rottin foam core on 25ft bow deck

Discussion in 'Fiberglass and Composite Boat Building' started by blink2u, Jan 6, 2013.

  1. blink2u
    Joined: Apr 2010
    Posts: 7
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    Location: duncan BC

    blink2u Junior Member

    Hi guys,I have an early eighties 25ft Farrolon power boat,the fore deck on the bow,over the cuddy cabin,is a foam cored deck that is "rottin",the inner fiberglass layer has delaminated from the foam core,over the entire deck,making a very soft deck.I openned the deck up ,and the coring was a grey foam ,that was soaking wet and was very crumbly.
    My question is,what would be the best material to replace this entire deck,I have had no experience in any of the different types of cores,but have worked with plywood as a core material,with epoxy.Any input would be appreciated
  2. Herman
    Joined: Oct 2004
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    Location: The Netherlands

    Herman Senior Member

    Any pictures?

    As a replacement core you could opt for Core-Cell, Balsa, PVC foam.

    But first determine what caused the detoriation of the deck. This could be water ingress, combined with bad workmanship (unfilled kerfs in scrim cloth foam), but also just too low material specifications.
  3. swanson27
    Joined: Apr 2013
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    Location: melbourne

    swanson27 New Member

    Hi I have a swanson 27 with the same core problem.

    I would like to see if there is anything wrong with pulling all the inside fibreglass skin off, removing the the core and just replacing it with supporting arches/ribs made of wood or fibreglass ? Seems like less work and I would not have this problem again ?

  4. tunnels

    tunnels Previous Member

    Tearing the deck up from outside is a major as 99 times out of 100 the innerskin is weak and flimsy so redoing the core is not easy .
    tearing out from the inside is a little better but working upside down is not easy and will test you patents to the limit and beyond for sure !!
    The outside surface laminate will possibly be ok and support its shape ok . As for replacing with ribs ,again you need to get back the strength and so will have to build up a few layers of good glass to get you stiffness before fitting the ribs / frames etc !!

    All what you have both exsperianced is from Poor choice of materials combined with bad workmanship , when fittings and holes were drilled in the deck they were never sealled properly, again poor workmanship.

    Choice of core replacements really is your decission, there already been some good alternatives listed i would be in favor of going back tp using foam core-cell but theres nothing wrong with Balsa either . For the job being done from under the deck the replacement glass is another difficulty hanging a few layers upside down is a real challenge so think long and hard about how you going to do its for the job being done from the top your core could be sucked into an addition of 2 layers of resin rich csm and gently sucked down !Dont need a lot of suck just enough to get the core in on the wet glass and the penetration of the resin to come up through and around every part of the core

    Replacing the core is best done using a vac bag and sucking the core into a slurry or a couple of layers of wet csm so the resin or slurry comes up through any joins and crevises and joins !! they need to be filled 100% ,!!
    Then glass the surface , from the top will be easyer to work with , the same excise done from underneith needs to be done in sections that are managable , again Vac bagging upside down is best to use a semi stiff slurry buttered onto the core material that will be stiff enough to hold the core onto the surface when it pressed onto the surface and again suck the slurry into all the places it needs to be to fill any and all gaps

    Its not a easy thing but you will get a better job and if you add some decent glass when you replace what was there the deck will be a heap better than it ever was before !! remember the water would have come from fittings and what ever had been fitted from the outside and the fixture holes never filled with anysort of sealler filler !!
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