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what differance is there between marine plywood versus treated plywood?

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  • what differance is there between marine plywood versus treated plywood?

    what is the differance between marine plywood and treated plywood? and how hard would it be to redo a floor on a 24ft 1964 searay the floor is realy bad where the storage compartment in the floor is. could this storage compartment be done away with mabe just an overlay?


  • #2
    Re: what differance is there between marine plywood versus treated plywood?

    Buckeye, the big difference is the type of glue used to hold the plys together. Marine plywood is the only way to go. I tried it the other way before I knew better. Some of the treated has Phormaldahyde. I don't know if I spelled it correctly. Take your time you can do it successfully.

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    • #3
      Re: what differance is there between marine plywood versus treated plywood?

      Plywood marked "Marine Grade" and "Exterior Grade" or "Ext" are both made with waterproof glue. Treated, I don't know too much about. If not graded as exterior? Marine grade must also be made with no voids in the interior plies, and no knotholes on the veneer. Or is it no unfilled knotholes? Anyway that's what makes it so expensive and hard to find.
      It's all about the tools.

      "If the ocean is glass flat and the sun is shining, you open up the special memory compartment of your brain and start recording the smells, sounds, sights and feelings." -- Philster

      "Poets talk about 'spots of time,' but it is really fishermen who experience eternity compressed into a moment. No one can tell what a spot of time is until suddenly the whole world is a fish and the fish is gone. I shall remember that son of a b**** forever." -- N. Maclean

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      • #4
        Re: what differance is there between marine plywood versus treated plywood?

        Moving to Project Boats
        sigpic

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        • #5
          Re: what differance is there between marine plywood versus treated plywood?

          Treated is the most weather proof so glue is probably the same as marine and exterior. Marine pt ply is manufactured but hard to find. Greenwood Products makes it and boat mfgs have been using it for years and years for stringers and transoms. Last time I checked it was about $95 a sheet for 3/4" and I had to order it special.

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          • #6
            Re: what differance is there between marine plywood versus treated plywood?

            BillP is correct. I would recommend XT ply and treat yourself with oil paint thinned 50%...do all edges and sides. I countersink rivets in the floor ply, and after installing the rivets, or screws, I brush the thinned oil paint or resin over the holes.

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            • #7
              Re: what differance is there between marine plywood versus treated plywood?

              Buckeye you ask the difference. You might check out www.westsystem.com/webpages/epoxyworks/18/plywood.htmlThis will tell you the difference in treated and marine. They say don't use treated except in a cheap boat. Whatever that tells you.

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              • #8
                Re: what differance is there between marine plywood versus treated plywood?

                There is a world of difference between Wolmanized (treated) plywood and Marine grade plywood. The treated plywood is typically southern yellow pine and 4 ply thick. Treating only protects against rot and bugs, it WILL de-laminate and ripple. Marine ply comes in several species and the best will have a British Stanadrds stamp on it with a Lloyds of London certification stamp.The glue in marine ply has a fungicide in it(the good stuff). The least expensive marine ply is Fir but it needs to be glassed on both sides because Fir checks (splits) Okuume is what I used on my stitch and glue duckboat and it was void free and smooth as a babies butt. Check out Glenn L's site and World Panel's site for real good info on this subject. It's expensive to buy but cheaper to own..if you get my drift...

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                • #9
                  Re: what differance is there between marine plywood versus treated plywood?

                  I'm not sure where Centerville is but I just bought a sheet of 3/4" Meranti Marine plywood at Paxton Lumber in Madeira (east side of Cincinnati). They have it in stock and I paid $80.00 + tax. The 1/2" is $55.00. I believe they also have 1/4".I guess it is made of some kind of Mahogany, the 3/4" is 13 plies and smoother than the babies butt. It looks so good with epoxy on it you almost hate to cover it up. The thing I REALLY like about it is it's extremely flat and it machines well.

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                  • #10
                    Re: what differance is there between marine plywood versus treated plywood?

                    Here's some advice I got from the guys at the West Marine outlet in Dallas.To avoid water infiltration through bolt holes: drill your holes a larger size than the bolts, fill them in with resin, and after it cures drill the correct size bolt hole thru the resin.If you only need a half-sheet (most outlets won't sell less than full sheets), buy a smaller thickness, cut two pieces and glue them together with opposing bias. You'll get a stronger deck/floor/whatever for less.
                    It's all about the tools.

