Pressure treated lumber and aluminum

Discussion in 'Boating' started by Ictalurus Punctatus, Feb 5, 2007.

  1. Ictalurus Punctatus

    Ictalurus Punctatus New Member

    Messages:
    353
    State:
    Greensboro, NC
    I read about not putting the two together in the thread about Mark's pontoon restoration (glad I came across that little tid bit). I was going to put a floor in my 16' aluminum Jon boat out of, you guessed it, pressure treaded plywood. Is there anyway to still use it but keep the two from directly contacting each other? Perhaps by putting some sort of barrier between the two (Neopreme, rubber, fiberglas, or something on the stringers)? I know in the perfect world, aluminum would be the way to go, but availablility, cost, and my own degree of expertise really point to wood.

    Jon
     
  2. buddah

    buddah New Member

    Messages:
    1,622
    State:
    Pennsylvania Wi
    What happens when they touch? :eek:oooh:
     

  3. fishhook

    fishhook New Member

    Messages:
    658
    State:
    Willow Woo
    I don't know what would happen either. I built a complete deck with rod holders and storage compartments on a 14' aluminum flat bottom boat which I kept for about 15 years and just sold it last fall still in good shape.
     
  4. fishhook

    fishhook New Member

    Messages:
    658
    State:
    Willow Woo
    I forgot to mention in the previous post that it was built using treated plywood.
     
  5. Ictalurus Punctatus

    Ictalurus Punctatus New Member

    Messages:
    353
    State:
    Greensboro, NC
    Mark J and Bubbacat mentioned that treated lumber contains copper sulfate and will damage aluminum. I don't know one way or the other but I figured the opinion and experience of folks who mess with boats more than I, was worth asking a few more questions before I get started on my project.

    Jon
     
  6. AwShucks

    AwShucks New Member

    Messages:
    4,532
    State:
    Guthrie, Oklaho
    Just use regular plywood. Sure, it will rot out in a few years, but you would have gotten your use out of it by then. You could even seal the edges with fiberglass to keep a lot of the water/moisture out.... or even paint the wood would add several years of life to it. By then, your ready for a new piece of wood anyhow.
     
  7. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Pay attention to the third paragraph in this link .
    I was wrong saying it was copper sulphate. We use alot of bluestone I guess.
    Its copper chromate on the old and the new is a copper based preservative without the arsenic.

    Be wary of bottom paints too. You have to get a bottom paint made for aluminum because the regular bottom paint also uses copper.


    http://home.howstuffworks.com/question278.htm
     
  8. Katmandeux

    Katmandeux New Member

    Messages:
    1,618
    State:
    Checotah, Oklahoma
    It creates what is, in effect, a battery, and the resulting electrolysis erodes the aluminum.
     
  9. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Buddah, this link explains the process but what it boils down to is that some metals being dissimilar with each other will oxidize (eat each other).
    This link tells the 3 things that has to be present for it to occur.
    http://www.engineersedge.com/galvanic_capatability.htm

    Keep in mind that water carries current particurly moving water and salt water. (Brine water is used for a conductor in the use of an electric chair)
    Ever seen marinas with all those pontoon boats and aluminum hulled houseboats tied up?
    All it takes is an electricity leak from the dock electrical system for the process to begin.
    This process is why outboard motors have replaceable sacrificial anodes on them. The anode is like the soldier that jumps on a grenade to save his buddies.
    Keep a check on those anodes.
     
  10. navigator

    navigator New Member

    Messages:
    199
    State:
    NC- Brunswick County
    it could be that in the cases where there is no noticable issue that there is enough paint between the boat and the aluminum to prevent any issues.
     
  11. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Treated lumber is way to heavy to use in boats.
    You shoulda been there yesterday I managed to get two full sheets of treated 3/4" plywood off the pontoon boat. It weighed 100 pounds a sheet if it weighed 10. At 5 sheets that 500 pounds of floor.
    Boats like planes dont like alot of weight and the weight they do have to tote has to be distributed properly.
    To build light costs more money but fishing out of a boat as opposed to bank fishing costs more money.
    Treated lumber is not a cure all. Treated plywood is pine or fir. Pine and fir checks. When pine checks it lets water in which WILL debond the plies over time. Rotting isnt the only issue here or is treated lumber eating aluminum for breakfat.

