Plywood:

Discussion in 'Boat Modification Journal' started by kat in the hat, Jan 12, 2008.

  1. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    Well, TCAT and I are embarking on a super-overhaul of his '92 18' jonboat. It will be a huge undertaking, and chronicled on here when project starts shaping up. I'm sure both of us will ask a million questions during the process as neither of us have done anything of this magnitude.

    This question is obviously about lumber. I have read a few posts, and grasp the concept that all the lumber should be saturated with epoxy resin.

    I have noticed in my search of appropriate lumber that there are many, many choices. We have opted to keep the cost of the lumber down to facilitate funds for gadgets, and accessories.

    I know that some of the treated lumber is corrosive to aluminum. Does AQC lumber need to avoided totally, or will sealing it with epoxy stop the corrosive properties of it for a number of years?

    There will be a 4" subfloor, and all the decking made of wood. Gotta find a happy medium between "the best possible" lumber, and something that will work just fine at a minimum cost. ACQ is $25 a sheet, which is well within budget. We could spring for a little more if there is a better alternative for less than $40 a sheet. Most of the actual marine grade lumber I've found seems to be in the neighborhood of $65-$100 a sheet. We could go that route, but would rather get some goodies for the money saved.
     
  2. Ketch

    Ketch New Member

    Messages:
    469
    State:
    Minnesota
    There are several different options available Kat.

    I have always been an advocate for using lumber for flooring that is naturally rot resistant.

    Cypress lumber has excellent rot resistance naturally and is very strong. If you go to a sawmill and pick your lumber, get heartwood since it is less prone to warpage. It will not require epoxy coating to prevent decay.

    The other obvious option is using cedar. Last year I constructed a handicap accessible ramp for a neighbor of ours and went to the lumberyard looking for lumber. I considered getting treated lumber, but decided to use cedar instead. I purchased 5/4 decking boards for $6 bucks a board at 8 foot lengths. I know the guy at the lumberyard well, so I don't know what the advertised price would have been. Since cedar is so light, the extra thickness doesn't translate into much weight at all. Simple deck coating will provide you with years of use and may give you the most bang for the buck.

    Like I said though, I don't know what the lumber would cost for someone off of the street. This would definitely make the job simpler to install. If you went this route, you would want to reseal it every couple years depending on the conditions the boat is stored in.

    Also, composite decking might be a viable solution as well. Easy install and absolutely no maintenance.
     

  3. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Nothing like a quality marine plywood like Meranti or Okoume because you can epoxy coat it and it wont ever check plus the added fact its lighter then domestic plywoods including domestic marine grade fir.

    Exterior plwood would be OK for a floor if you use a thin glass like 4 or 6 oz. cloth and epoxy on the top of the floor. The cloth is going to keep it from checking and give it some impact resistance from say an anchor banging around or a scuba tank falling over.
    The edges of the plywood is where you have to be really careful since its exterior and no doubt full of voids. 3 or 4 coats epoxy will seal it.

    You can use treated plywood but you'll need to buy it and rack it to dry over several months. You'll still need to epoxy coat it and glass the top to prevent it from saturating with water again.
    I wouldnt attempt using treated plywood without a moisture meter for the simple fact that epoxy isnt going to let wood saturate and its also not going to let plywood saturated with water release that water.
    It'll mold and wet rot not to mention if you epoxy wet plywood its probally going to effect the mmechanical bond and outgassing will be a royal pain in the butt as the epoxy hardens.

    As far as thickness of plywood I say no more then 1/2".
    If you go 3/4" you are looking at around 70-80 pounds a sheet.
    Anytime you build or restore a boat, material weight should always be in your thoughts.

    If you are raising the floor 4" off the bottom of the boat I would consider building some temporary boxing and filling those boxes with pour in foam then cutting the foam back to the top of the boxes before removing them. This is going to give you floor support.
    I dont know the physical dimensions of the boat but I would leave a strip right down the center of the boat unfoamed , say a foot wide.
    This is going to allow any water that gets below deck a way to get to the drain hole plus leave space to snake a wire later.
    Once the floor is in you'll need to caulk around the edges with 3M 5200 to prevent water from seeping around the edges where it can be trapped by the foam and has no way to get out.

