Boat/Deck Rework

Discussion in 'Boat Repair Help' started by BKS72, Oct 8, 2007.

  1. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    I have a 20' 1984 Lowe Jon that needs new decks. I've priced out aluminum sheeting to do the job, but I was wondering if marine plywood would work as well? I prefer working with metal (I've been a millwright most of my career), but if the marine plywood is cheaper and reasonably durable, I wouldn't mind using it. I know some of the newer aluminum boats I've seen use wood for decks/rod boses, etc, just curious if this was a viable option. Thanks!

    Branden
     
  2. baitchunker

    baitchunker New Member

    Messages:
    1,689
    State:
    alabama
    well wood is not as nice as metal in my opinion....

    but, being as im in the buisness of treated lumber, i think i'll give the indusrty a plug. in the last 2 years i have helped put 2 new decks in 2 diff. alum boats. treated plywood will last a pretty long time, especially if you take care of your boat. i feel like you have more room to be creative with wood(add boxes-or compartments).

    there are some things you need to know about marine grade plywood. not all chemicals are the same. just because you buy a sheet of pressure treated ply doesnt mean that it will be as good as the next. certain co.s inject more chem. pounds into thier lumber than others. obviously, the higher the retention of the chemical in the lumber, the better(in your case). also, some of the products on the market are corrosive, and can be particularly bad around alum.

    i would recommend something treated to about a .40 retention mcq (micronized,copper,quat). it is safe for contact with alum. it is durable and will keep the ply preserved in your boat for a long time. although i would still use hot dipped galvanized fasteners. some chemicals to stay away from would be acq, cca, or any of the others that are highly corrosive. also, most treated lumber has a manufacture's warranty (that no one ever seems to use).

    i hope this helps you out a lil bit. oh i almost forgot! because of the crazy housing market, most parts of the country are boasting some of the cheapest lumber prices you will ever see.

    good luck with your project.

    j.d.
     

  3. olefin

    olefin New Member

    Messages:
    3,908
    State:
    Texas
    Very true what baitchunker says about marine plywood not all being the same. I have a 1993 Kayot pontoon. The plywood still looks new as day one and the boat wasn't taken out of the water for 10 straight years. Suppose that is one reason Kayot's cost more.
     
  4. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    As far as marine grade plywood goes, there is nothing added to the plywood to make it not rot. What makes marine grade a marine grade ply is the glue holding the laminations together, the lack of voids, more plies, and the inner plies aren't junk wood. Its lighter and its sheer strength is alot higher then your standard plywood. It also does not check with the exception of our native douglas fir. Lighter stronger plywood means you can use less thickness and save even more weight.
    There are different grades of marine plywood but those grades are mainly appearance grades. If its got a Lloyds stamp you've got good plywood regardless of the grade.

    In fact most of your marine plywood species are less rot resistant then pine plywood.

    Installation is the key to making marine plywood last. If you aren't willing to spend the money in epoxy and glass dont spend the money for the plywood. You'll be throwing that money out the window.

    Personally after working with marine plywood like Meranti and Gaboon I'll never use anything else in a boat unless I go metal.. Its far superior then anything produced in the states and its LIGHTWEIGHT compared to domestic plywood.
     
  5. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    Will the treated plywoods take the glass and epoxy? I'd planned on coating whatever I put in, but wasn't sure how the treatment woud affect the bonding of the epoxy/glass resins. I know some of the treated woods I see at Depot and Lowe's are still wet feeling, and that didn't bode well for application of any kind of resins.
     
  6. AwShucks

    AwShucks New Member

    Messages:
    4,532
    State:
    Guthrie, Oklaho
    If you are going to seal both sides AND the edges with fiberglass, there is no need for treated plywood. It just makes the job more expensive and adds weight to the boat.
     
  7. BKS72

    BKS72 New Member

    Messages:
    3,361
    State:
    East of KC
    That's kind of what I was thinking, but wasn't sure. I used regular plywood and glassed everything when I re-did my old fiberglass boat, and it's held up well. Thanks Lawrence!
     
  8. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    The key to using regular exterior plywood is glassing it and using epoxy.
    Epoxy is 99.something or other waterproof. Just enough to allow any water vapor in the wood out. If it were 100% waterproof you would wind up with mold and dry rot. Believe it or not dry rot is problem with boats as much as wet rot.
    Using the cheap route with vinylester or polyester resin is a waste of money and time. Those products are nowhere near waterproof and bond very poorly with wood. Thats where all these rotted floors in boats come from. Improper materials and installation. The right way puts a dent in the profit margin.

    Its like the new creative advertising boat companies use. "There is no wood in our hulls". Nothing wrong with wood in a boat or the whole boat being wood if you are willing to do it right. When I see that kind of advertising campaign my first thought is this is a company that knows the right way to do something but isnt willing to do it. Take the wood out and and replace it with 3 times the thickness of chopper gun glass which is crapola.
    I'll take wood over glass and aluminum anyday. Those wood hulls will take a heckuva shot and with todays building methods often be lighter then an identical aluminum boat and require less horsepower.

    One advantage in going with Meranti or Gaboon is it doesnt check. You can get by without glassing it and by just epoxy coating and painting it.
    With regualr plywood like produced here in the states it will check.
    You can put 50 coats of epoxy on it and its going to check and compromise the epoxy when it does.
    So if you use regular plywood the only way to avoid the checking is to use atleast a 4oz, layer of glass cloth and epoxy.

