Infusing flax

Discussion in 'Fiberglass and Composite Boat Building' started by rob denney, Jun 19, 2020.

  1. ondarvr
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    ondarvr Senior Member

    The current layouts used for glass fabrics are designed to enhance flow. It can be used to speed up flow, or slow it down as needed.

    Flax, or any natural fiber can't be as easily manipulated to achieve the same results.

    The results of this test are typical when comparing any two fabrics with different properties.
     
  2. ondarvr
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    ondarvr Senior Member

    Glass itself conducts heat rather well, natural fibers tend to be better insulators.

    Glass fibers absorb no resin, natural fibers tend to at least absorb some.

    Both of these can result in different peak exotherm readings.

    Mold surface material plays into the temperature, but these were done at the same time on the same surface, so it eliminates that variable.

    You would need to repeat the test several times to determine what the actual difference is.
     
  3. ondarvr
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    ondarvr Senior Member

    Uneven cure resulting in a warped panel has been understood since composites were first used.

    Even just putting gel coat on one side of a laminate can cause it to warp.

    The most difficult thing to make is a large flat panel.
     
  4. Eric ruttan
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    Eric ruttan Senior Member

    You keep saying things that, imho, seem irrelavant to the topic.
    Why do you do that?
    You reply, but neither answer any questikn asked, not post any relevant thoughts i can discern.
    Why do you do that?
    The flax stack was thicker and the fibers bulkier. Thus the gaps for resin to fliw must be larger, yet the epoxy flowed a small fraction of the distance vs the glass stack. This ovservation seems central to the post.
    Why do you not address this?
    You have restated what has been stated many times, but added no information or thoughts at all. I ask how this thread would be different if you deleted everyone of your posts in it?
    I suggest there would be no discerable difference, and you would have saved expensive bandwidth.
     
  5. Eric ruttan
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    Eric ruttan Senior Member

    Rob Denney literaly designs boats and boat furniture based on large flat panel infusions.
     
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  6. ondarvr
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    ondarvr Senior Member

    You don't seem to understand what what I'm referring to, so I'll adjust it a bit.

    Resin flows very well when the fibers are straight and uniform. Some fabrics have incorporated flow channels that are slightly wider to enhance the flow even further.

    This is why CSM doesn't work well for infusion, the random short fibers tend to block the the resin.

    Woven products don't typically flow as well either due to all the pinch points from the weave.

    Natural fibers can't be engineered to allow as predictable of a flow. The exact crop of fiber will influence the flow, due to its unique growth patterns and genetics.

    In some situations this may speed up the flow, or slow it down more than desired.

    Just because some gaps may be larger, doesn't mean the resin can flow freely through the entire length of it.
     
  7. ondarvr
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    ondarvr Senior Member

    I was the plant manager at the largest supplier of flat panels I know of.

    They were 60' x 10', we made more than 75 per day when needed. This was only one of the locations. We could make more per day, but it wasn't easy.

    I also do a great deal of work with panel manufacturers around the world.

    Making a flat panel truly flat is no easy thing.
     
  8. ondarvr
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    ondarvr Senior Member

    The shear forces on the resin aren't great enough in infusion to really reduce the viscosity.
     
  9. rxcomposite
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    rxcomposite Senior Member

    How can it be confusing when I agreed to what you and Rob is saying?

    Rob said the flax is "much warmer". Resin exotherming is the source of heat. Glass is harder to heat than wood. By ratio and proportion based on Fiber Volume ratio, glass absorbed less resin than flax. There is less heat source for the glass than the flax, ergo, the flax with the higher heat content (and lower heat loss) is warmer.

    I did not respond to the resin flow of glass fiber and flax as I did not see it nor I have any information on what happened during the infusion process.
     
  10. rxcomposite
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    rxcomposite Senior Member

    What? Conductors and Insulators.png
     
  11. ondarvr
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    ondarvr Senior Member

    We weren't talking about electricity conductive materials.

    The discussion is about thermal conductivity.

    Glass conducts heat rather well compared to natural fibers.
     
  12. rxcomposite
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    rxcomposite Senior Member

    Of course it does not so does the natural fibers. It is the space in between that is filled. That is what you and Gonzo have been discussing. The packing density or the "circular rule".
     
  13. Dejay
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    Dejay Senior Newbie

    Would it also be possible that flax is more porous or has different "surface tension" so requires more energy to wet out? So that more energy from the vacuum would be converted into heat by friction.
     
  14. ondarvr
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    ondarvr Senior Member

    Gonzo was using the circular rule, I was saying that it doesn't apply as well with natural fibers because they are inconsistent in roundness and diameter at the same time along their length.

    Which is what the report noted.
     

  15. ondarvr
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    ondarvr Senior Member

    Heat requires energy, there's very little energy involved in moving the resin slowly through the laminate.

    If was injected under high pressure quickly some heat could be generated.
     
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