bagging 101

Discussion in 'Fiberglass and Composite Boat Building' started by Tungsten, Jun 24, 2012.

  1. sigurd
    Joined: Jun 2004
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    sigurd Pompuous Pangolin

    How do you know if you have too dry laminate? should I put a leak in the fridge pump hose?

    What is the perf film for, between breather and peel ply?

    The seal tape from fibermaxcomposites works good, it is not tape but some sticky stuff drawn to a strip. can be used again and again, even transferred to another mold. Pic in the carbon planks thread. I bet plasteline would work as well, but the rolls sure are quick to apply.
     
  2. groper
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    groper Senior Member

    How do you know if its too dry? With carbon its hard to tell, but with glass you can see all the white fibers when its too dry...

    The perf film is only there to allow you seperate the breather (now soaked in excess resin) from the finished part. You can experiment yourself just by leaving the breather in place for about a week or more so the resin is more fully cured and very tough before you try to remove it - its very difficult to get the breather off compared to when its still green! Without the perf film, it would nearly be impossible...
     
  3. Herman
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    Herman Senior Member

    It also limits resin flow from part to bleeder. As a start I recommend P3 perforation, and 0,5 bar or 50% vacuum.

    More vacuum, less perforations.
     
  4. Tungsten
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    Tungsten Senior Member

    So what kind of pressure is too high?If 50% is ideal with the P3 release film.then when does it get to be too much?

    Say your layup is 3 layers of stitched cloth(12oz) compared to one layer of 6oz.Would the 3 layers need more or less vacuum then a one layer?

    or is it just 50% across the board regardless of the amount of glass?
     
  5. Tungsten
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    Tungsten Senior Member

    K so onto some tests,

    a 6"x6 foam and a 9x4 honeycomb.

    [​IMG]

    a trip to the scale says 40 grams of glass uses 30 grams of resin.

    pump set at 15.5"dropping to 13" each cycle P3 realese.

    [​IMG]

    [​IMG]

    [​IMG]

    do my numbers sound right?
    looking at the piece they look a tad white?
    I'll take a close up later.
     
  6. Tungsten
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    Tungsten Senior Member

    What do you think?

    some close ups,
    foam
    [​IMG]

    [​IMG]

    honeycomb
    [​IMG]

    [​IMG]
     
  7. Herman
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    Herman Senior Member

    Not bad for a first timer. Usable stuff. A few comments:

    -make pleats in the bag at the edges of the part, so the bag will sit tight to the product on the edges as well.

    -Use a tad more resin in the first layer. This will cause some movement of the resin once vacuum is on, picking up air bubbles on its way. But to start with, make sure you do not have airbubbles. (requires some skill) This is where infusion definately has an advantage. The skill part has been moved from laminating to placing the materials.

    -be careful with excess fibers under the bag. When under the sealant tape, they will cause a leak path. Not immensely critical when wet bagging, but with infusion it is critical.

    -more layers do not need more vacuum. And keep in mind 50% and P3 is just a starting point. Depending on geltime and viscosity of the resin it could be more or less. Another trick is to wait for the resin to gel a bit (could take hours depending on the resin) and only then pull a vacuum.
     
  8. Tungsten
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    Tungsten Senior Member

    Ok thanks Herman,i think a little less vacuum on the foam will be next.

    You don't think the foam looks a little dry?
     

  9. Herman
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    Herman Senior Member

    dry-ish, yes, but not too bad.
     
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