Fiberglass help needed

Discussion in 'Fiberglass and Composite Boat Building' started by Wynand N, Dec 11, 2008.

  1. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    Whilst hand laminating with CSM, some bubble like dry spots appear that refuses to be wetted or lay down - what can the cause of this be?
    The problem is isolated to a few places (on flat areas) and it is laid down on gelcoat. Now that it is set, can it be repaired by injecting resin into the void between the gelcoat and the CSM with a syringe to fill it solid before laying the next layer of mat?
    Or how do one repair that without serious surgery....
     
  2. MarboMan
    Joined: Nov 2008
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    MarboMan Junior Member

    Did you get anything on the CSM before using it?

    What about storage...kept in a relatively cool, dry environment?

    Syringe might be a good idea! Do it as soon as possible to get best chemical bond to surrounding resin.
     
  3. Manie B
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    Manie B Senior Member

    sorry i only saw this post now after i posted my previous reply

    i had similar problems with my epoxy ( which is very different ) but in my case it was surface contamination = not clean enough

    after all the **** we had on the mine with the fibreglass spirals = mineral benefication plant i firmly believe that a surface must be clean and either acidic or alkaline depending on your application

    i realise that you are probably applying wet on wet - what we did was mix short chopped fibres 20mm (sold by Harveys) into the polyester resin mix to make a thin light paste = porridge

    it worked very well as our outer surface on the spirals was **** anyway

    i am sure that if you rolled it out well you could get excellent results
     
  4. Wynand N
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    Wynand N Retired Steelboatbuilder

    Manie, the surface is clean - the plug was gelcoated this afternoon and I let the gelcoat cured past the finger pull scream test, about 3 hours total. Then a barrier coat of clean laminating resin applied and waited until it kicked, followed by the first CSM coat giving the problems now.
    The CSM is kept in a cool dry place on its roller with the plastic bag/wrapper pulled over after use.
     
  5. Manie B
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    Manie B Senior Member

  6. Manie B
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    Manie B Senior Member

    it could be that you waited a bit too long and the first blush was surfacing

    dont worry about small bubbles

    fill with syringe - common practice
     
  7. AndrewK
    Joined: Mar 2007
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    AndrewK Senior Member

    Once the resin has set the only way is to grind out or fill with a syringe that I know of.
    How big are they, send a photo.
    These bubbles, were you able at first to roll them out and then they reappeared? or were they not be able to be rolled out in the first place?
     
  8. fiberglass jack
    Joined: Dec 2005
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    fiberglass jack Senior Member

    did you wear gloves while you were cutting the fiberglass, i see this problem with guys waxing moulds and not properly washing the wax off there hands and you end up with areas that the resin wont wet out. also what resin are you using u said you are using csm which has a binder to hold it together needs the syrine to disolve, also a drop of sweat can do something simalar, best thing to do is carefully grind the area out with a diegrinder and make a paste from the gelcoat and fill and carry on with the layup. if you dont fix the area will bubble and blister in the hot sun
     
  9. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    No gloves were used, but hands were clean at the time. The problem manifested itself at the aft flange when we started the CSM. Then it went well till about midships and **** hit the fan. Funny, the problems are at the same place both sides of the hull....

    Will start filling those that did not bubbled out with a syringe and the bad ones that popped out be we grind out carefully and patched before the next layer goes on.
    The mat at places refused to be wet out and some of the bigger spots (two the size of my hands) did wet out and bond as the steel roller went over and then just lifted off again - no matter how much you roll it down.

    Decided to use woven roving for the next layer as it wet out easier to get things back on an even keel before putting the next CSM down.
     

