Print through from foam edges?

Discussion in 'Fiberglass and Composite Boat Building' started by DennisRB, Jan 22, 2014.

  1. DennisRB
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    DennisRB Senior Member

    I have put an offer on a 43 foot cat which is going cheap as it needs a lot of work. It was built by Lloyd Powell from the Cat Factory WA for his father. I spoke to him and he says it was a great boat and was very fair when they built it.

    I showed him the pics and he said it is just print through from the foam edges which have showed up over time due to heat cycles. Foam is divinycell and vinylester resin. He says these days they would have post cured the hull and it would not have happened. He said if they put more glass on it also would not have happened. But he built it for his father and they wanted to keep it light (I like light).

    So has anyone else seen anything like this? I am only familiar with the weave showing not foam edges? Would this be a worry if you planned on painting and fairing it anyway? Does it point to any meaningful degradation of strength etc? Lloyd said all I need to do is try to sand the lines down, but if I come to glass I will need to add filler in the low spots.

    Will it come through again after a new paint job etc?

    Cheers.
     

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  2. Mr Efficiency
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    Mr Efficiency Senior Member

    Sounds like there is not a lot of GRP between that foam and the outside world. What was the laminate schedule for the area that concerns you ?
     
  3. DennisRB
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    DennisRB Senior Member

    I have no idea, other than the builder saying post curing it can avoid the prob or thicker glass, but he wanted to keep the boat light. I already sent him another email. If he replies I will ask, but he is going from memory and the boat is 12 years old. He said the forward sections and underbody to the daggerboard have kevlar as well for impact.
     
  4. redreuben
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    redreuben redreuben

    If it's 12 years old you can be assured it is post cured !

    Those lines are from filler/resin on the foam joins, no big deal apart from the aesthetic. Sanding down, hi build and paint would do the job. Whatever you do, DONT sand into the kevlar !
    The lines may re-appear over time but probably not as pronounced.
    After the high build has been sanded fair give it some time to harden before the finish sand and topcoat.
     
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  5. Steve W
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    Steve W Senior Member

    Everything the builder said is correct and as has already been pointed out, its post cured by now. Its amazing how little it sometimes takes to fair out ripples, sometimes not much more than the paint thickness.
     
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  6. DennisRB
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    DennisRB Senior Member

    I love this boat and my offer has been accepted! A friend knows a Crowther guru who has built several foam crowthers, and when he saw the pics he was concerned about delam. He says it may not be delam but I better be very sure about it before I buy.

    I will go down again with a hammer before handing over the deposit. Any tips for sounding for delam?
     
  7. TeddyDiver
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    TeddyDiver Gollywobbler

    You don't need a hammer, just knocking like you would knock a door. It's pretty thin skins.
    And you'll know what it sounds if you find a delaminated spot. Most important it's quite surroundings or you don't hear anything.
     
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  8. DennisRB
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    DennisRB Senior Member

    Cheers guys please keep the comments comming. This is getting serious now as I need to pay a deposit (yes I WILL be getting it surveyed of course)
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    I'd expect delamination from divinycell would be unlikely.
     
  10. groper
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    groper Senior Member

    You won't know unless you can sand off the paint. My concern is if there is air gaps between the foam sheets which has allowed the skin to wrinkle with the movement. You can't tap the hull and hope to hear this, but drilling some small holes into the seams might show something up...? Good luck getting that written into the contract :)
     
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  11. DennisRB
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    DennisRB Senior Member

    Even with vinylester?
     
  12. DennisRB
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    DennisRB Senior Member

    Yeah drilling it is not going to really be feasible. I will be using a respected multihull expert in the survey though.

    I really think you would have to be a pretty shoddy builder to leave are gaps between the foam. Especially if you are a pro boat builder building the boat for your father and yourself to use.
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    It is basically a mechanical bond, with the resin infiltrating the cut surface cells of the foam, and 'keying' the laminate to it. I don't know whether vinylester has some kind of chemical attachment to PVC foam,as well.
     
  14. groper
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    groper Senior Member

    The resin iteself means nothing - its all in the process they used and if they made mistakes, which is often unknown by the builder themselves, or overlooked, or simply an apathetic attitude -she`ll be right mate!

    You comment about being a pro builder and all that, well ask yourself why the boat looks like it does - it certainly would NOT if it were built properly WOULDNT IT!
     

  15. DennisRB
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    DennisRB Senior Member

    I guess you are right. But do you think the boat should not be considered for purchase because of it? The fact it does have this prob is factored into the price and I have allowed for the fact I will have to paint the boat. Note that this is only one minor prob, the boat has been let go bad and it needs a full paint job anyway. The boat is not cheap because it has print though! The builder himself said this does not happen anymore with his builds due to post curing and/or more glass. He said in the WA heat this was a common occurrence before post curing. He has no concerns at all about the structure of it, however I do realise a pro builder still in operation is never going to say they built a crap boat!

    http://catfactory.com.au/

    After reading your awesome and very informative threads regarding foam construction (one which started on DIY yachts), I have learned usually more glass is laid up than is needed for strength due to impact denting etc. So I do value your opinion. The builder said he kept this boat light, so this is why it has shown up more than usual.

    Now I am fine with it if it is cosmetic as most people seem to agree it is. However if its structural I am not interested. This "print thought" seems to be a fairly common and understood phenomenon and it took years to come through on this boat.

    So its not a question of if this problem could have been prevented with better practices, rather is this prob just a cosmetic issue with no serious structural implication?
     
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