Vacuum Infusion Advice

Discussion in 'Fiberglass and Composite Boat Building' started by GreenFreak, Dec 3, 2019.

  1. GreenFreak
    Joined: Dec 2019
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    Location: Petawawa

    GreenFreak New Member

    Hello,

    I'm planning to make a Composite Whitewater Kayak as a hobby project and am looking for some advice. The boat I'm planning to make is very small, ~6'L x 2'W x 1'H. very similar to: PROJECT X 56 - BlackOut https://www.wavesport.com/en/products/project-x-56-blackout

    From the research I've done, vacuum infusion seems to be the way to go, although does have some quirks.

    My main question is around the need to use flow media in areas where I will have a foam core?

    The bottom of the boat is fairly flat though there is a small amount of curve both front-back & side-side and will be using a Corecell M80 Contour Scrim 6mm foam knife cut in 1 3/16" squares in this area.

    My layup will be:
    Vac-Bag
    ?Flow Media?
    Peel-Ply
    11oz Carbon Twill
    Foam Core
    11oz Carbon Twill
    11oz Carbon Twill
    Mold

    My concern is that if I use flow-media, the epoxy will flow too quickly across the top of the stack trapping air/not fully wetting out the tool side of the stack. Though the concern with not using it is that resin will travel too slowly, not filling the part before it gels. Trying to get a feel for folks experience with resin traveling through contour scrim foam.

    I'm planning to use Pro-Set Infusion Epoxy INF-114 with Extra Slow Hardner INF-213 which has a 500g pot life of 175 minutes @ 25C, viscosity of 325cP, and an approx working time of 10-hrs. I'm estimating a need to use ~2 gallons of epoxy so will likely be mixing in batches larger than 500g.

    I'm hoping with the rrreeeaaallllllyyy long working time I can get away without flow media in the areas where I have foam to help ensure full wet-out.

    Thanks!
     
  2. Hafidd Ali Omer
    Joined: Oct 2019
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    Location: Yemen

    Hafidd Ali Omer New Member

    please advice where to put the resin in spiral tube over or beneath the peel ply ?
     
  3. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    Who spec'd that layup?

    it seems a bit .. incongruous re: elongation

    I don't profess to be an infusion expert, but I was told I had to use media if the foam didn't come with channels for the resin..Gurit has a great tech line. I suggest you call them. They are exceptional. It must be noted; I opted to wet bag.
     
  4. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    What material is the wave sport kayak made from.

    And where did you get the info to build it with the materials you mentioned?
     
  5. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    If you hit a rock with that layup; your carbon will probably break and delam most likely because the Gurit is able to elongate while the carbon is not.

    You want elongation properties to match better. I am guessing here without researching your elongation numbers and with my general, but limited, knowledge.

    Roughly speaking, I'd say your Gurit is about 8% and the carbon less than 2% on memory and guessing. Not sure on your resin; probably 6% before any post cure, but a total guess.
     
    Last edited: Dec 8, 2019
  6. AndrewK
    Joined: Mar 2007
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    Location: Australia

    AndrewK Senior Member

    Unless you are prepared to do a bit of testing to determine how far the resin you are going to use with your laminate schedule will flow with and without flow media then dont use infusion especially with carbon.
    If you did not want to use any flow media then a fish bone/fern leaf resin distribution would work. Main distribution line along the centre line and many close spaced (~6") risers at right angles, finishing ~2" short from the edge of the laminate.
    A 12" resin break (peel ply only) from the edge of the laminate to the vacuum line would be the best way to go, if you only have a short resin break then break up the vacuum line into sections at the ends. This way if the ends fill quicker than the mid section you can clamp off these vacuum lines.
    You do need to use perforated release film ( like the crispy wrap that french bread sticks come in) under the distribution line.
     
  7. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    Carbon uni is usually rated at 0.9 % by Class Rules. Some even rate it lower. For a 6% resin elongation, I would say that is too much. Since a "neat resin" curve is almost parabolic, it will cut off early, reducing the usable strength of Carbon. I would estimate resin elongation to have between 2.5 to 3% to be compatible.

    The foam elongation will not matter much as it is the shear properties that is important. Foam that elongates too much will not be compatible.

    It is generally perceived that carbon being stiff will not handle impact load. Test showed that due to greater strength and stiffness, the carbon was able to handle impact better than Eglass. It resisted the impact and spread the load reducing the footprint of the impact. Not the same for medium elongation foam and eglass though. It deformed, with the foam acting as a cushion but resulted in less delamination.

    There are basically three types of foam in the market today with varying elasticity. The result of the test I have was for medium elongation foam which is SAN (corecell) which handled impact better with Eglass. Cross linked PVC which is classified as brittle have long been improved. Should work well with carbon.
     

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  8. rxcomposite
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    rxcomposite Senior Member

    This is the result of using resin with too much elongation. These are called "tough resin" and refuses to fail even after stretching to 8%. It generally has a low modulus and low tensile strength. The curves emulates that of steel which will just stretch and stretch without rupturing. The carbon fiber strength is wasted as its elongation/strain (red lines) has been exceeded by the resin which refuses to fail.
     

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  9. fallguy
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    fallguy Senior Member

    so, you are agreeing the there is a mismatch of Gurit corecell and carbon, correct? And then you suggest an alternative core with a caveat. And that caveat is the elogation properties of the resin exceed that of the carbon, but is that result also failure of the carbon/pvc option at lower elongation than san/e-glass?

    what is the bottom line here?

    is it simply a tradeoff; you get a boat less capable of impact resistance, but gain less weight?
     
  10. rxcomposite
    Joined: Jan 2005
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    rxcomposite Senior Member

    Choice of material.
    1. The fiber and the resin must have nearly the same modulus with the resin having slightly more elongation than the fiber to achieve higher strength.
    2. With high modulus face like carbon, the core can be thinner/with a higher modulus.
    3. Mid modulus laminate (Eglass/epoxy) is more compatible with SAN.
    4. Low modulus laminate (flexible) is more compatible with linear PVC.
     

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  11. rxcomposite
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    rxcomposite Senior Member

    Impact resistance has nothing to do with weight.
     
  12. fallguy
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    fallguy Senior Member

    so what core for his carbon layup?

    sorry, reread cross linked pvc
     

  13. rxcomposite
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    rxcomposite Senior Member

    Sorry but that is design. You can see that up to this point I have mentioned only general classifications of materials not brand names.

    I tend to have tunnel vision as I look only at the properties of materials. For example, foam cores have several different grades. Carbon will have differing properties depending on the type and the kind of weave. A woven CF will have a lower modulus than a uni. So many variables.
     
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