infusion media questions

Discussion in 'Materials' started by JohnMarc, Feb 14, 2020.

  1. JohnMarc
    Joined: Feb 2018
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    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    I know this is not boatbuilding but I am doing this little project as my way of practicing with vacuum infusion and getting to understand fibreglass epoxy etc.
    I am wanting to change the back window of my land cruiser with carbon fibre replacement with a hatch.....
    My question is to you fibreglassing buffs out there is this:
    I want to add a "bead" (coloured in red in the attached picture) around the entire panel to add to the rigidity of the panel and I want to know what to build it up with in the mould before laying my carbon fibre, mycell, and glass fibre....
    what do I add to the epoxy resin to make the bead strong enough to resist the flexing.

    probably not making a lot of sense but hopefully the pictures will explain a wee bit clearer.
     

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    Last edited: Feb 15, 2020
  2. Jolly Mon
    Joined: Jun 2019
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    Jolly Mon Junior Member

    John,
    if you’re making a mold to vacuum bag then why not use the carbon in the bead? You also mention carbon and fiberglass. Why are you using both? As a beginner I would recommend one or the other. If you decide on carbon be careful because carbon is an electrical conductor.(dust in the air and in/around electric tools.)

    Rob
     
  3. JohnMarc
    Joined: Feb 2018
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    JohnMarc <--- My ultimate goal

    Thanks Rob appreciate you coming back to me.
    Two reasons I didn't think I could use the Carbon in the bead is firstly from the appearance point of view, I am imagining that the "bead" will distort the direction of the carbon affecting the finished appearance, and secondly I want it to be flat on the inside. I was imagining filling the bead first with something like a flaring resin creating a flat surface to lay my reinforcement material on. I am infusing this, I have had some experience, although I remain an absolute beginner, but I wanted to try some new product (hence the carbon) The reason why I am thinking of using fibreglass on top of the two layers of carbon is economics really, I wanted to "bulk" up the thickness of the finished product and the carbon is a wee bit pricey ...... If I mixed cotton flock with resin creating a peanut butter viscosity would that add the rigidity to the bead I am looking for?
     
  4. Jolly Mon
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    Jolly Mon Junior Member

    If you’re just doing this for fun and not engineering this panel for a specific load I understand wanting to get experience. However when building something out of fiberglass and then adding “a layer” of carbon is generally not a good idea. Carbon is much stiffer than e-glass. So when a force is applied and the panel flexes the carbon will take the full load (while the fiberglass flexes)until it breaks and then the fiberglass is left taking the load.
    I haven’t worked with the cotton flock but I like it’s pricing . Cabosil is a common additive when making fillets in boat building. It’s hard when cured and difficult to sand.
    Are you planning on painting the panel when finished?
     
  5. JohnMarc
    Joined: Feb 2018
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    JohnMarc <--- My ultimate goal

    Thanks Rob, okay so going to go with the carbon only as it will be replacing a glass window, and thanks for the tip on the fumed silica, typical beginner that I am and living some way from suppliers, I ordered a load of material a while ago covering all bases and I actually have fumed silica so will go with that. Seems a remarkable product.

    Many thanks
     
  6. JohnMarc
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    JohnMarc <--- My ultimate goal

    Forgot to answer this, I actually am undecided, I am wanting to practice with Carbon Fibre for eventually constructing certain pieces of the boat, so in truth I probably won't get the perfect finish with my first try and yes will probably end up painting it.
     
  7. fallguy
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    fallguy Senior Member

    you can get a great finish with 0.030 peg or mylar

    you can make the bead with glass strands, but you will need to make a mould, the strands can be from something like the zero strands from triax or heavier strands from any variety of stitched or other glass with easy to split out strands; then bed the strands in epoxy in the mould and fill with thixo for body
     
  8. JohnMarc
    Joined: Feb 2018
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    JohnMarc <--- My ultimate goal

    Thanks for this, yes I am making a mould (as per my drawings....I called it a plug, perhaps not the correct term :(), even though I will only be infusing one piece (although it might take a few attempts) it is all about practice and learning. When you say lay the glass strands in epoxy first, are you suggesting I pour in epoxy into the bead section of the mould (say 25%) then lay the glass strands into it then fill the remainder of the bead with thixotropic thickened epoxy followed by the layup of carbon etc..... Bearing in mind I want to infuse the carbon under vacuum, am I right in assuming I wait for the thixo and epoxy in the bead to cure to "tacky" (not too sure of the correct term) prior to lay up of the remainder of the reinforcements.

    Thnx
     
  9. JohnMarc
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    JohnMarc <--- My ultimate goal

    Judging by previous posts on this forum, I realise my ignorance might be exhausting for some and apologise in advance, but what is 0.030 peg or mylar
     
  10. fallguy
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    fallguy Senior Member

  11. fallguy
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    fallguy Senior Member

    I have not infused carbon. Everything you said was correct, but you might not need the thixo.

    The petg is used in handlayup. You can see through it and work out bubbles. I am going to use a ply backer.

    It would take more than a single layer to stiffen up.

    I don't see why you would infuse and am not the best advisor for the stack.
     
  12. fallguy
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    fallguy Senior Member

    Also, lay wetted glass strands into the bead mould; then fill with epoxy or a thickened epoxy. I can see potential problems with thixo pulling things apart; so straight epoxy might be better. For example, air pockets are less likely if you wet the bead, then lay in glass; then pour epoxy; then look for air and use a stick to force them out. You couldalso buy fiberglass rod and just bond the carbon to it.

    If you still want to infuse a carbon layup; you could just wait a day and cleanup the bead and infuse. Find an infusion resin with a 24-72 hour primary bonding window or rough sand the bead prior to infusing for secondary bonding.
     
  13. JohnMarc
    Joined: Feb 2018
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    JohnMarc <--- My ultimate goal

    Yup thanks sounds like a winner, will do exactly as you suggested, and let's see how it all works....will keep you posted. As regards the layup I am still undecided but the main reason why I infusing it is to get practice with the process ..... I go by "if at first you don't succeed....."
    Appreciate your input thus far.
     
  14. JohnMarc
    Joined: Feb 2018
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    Location: Knysna South Africa

    JohnMarc <--- My ultimate goal

    I trust all had a peaceful safe and healthy easter in these extraordinary times.
    This seems to be a question with extremely varied answers...... how much resin should one mix for vacuum infusion. I have 704 grams of fibreglass...... so assuming the suggested ratio I would mix 40% giving me 282 g of epoxy add say 150g for the lines etc. .... the part that has thrown me is the mesh.... it is suggested I use 700g per m2 this effectively means I would be using a further 840g (working on 1.2 M2) of resin just for the mesh ?????? surely this cannot be right...... please any advice would be appreciated.
     

  15. fallguy
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    fallguy Senior Member

    What is the entire stack? I am not an infusion guy, but if I were, I'd need to know the stack to help.
     
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