                    "If the ocean is glass flat and the sun is shining, you open up the special memory compartment of your brain and start recording the smells, sounds, sights and feelings." -- Philster

                    "Poets talk about 'spots of time,' but it is really fishermen who experience eternity compressed into a moment. No one can tell what a spot of time is until suddenly the whole world is a fish and the fish is gone. I shall remember that son of a b**** forever." -- N. Maclean

                    Comment



                    • #11
                      Re: what differance is there between marine plywood versus treated plywood?

                      WEST system's info is VERY dated about pressure treated plywood. They are talking about non marine type ply that is a petroleum based process that won't let resin stick. CCA treating for the last 15-20 yrs is water based and what true pressure treated marine ply uses. WEST doesn't even acknowledge the existance of pt marine ply. Maybe it has something to do with they don't sell it? A little research with ply mfgs and boat mfgs using the stuff with prove fact from fiction.If it matters to anyone, I bought a load of the 5' x 5' x 5mm sheathing ply from WEST a few years back to sheath a 32' sailboat. The spare sheets delaminated while hanging in the rafters. I have no idea what the sailboat looks like now but it's the last time I used a non exterior glued ply. Even with epoxy it is difficult to keep it perfectly watertight. Harker...where can I read about the plywood glue having a anti fungicidal compound in it? That is new to me and I want to learn about it.

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                      • #12
                        Re: what differance is there between marine plywood versus treated plywood?

                        Bill, I believe it's on www.worldpanel.com...it would be the marine plys with British standards approval..ie: BS1088, as far as I know fir marine grade doesn't have the fungicide in the glue. I read so much on plywoods while debating what to use on my Devlin BB2 duck boat that I had information overload.

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                        • #13
                          Re: what differance is there between marine plywood versus treated plywood?

                          Harker...thanks for the info. I know what you mean about information overload. Several years ago I contacted the naval architect Tom Colvin about using pt ply for a 50'sailboat project. He recommended imported ply as the best for yacht construction.

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                          • #14
                            Re: what differance is there between marine plywood versus treated plywood?

                            First of all, both marine grade and treated plywood use exterior glue. Neither should delaminate under exposure to water if they are manufactured and graded properly. (Many mills cheat on the grade of treated plywood, and you will find individual sheets that do delaminate)Treated plywood is never a sanded product, and marine grade always is. While treated plywood should be made out of exterior veneers, personal experience says that most plywood is treated after it leaves the plant, by someone else, and a consumer is never quite sure whether all the rules were followed or not. Once a panel leaves a mill, they lose control over how it is used.What you need really depends on what you use it for, and what kind of conditions it is exposed to.If it is only occasionally exposed to water, and allowed to dry, and stays mostly dry, and you want to glue a carpet or something like a carpet to it, all you really need is a good ACX sanded(preferably west coast fir) panel. It is exterior, won't delam under normal circumstances, and will last a long time if kept reasonably dry most of the time. (I can get into the technical reasons why an ACX panel is considered an exterior panel, where an ADX panel is not, even though they both use waterproof glue, if anyone wishes)Treated plywood will be difficult to get anything like a carpet to stick.Marine grade, while an outstanding panel, is usually a fair bit overkill, and is generally only needed if there is serious constant wetting of the panel--and as it is made out of wood--it is not a perfect product and there are lots better, cheaper materials to use these days (like fiberglass or something similar) which of course is why it is less used, and often difficult to find these days.

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                            • #15
                              Re: what differance is there between marine plywood versus treated plywood?

                              A lot of info can be had on the subject of American plywoods at APA's website (American Plywood Association) do a google search. I agree that AC fir plywood could be used for marine applications as long as it is totally sealed against moisture penetration with epoxy. Many applications other than hull or structural components which can lead to catastropic failure could be served well with non marine grade plywoods..I personally would never advocate use of anything but marine grade for parts that will make the difference between being ON the water instead of IN the water. The slight cost difference in the project doesn't really warrant doing it "on the cheap" when you figure your time and other materials that would also be lost if there is a problem.

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