    If you know where your water line is and 4" is going to keep your sole above that line you could make that boat self bailing.
    I love a self bailing boat. Any water that gets in the boat runs out of the boat without a pump or pulling a plug.
    Just remember the higher you raise that floor the higher you are making your center of gravity.
     
  4. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    Yeah, I thought about the drying of treated lumber. Didn't know it took months.:sad2: Now possibly considering some cedar 1 bys for the frame. Havent checked the prices on composite decking yet. I kinda thought that was just 2X4s, and stuff. Maybe they have it in a sheeting. Gonna have to check on it. The other option was high density polyethelene. Seems like that stuff, although practically indestructible, would not be cost effective, heavy, and difficult to work with.

    I think it was the Meranti that I did some checking on. I think it is about $65 per sheet. It's not out of budget, but thought maybe there was a more economical alternative.

    Yeah, the plan is definantly to foam the floor. There was gonna be a void in the middle for the helm, and livewell, but never considered leaving it open all the way to the back. That make sense because I was thinking about some sort of drainage. Leaving it open sounds alot simpler.

    Don't know if you noticed, but TCAT is a good size boy, so the strength of the floor is gonna be important.

    Here's what we're working with. Spent last sunday guttin' her out.
     

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  5. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    Then again, looking at the pic, there doesn't seem to be a way to drain the boat down the middle due to the ribs. Maybe run pvc through the 4 grooves on either side?
     
  6. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    Yeah, a 1/2" 4X8 sheet of composite sheeting costs $130. Not in the budget lol.
     
  7. Ketch

    Ketch New Member

    Messages:
    469
    State:
    Minnesota
    If you are going to use cedar, go with the 5/4, not 1".

    Cedar weighs between 1.9 and 2.4 lbs per board foot at 12% moisture content as compared to oak with a weight of over 4 lbs per board foot. So the added thickness won't result in added weight. 5/4 cedar is a standard for outdoor decking, that is why I suggested that one. It comes in 6" widths (that's what I had) If he can walk on a deck, he won't have a problem in the boat. I wouldn't go with sheeting, just narrow up the gaps to allow water to drain in between the boards.

    I have seen some one by composite decking, but don't know who made the stuff. It was channeled and textured to be more slip resistant. Extremely light and durable.
     
  8. Wabash River Bear

    Wabash River Bear New Member

    Messages:
    3,019
    State:
    Indiana
    I used 1/2" MDO (sign board) for my deck and floor. It's a ridgid hardwood laminate coverd with a sort of hard paper made for painting on. I think it's what they use for billboards, store signs and such. I scuffed it and applied 3 coats of Kilz primer/sealer, scuffed it again then applied 3 coats of Tuff Stuff non skid coating to all sides. It turned out great, totally sealed, and flexes very little. The MDO was $39.00 a sheet at my local Menards.
     
  9. justwannano

    justwannano Active Member

    Messages:
    1,003
    State:
    SE Iowa
    Have you considered the recycled plastic "boards" that they use for building decks. I've seen plans for making boat docks with it.
    They sell it at Menards but this is the wrong time of the year to see it in their cataloge so I don't know if it is price competitive.
     
  10. baitchunker

    baitchunker New Member

    Messages:
    1,689
    State:
    alabama
    i think everyone else has pretty much answered your question. just a little bit to add. since i have replaced 2 decks in aluminum boats with treated ply in the last year and a half and have loved the results. do not use acq treated ply. it is very corrosive to aluminum. mcq however is not. and shouldnt be that much more expensive depending on your reghion. of course marine grade is the way to go, but that stuff is expensive. dont bother with the moisture meter test if you buy the treated ply in a store. its been pressure treated which means the individual wood cells have been injected with a certain amount of chemical per cubic ft.
    we went with a spray in bedliner over the ply and like it alot. as far as draining goes, we just cut a small strip off of the back sheet next to the transom. that left room for a little bilge pump- room to insert plugs-etc.
    drying the ply? we didnt do that, maybe we should have. we werent worried about it warping or anything like that, being as we were screwing it straight to the ribs, no problems.

    for the record, mark knows a lot more about building boats than i ever want to, and i really like what ketch was saying about the cedar deck boards. but, because i run a wood treatment plant, i figured i would throw my .02 anyway.

    best of luck, it looks like a fun project.
     