    The options are marine plywood like Meranti or Gaboon that dont check but still have to be coated in epoxy to keep from rotting.
    Or exterior plywood (not treated) that is glassed with epoxy and cloth. Thats the only way to keep it from checking. The upside here is by using the proper glass and glass weight you can undersize the plywood and still come in lighter.

    Like I posted in the toon thread, you'll be able to play football with scuba tanks on it and I'll leave this world before it does.
    I'll get some pictures of treated plywood failure from checking. I've got 5 sheets of it.
     
  12. Foxhound

    Foxhound New Member

    Messages:
    403
    State:
    Georgia
    Another option would be to use aluminum honeycomb panels. They are expensive but can be purchased with different face layer thicknesses. Some pontoon boats are now coming with this as UPGRADED flooring. The drawback here is that the edges on any cut has to edge filled and the fastener holes use special inserts to prevent crushing. Properly installed, this stuff is tough as nails and has been used in aircraft manufacturing for years. This is what I plan on using next year when I re-deck mine. Once completed, I intend on using rhino lining on the top instead of carpet. These honeycomb panels are easily cut with a jigsaw and bondo works fine as edge filler.
     
  13. curveball

    curveball New Member

    Messages:
    39
    State:
    Saint Clairsville, Ohio
    I have now found that I should have used regular exterior plywood on my deck and not the pressure treated, next time I will. I will seal it and paint it and then put carpet over it and it will last longer than I will.

    You gentlemen are the greatest with all this good information. I guess it is true that we get smart to late. I just hope that others will read this good material and save them a ton of work, money and worry.

    Since I redo the interior of my boat every winter watch out next year. If I cannot get aluminum because of cost or the State won't throw away any road signs I can get I will hit the plywood trail for the deck.

    By the way, I went to the State Highway Department and they could not sell me old road signs or give it to me. However, they told me where they would be throwing the old signs away, the dumpster, and said they would call me when the sign crew was ready to get rid of them.

    I am also going to a scrap yard looking to buy (cheap?). If anyone knows of any other way to get aluminum for boat deck other than this I sure would like the help. Thanks to all.
     
  14. catfish101

    catfish101 New Member

    Messages:
    35
    State:
    nc
    i would use aluminum 1 sheet will do job i got a 5 by 10 sheet a few years ago and put sheet foam in between ribs for less than 100 on 18 foot boat 16 foot boat you might use 4 by 8
     
  15. Team StrayCats

    Team StrayCats New Member

    Messages:
    244
    State:
    florida
    Well that just saved me some extra work on my 14ft alum. boat. Thanks
     
  16. luke1wcu

    luke1wcu New Member

    Messages:
    56
    State:
    North Carolina
    I've heard of people using plywood with a couple coats of fiberglass resin. It shouldn't add too much weight.
     
  17. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    There is two major problems associated with fiberlglass resin.
    Fiberglass resin in polyester or vinylester form are not waterproof and neither one bonds to wood well.

    If you've owned boats with floor problems and remove the floor you know what I'm talking about. The fiberglass is always seperated or in the process of delaminating itself from the plywood.
    This occurs because its not waterproof and moisture build up between the wood and resin delaminates it.

    Epoxy coatings not only coat the wood but the top layer of plywood absorbs them. Epoxies are purposely formulated to bond with wood.
    It usually takes 2 coats for the wood to absorb all it can.
    A much much better choice is to go epoxy even if it does cost 60-110 dollars a gallon depending on brand. There is no comaprisons between the two other then one works and one dont.

    A few things I learned a long time ago.
    Use the right product for the job.
    There is no cutting corners that work as well as not cutting corners.
    Subscribe to Wooden Boat magazine. (These guys will teach you alot).
    Do alot of research on the products offered today. I've got probally 7 or 8 years worth of research and use of the products that work and probally 15 more years of the school of hard knock ideas that dont.

