marine plywood or treated plywood?? whats the real deal???

Discussion in 'Boat Modification Journal' started by biga, Sep 13, 2008.

  1. biga

    biga Well-Known Member

    Messages:
    2,112
    State:
    evansville
    ok im getting ready to put a floor in my aluminum deep v but i am getting all kinds of different info... all 4 boat shops here in town have said use pressure treated and forget it... and a few individuals i know have said the same thing. but then i have heard people say you cant use treated in aluminum boats because the cemicals cause corrosion of the aluminum??? what i need to know is has anyone ever had trouble with using treated plywood in aluminum boats [first hand experience not i heard it from my uncles cousin that seen it on the internet] marine plywood is expensive so i really dont want to go that route and all the boat shops have told me dont waste my money but i want it right the first time so i would like to have some more input!

    thanks adam
     
  2. smokey869

    smokey869 New Member

    Messages:
    966
    State:
    frederickt
    we used treated in redecking a pontoon, no problems so far, local marina said only to use marine if you are going to use in saltwater, id use the treated, hope this helps
     

  3. catman4926

    catman4926 New Member

    Messages:
    1,602
    State:
    Texas
    I suggest that you goggle this and see what it says the new treatment is 20x's more corrosive then the old treatment. There is a lot of good in-fro there and maybe you will want to call the manufacture All I know we use to use a g90 nail but now we have to use a G nail twice the galv coating also you might want to ask baitchuncker about it he works for one of the manufactures here in Alabama

    Hope this helps you
     
  4. Bubbakat

    Bubbakat New Member

    Messages:
    4,532
    State:
    McMinnvill
    Adam I have used treated on an aluminum boat and about 2 years later it started corrosion under the floor from the water dripping down across the wood. Little holes all in the bottom. I redone another on and I was like you didn't want to pay that high price for the marine ply so I bought exterior ply and put a good coat off epoxy on it followed by some good exterior paint and then installed it. The boat has been used for 6 years now with no problems.
     
  5. JimmyJonny

    JimmyJonny Well-Known Member

    Messages:
    4,059
    State:
    sc
    I install replacement windows for a living. Sometimes we have to reframe around windows but we can not use any PT wood. The aluminum coil we use to wrap the outside wood with says do not use on PT wood , it will eventually react ruining the aluminum.....says it right on the box.

    I cant say much about boat work but I do know PT wood and aluminum do not mix.
     
  6. porboy

    porboy New Member

    Messages:
    629
    State:
    TX Panhand
    I have a friend that used it and says never again. It started eating his boat up. He pulled it off and done what bubbakat said and has no problem since.
     
  7. germanmudfish

    germanmudfish New Member

    Messages:
    492
    State:
    Gray, GA
    The current pressure treated lumber is treated with copper based chemicals. Copper and Aluminum do not mix. Exterior grade ply should hold up since it is not in constant contact with water. Sealing it would be a very good idea. Given the amount of flex in the ply, I would suggest a good latex based sealer or a penatrating sealer that will not react with the aluminum or the glue binding the ply. Paint stores can direct you there. Finally, if you can, try using the marine plywood. The glue is made to hold up under water and should not fail you. Like everything, it comes down to what we can afford. Good luck and please let us know which way you went and how it worked out for you.
     
  8. Iablue

    Iablue New Member

    Messages:
    91
    State:
    IOWA
    Adam, I had a pole building put up a few years ago. The contractor put tar paper sheeting between the metal sheets that form the wall and the treated 2x12's to keep them from touching. He told me then that a chemical reaction forms when the two touch. Something about the new way the wood is treated now compared to the old. Good luck.
     
  9. metalman

    metalman Well-Known Member

    Messages:
    3,456
    State:
    IN
    Name:
    Winston
    Adam,
    Call me...W
     
  10. Smellycat

    Smellycat New Member

    Messages:
    530
    State:
    Harrison Arkans
    I put a plywood floor in my boat when I bought it to cover with carpet. Read up on it and found that its better to use plain ext ply and seal it with a good oil stain. Its been on five years and still in good shape, except the carpet will come loose if you spill gas on it! Ha
     
  11. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    The real deal on marine plywood is simple.
    Marine plywood is not treated with anything to prevent rot.