  11. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    So, chunker...is MCQ available at like Home Depot? I haven't done a search for it yet, but my buddy that works for LaCrosse Lumber has never heard of it. Yeah, cedar may be the way we go as far as the floor framework, but will use some sort of sheeting for the deck. Gonna go shopping SOON.:big_smile:
     
  12. baitchunker

    baitchunker New Member

    Messages:
    1,689
    State:
    alabama
    the home depot stores "should" carry it. home depot buys most of thier treated lumber from great southern "yellawood". they buy thier chemicals from a co. called osmose. which sells mcq. it is basically the same as acq with one key difference. acq and mcq are both primarily made up of copper, quat, and water. acq has an added chemical to help break down the copper. that added chemical "m.e.a." is what makes acq so corrosive. mcq however is "micronized" copper and quat. it is actually approved for contact wqith galvalum. etc. home depot should carry it, but i am not real familiar with your region.

    and in all honesty cedar would look sweet. i guess it just comes down to the $ thing.
     
  13. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    and in all honesty cedar would look sweet. i guess it just comes down to the $ thing.

    This will be a vessel dedicated to catfishing, not a pleasure cruiser lol. The surface of the deck will be coated in a non-slip material of some sort, and painted, so the beautiful grains of the wood won't be a consideration.:smile2:
     
  14. Johner

    Johner New Member

    Messages:
    4
    State:
    Ohio
    Kat:
    Last summer I put a floor in my Fisher 16' well, really only got the area between the center seat and the back seat. I used 10mm corogated plastic (coroplast) I'm a sign maker and the coroplast was cheap to me. I used recycle board for the 3 stringers. Then used 3M 77 spray to glue the carpet to the coroplast. The jury is still out on how it will hold up and I haven't started the front floor. I plan to raise it up to the level of the front seat and probably use aluminum stringers and plywood for floor.
    interesting discussion.
    Johner
     
  15. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    Matt, I think as long as you buy a decent grade of plywood (I used arauco -I'm sure I butchered that spelling -for my storage areas and lids) and laminate it with epoxy, you'll be fine. It was around $20 a sheet and had a nice, sanded finish. It took the epoxy well and is pretty sturdy. I have about 2 sheets, or 128 square feet (counting both sides of sheet since you'll laminate both sides) in mine so far and 1/2 gallon of epoxy was plenty to laminate all of it. The epoxy will also take paint well and I know you're not looking for asthetics, but once you've sanded and painted the epoxy no one will know it's wood under there but you and TCAT.
     
  16. kat in the hat

    kat in the hat New Member

    Messages:
    4,875
    State:
    Missouri
    Branden, when you say 'laminate', does that mean with epoxy AND cloth? If yes, do you just apply the cloth to visible surfaces, and sand it, then more epoxy? I was just gonna apply a few coats of epoxy, sand and paint.
     
  17. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Depends on what that plywood is.
    If its birch or pine in origin it will check with 50 coats of epoxy on it.
    Thats one of the things marine plies like Meranti and Okoume have to offer.
    They dont check.

    Once it checks and compromises the epoxy, the innards of the plywood are open to the elements. Its just a matter of time after that.

    The only way that I know to prevent checking is to laminate it with cloth.
     
  18. kmcalester

    kmcalester New Member

    Messages:
    1,340
    State:
    Kansas City
    This is such an inspiration, I don't have a boat, but I alwasy see this boats that are for sale everywhere that need some TLC for under $500.

    I might have to think of doing some of this stuff myself.
     
  19. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Most of those boats needing TLC arent worth the time and money to fix right.
    The advantage to dumping money into some of the old tubs is the same advantage as building a boat.
    When it hits the water its paid for.
    When you are out there floating around, you know what you got from top to bottom.

    All you owe is the next launch fee.
     
  20. jeepnsammys

    jeepnsammys New Member

    Messages:
    10
    State:
    nebraska
    no payments is always good