Need help identifying materials of layers in restored fiberglass boat

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

  1. Nidza
    Joined: Nov 2016
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    Nidza Junior Member

    I would appreciate if you could help me identify material of all layers in my hull, I am aware of some and guessing on others. Here is the photo of "plug" that was cut from the hull to attach the echo sounder transducer (long story why it was cut that way and out of this scope, so I will skip on that).

    20171105_065851.jpg

    Take into consideration that the boat was originally "hand" built in factory since it was built between 1965 and 1970, so that probably explains the thickness of the hull and some layers. As shown in the photo, top side of photo is internal to the boat (in engine room, where the hull has the greatest thickness), and the bottom of the photo is underwater part of hull. From top to bottom, I know it starts with gelcoat (I will show that on one following photos), then it has this very thick layer(s) of fiberglass (I presume many layers of mat and polyester resin), then the core. How can I know if this is PVC or polyurethane foam? I always thought it was polyurethane, but when working with it it is pretty hard/stiff, not soft or elastic, like polyurethanes that I was working with, but you can rip it using i.e. sharp knife or screwdriver and it does make dust when doing it. Going further down, it has one more thick level of fiberglass, but much thinner then the upper one. From there, the mystery layers start for me. Since the boat restoration was started in 1980s, before my time and then stopped until I started it, I only know some fragments. I know that I have found in the garage some cans of tar epoxy from International, but not sure that it was used, since it is completely black in color and not obvious on this "plug". Then again, I do know that it was used something from West Epoxy with microbaloons for the bottom, but at the moment I can't find that document with exact numbers/names (I will send another post when I find it). Anyway, it seems to me that there are at least three layers below the fiberglass, which I cannot identify, and I presume that one of them, if not last is the epoxy from West Epoxy with those microbaloons. When I finished the restoration of boat, my choice for the bottom protection was to paint two layers of underwater primer by Hempel (from what was available in my country), and three layers of hard anti-fouling paint, I hope I was not wrong, and it has shown OK for two seasons. Anyway, I would like to find out more about these layers, if possible, so if and when needed I can perform adequate repairs. Here are a couple more photos of the "plug" so you can see more details.

    Top:
    20171105_070819.jpg

    Bottom:
    20171105_070752.jpg

    Bottom layers detail:
    20171105_070516.jpg

    Thanks in advance for your help.
     
  2. rwatson
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    rwatson Senior Member

    You can get a bit more information if you cut each separate layer horizontally, and sand one of the surfaces smooth using a grinder and wet and dry paper.
    The patterns and type of cloth become easier to see, including the width of the threads.
     
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  3. rwatson
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    rwatson Senior Member

    PS - I just remembered and article in Professional Boat Builder how they reversed engineered layup materials by taking a sample and using chemicals and heat to destroy the resin component of the sample, and leaving the glass intact, to see what size/weight had been used in the original.
    You might be able to look it up
     
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  4. TANSL
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    TANSL Senior Member

    This is done because it is the only way to find out the amount of existing glass. As the resin disappears, the sample is weighed before and after burning and the % of glass content in weight is obtained. There is no way to find out the composition of the various layers of the laminate but the % glass, by weight, helps us determine the strength of the total laminate. With that, a new schedule with the same glass content can be prepared. The method may not be totally correct but there is no other method.
     
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  5. ondarvr
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    ondarvr Senior Member

    Yes, burning can sometimes leave the glass untouched and you can identify each layer. Plus like mentioned, weigh it before and after and you'll know the glass %.

    Although none of this really matters much, what was used back then will likely be weaker than what would be used today as far as fabrics go. So just matching the thickness of what's there now will be sufficient.
     
  6. TANSL
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    TANSL Senior Member

    Trying to match the total thickness can be a very serious error because much of it is due to the resin (which contributes very little to the strength of the set). It can not be assured that the fiber thickness is the same as that existing in the burned sample.
     
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  7. Mr Efficiency
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    Mr Efficiency Senior Member

    That core very much has the appearance of a PVC of one brand or another. It seems odd that the (outer?) laminate is as thick as the core. If you can't see distinct plies it is more likely a resin-rich lay up, if layering is visible, it should be possible to prise it apart with a sharp chisel along the line, to reveal the type of material. TANSL I think misunderstood what ondarvr was saying, which I interpret as being that "back in the day", high glass content was not a typical lay-up, so if you go with a similar thickness in a high glass content laminate, it will likely exceed in strength what is already in place.
     
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  8. TANSL
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    TANSL Senior Member

    Yes, I think I understood him correctly and, basically, I agree with him. I hope to know how to express myself in a way that makes me understand. What I want to say is that the only thickness that we can measure is that of the unburned sample and that a large part of it, but we do not know how much, is due to the resin. Therefore, the thickness of the new layers, which will increase place the resin, we do not know what it is. I think that if you forget the thickness data, placing something equivalent in glass, you do not need to think any more. We also have, of course, the best quality of current fabrics.
    On the other hand, if the initial laminate was well done, it would not be possible to know how many layers it had, how thick each one was, and how rich in glass each was.
     
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  9. Nidza
    Joined: Nov 2016
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    Nidza Junior Member

    Everybody, thank you for technical discussion, I will cut it horizontally so we can see the structure. I have found out the document that for some layers, the last external one, were used epoxy 105+205B and microspheres 409A, all by West Epoxy. I am not sure if and where was used that tar epoxy from International (which was in their manual used for fiberglass hulls at that time), that stuff in the can is completely black. We shall see after cutting the layers.

    How can I distinct if the core is PVC or polyurethane?
     
  10. redreuben
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    redreuben redreuben

    Be aware that if that plug was cut from the centreline that you will be dealing with overlaps in the layup as the mould was rotated from one side to the other, probably more likely on the inside skin than the outside skin, overlap could be anything from 100-300mm
     
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  11. gonzo
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    gonzo Senior Member

    There are many ways to find out the composition of the laminate. However, it is likely more than the OP can afford. The photo shows a resin-rich low tech laminate. If he simply wants to know if it is epoxy or not, the smell when it burns will tell.
     
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  12. TANSL
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    TANSL Senior Member

    Speaking very seriously, Gonzo, I would like to know some of these methods.
     
  13. gonzo
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    gonzo Senior Member

    We use several types of spectrometers and all the typical chemical analysis, like how a material reacts to a know reagent. For structural analysis we have an XRD and electron microscopes. We can also do other material analysis like tension and compression with the Instron testers.
     
  14. TANSL
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    TANSL Senior Member

    Thanks for the reply, Gonzo. I have studied these techniques a long time ago but it seems to me that they allow to obtain the chemical components present in a sample and its proportions, but nothing else. Tension and compression test, I think, are not useful in this case.
    By the way, who do you mean when you say "we"?.
     

  15. gonzo
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    gonzo Senior Member

    The people in the research team. If you studied them a long time ago, the new technologies would surprise you with the accuracy of Parts per 100billion.
     
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