    Take boat advertisements with a grain of salt.
    I know we've all heard the adds that claim "there is no wood in our boats"
    All that tells me is that , that manufacturer is unwilling to install wood correctly or they wouldnt have a problem. What else has he installed incorrectly? Instead of using epoxy they use what they have on hand. Polyester or vinylester resins. Thats why there are so many boats with soft floors. Improper use of materials.
    Wood floats naturally. Aluminum, steel, and fiberglass do not.

    If you get Wooden Boat magazine you will see in every issue some old wooden boat or SHIP being restored that is 60-120 years old!!!!
    Wood is for life if you install it correctly the first time.

    Marine plywood.
    Marine plywood is not some magically treated wood. In fact its not treated with anything. In fact most marine plywoods are not even as rot resistant as pine plywood. Confused yet? Well let me unconfuzzle you.
    Marine plywood for the most part is made entirley different in the way the plies are milled. The majority of the marine plywood is Meranti or Gaboon. Both tropical woods and produced outside the US. There isnt a mill in this country capable of producing plywood this way.

    The glue holding the plies together is wate proof. So is the glue in exterior plywood. Same glue.
    Where marine plywood surpasses exterior plywood is in the laminations. Quality grade marine ply has no voids in it making it stronger and no place for moisture to sneak into and hide.
    Marine ply has more laminations giving it alot of shear and lateral strengths.
    Marine plywood is lighter minus the fir marine plywood.
    The tropical marine plies dont check (crack with age).

    There is a big misnomer or misunderstanding that marine plywood can be used without doing anything to it to preserve or protect it. Nothing could be further from the truth.
    You have to use epoxy on it or you would have been just as well off to go buy a piece of cheap exterior plywood from Home Depot.

    Dont rely on a salesperson to know what marine plywood is. Just because it has a Meranti label and Lloyd's stamp on it doesnt mean its marine plywood.
    Know all about this stuff before you go drop cash on plywood that costs 30-100 bucks a sheet. Its not that someone is trying to rip you off. Its that they have no clue themselves. If someone has 1/2" marine plywood at a great cost reduction like 30 bucks a sheet walk away. It aint marine plywood.
    A simple test to determine if plywood is marine plywood is the boil test. Take a piece or two and throw in a pot of water and boil it for 30 minutes. If its marine plwood it wont delaminate or shows signs of weakening.

    The weight difference. A piece of 1/4" pine ply with 3 plies weighs an average of 27 pounds a sheet.
    A piece of Okume O-ku-me (Gabboon) with 5 plies weighs about 18 pounds.
    It doesnt sound like alot but when you are building an 18 foot boat with 13 sheets of plywood it is a whole lot.

    Half the battle is knowing the materials and what materials to use together to make it become a heirloom instead of a disposable.
     
  18. RivrLivn

    RivrLivn Member

    Messages:
    194
    State:
    Missouri
    If you want to use wood, most good boat manufactures will use 7plye MDO 3/4" wood. This is an exterior grade plye wood that is very smooth and water resistant.
    I have mine covered with the marine vinyl flooring and really like it. It is definitely heavier than the and aluminum floor, but is much quieter also.
     
  19. Randy

    Randy New Member

    Messages:
    64
    State:
    Trinity,Texas
    The new treated plywood has a acid treatment thats hard on aluminum, and is heavy mostly because of the moister content. Well I didn't now they changed to acid and found a sheet of 1/2" that was curved and fit perfect in the bottom in my Grizzly 1860. Used another sheet to trim around the edges then used that spray expanding foam around all the cracks and between the ribs. All but about a foot down the middle for water to drain. After drying for 90 days I covered it with Hurculiner. The boat was new with good paint to protect it from the acid.
    The boat is so much quieter and rides so much better and is so much easier to git around in. It's the best thing I've done to the boat yet! I'm going to put another coating of Hurculiner but this time cover the front deck too. Is the Grizz nice wooden boat, Nope its a ruff catfish boat meant for a hard life.