Deck replacement question - Plywood fit?

Discussion in 'Fiberglass and Composite Boat Building' started by thill, Aug 12, 2010.

  1. thill
    Joined: Mar 2007
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    thill Junior Member

    I'm replacing the plywood deck of an 18' Glassmaster center console. I know basic fiberglass work, but not much about proper technique. The previous owner removed the deck, so I can't copy what was there. Fortunately, at least the stringers are in good condition.

    I plan to use 2 oz glass matt with polyester resin top and bottom, and at least two layers of 6" glass tape to resin the floor to the hull. Here are my questions:


    1. I cut and beveled the plywood decking tight to the hull of the boat. Is this right, or do I want a gap all around?

    2. Do I want to make a small fillet with a strip of glass matt between the deck and hull of the boat before glassing?

    Thanks.

    -TH
     
  2. thill
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    thill Junior Member

    ... Also, do I want to thin some resin to impregnate the fir ply before glassing, or will the laminating resin take care of it?
     
  3. ondarvr
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    ondarvr Senior Member

    Don't thin the resin.

    Its best not to have the plywood in contact with the hull, it can create hard spots. A small gap is fine and takes less putty to fill.
     
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  4. pescaloco
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    pescaloco Senior Member

    You do want a gap, it will help to prevent a hard spot where the deck and hull sides meet.

    You can make a fillet with putty or just drape the glass across your small but even gap between the wood and hull sides.

    If you are using 2oz matt you may find it difficut to get full saturation (wet out) of the fibers. I personally would perfer some 1oz or 1.5oz in two layers
     
  5. thill
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    thill Junior Member

    Ondarvr,

    #1 - Thank you, I will cut it back from the hull.
    - Would a 5mm (3/16") gap be OK?
    - "Putty" with what? Spray foam or caulking, to back the resin without causing hard spots, or something hard/structural?


    #3 - I will use the resin full-strength. (I just read another thread about that topic, and I understand, now.)

    Thank you very much for the help. I am following instructions from a book about boat repair. It has step-by-step instructions for deck replacement, but is missing certain details.

    I am spending hours on this forum, reading many posts. There is a lot of knowledge here! THANKS TO EVERYONE FOR SHARING.

    But now I'm questioning the hull-to-deck layup I'm given in the book... Does the 6 ounce biaxial tape/2ounce CSM/6 oz tape seem like enough of a layup? Should I revisit that, or just stop worrying and just get it done?

    Thanks again.

    -TH
     
  6. thill
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    thill Junior Member

    Pescaloco,
    Sorry! We were typing at the same time! Thanks for the information. I also have a roll of 1 oz, I just thought it was too weak for this application, and was mainly for smoothing things out.

    The putty sounds like something soft. Is it?

    Thanks.
     
  7. ondarvr
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    ondarvr Senior Member

    The putty can be anything, or nothing.

    The only goal is to not have the plywood touch the hull, filling the gap makes it easier to laminate over, but really doesn't do much beyond that. The size of the gap depends on your skill and attention to detail, the smaller the gap the easier it is to glass over.

    2 oz is OK for covering the wood, you should be able to wet it out easily on a flat surface.
     
  8. thill
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    thill Junior Member

    Thank you for the clarification, Ondarvr!

    I'm starting to feel confident again. I guess it's time to get off this computer and get back to work.

    Thanks again.

    -Tony
     
  9. pescaloco
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    pescaloco Senior Member

    putty can be the resin that you are using with some dry filler materials added to thicken the resin to the consistancy of peanut butter.

    I like to mix micro ballons and cabosil or milled fibers

    Two oz matt is fine but it sucks up a lot of resin and can be subject to dry spots if you run short on time. be aware of high ambient temperatures, work area EXPOSED TO DIRECT SUNLIGHT or catalyst ratios too high. Be carefull of that direct sun and also remember that the surface temperature of your substrate can be a problem (if it's hot), meaning your resin kicks off in 10 or 15 minutes and you end up with a mess.
     
  10. apex1

    apex1 Guest

    1mm is enough of a gap (make sure it is ONE all around!), filler can be the resin you use and just sawdust added to build up a "peanut butter" consistency.

    Cover with thin (the 1oz mentioned) glass tape. Paint proper (several layers) over it!

    Regards
    Richard
     
  11. ondarvr
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    ondarvr Senior Member

    1 oz CSM is too light for a reliable coating on a plywood deck (floor), being that thin it will typically crack and peel after a year or so, this is one of the main reasons they rot out in so many small boats. The chopper gun operator makes a light half hearted pass over the plywood and the clock starts ticking.

    A light mat and a light cloth work well together for this, but if going with only CSM it needs to be thicker, at least 1.5 with 2 oz being even better.
     
  12. apex1

    apex1 Guest

    Concur,

    but did not say MAT !

    Never use CSM as the only reinforcement.
    CSM is a "filler" and has nothing to do with boatbuilding, accept for reducing print through (and such).....

    But a fabric of the desired thickness is a valid solution, even at those minimal figures.

    Regards
    Richard
     
  13. ondarvr
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    ondarvr Senior Member

    Agree, but what 1.oz glass were you referring too? He said he had both 1 and 2oz CSM.
     
  14. apex1

    apex1 Guest

    CSM only? Must have missed that.........
     

  15. thill
    Joined: Mar 2007
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    thill Junior Member

    I just wrote a full report, but it VANISHED when I hit post! GRRRRR!!!

    Anyway, long story short, the floor went like clockwork! Much better than I'd even hoped, in fact. The layers of glass went down beautifully- smooth, flat and tight. The resin stayed tacky long enough for everything to bond well and fuse into a beautiful, clear layup.

    After letting it cure for two days, I've jumped and stomped all over, and that is one solid floor! I'm very pleased.

    Now... any suggestions for topsde paint? Or should I gel-coat?

    Thanks.

    -TH
     
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