    What makes marine plywood so special?
    It is glued using a glue that is impervious to boiling, freezing, and water.
    It has little to NO voids which trap and hold water vapor causing it to rot from the inside out.
    It has more plies then your run of the mill plywood making it stronger in both shear and lateral. That translates into being able to use less thickness in many cases which saves weight. Alot of weight if you are building a whole boat.

    Marine plywood comes from overseas minus the Douglas Fir that is heavy and substandard. Its alot lighter then what we have available in the US for plywood.

    If you build a boat from American plywood then build one from marine plywood you'll never use American again. It is a dream to work with from bending to machining to finishing.

    Even in my canoe builds there is a HUGE difference to be seen in luan vs. Okoume. Even though the luan is 10 bucks a sheet I've cussed enough, drank enough, and used more then enough material to whoop it into shape to pay for the 60 dollar a sheet Okoume. And to think, this is 3/16th thick plywood we are talking about here. There is a HUGE difference in workability.
    Same if you were building a much larger boat.
    With marine plywood you get a graceful curve or arc where you need one.
    With American plywood you get a haphazard arc and curves where you least want them. To get them where you want them you have to beat up on it, spend time and money to make it happen.

    To sum it up.
    Marine plywood is stronger, lighter, and easier to work with.
    It's not always cost effective to use it particularly if you just need a sheet or two and it has to be ordered.
    The better plywood is marine plywood.

    The downside to treated plywood is weight. It's saturated with water.
    If you are patient and rack it up to dry before using it it will lose alot of weight BUT once installed if you dont seal it with epoxy it's going to resaturate and gain that weight back.
    SO if you have to use epoxy, whats the point in using treated plywood to begin with whether it eats aluminum or not?
     
  12. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    I just want to make it clear that marine plywood IS NOT treated with anything to prevent rot.
    In fact you can take a high dollar sheet of Okoume plywood and throw it next to a cheap exterior plywood in the woods and see which rots first. The Okoume will.
    But by weight comparison. A sheet of 3/16th exterior luan weighs about 20 pounds. A sheet of 3/16th Okoume weighs 12 pounds.
    Thats only 8 pounds difference. By the time you build a boat that can easily translate into 500-600 pounds.

    Many of the tropical species are not as rot resistant as some of the trees we have here.

    Seen some folks post on here that they bought and used marine plywood without doing anything to it.
    Next they'll be blaming the plywood.
     
  13. Katmandeux

    Katmandeux New Member

    Messages:
    1,618
    State:
    Checotah, Oklahoma
    I sometimes wonder if treated lumber isn't overused. It's engineered to resist rot in ground contact...does it provide any benefit when used in other applications?
     
  14. peewee williams

    peewee williams New Member

    Messages:
    3,111
    State:
    Pembroke,Georgia
    50+ years of personal experience with Aluminum boats and plywood.Treated wood will react and corrode Aluminum be it 2x4 or plywood.

    Carpet will hold water and cause wood rot.

    I cut and laid exterior plywood covered with Sears porch oil based paint for many years with sand sprinkled on the last wet cote for anti slip.I cut 2x4 to fit for braces where needed.

    After Astro turf,I just laid it cut to fit on bare plywood.

    I removed,rinsed and cleaned carpet and plywood after each trip and stored it in a dry place where Termites could not get it.This seemed to last as good as original factory job.All rotted when stored out in the weather.Good paint last longer outside.

    I liked to just lay Astroturf where possible on bare aluminum for noise.I learned to avoid wood as I bought the Aluminum to avoid maintenance.

    If it is not easily removed for clean up,it will STINK and attract Rats,Mice,Possums and even Buzzards when used for fishing.The smell will reoccur with each wetting!

