cheap vacuum bag materials/sources

Discussion in 'Materials' started by sigurd, Feb 9, 2009.

  1. sigurd
    Joined: Jun 2004
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    sigurd Pompuous Pangolin

    Hello, I see that I can buy vinyl or polyurethane bag material for about the same as the rest of the boat.

    I want to know what other cheapskates have used when bagging a hull?

    Black trash bags? Heavier transparent trash bags/building plastic?

    As long as it is airproof and I can get it off of the laminate in the end, it is ok?

    Don't really plan to use peel ply but some parts may need a smooth surface, a cheaper (don't know if I can get pp here so shipping comes into the equation) or more available solution might be difficult to find as it is both porous and non-stick?
     
  2. robherc
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    robherc Designer/Hobbyist

    I've heard of people successfully using food handling plastic-wrap as release film when vacuum bagging. It's now porous like peel-ply but, if applied correctly, could leave you with a smooth surface, and (more importantly for us cheapskates) keep the resin from sticking to your vac-bag film, so the film is still reusable. ;)
     
  3. sigurd
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    sigurd Pompuous Pangolin

    Humm. So, then the resin had to get out from under the edges of the saran(?) film? Seems a flow media like netting will be useless then, unless putting it inside the saran - and then no smooth surface.

    A bit concerned that the resin won't exit, but even if the resin/fiber gets high, it would still be a good way to compress the laminate.

    EDIT: But I suppose it would not be too much work to pierce 3784 holes in the saran, before it is taken off the roll! ???
     
  4. robherc
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    robherc Designer/Hobbyist

    No, I think you'd be trying to keep the resin on the part with the saran-wrap (at least, if you aren't using peel-ply too). You'd still get the clamping benefits of the vacuum, but you wouldn't be able to bleed-out excess resin, so the parts might still be a little heavy. If you wanted to try it that way, you'd have to put the flow media on the OUTSIDE of the plastic wrap (between it and your vacuum bag film) so you'd get a smooth surface under the plastic wrap, otherwise the flow media would become a permanent part of the laminate.
    I highly doubt you could ever successfully poke small enough holes in the plastic wrap that you could use it as peel-ply. If you decide to try it, PLEASE do so on a "test part" that you're already planning on scrapping. ;)
     
  5. sigurd
    Joined: Jun 2004
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    sigurd Pompuous Pangolin

    Hehe, thanks for the concern...

    Hey, I found much cheaper materials than I had earlier found, bag material and peelply and other release films.
    http://www.fiberglasssupply.com/Product_Catalog/Vacuum_Bagging/vacuum_bagging.html
    http://www.acp-composites.com/home.php?cat=4752
    It looks like using properly tested materials is within my reach after all.


    What you say about the flow media becoming a part of the laminate: I just read somewhere here about one of the South African fellows' resin infusion. I think that in one of the tests he did not use peel ply, he had a mosquito netting (something like that) directly on top of the laminate, as flow media, and afterwards it released no problem. He had a very low resin/fiber which is probably necessary for that to happen?
    This approach will leave marks after the netting I guess, which will be great for secondary bonding?
     
  6. robherc
    Joined: Dec 2008
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    robherc Designer/Hobbyist

    Resin infusion is a different process from vac. bagging. They both use a vacuum pump to clamp the part & reduce the resin-fiber ratio, but in very different ways. I would be very interested in finding out more about his success using mosquito netting in resin infusion, but I would hesitate to try the same thing with vacuum bagging. If there is enough resin to surround the fibers of the mosquito net, I'm fairly certain you would NOT be able to remove it afterwords.
    Yes, I believe that the print from the mosquito netting would probably help with surface prep for secondary bonding for VIP parts, assuming you used the right netting & were able to get it to release (more experimentation).
    If you're interested in learning to use resin infusion (Vacuum Infusion Process), I would suggest you check out the learning resources available at http://www.fibreglast.com/contentpages-Learning-Center-286.html . They have a nice tutorial-style pdf about infusion molding there that should help point you in the right direction for further learning/experimentation. Also, VIP parts generally tend to be lighter, have better fibre-resin ratios and, it seems, the process may waste a good bit less materials in the process (a BIG plus for us cheapskates) once you get the process down (they say to expect to ruin a few parts before you get the hang of it).

    P.S. I've found that US Composites: http://www.shopmaninc.com/index.html is cheaper than even fiberglasssupply.com on a few products, though I haven't compared shipping rates on everything yet...I guess I'll have better info there in a week or so when I place my first order from them. :p
     
  7. sigurd
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    sigurd Pompuous Pangolin

    Here and more on the subject of F.U. infusion here

    For sure i will try both vacuum bagging and infusion. Would be nice to have a transparent bag. Any alternatives there? The ones in fibreglast are green and orange, the acp ones, don't know.
     
  8. robherc
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    robherc Designer/Hobbyist

    I've been contemplating using clear-plastic drop-cloths to be cheap...but if I remember right, there are many clear vac-bagging films available. Also,fibreglast recommends that you watch the resin infuse the fibers, so I'd be willing to bet that they sell clear bagging film too.
     
  9. sigurd
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    sigurd Pompuous Pangolin

    What is drop-cloth? As in paint drop? I just heard from an experienced person that you can use the transparent building plastic (and to a lesser extent packaging tape for sealing it)
     

  10. robherc
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    robherc Designer/Hobbyist

    I think what you're calling "transparent building plastic" and what I'm calling "drop cloth" are the same thing.
    Different countries, different names, same cheap transparent plastic sheet. ;)
     
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