Blisters

Discussion in 'Fiberglass and Composite Boat Building' started by fallguy, Jul 31, 2018.

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  1. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    AD79A15B-726E-43B2-B9AC-57CA416B0104.jpeg
    Upside down pic

    E0016E3C-4877-4BD0-B01F-C0743FF61F7A.jpeg
    Upside down-this is near the transom


    90095B2E-3AD7-4C35-9AE7-142DCA19E37C.jpeg

    Sideways pic this is aft hull side

    7E485473-642C-4EB1-8116-F644ED80376C.jpeg
    Again, near transom.

    This is a '69 Whaler Sport 13'. I got it a few years ago and it was fairly light and thus fairly dry.

    I flipped it over and it was bottoms up for about two years.

    Brought it inside about two years ago or more and sanded off some of the poorly done two part paint. Cut open the transom eye locations (on the top of the transom or now the bottom upside down and found the foam to be dry. The eye spots had been crushed from years of overtightening, so I put some plywood fillers and puttied them heavily. The transom has a piece of wood inside and the wood was damp; not rotten. So I used heat lamps to dry it and had holes where most of the steam went out or could escape.

    I skinned the boat bottom and sides with epoxy and 6 oz glass under vac and faired it and primed it. Some gelcoat is under the skin. The gelcoat was thicker than the laminate in places, so I decided to not remove it all.

    This weekend I moved it outside for the space and it got a wee bit of rain and so I washed it off Saturday, so a bit more water hit it.

    Sunday, I noticed some blisters about dime sized aft hull sides, kind of up where steam might have migrated. There were about 15 blisters. I pushed on one and it seemed to move. Not sure if it was delaminating my glass or moving under the gelcoat.

    I cut into the blisters and some brown goo came out.

    The water either got introduced during my heat lamp drying of the transom or sitting outside for two nights and getting rinsed. I think probably the lamp drying and then the boat heated in the sun.

    What should I do to either manifest or reduce the problem?

    I figure I need to grind these out, but I think there might be more water inside and I'd rather find out now than later after final paint.

    Any surefire was to get this problem to either go away or max out?

    Can I heat the hull up in an oven to say 120 degrees for a few hours and expect more blistering? Or should I hole all the blisters and then warm the hull for a few weeks? Or hole closer to the chine edge?

    Or bite the bullet and expect some blistering due to my method of drying the transom wood?

    Thanks for any.

    Note: pics are all flipped every which way-boat is upside down; blistering is near transom on hull sides toward the chine which is why I am thinking I sent some steam over there in my lamp work - I am guessing the mould for the Whalers must have some hard stops at the chines that would reduce water migration theoughout the boat, but could be wrong.

    I know the foam goes around the corner which I learned in the transom eye repair work.
     
  2. ondarvr
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    ondarvr Senior Member

    You didn't do anything to cause the blisters, any blisters that ooze dark liquid have been there a long time, the heat may have made them a little more noticeable though.

    You may have many more on the hull, but sometimes they're just limited to a smaller area, it's hard to tell without further inspection. Grind these out and remove the gel coat in a small area to see if there are more hidden blisters just below the surface, they will normally look like lighter colored areas in the laminate.
     
  3. fallguy
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    fallguy Senior Member

    Thanks Ondarvr.

    If I open the boat up and it dries more; will it help or is the water trapped?
     
  4. ondarvr
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    ondarvr Senior Member

    It takes a long time to dry out, and as soon as you put it back in the water it will suck it up again.

    Check and see if you have more blisters, then a plan can be put together.
     
  5. fallguy
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    fallguy Senior Member

    How would water get through and epoxy/glass laminate and an epoxy primer and an epoxy paint?
     
  6. ondarvr
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    ondarvr Senior Member

    I forgot you had covered it with cloth.

    Well, if there's water in it now, and hull is foamed, it won't every dry out. Remove the foam and it will slowly dry out.
     
  7. fallguy
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    fallguy Senior Member

    Can I just hole it and let it dry? It might be another year in a VERY dry environment. Climate controlled with a furnace that sucks all the moisture out of the room.

    Maybe say 4 holes 3/4" each where the steam might have migrated?
     
  8. ondarvr
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    ondarvr Senior Member

    The blisters (water) were there long before you heated the area, heating it made them noticeable.

    If an old hull is coated with epoxy before being allowed to dry out, and the laminate is susceptible to blistering, then the blister process continues under the epoxy.

    You heated the laminate, this can soften the epoxy and cause the water to expand, so now you can see the blisters in this area.
     
  9. fallguy
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    fallguy Senior Member

    Can I just warm the hull up to say 120F and manifest the issues?
     
  10. ondarvr
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    ondarvr Senior Member

    You won't get rid of the water, but you may create visible blisters on the entire hull. What is the ultimate goal?
     
  11. fallguy
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    fallguy Senior Member

    Goal is to make it blister free before paint.

    It hasn't been topcoated, yet. Well, it was, but I sanded it all off because I didn't like the primer coat. I tried to r&t Awlgrip primer and it is a marketing ploy. The topcoat just showed how poor my primer coat was and I couldn't sand it out with 320; so I went to lower grits.

    It was a very dry hull when I got it. There was dampness in the wood insert in the transom and I used a heat lamp and honestly think that might have been the water source as the blisters are near there
     
  12. kapnD
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    kapnD Senior Member

    image.jpg I have a whaler of similar vintage, and would like to repaint it, but have been hesitant to do so for fear of the very problem the OP has.
    Looks like the original layup was chop sprayed over wet gelcoat, a great bond between them, but the fibers are under very tihin gelcoat, and seem to have wicked moisture through it.
    Likely the foam is moist throughout the hull, with no non destructive means of drying it out.
     
  13. ondarvr
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    ondarvr Senior Member

    Yours is just has bad gel coat, they messed it up when it was applied. To fix it correctly you need to remove it completely, then apply a new finish.
     
    Last edited: Aug 2, 2018
  14. ondarvr
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    ondarvr Senior Member

    How do you know it was dry, did you use a moisture meter, and if it was dry there can still be blisters, although they may be dry at the time, they're still there and will rapidly absorb water again.

    Blisters are a very complicated and misunderstood defect/problem.
     

  15. fallguy
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    fallguy Senior Member

    I know the boat was relatively dry. I had it upside down and tilted for like a year and then opened it at the transom hooks and wasn't any water puddled. Foam was dry to the touch. No meter. The transom wood insert was damp and I heated it with external halogens and some of the steam migrated.

    I think I caused the blisters by sending some hot steam into the aft section because they seem to be where the steam would have likely gone.
     
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