Need help identifying materials of layers in restored fiberglass boat

Discussion in 'Materials' started by Nidza, Nov 26, 2017.

  1. TANSL
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    TANSL Senior Member

    The parameter that is used to know the mechanical properties of the fiber is not the ratio fiber mass/ resin mass but the ratio (fiber mass) / (fiber mass + resin mass). In the attached picture you can see the formulas used by ISO 12215-5 to determine the mechanical properties of an E-glass composites.

    Fiber content.jpg
     
  2. PAR
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    PAR Yacht Designer/Builder

    I do think this is still being over thought. The OP's intent seems to be to make some repairs, modifications or reinforcements, maybe simply check someone else's efforts. There's absolutely no need for FEA or precise assessment, simply prudent practice and method. Maybe it would be simpler to discuss what the OP is actually interested in performing

    Your questions and/or intrest can be answered with a few books or some online research into polyester repairs. Painting the hull with epoxy is just a paint type and though preferred by many, isn't the toughest or most durable top coat going. It's also not going to impart any strength to the effort in a repair. In fact, on your boat the proper repair would have been a polyester laminate with a gel coat top coat, matched to your hull shell as best as practical on old 'glass that will get a bottom coat anyway.
     
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  3. TANSL
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    TANSL Senior Member

    I totally agree with you but it is not bad at all, and precisely that is one of the charms of this forum, that comments appear that can help us increase our general culture, even if it is not a direct response to the question of the OP. Many of the threads derive on totally different topics than the original theme. And that is great.
    With construction with composite materials, much progress has been made in the last 20-25 years and "normal practice" has been demonstrated, in some cases, not being the most appropriate. It has been very normal to verify that methods and concepts of wood construction have been exported to the construction with compounded materials, and that was very dangerous. In this field there are very few people who know how to perform FEA of the structure or, even much simpler calculations, but there are a few concepts that every boat designer in PRF should know. For example, that a very large thickness does not guarantee anything.
    If we all go, little by little, learning some things because a conversation has gone by paths not initially planned, it would be a reason for joy for all. So, imo, it is good that conversations derive at will and that each one takes from them what interests him.
    Having said all this, I say again that I agree with you and that a solution, the simpler, the better. but, careful, because it may be simple but incorrect.
     
  4. rwatson
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    rwatson Senior Member

    "I would like to know what resin to use that will bond "properly" to the structure of the hull and be watertight so that boat is usable in following years or hopefully decades."

    Under what circumstances would a repair NOT be done in EPOXY ??

    I know matt almost always infers Poly resin, but in a repair situation, Poly is not all that good at adhesion, and for the sake of say half a metre of resin, who on earth would specify Polyester as the ideal material ?

    Not on my boat.
     
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  5. gonzo
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    gonzo Senior Member

    Spectrometers work by burning a sample and analyzing the gasses
     
  6. ondarvr
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    ondarvr Senior Member

    Epoxy is great, but it's not like it's required when making repairs. I can safely say that in forty plus years of doing repairs on polyester and VE items I've rarely found that using epoxy was a requirement for success. If the person is half way competent a polyester repair will hold up fine.

    There are times where epoxy is clearly the better option, but in this situation it's not going to make a difference. That is unless the prior repair was done with epoxy, but chances are it's not.
     
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  7. PAR
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    PAR Yacht Designer/Builder

    Precisely my point, with the addition most don't need, nor can afford the "best route" just a sufficient one, that is neither much less or above the surrounding hull shell's general integrity.
     
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  8. rwatson
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    rwatson Senior Member

    Got a few IFs in there mate.

    "in this situation it's not going to make a difference. " assumes " the person is half way competent "

    In general "If the person is half way competent a polyester repair will hold up fine." means you have to wait 5 years to see if the repairer was indeed competent. We cant ALL hire Ondarvr or Par to do repairs.

    For the sake of a few bucks - why not remove all doubt ?
     
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  9. Barry
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    Barry Senior Member

    Will ethanol, MEK, Methylene chloride or Nitric/hydrochloric acid dissolve the resin or would it take to long?

    Mechanically,
    Set the plug up vertical, mark the core and cut it out on a band saw
    You will then be left with two thinner discs.
    Looking at the thin side of the disc, horizontally, sand an angle from the top of the right side to the bottom of the left side which if the angle is small as possible should reveal the layers
     
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  10. rwatson
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    rwatson Senior Member

    A method of dissolving cured polyester
    EP 0485063 A2
    ABSTRACT
    Cured polyester resin can be dissolved by solvent mixtures containing alkylene carbonates, preferably ethylene carbonate or propylene carbonate, as co-solvents. For instance cured fibreglass resin can be removed from tools or substrates in this manner.
    A preferred solvent mixture comprises the alkylene carbonate and tetramethylene urea.
    Patent EP0485063A2 - A method of dissolving cured polyester https://www.google.com/patents/EP0485063A2?cl=en

    or

    For polyester resins you could use isopropanol or sulfuric acid.
    https://www.researchgate.net/post/W...d_to_dissolve_the_cured_polyester_epoxy_resin
     
  11. ondarvr
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    ondarvr Senior Member


    There are "if's" in everything in life, especially when it's just an internet discussion on repairs, there's no way to make detailed instructions for every imaginable repair. And there is no one way, or product that is the right one in every application.

    This repair is about as elementary as they get, a person with zero experience could do it and have no issues even if they did a sloppy job.

    Dissolving resin in a solvent typically takes quite a while, and many times the glass gets moved around and is harder to identify.
     
    Last edited: Dec 17, 2017
  12. gonzo
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    gonzo Senior Member

    On a repair, epoxy would be a good choice. However, polyester and vinylester are more forgiving when there is contamination; particularly oil. As I write this, it comes to mind to make some tests, which will take some time, and then post the results.
     

  13. Steve W
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    Steve W Senior Member

    When burning the resin out of a sample I have better luck with a larger sample, small samples such as above just fall apart although it is easier with the old woven fabrics than the current stitched fabrics.
     
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