Newbie questions- fuel tank platforms

Discussion in 'Fiberglass and Composite Boat Building' started by Downtown, Jan 5, 2011.

  1. Downtown
    Joined: Dec 2009
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: NYC

    Downtown Junior Member

    Pretty much of a newbie on the site. Been on the site, but never posted.

    I am building platforms on either side of my engine room on my 1982 Marine Trader - 44DC to hold new aluminum fuel tanks. I have cut out the beams the platforms will sit on to hold the fuel tanks. The beams that will sit on the hull are all slightly different sizes, as the hull tapers. The platforms will be around 10 feet long and 2.5 feet wide. The beams have been cut out of pressure treated 2 x 8s.

    My questions: is the pressure treated okay to use. Should I, can I, epoxy coat it? I heard after six months, it can be painted or epoxied.

    I was going to hold them in place with fiberglass matting and epoxy resin. Have never done that before. Any tips would be appreciated. Do I need to bed them in putty first. (Stupid question?)

    Once beans are in place I plan to use marine plywood, but have read about many different classifications. Do I need to epoxy coat this, as well. Or can i just paint it with Awl Gard.

    Not sure what I'm leaving out, but that's it for now.
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 476, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The newest forms of commercially available (Lowe's/Depot) PT don't epoxy very well. If you can get the old style of PT treatment (CCA) then you'll be better off, though in all honesty, you don't need it if using proper epoxy encapsulation techniques. Also, if you employ epoxy to "tab" in your new structural members, then use just cloth and skip the mat. Epoxy doesn't need the assistance of mat like polyester resin systems do and it just increases you resin requirements exponentially, which is literally just a waste of resin. Yes, you should epoxy coat (3 coats on every square inch, especially end grain) the plywood too.

    Do yourself a big favor and log onto www.westsystem.com and www.systemthree.com and download their user's guides. These will explain the products, the methods, techniques, fillers, etc.
     
  3. Downtown
    Joined: Dec 2009
    Posts: 13
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: NYC

    Downtown Junior Member

    What I'm getting is --

    if even regular plywood is epoxy coated, it's good to go. So no marine plywood?

    And I should epoxy coat the PT beams.

    And use cloth not mat with the West System. I did work with it once, but not with cloth.
    Does the entire beam need to be covered with cloth?

    I will recheck user guides.
     

  4. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 476, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    To protect wood, it must be encapsulated, which means completely coated with sufficient film thickness to prevent moisture vapor from getting to the wood. This means, as the word suggests, every single square inch must be embalmed in epoxy or you've just wasted a lot of money and effort.

    Again, as I mentioned the new PT coatings (CA) don't work with epoxy. If you can get the industrial grade treatments (which is still the old CCA treatment) then yes you can coat. In short, you don't need PT, particularly in light of the incompatibility of the new chemicals.

    Regular plywood (assuming exterior grades) do not have the construction to warrant a marine label. Marine grades have a higher veneer count, much better internal construction, no over lapping plys, no voids or internal defects, while construction grades are full of defects, voids, etc. If you are supporting a hefty load in a marine environment, it's false economy to try house construction grades of plywood. If you want to save some money use a BS-6566 grade of marine plywood, which is considerably cheaper then the good stuff. It's just for holding up you tanks, which is just what the BS-6566 grade was developed for. It's a strength and quality issue, not a rot potential issue.
     
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