fiberglassing plywood boat deck

Discussion in 'Materials' started by KMD, Nov 2, 2005.

  1. KMD
    Joined: Oct 2005
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    KMD Junior Member

    I have a 37' chesapeake bay work boat. I tore out the plywood floor, and floor trusses. I have re-done all the trusses with PT wood and stainless fastners. I am going to do the floor with 3/4 marine plywood. Traditional floors in this type of boat is just marine plywood painted. I want to fiberglass the pieces of plywood before I put them down. The boat hull is wood and i want to be able to pull the deck up if I need to repair anything or re-seal the inside of the hull. I will fasten the pieces of plywood down with SS screws and finish washers.
    I have never fiberglassed a boat deck before, this is not yacht quality finish, I will paint the deck when done to give the boat the traditional workboat look. The boat is used as a pleasure boat so the deck wont be getting heavy use.
    What type of fiberglass Cloth and resins/hardners should i use? I used west system on a small cabin roof once and it worked out well but I know it was pretty pricy. Any suggestions would be appreciated
    Thanks
     
  2. boatbuilder.org
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    boatbuilder.org Junior Member

  3. cyclops
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    cyclops Senior Member

    Do all the steps to seal the wood. Anchor all the plywood down. Then remove 1 sheet at a time and drill screw clearence holes in the plywood sheet. Coat the raw wood edges of the screw holes with Epoxy. If they close up, redrill out the holes. Squirt a dab of Silicone Rubber into each beam hole. Then screw down the plywood. You will not have any wet wood problems.
     
  4. chandler
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    chandler Senior Member

    why is everyone using pt for boat repair?
    I wouldn't use pt on my dog's house!
     
  5. gonzo
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    gonzo Senior Member

    What do you find wrong with PT lumber?
     
  6. chandler
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    chandler Senior Member

    It's very unstable, ever use it to build a deck? it shrinks.
     
  7. wdnboatbuilder
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    wdnboatbuilder Senior Member

    I have used Raka Epoxy System and has worked out very well. Not a Big Fan of West. never used MAS. and System 3 is also good was better before Chem-Tec sold out. But most important make sure you seal every thing. alot of people think sealing one side will do but don't fall for such hog wash.
    As far as the PT goes, too many voids just not a very good plywood for boats. Not say it can't be done. Even would have heard you used fir instead of PT wood. I have seen PT sealed in epoxy and held up well. Remember they force moisture in wood to make it PT and you should wait till you get to that 8% moisture content before applying epoxy. Of course the wood harvested is hybrid tree that can be harvested in 10yrs, milled and sold to home builders so the grain is not very tight.
     
  8. PAR
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    PAR Yacht Designer/Builder

    PT treatments have given rise to much inferior lumber and panel construction practices in the their industry. Solid PT dimensional lumber suffers from being cut out of farm raised, very young trees, many of inferior quality. The growth rings width clearly show a fast growing material and the diameter of the trees are barely above that of a sapling. Most PT lumber is full of pith, wild grain, live edges and internal stresses galore. I've seen PT 2 x 6's come out of the table saw at 45 degrees to the cut, not the most predictable stuff in the world. That said, any softwood can be treated and good examples of tight grained fir can be found with some looking. I don't personally think it's worth the bother, but some do.

    PT plywood has similar difficulties as does the solid PT. The use of lesser materials and poor construction, makes for bad panels and unreliable use in normal boatbuilding efforts, which typically require the sheet goods to bend. Used as a sole or lightly crowned decking, some of these issues can be forgotten, but it's still a lesser material and need to be covered to finish off.

    The other major complaint I have with PT in boat construction is the wet nature it is normally found in at the local Lowes/Depot. Seems like they come directly from the PT autoclave, still very wet from the treatment, requiring much time to let it dry out.
     
  9. gonzo
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    gonzo Senior Member

    That is true, but there are companies making marine grade PT plywood. I questioned the blanket statement that because lumber is PT it is of inferior quality.
     
  10. cyclops
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    cyclops Senior Member

    Right. The marine grade is the Lifetime Warrenty stuff used in a lot of MFG. boats for seat boards. Should be pricey?
     
  11. chandler
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    chandler Senior Member

    I agree with par on this. The stuff is made from trees that are only 20 years old yet they're 30 ft. tall.
    I build quite a few decks, the stuff is great for framing, I strongly advise against using it for the decking. 1 it's toxic to bare feet. 2 it shrinks worse than a pecker in ice water. 3 it never stops checking. Against popular belief it does hold stain . 4 Go down to the local lumber yard and see if you can pick up a 16' 2x12 and load it on your truck by yourself! And I'm not that old!
     

  12. PAR
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    PAR Yacht Designer/Builder

    I agree that you can get good marine grade stock in PT.

    It was my impression the original poster went down to the local box store and pulled some 2 by stock for his sole support structure (he called them trusses) and intends to use marine ply (3/4") for his sole.

    A good coating (minimum two coats each side) of epoxy then set down 6 or 8 oz. cloth in more epoxy, will provide a nice base for your deck. There are many anti-skid paints and paint additives available. There are also other products (sort of like vinyl flooring) that can serve as well.
     
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