was a generalization that foam cored hulls is an all around “terrible” idea as he said. Perhaps at some point he went into details on the exact materials, construction methods or poor design but all I read or all I retained was “terrible” idea. I’m reading them again but in my defense he does have an overall unpleasant belief in foam cores in general as the topic comes up in several unrelated articles.
    Seemed like a lot of the issues had been with sail boats or boats with greater curves in the hull design opposed to v hulls and the like where I believe he was slightly more ok with them. Either way there still is a ton of good information and even more thought provoking topics that he discussed with seemingly great experience and knowledge. I would agree that the articles are a solid read for any new or experienced builders specifically dealing with foam.
     
  11. gonzo
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    gonzo Senior Member

    The design and construction techniques of anything has to take into account the properties and limitations of the materials. Using a badly built or poorly maintained example to dismiss a material is wrong. In production boats, the usual core failure is from water intrusion through fasteners or unsealed edges. That is not an inherent problem with the material. He is confusing poor build quality with a material failure. Poor build quality, with any material or design, is a separate issue.
     
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  12. missinginaction
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    missinginaction Senior Member

    Sounds like the OP has a cored boat.:eek:

    I can only speak from my personal experience. My hull is solid fiberglass. 48 years old. No problems. Not even a blister. I'm a lucky guy. There were issues with the original build, there always are but the hull wasn't one of them.

    I have a hatch on the back deck for engine access about 3' x 4'. That hatch was cored, maybe Silverton wanted to keep it a little lighter, I don't know. When I bought the boat years ago the hatch was spongy. Eventually I cut it open. There were hundreds of these soaking wet little balsa blocks. I scraped and ground them down until the cavity was clean. Then I took a couple of good pieces of marine ply, coated them three times with epoxy and laid them into the cavity. Any small voids were filled with resin. It's never been a problem since. Of course there are no screws in it.

    The hatch wasn't even in the water and over the years it got soaked and rotted.

    Cored boats? Not for me.

    MIA
     
  13. Mark C. Schreiter
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    Mark C. Schreiter Junior Member

    I am actually working on building a 14 foot foam boat. Im certain that most of what the issues are that he mentioned shouldn't be to big of concerns for my little slow boat, especially considering its hull shapes are not very curvy. my no 1 must have was to build it myself. I searched and searched for plans for a solid glass hull plans but I don't think they exist or at least from what i've seen. sure I could've figured it out, make a mold and so on but that build would be pure speculation and guess work as far as the lamination schedule. at least building from plans give me general guidance and rules of thumb. I really haven't read to many bad things about foam core boats until these articles and he seems very adamant about them not being a great solution so i was just taken back a little.

    I'm doing my best to ponder on ways to keep mechanically fastened items limited to the necessary. I've thought about some sort of cleat inserts that can lock into rod holders. rod holders would be bonded into position with high density foam and have slightly more structure built in them to take the forces of the 14 foot boat, whatever those may be. composite rub rail that is bonded into the hull and would have replaceable rubber inserts? just ideas.
     
  14. fallguy
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    fallguy Senior Member

    You have a core!

    It is a plywood core.

    It was a balsa core coated in polyester which is not waterproof and probably was holed for latches or hinges and not properly overbored and refilled and sealed inside the hole.

    Solid frp is nice, but only if you can afford the weight penalty in the design AND have a mould.

    Cored boats not for me is an absurd generalization.
     

  15. missinginaction
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    missinginaction Senior Member

    You're right but it's only a hatch. And that was the only place the original builder (Luhrs/Silverton) did it. None of those little balsa blocks were sealed. As soon as some water got through the polyester resin covering them it was "game over". I'll bet that that hatch was soft within a couple of years of it's manufacture. So yes, I recored it but I did it correctly using generous amounts of epoxy. How many production hulls are built with epoxy?

    Back to the OP's comment. David Pascoe has passed away but I've read a lot of his writing. A lot of boats are poorly built and I think that's what had him angry. He didn't like people spending large sums of money on boats that were simply not worth it.

    The other side of that argument is that if boats were all built to really last for decades, the costs would be so high that no one could afford them.

    MIA
     
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