Boat Repair/Bonding Epoxy to Fiberglass Question

Discussion in 'Materials' started by thill, Mar 8, 2007.

  1. thill
    Joined: Mar 2007
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    Location: Virginia, USA

    thill Junior Member

    Greetings,

    Thanks to everyone for your helpfulness. There is a lot of experience here!

    Epoxy resin is highly recommended for saturating wood before installation, but I understand that epoxy and poly resin do not mix. How do you bond the 2 substances together?

    Here is my situation:
    In my boat, one of the storage compartments was made from painted plywood. This box hung from the bottom of the inner shell of the boat, and was connected by glass tape and resin. This box has rotted out.

    I want to fabricate a new epoxy-saturated plywood box, using glue and stitch methods. But HOW should I connect the epoxied box to the underside of the existing shell? This is a structural connection, and will have to withstand approximately 150 lbs of gear bouncing around at any given time.

    Or...Would you recommend other methods to fix this situation?

    All suggestions are appreciated. Thanks in advance for the assistance!
     
  2. RingLeader
    Joined: Feb 2007
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    Location: Slidell, LA

    RingLeader Junior Member

    Epoxy is compatable to cured polyester. You will have to rough up the surfaces of the existing polyester laminates for the epoxy to get a good mechanical bond... which is all you would get if you were using polyester resin to glass to the cured polyester laminates in the first place, a mechanical bond.

    Use epoxy resin for the whole project. I would build the plywood box and not only coat it with epoxy resin, but lay a layer of 6 oz cloth over it. I would lay small fillets in the corners first, then glass with 6 oz cloth, and once that is cured I would install it into the boat by tabbing it to place with a 1708 tape.
     
  3. thill
    Joined: Mar 2007
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    Location: Virginia, USA

    thill Junior Member

    Thanks!

    Ring Leader,

    Thank you for the reply and the info! I've got epoxy and glass on hand, so I might as well go ahead and do it right. Maybe I can even leave the glass tabbing partially in place, to help give a better grip.

    Thanks again.

    -TH
     
  4. RingLeader
    Joined: Feb 2007
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    Location: Slidell, LA

    RingLeader Junior Member

    Good surface prep is key. Rough grind the old fiberglass that you are bonding to and clean it well with acetone. I'm not sure what part of the box your tabbing will extend onto. If it is an area that you are glassing with the 6 oz, you must make sure that surface is prepped right before tabbing as well if the 6 oz laminate is let to fully cure. With fully cured epoxy you have to wash off the amine blush first (water and a scotch brite pad), then rough sand the surface, and finally wipe well with acetone. However, if you time it right, you can have the old fiberglass prepped and ready, laminate your box, and let that just start to kick off its cure. But don't let it fully cure, while its still in a rubbery state (still green), you can go ahead and tab that freshly laminated box into the hull without having to do any prep work to it. It just saves some time.

    If I am doing something that I want to have faired out nice and smooth, I'll let that epoxy laminate just begin to kick off, and then I'll wipe on a nice coat of epoxy fairing putty while its still green. That way I skip alot of work in that I don't have to clean and rough sand the new laminates before putting a coat of fairing putty on. I just go straight to fairing. It saves darned near 2 days of work/waiting.

    The added bonus of all that is that the fairing putty is not just sitting on the fiberglass laminates with a mechanical bond, it is actually chemically bonded to the laminates. Any further coats of putty however will be only mechanical bonds.
     
  5. fiberglass jack
    Joined: Dec 2005
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    Location: toronto

    fiberglass jack Senior Member

    36 grit on a grinder and go to town on it remember your replacing the glass so dont be shy, vaccum up the dust , and wipe down with acetone, with epoxy use cloth not chop mat, to make life easy make up some paste thats resin mixed with some fiber and cabosil and place a skim over the area you grinded this will help remove any low spots that might trap in air, do a lay up in two stages this will make your job easier, if you place to much on the wieght of the resin will let the fibreglass to fall off if you are inexperanice
     
  6. Oyster
    Joined: Feb 2006
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    Location: eastern United States

    Oyster Senior Member

    Ring Leader speaks from some experience here. He has a couple of small projects that he is doing that requires him to practice what he actually preaches.;) :D You lost there fellow? :p
     

  7. RingLeader
    Joined: Feb 2007
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    Location: Slidell, LA

    RingLeader Junior Member

    I'm always looking for something new and interesting to read.
     
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