Refinishing Hull

Discussion in 'Fiberglass and Composite Boat Building' started by RufNutt, Jan 8, 2013.

  1. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    It's odd the gel coat would come off this easily by just scraping it, I've never seen this happen, and I've seen many unusual things over the last 45 years in composites. There are a few scenarios where I could it happen though.
     
  2. RufNutt
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    RufNutt Junior Member

    It was using a scraper to get under the edge then tap it with a finishing hammer and when I was able to get under it you could basically push the scraper right along by tapping it with your hand.
    By the photo I have attached you can clearly see I never took off very much of the laminate with it . Some of the pieces actually had very little resin on the backside and no fibers coming off at all.
    Basically that is why I decided to strip the hull until I got to sound gelcoat just above the water line .
    This is a good scenario why blisters come back with just repairs of individual spots.

    The picture is of a piece about 20 inches long and could have been twice as wide if my scraper was

    [​IMG][/IMG]
     
  3. ondarvr
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    ondarvr Senior Member

    This is an interesting failure and there are a couple of possible causes. Hard to know exactly what it’s from by just looking at the pics, but here goes.

    Since the skin coat looks like it bonded well to the gel coat (amber colored resin and fibers on the gel coat) it could be from the skin coat either being left to cure too long before the rest of the laminate was applied, or the surface was contaminated slightly compromising the bond.

    Next.

    Either the skin coat or the next layer didn’t cure properly from too much or too little catalyst, cold weather, contamination, etc, the poor cure (cross linking) would leave it more susceptible to water damage and de-lamination. This would explain why you were able to easily peel this layer off and not go deeper.
     
  4. dzausta
    Joined: Feb 2013
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    dzausta Junior Member

    Could you tell me more about time frames when laying glass and working with vynalester? how long do I have between laying layers, and how does time impact the layup (before full cure)?
     
  5. ondarvr
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    ondarvr Senior Member

    Ideally you would apply you next layer right after the first layer cooled from its peak temperature, there are many variables though, so real world time frames are difficult to nail down. If it’s indoors and not hot out you normally have at least a few days.
     
  6. RufNutt
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    RufNutt Junior Member

    Hello ondarvr,
    Thanks for dropping by and looking at my situation. I have read alot of your threads at different forums.

    My biggest question is where to go next. I know you have been supplying and troubleshooting fiberglass products for years. As you can see in the pictures after I sand down the laminate that is on the boat I will not have removed much material. It is basically the skin coat where I see the problem.

    I myself do not feel I will be removing enough materia lfrom the laminate to go for a complete new layer of some fiberglass cloth and epoxy. I feel I could sand the laminate and fill in the blisters that were there with a good strong epoxy filler followed by at least 5 coats of epoxy to seal the laminate. Then do a final fairing and cover with an epoxy product again.

    What do you think?

    Thanks
     
  7. RufNutt
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    RufNutt Junior Member

    Hello again I am not going to hold anyone to their ideas and suggestions. I just would like some opinions is all . Whatever I do to the hull if the repair fails so be it, it is only on the bottom of the hull and LOL nobody noticed it and thought the boat was in great shape for the year until I flipped it and revealed the blisters it developed. I just want to try to do the best job i can do instead of just throwing product on the hull before I try and fix the situation. So Please and suggestions would be appreciated.I am still on the repair path PAR suggested before I revealed what I found. Should I still continue with them plans.

    Thanks
     
  8. ondarvr
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    ondarvr Senior Member

    If the laminate there now looks solid the plan you have should work fine.
     
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    As far guide coats, this is part of the fairing stage (as you know) and you're not there yet. If you're done picking at the laminate dry spots, done any reinforcement or repairs, the it's time to seal the laminate. Coat the raw laminate wholesale with straight epoxy. Do a first coat and see if you have dry spots (you probably will). Recoat these areas next and when no more appear, apply two more straight epoxy coats, over the whole bottom. Consider these coats are the base, that you don't want to sand through, so some argument could be made to tint (pigment) the last of these epoxy coats, so it tells you when you've sanded down too far. Pick an odd color, so you're not confused with primer.