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  10. Manie B
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    Manie B Senior Member

    Wynand your pics look very similar to the problems we had on the mine with the "spirals"

    we were never 100% sure but put most of it down to contamination - sweat - slight grease on hands or clothing

    that is why i have different gloves for different usage
    sweat plays havoc in our hot climate
    i have a constant battle with it here

    i now wash everything with vinegar
    i have had massive success with white vinegar
    all the other stuff - meths - alcohol - acetone dont even come a close second

    i am not saying this will work for you but its worth a try - if a drop of sweat gets wiped up with a vinegar cloth it dries quickly and you can proceed - it really goes fast

    and dont "barbeque" any where near your work piece - we were even worried about that fatty smoke

    i know it sounds like madness - but in our exteremely hot and dry climate at a very high altitude - things are different - and i solved many of my problems by working "cleaner"?

    even your beautifull table in the back must ONLY be used for cutting fibre - build another table to pack things on - that table must be spotless, and cover your rolls with plastic so that no dust and **** can blow on it

    sorry, just trying to help sport - not critisizing
     
  11. Wynand N
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    Wynand N Retired Steelboatbuilder

    Decided what the hell and let the apprentice and helper loose with small grinders fitted with sanding discs. Smoothed down the whole hull down and removed the "cancer" spots altogether rather than injecting resin and do battle that way. Now there are no voids between gel coat and glass that may cause mayhem later.

    Will blow the plug clean, wipe down with acetone and lay down the woven roving and hopefully will end up with a smooth and solid surface to laminate onto further...
     

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  12. ondarvr
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    ondarvr Senior Member

    If these spots refused to saturate with resin and returned immediately after rolling, then it's an issue with the mat. It may be the binder was applied incorrectly (uneven), or from handling it you contaminated the surface with catalyzed resin that gelled creating stiff spots that spring back.

    It's best to not apply roving directly over any cured laminate, the bond will not be as good as when mat is used as the first layer. the next layup should be a layer of mat then a layer of roving, if the part needs to thicker you can add more glass at a time though, you're not limited to one or two layers at a time. If you do plan to use more layers of glass be sure to catalyze the resin at the lower end of the recommended range so you have enough time and the layup doesn't get too hot.
     
  13. Wynand N
    Joined: Oct 2004
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    Wynand N Retired Steelboatbuilder

    ondarvr, it must have been the binder in the mat as no contamination was cause on my side, and the fact that most of the serious damage was on the one strip over the midship area and to a lesser amount elsewhere.

    Nevertheless, all the spots were sanded out and in fact the whole laminated sanded smooth. I laid down a cloth instead of wr and all went well and the plug is now evenly covered with a rather fair and smooth surface to build upon.
    My next rum would be CSM again - but 300g/m sq instead of the 450g/m sq used - from a new roll, followed by 2mm Coremat and another two coats CSM.

    All layups will go on singular up to the CoreMat, but the last two CSM's will go on together the prevent heat buildup close to the gelcoat and to prevent warping of the mould.
     
  14. ondarvr
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    ondarvr Senior Member

    I must not have paid attention the making a mold part, I was thinking you were making a part.

    The same holds true for cloth, layers of cloth and/or roving alone don't bond as well when used without mat, even a thin mat helps a great deal.

    For making molds one layer at a time the resin needs to be of the correct type, skin resins are promoted so they cure better in a thin laminate resulting in less post cure. What frequently happens with the slow build method is each layer never cures completely, so after the mold is complete and a few parts are built it starts to change shape. The amount of change depends on how thoroughly cured it was to start with and the temperatures reached by the parts being made, this post cure can continue for a very long time. It starts a as a pattern in the mold surface, the pattern can be from the glass used in making the tool, or from the part being made. Sometimes reworking the surface eliminates the pattern for good, but it may continue to return.
     

  15. AndrewK
    Joined: Mar 2007
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    AndrewK Senior Member

    Looking at the photos it does look like contamination problem, I am guessing not a binder issue but some other contamination that could have happened during the mat manufacturing.
    As ondarvr mentioned you most frequently see this happen as a result of contamination with gelled resin.
    Is this going to be a female mold that you will use with infusion? if so I recommend larger flanges say 200mm.
     
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