Vacuum Bagging Problems

Discussion in 'Fiberglass and Composite Boat Building' started by flamenco, Mar 1, 2012.

  1. flamenco
    Joined: Nov 2010
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Malta

    flamenco New Member

    Hi everyone,

    I'm experimenting with vacuum bagging and came across some minor problems. Basically I know that I've put some extra resin during hand layup, and the breather absorbed most of it. However some resin also passed through the vacuum connections and through the resin catch pot. My problem is that once the resin was fully cured, the plug and socket were clogged with resin. Now someone already suggested to add a couple of layers of breather fabric under the breach unit so that no resin will enter the system...but then what would be the purpose of the resin catch pot?

    I'm using these plugs and sockets:
    http://www.vacinnovation.co.uk/page/1qxal/Vacuum_Connectors_Hoses_and_Gauges/Vacuum_Connectors.html

    Also, is there a way to take off the hardened resin from these brass fittings, perhaps immersing them in acetone?

    thanks for your help
    jeremy
     
  2. groper
    Joined: Jun 2011
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    Location: australia

    groper Senior Member

    You should not be sucking that much resin so that it clogs your lines and or socket... the resin catch pot is only there as a redundancy to save your vac pump filling with resin if you get things wrong...

    Are you using perforated plastic release film between the peel ply and breather? This helps limit too much resin being pulled out of the laminate aswell as removing it after cure...

    How much vacuum pressure are you applying? High vacuum pressures are not needed for vacuum bagging and can cause a range of problems if the vacuum is too high...
     
  3. latman
    Joined: Mar 2010
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    Location: Australia

    latman Junior Member

    cured resin should not soften in anything , often brass fittings are designed so you can drill out any mess ?
     
  4. flamenco
    Joined: Nov 2010
    Posts: 2
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    Location: Malta

    flamenco New Member

    groper, I am applying a pressure of 14 inches of mercury (approx -0.5 bar).

    Yes I am using the p3 release film between the breather and the peel ply. I did another trial today where I added two layers of breather material and 4 layers under the breach unit...I also used less resin. I hope all goes well!
     
  5. groper
    Joined: Jun 2011
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    Location: australia

    groper Senior Member

    indeed, you do not need to add "extra resin" to your layup just for the sake of sucking it back out again into the breather... layup your job as you would for a normal hand layup, the vacuum bag process simply consolidates the layup and compacts it more tightly whilst releasing any trapped air. Only a small amount of excess resin should be removed from your layup and into your breather... which ideally amounts to the difference you would get solely from the improved fibre/resin ratio possible under vacuum pressure applied.
     
    1 person likes this.
  6. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    What I do when wet bagging, is laminate the first layer relatively wet. (not soaking wet, but well impregnated). Especially when doing carbon visual stuff. The rest of the layers can be done with a normal amount of resin, and the last layer, depending on the number of layers, can even be done extremely dry.

    P3 and 0,5 bar are OK, I would not change that for now.

    Other tricks are a larger bag, and the breach unit further away from the part.

    The breach unit should never be immersed in resin, they do not like that. What you can do is soak in methylene chloride or methyl ethyl ketone, to dissolve the resin. Both chemicals are nasty stuff, so at least keep a good ventilation going, and protect yourself. Very likely the seals are toast. Dismantle the units, and get new seals. Order them the first time from your supplier, measure them, then buy a couple of sets in industry suppliers. Much cheaper.
     

  7. CatBuilder

    CatBuilder Previous Member

    If time is a concern, buy your vacuum fittings in bulk and in plastic. Just throw them out when you are done.
     
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