    With the laminate sealed and possibly tinted, let it dry for a few days, so it's good and hard, then scratch it with 100 - 120 grit and apply a very contrasting building primer (epoxy primer is perfected). Next, it's time for the board 'o pain, the boogie board, the long board, the elbow breaking, patience testing *****. Working at a single angle, say about 30 to 45 degrees to the centerline, lightly scratch the primer, from one end of the hull to the other, leaving a common diagonal scratch, all in the same direction. Next, come back the other way on the perpendicular angle, so the result is a cross hatch pattern, no swirls, no wiggles, just a clean, straight cross hatch. This will quickly identify the high and low spots, so you know where to focus your energy. Do it this way and you'll save lots of hours fairing her up. This is where guide coats are handy as hell. If you don't have different color primer, just mix in some similar topcoat paint (if they use the same thinner, they'll be compatible enough). When you make the cross hatch pattern, the lows will still have the latest color of primer, but the highs will show the previous color.

    Fill lows, grind down highs and repeat the cross hatch routine, until you can't see any lows or highs. When this occurs (a pro makes 3 passes) it's time to apply a finish primer, which has much less silica and talc in it (less build) and sand much smoother. Smooth up at least two coats (I use 3 or 4) of primer, then you're ready for top coat. Again a guide coat can help fine tune a surface, so it's like a mirror. A light dusting with an aerosol can primer is good for this.
     
  10. RufNutt
    Joined: Jan 2013
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    RufNutt Junior Member

    Hello Par thanks for the info and plan I really appreciate it . Thanks ondarvr for the opinions on the problem. Just curious as to what brand of epoxies primers for high build and regular you recommend as my resources up here are basically water base products because of the new laws. I don't know if that is the way to go. Any suppliers I have access to up here are automotive epoxy primers. I don't think they would be compatable to marine or are they. We are still aloud to use the other products if we can get access to them. I have brought alot of products across the border in the last few years and have had no issues. So I can just order them from a us supplier and get them shipped to my us broker.

    Thanks again
     
  11. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    On line and mail order is the ticket to the best pricing and choices for these products. Most of the major epoxy formulators have primers, but try www.epoxyproducts.com and www.bateau.com for some alternatives. Automotive primers aren't much different than marine.
     
  12. RufNutt
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    RufNutt Junior Member

    Hello again, I just got a quick question. I have been sanding the laminate down with 80 grit and is going pretty good. I am still in the lay up layer so all is good.

    In the image you will see areas I am coming accross. There seems to be areas with alot of air bubbles or contamination from the build. I could keep on sanding until I get the laminate layer completely off but it seems to be pretty sound. I was wondering if I could take my grinder with a small pad and hit these areas of bubbles and just fill them full of fairing compound . In the photo you can see in the lower left hand corner I have started to use the grinder with a small pad and it seems to take out the air bubbles . It is almost like you have little pieces of brown packing tape all over with a little air void underneath. The depth of these bubbles is only a little thicker then couple pieces of tape. I figure I can spend my time sanding and fairing the hull after hitting these areas with a grinder then trying to sand the complete laminate down to the next layer beyond the bubbles.

    [​IMG]

    What do you think of my idea.

    Also I found a couple of voids in the outer stakes edges can I just mix up a good mixture of epoxy, cabisol and milled fibers to build these stakes back up?

    Again Thanks in advance.
     
  13. ondarvr
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    ondarvr Senior Member

    Small pockets of air in the laminate are common, and yes they can be sanded out and filled. They can also be from new blisters starting, the two frequently go together.

    You can fill the air bubbles in the strakes and sand them back into the correct shape, don't over fill much because epoxy can be very difficult to sand if you just use milled fiber and Cabosil.
     
  14. RufNutt
    Joined: Jan 2013
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    RufNutt Junior Member

    Ondarvr Exactly what i was thinking too about the air bubbles. I presume that is why when alot of boat owners just do blister repair on what they see is why down the road new blisters arise. I know taking off the gelcoat is alot of work but in the end I think I will have alot of future problems covered by eliminating as many air bubbles as possible.

    I was thinking the milled fiber mixture and cabasol for structure but just for filling in air bubbles and imperfections I will go with a fairing compound

    Thanks again.
     

  15. RufNutt
    Joined: Jan 2013
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    RufNutt Junior Member

    one more question I have is I have been reading alot about AMINE BLUSH . So if I decide to put some fairing compound on the hull but can't get at it for a couple days to sand it.

    Do I have to clean it with something before sanding in case there is amine blush.

    Is amine blush a real big deal during the fairing stage with fairing compound.

    Should I clean each time between applying fairing compound and sanding.
     
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