    I love you Brothers and Sisters.peewee.
     
  15. biga

    biga Well-Known Member

    Messages:
    2,112
    State:
    evansville
    this is the kind of solid information i was wanting!! thanks a bunch.. i gave winston-[metalman] a call this morning and we discussed putting an aluminum checker plate floor in it .. so i will be getting some prices in the morning!!
     
  16. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    I use it for decks and things outdoors including ground contact as a necessity. I'm a perfectionist by nature. It's aggravating to do some nice looking joinery on an outside project to see it go to pot when the wood dries.
    You get alot of shrinkage.

    What I try to do is buy several months before I plan to actually use it especially for decking. Rack it up and let it dry.

    The only feasible use I've seen for it in boat construction and that would be for solid treated lumber not plywood.
    I would consider using it for stringers AFTER I racked it up and got the bulk of the moisture out of it. That is about the extent of what I would consider using in a boat. It's not a candidate for a transom in my book. Marine plywood would be much stronger.

    Best way I've found to cheaply speed the process is to build a simple drying kiln out of old storm windows someone is getting rid of.
    A solar kiln.
    You can also build one that isnt as effective out of clear plastic.

    Of course nothing beats shelter or barn space if you have some time to kill on other projects.
     
  17. cantstopgrandma

    cantstopgrandma New Member

    Messages:
    955
    State:
    MD
    You can pay now or you can pay later. I would check into aluminum for the floor. It might cost a bit at first, but you should never have to replace it. The most you may have to do is put new carpet over it, or repaint it. By the time you replace plywood several times over the life of the boat, you could probably have paid for the aluminum. I used road signs for my floor (i got them legally by talking to the county roads dept.). They flex, but no problems, and should last as long as the boat does.
     
  18. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Absolutely nothing wrong with wood in a boat. The problem with wood in a boat is the installer and nothing else.
    Installed like it should be it'll outlast the aluminum hull and it wont flex when you stand on it.:wink:
    And you can do it cheaper then buying aluminum plate.

    If wood is so wrong why are there 100's of 100 year old plus boats and ships that are still usuable and valuable?
    How many of these aluminum boats do we see?
    I haven't seen an issue of aluminum boat magazine yet.

    The installer is the problem. Everything from lack of knowledge, the wrong materials, to just being too cheap to do it right the first time.
    There is no short cuts.

    I'll take a wood boat over any other material out there without batting an eye.
    There is alot to be said for strength to weight ratios.
     
  19. peewee williams

    peewee williams New Member

    Messages:
    3,111
    State:
    Pembroke,Georgia
    Let me say.I am not a expert with few years in aluminum boats.I am a old man with 55 years of experience in my use and ownership of aluminum boats.Also over 40 years of maintenance work with aluminum in Submarines,mills and Chemical plants.I have a opinion born of experience and nothing else.

    The above post is very good advice.Around brackish,polluted or saltwater it is even better advice as these conduct the electricity needed for electrolysis.Even air pollution accumulating on a boat stored outside can do it with the dew fall at night.I have seen this on boats stored outside in the Savannah Ga.area near the paper mills.The chemicals their selves also corrode aluminum.

    Anything brass or copper is BAD NEWS.A small brass swivel lost in the bottom of the boat.Brass screws holding a transducer.This and cleaning is the reason I like removable floor boards.Maintenance free outside storage is the reason I love bare aluminum boats.I used 3 for seven years stored outside on coastal Tybee Island Georgia with Salt spray as a regular drenching.In fact.It ate the fins out of my F-150 radiator parked alongside.The only damage to my boats was where a small brass swivel lay undetected for a while.

