small Bubbles in csm fiberglass

Discussion in 'Fiberglass and Composite Boat Building' started by JEFFHEENAN, Feb 3, 2016.

  1. JEFFHEENAN
    Joined: Oct 2014
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    JEFFHEENAN Junior Member

    hello, I laid up two to three layers of csm. The first layer went down perfectly. The second and third however began to have small bubbles. Bubbles the size of a grass seed usually grouped together. I could see these bubbles forming but no matter what I did I could not roll them out. Does anyone have a explanation or advise.
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    It could be too dry.
     
  3. JEFFHEENAN
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    JEFFHEENAN Junior Member

    What do I do about it being to dry. How do I fix, or are the bubbles to small to bother with
     
  4. JEFFHEENAN
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    JEFFHEENAN Junior Member

    Thanks for the reply gonzo. Another thing is I am mixing with a drill. Could this be causing the bubbles?
     
  5. messabout
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    messabout Senior Member

    Yes, if you are mixing with a drill you will be making tiny bubbles that do not burst readily.

    Bubble entrainment is to be avoided. Mix slowly and carefully with a paddle, like doing it the hard way. There are some chemicals available that help disperse the tiny bubbles. Best not get bubbles in the mix in the first place.

    People who have done transparent table tops have fought that bug bear and have worked out methods for avoiding the problem. Thinning the mix is one of them. Denatured alcohol in small ratios is sometimes helpful.
     
  6. SukiSolo
    Joined: Dec 2012
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    SukiSolo Senior Member

    You do not inform us as to which resin type you are using. Polyester rarely produces bubbles and if your getting them, the CSM is perhaps too stiff and springing back. Perhaps change to more layers but lighter weight?. Less spring back will let the mat sit down properly. Important to fully wet out and ensure the mat is properly down. It is also important to put a (thin) layer of resin down first then lay on the mat as this helps fill the mat from the underside so to speak. This is more useful with the heavier CSM materials and fully woven cloths.

    If your using epoxy, you may be wetting out too early, whilst the resin itself is full of tiny bubbles. A few things worth trying are, wait 'til the resin exudes most of the bubbles (heat helps a lot but beware of an over fast reaction!), or wave a hair dryer/paint stripper gun/propane torch over the laminate to release the air bubbles. You may find a combination of rolling and squeezing the laminate along with applying some warm air or direct heat will let the entrapped bubbles escape. You also get some time to do this with epoxy as a relatively thin layer takes a while to cure.

    If casting with clear resins the best technique I've come across and used is applying a vacuum. However this is not always super easy to set up.
     
  7. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Maybe it would be more helpful if you told us what you're attempting to do and how you're doing it. Generally, as mentioned, machine mixing will introduce lots of bubbles, unless you have special resin mixers. Resin application can also introduce lots of bubbles too, so how are you applying the goo?
     
  8. JEFFHEENAN
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    JEFFHEENAN Junior Member

    Thanks guys for weighing in. I am building a fiberglass drift boat with poly resin from a mold. First time. My layup schedule is 3 layers csm, 1 layer 18 oz wr. at 45 degrees then csm then final layer of 18 oz at 90 degrees. the bubbles are starting on the second layer of csm and increasing. I am on the 3rd layer. I have sanded them out the best i could but the tend to be lows. I think you guys are right I am mixing in the Bubbles. I will find out later today.

    On a completely different note. Do I gel coat the inside of the boat before I glass in the components, seats and storage.? Or do I wait and gelcoat when I am done.

    Thanks a bunch everyone and suggestions or criticisms are very much appreciated.

    Thanks, Jeff
     
  9. philSweet
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    philSweet Senior Member

    It is best to do it later after all the bits are tabbed in place. In a production environment when you want a good finish on both sides, you tend to make a liner and a hull and bond them like a sandwich. For a drift boat, nonskid is a good idea and a webbed finish can hide many sins.

    random webbing picture.

    [​IMG]
     
  10. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    That isn't the best laminate schedule for a drift boat, it will be relatively weak and heavy.

    One layer of 1.5 oz mat, then a 24 oz roving, repeat as many times as needed. Better yet, use some 2408 biax, it will lighter and stronger.

    Also doing one layer at a time is slow and comes out worse than doing several layers at once. Do at least one layer of CSM and a roving at a time, doing two of each is fine if you can manage it.

    The chine should have several more layers of glass than the rest of the hull.
     
  11. JEFFHEENAN
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    JEFFHEENAN Junior Member

    Thanks again good info. Phil what is random webbing?
     
  12. philSweet
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    philSweet Senior Member

    I just meant that that wasn't me or my boat. Just a Googled image.
     

  13. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Random webbing is a look (see image above) that many low cost builds employ, to hide obvious flaws in the finish. It can be done with paint or gel. The advantage is you don't have to have a high level of finish, saving effort.
     
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