Realistic hull blister protection techniques

Discussion in 'Materials' started by makobuilders, Dec 24, 2018.

  1. makobuilders
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    makobuilders Member

    For a new construction fiberglass boat, trying to watch budget, would it be sufficient for long term blister protection to rely on an upgraded resin (vinylester instead of polyester) plus use an epoxy primer?

    Ideally vinylester resins would be used below the waterline, but the cost different adds up.
     
  2. ondarvr
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    ondarvr Senior Member

    It depends on the size of the boat and how it will be used.

    Blistering has become less of an issue because builders started using resins designed for marine use instead of the lowest cost product available. Going to a VE tends to reduce the chance of blisters to almost zero.

    I wouldn’t expect any boat I purchased new to blister now, but on a larger boat it doesn’t mean I wouldn’t apply a barrier coat.
     
  3. makobuilders
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    makobuilders Member

    To clarify, what I'm wondering is if the gelcoat itself offers enough protection?

    So a vinyl ester gelcoat with "normal" polyester resins in the fiberglass layup. This would easily be supplemented by an epoxy primer barrier coat.
     
  4. ondarvr
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    ondarvr Senior Member

    Again, this depends on the boat and how you plan to use it. Leave it on the trailer except when in use, and any resin and gel coat may work. If it’s in the water for 10 years at a time, then the products used make big difference.

    Gel coat does not offer much blister resistance to the laminate, marine gel coats are formulated to not blister themselves.

    The normal location of a blister is in the laminate, VE resin can all but eliminate the possibility of laminate blisters.

    Most builders don’t use a VE gel coat, they have terrible UV resistance and can be difficult to use. Although there are VE barrier coats that are used behind the gel coat that do an excellent job.
     
    Last edited: Dec 24, 2018
  5. redreuben
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    redreuben redreuben

    Makobuilders, are you builders ?
    What sort of a reputation do you wish to cultivate?
    Hulls are a one off cost and about a third total cost, an engine, fridge, or mast can all be changed easily enough if they fail.
    A crap hull is a write off.
    For the few extra bucks a Vinyl Ester backing coat costs the peace of mind is bulletproof.
     
  6. makobuilders
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    makobuilders Member

    Reuben, those are good words of wisdom. So when you say “backing coat” do you mean the first couple of layers of glass use VE resin, then the balance of the layup can be polyester?
     
  7. redreuben
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    redreuben redreuben

    Yes one layer behind gelcoat, usually 300 gms of split strand mat. Nothing wrong with 450gms normal csm if thats all you stock.
    Still use a good isothalic behind it.
    Save the ortho for the furniture
    Merry Xmas
    VE likes to pickle thin gelcoat, make sure sprayer gets the thickness and catalyst levels right. Resin needs to be on the warm side too. Tip moulds or use fan so styrene doesn’t pool.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    I heard recently of a near new and very expensive rescue boat that had developed blisters, sounds like a simple and not very costly alteration to the layup schedule could have avoided it.
     
  9. missinginaction
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    missinginaction Senior Member

    I just happened across this thread and have a question. I've an old Silverton that I restored. It's 45 years old. Polyester hull. Solid fiberglass, no core. About 3/4" solid glass at the transom area tapering as you go forward. My question is simple. I like the design of my boat and fixed all of the issues that I could identify from the original build (there were many) as I restored the boat. One thing always struck me. There isn't a blister anywhere to be found. I stripped all the old bottom paint off of her a couple of years ago and it's smooth. I had a pretty easy time with a good quality scraper because it was so smooth. Silverton's from the early seventies were not considered to be very well built. I restored this one because I liked the design not because of OE build quality. Why are there so many issues with blisters if a boat this old could be built not to get them? Not trying to hijack the thread just trying to understand.
     
  10. ondarvr
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    ondarvr Senior Member

    There can be many reasons for a laminate to blister.

    You can use the best resins and gel coats, but if not catalyzed correctly it may blister. Lots of air pockets can lead to blisters.

    The type of glass used can increase the likelihood of blisters. Contamination can lead to blisters.

    Then you get down to just using the wrong products, cheap was the name of the game for many years, and the result was blistered boats.

    Over time the causes were better understood by the experienced builders and the chance of blisters popping up was reduced, but mistakes still happen.
     
  11. redreuben
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    redreuben redreuben

    What ondarvr said.
    Also in my experience it seems to be more common in chopper gun boats than hand laid, but not exclusively.
    Looks like you chose a good hull to keep.
     
  12. ondarvr
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    ondarvr Senior Member

    Interesting you mentioned chop.

    Chop (gun roving) itself has a lower chance of blistering than CSM, but....

    External mix chopper guns can increase the chances of blistering 10 fold. So the variable is how good the operator is at adjusting the gun, poor adjustment means blisters are likely, good adjustment and there may be no problems. Internal mix chopper guns are less common, but do a much better job at preventing blisters.

    The binder in CSM can cause blisters, not so much now , but a couple decades ago it was a bigger issue.
     
    Last edited: Dec 26, 2018
    redreuben likes this.

  13. redreuben
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    redreuben redreuben

    External mix guns - exactly
     
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