    I have a OLD aluminum Grumman Dinghy that I once purchased from a elderly vet who ran a military surplus store for many years.He said that he got many from the Army,Navy and ARMY Air force ( no US Air Force until 1947!) after WW2.He sold them as Yacht tenders.I have no idea how old this one is or even if it is surplus.It supposedly came off a stripped old wood yacht.It has the old wooden (Heart cypress?) keel between two pieces of aluminum.This was done so that you could grab the bow and pull it up on a rocky shore without damaging the bottom.You could also replace the wood as it wore down.The boat is in very good shape.It is slow but steady going upstream in a river with a 2 HP 2 cycle Mariner outboard.My 4 HP 2 cycle Mercury did not push it any faster.I recently gave my son my old HEAVY,heavy duty made Grumman white water canoe that was old when I bought it many years ago.Dents and a bent bow from a heck of a lick but in great user shape.They have not made them for many years either.I used it to walk it and my 240 pounds across logs while remaining in the boat in swamps and rivers.This would have destroyed other boats.A 2 HP 2 cycle Mariner with a quickly install/removable side mount works fine.

    Most aluminum boats are destroyed by their owners.Many by the pounding of fast motors.The vibration will harden and crack many types of aluminum over the years.Also.Many self styled experts including some welders will tell you how much better welded aluminum boats are than riveted ones.They do not wish to discuss why JET aircraft are still riveted.Cheap is cheap.Grumman quit making the riveted boats that I am talking about as the craftsmanship involved was too expensive.So did Fisher marine and Monark.It is much cheaper to use heavier cheaper grades of aluminum and weld them.And yes,they were better than the cheap crappy riveted boats.I have had them both.My 4 finely built with craftsmanship riveted aluminum boats are still with me after many years.Their main drawback is freezing water forcing a seam as they will in any crack in a welded boat.It did my welded one where the drain plug was welded in!Upside down storage is the best in freezing weather!

    My two welded aluminum boats are the ones that failed.Both at welds cracking.One was a accident with a Gator.The other was from the force of the motor.It was rated for a 15.It never had over a 8 on it and it was never trailered with the motor on it.

    If you notice.Nearly all old boats of all kinds are the SLOW boats.Speed not only kills people.It kills boats,automobiles,ATVs and even Horses!

    And before the experts holler.I passed my welding certification tests many years ago and all of my welds of all types were perfect when machined on the first try.I could have gone to work building any of the nuclear power plants that they were building at the time.Some of my welds are still holding in OLD Drag-line booms,boilers,fractionating/distillation towers to woodyard pounding after 35+ years.A GOOD welded or aluminum boat is a good boat!A bad one is a bad boat!

    Remember metals including aluminum alloys change.Often with bad properties along with the good.The good are always promoted.The bad seldom mentioned.No manufacture mentions a problem with their product unless forced.Most stretch the truth to it's legal bounds and many so called reputable ones have been caught telling a downright lie.For some reason telling a lie is no longer considered dishonest by many.

    Remember that EVERYONE makes the BEST boat.This means that all but one is telling a lie!We have many on here who believe that they can tell which products are the best.I say this as they are claiming this and that is the best.Some just know without even trying other brands.They believe that they have this gift.I believe that they are crazier than I am.I believe that none knows it all.I believe that we have the most knowledgeable and the least.All the rest of us are somewhere in between.

    I once had a 8 foot Gator break the transom from top to bottom alongside a weld on one side on my boat while I was planing down the middle of Billy's lake in the Okefenokee Swamp.A 14 foot Gator lunged at it and it tried to come in my boat to get away.It hit me,my trolling motor mount and outboard.It was drought,Gators were concentrated and the big ones were eating the little ones.I do not believe that I could have killed it and the hundred more that I could see like Tarzan in the movies with my trusty Bayonet I call "Pig Sticker".I had worked waist deep cutting out canoe trails for 3 days and almost got it when I was safely in the boat almost to the landing.It would not have hurt the boat at slow speed.


    I love you Brothers and Sisters
     
  20. biga

    biga Well-Known Member

    Messages:
    2,112
    State:
    evansville
    well for .125 aluminum tread plate it is $954 for enough to do the floor them figure another $100 for paint .. thats not cheap at all.. compared to $260 for the wood + sealer