My mold all bubbles

Discussion in 'Fiberglass and Composite Boat Building' started by hyboats, Jul 7, 2010.

  1. hyboats
    Joined: Jun 2010
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    hyboats Junior Member

    Yersterday I released my mold. There are so much bubbles on the surface like much millets. Now what should I do to repair it ?
    Gel coat is vinyl then five layers mat with vinyl resin others are polyster resin.
     
  2. tunnels

    tunnels Previous Member

    Post some pictures and lets have a looksee at what you are talking about !!!!:confused:

    Surely what ever the defects are (bubbles ) they must have been visable before you glassed over the gelcoat !! You could have stripped it all off and done it a second time !!
    Sounds like the incompatability between two of the products you have used if its all over . NEED PHOTOS !!!

    Lets go back a few steps to the stage of waxing the plug ,how many coats of wax? and what else did you use on top of the wax before you applied the gelcoat to the mould or thin gel coat possibly undercured that has caused alligators !!
    Even this will have shown up in the first layer of glass !!!
    Did you use any PVA release agent ??
    If you did how did you put it on and with what ??
    How long was the gelcoat on before you started to glass over it ???
    Explain the first layer of glass you applied over the gel coat , what was you catalyst ratio or the resin for this skin ? sounds like a slow brew of resin that could have attacked the gel !! but need to see some pictures .
    Repairs wont be easy !!!

    There is no advantage using vinylester resin to build the mould ,just use all polyester !! Mixing products is not a good idea and can lead to other problems down the track .
     
  3. ondarvr
    Joined: Dec 2005
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    Location: Monroe WA

    ondarvr Senior Member

    If by bubbles you porosity, then yes this can happen, it typically is a result of spray technique. Spraying the first pass too thin or too thick can cause it, so can the catalyst type and level.

    VE gel coats are more difficult to spray than polyester types and porosity is the most common issue.

    Using VE skin coats is very common in both tooling and production, it can yield a more durable, crack, water and heat resistant tool or product.
     
  4. hyboats
    Joined: Jun 2010
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    hyboats Junior Member

    pictures of the bubbles

    Thank you Tunnels the pictures as following.
    I washed the male mold with a liquid (also a type of wax which can help releasing ) 6times, then wax 5times. Then painted the mold with vinyl gelcoat two times painting after the first one harden then paint the second time. About 4hours later I laminated with vinyl resin and mat 2% harder.
    What materials should I use to make mold ?
    Now how to repair it ?
     
  5. tunnels

    tunnels Previous Member

    Need to see pictures first !!:confused: Then will try to get you through it !! :D
    Do you have product names and product discriptions of everything you used .
     
  6. hyboats
    Joined: Jun 2010
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    hyboats Junior Member

    pictures

    pictures I don't know how to upload it
     

    Attached Files:

  7. hyboats
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    hyboats Junior Member

    Hello pictures

    The three pictures are in same area. When I open flash lamp then it looks clear
     
  8. tinhorn
    Joined: Jan 2008
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    Location: Massachusetts South Shore.

    tinhorn Senior Member

    Man, those look just like the bubbles than are normal in vinyl ester resin. Odd that they show up in the gelcoat against the mold, though--I used to use VE gelcoat and resin all the time, and while they were normal in the resin, I never had them show up in the gelcoat like that.

    How large is the mold? I'm afraid you may end up either refinishing it or building another one with polyester (tooling) gelcoat.
     
  9. tunnels

    tunnels Previous Member

    wow thats a new one on me !
    In all my 30 years I have never seen anything like that before !:confused:
    If its all over its got to be a reaction between the gel and what ever was on the mould !! just had a thought what was the weather like when you applied the gelcoat ? what about the air line to you gun if you sprayed did you have a water trap anywhere in the line ? To understand whats happened you need to reproduce everything last detail you did when making the mould to find which bit made it happen . Without a really clear picture or seeing it first hand its all guess work .
    How big are the individual bubbles ??:(
     
  10. hyboats
    Joined: Jun 2010
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    hyboats Junior Member

    my mold

    The mold length is 23ft.
    The bubbles are very very small diameter is about 6mils . Mold looks very glossy when I stand front it it looks like a mirror. but only these bubbles
    When painting I didn't use water trap
     
  11. tunnels

    tunnels Previous Member

    Ok ! ARE the bubbles easy to burst ?
    When you burst them is there water inside the bubble ? The compressor tank , when did you last drain it and let all the water out ? Its a good idea to make the drain tap hiss just a very small amount when you are spraying so any water naturaly leaks out. What is the capacity of the compressor cubic feet per minute and any other tanks as well as the one on the compressor its self !
    If you are running the supply hose directly from the compressor you need a good ,big ,water separator close to the outlet on the compressor . But if you are using a wall mounted air system it could need a very serious look at ! some really simple basic principles and moisture is a thing of the past ! well almost !!
    To repair the mould will depend if the bubbles are actually droplets of water and how deep they actually are !
    I have two options but if anyone else has any thoughts step up and add some words of wisdom !!:idea:
     
  12. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    Which type of spray gun did you use, a pressure pot, or an airless system?
     
  13. horacewimm
    Joined: Feb 2011
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    horacewimm Junior Member

    Saw this before once, and that was most definately water in the compressor coming through to the work piece. We have a dryer system fitted on our compressor and dont have this problem. But if you dont have one then this is the likely outcome. Screw compressors without a dryer are even worse at producing moisture in my experience. H
     
  14. jiggerpro
    Joined: Sep 2007
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    jiggerpro Senior Member

    Why would anyone insist on using Vynilester gel coats (tooling or not) if they are prone to bubbling ? if simple cheaper polyester gels can do the job waht are the benefits to taking those risks ??
     

  15. Herman
    Joined: Oct 2004
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    Herman Senior Member

    Higher Tg, better elongation, better scratch resistance, etc.

    If you are blowing water, then polyester gelcoat will look the same. High quality compressed air is vital, especially in higher humidity areas.

    On bubbling of vinylester resins: Very probably not the right catalyst / peroxide is used. Try and get a peroxide which does not contain hydrogen peroxide. This causes bubbling / foaming of some vinylester resins.

    Also, there are special peroxides for gelcoats, which cause less porosity, and a better cure level (surface quality) in shorter time. (Andonox MEC)

    I must admit that one of our best peroxides for infusion (Andonox MCP), giving long geltimes, only a small increase in viscosity up to the point of gelling, a low exotherm, yet a good final cure, has a small amount of H2O2 in it. When mixing with vinylester, you see some foam develop. However, after 2 minutes it is stable again, and with a bit of patience, or better yet, a degass procedure (highly recommended with any resin) the foam is gone.

    Another fun story: I was doing a demo at a customer, with an RTM infusion machine. They had compressed air, the compressor was outside. It had a freeze-dryer mounted. Temperature outside was some -5 degrees C.
    At a certain point the machine stopped working. Ice had developed around the air cilinder, where the air expanded rapidly. It turned out that the freezedryer stopped working, and wet, but still cold compressed air was driving the machine. As the air expanded, temperature fell below 0 degrees, and the water froze, jamming the cilinder. We managed to get the machine working again, with help of 2 hot air guns heating the master cilinder of the RTM machine.
     
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