    Wood boats last a long time built right. I subscribe to Wooden Boat magazine.
    Every issue there are several projects ongoing or new aquisitions of wood boats and ships that are being restored that are 50 to 100 years old. Thats a testament to wood.
    How good are plywood boats?
    Alot of the sportfish and pleasure yachts you see are built from plywood, epoxy, and glass.
    One of the premier builders is Jarrett Bay Boats. They sell 3 million dollar and up yachts as fast as they can build them made out of plywood the right way.
    You can go to Jarrett Bay's website and look at the building of these fine yachts.
    I love a wood hulled boat. You dont get the annoying hull slap and noise like you do with aluminum and they are lighter and stronger then glass boats.
    They'll also outlast the owner with some care.
    Wood naturally floats. Aluminum and fiberglass naturally sinks like a rock.:eek:oooh:
     
  9. Ketch

    Ketch New Member

    Messages:
    469
    State:
    Minnesota
    I would agree with much of what was said above, but I would make sure you choose the proper wood to use when you repair the project. Most people will choose plywood due to cost and stability purposes.

    My father designed fiberglass boats for almost 30 years. Most boat people, when doing their own boats don't choose to use a plywood for replacements. I would recommend eaither a highly rot-resistant wood or a highly pourous wood that will accept a heavier amount of resin, but this in turn will make that area very heavy.

    Personally, I like using cypress when doing boat repair work anywhere that the area is going to get wet often, or if the wood is not going to be coated with resin. Cypress has natural resins which prevent decay and rot (hey it grows in swamps) and is relatively affordable when compared to other wood products. Not to mention, since cypress is a slow growing and tightly grained wood, it is less prone to warpage and shrinkage which will prevent most all of the checking occuring on normal lumber.

    Do you know what fiberglass production shops worldwide use to reinforce aftermarket hoods and front ends? They most often use cardboard or balsa wood combined with along with some either 18 ounce fiberglass woven roving or 10 ounce fiberglass cloth in high impact areas over chopped roving.

    If I were to do the repairs you listed above, depending on the investment you wish to put into it, I would either use balsa wood with more resin (gotta watch the amount of weight this adds) or use cypress with 2 ounce fiberglass CSM (chopped strand matting). I wouldn't use metal sheeting personally since I haven't had nearly the experience working with it.

    As for resins, it depends on how long you want your repairs to last, how much additional work you are willing to do, and what kind of finish you want it to have when cured. Epoxy resins need to be sanded between layers and polyester resin doesn't. If you choose to use polyester resin, and cover the boards (or balsa) with fiberglass you really won't have a problem with moisture penetration for quite a number of years. Epoxy is definitely the better route to go, but last time I priced any it was considerably more expensive. Polyester resin (sometimes called finishing resin) will leave a smoother, clearer, and shinier finish, but if you are going to coat it additionally, I wouldn't bother with it.

    In a few wordes
    Epoxy=better but more work and mayber more expensive
    Polyester=easier and prettier and mayber cheaper.

    Are you glassing this right to the boat? Or coating and then fastening?

    If you are using fasteners, make sure you countersink all holes. Before you fasten, make sure you put some resin in the hole, then screw in moderately tight (if you go too tight you will squeeze the resin out). Then take some cabisil and mix with resin to cover the screw hole. Cabisil is essentially a powder made up of ground fiberglass strands.

    Also, to save money, don't go a store to buy this stuff. You are going to pay through your nose on this and you really don't want resin that has been sitting for a long time since it tends to crystalize even in tightly sealed containers. Do an area search for local fiberglass shops and stop by one to see if you can get your resin and catalyst there. It will save you a fortune if you can find someone to help. If that doesn't work, try online at a reputable distributor.

    Hope this helps.
     
  10. Ketch

    Ketch New Member

    Messages:
    469
    State:
    Minnesota
    Forgot to mention this in my rather long post above. During the 70's, 80's and even early 90's many boat companies made their own marine grade plywood. They bought the cheapest plywood available, and sprayed the entire board with resing and sent it through a drum sander or wide planer to get it back to dimensional lumber. Many reputable companies did this and it worked for a long time without issue. This worked for 2 reasons. Number one is that it is an effective moisture barrier preventing the wood from getting wet. Number 2, no one ever brings a boat back for rotting wood. Everyone accepts that as the norm.:smile2:
     
  11. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Epoxy was developed and formulated to bond with wood.
    Vinylester and polyester resins were not.
    Those resins are a POOR POOR substitute for epoxy under any circumstances when associated with wood. Between its poor bonding quality and it not being anywhere close to waterproof there is alot better way and its affordable.


    The crap like boat manufacturers have done and still do in coating wood floors with a product that doesnt bond with wood is why I'll never buy a manufactured boat. If there is a corner to cut, they'll cut it.
    Less people know about a boat then they know about a car or a house.
    The boat manufacturers know it and take advantage of it. Its a market that is prime for the pickings.

    If you lay glass on plywood with polyester resin and later peel a corner up to get a handhold on it you can pull the whole sheet of glass off the wood.
    Same scenario with epoxy, not possible. Its doing what it was designed for.

    Its all about using the right material for the right job. Not using a material to get by long enough to get it out the door and out from under a warranty.
     
  12. txthumper1691

    txthumper1691 New Member

    Messages:
    399
    State:
    Temple, Tx.
    thanks for th advise guys, but I am wkn on re-flooring a 20' bass boat, all fiberglass, would using marine grade plywood and epoxy be best for me, or reg ply and epoxy n fiberglass. new to boat repair, but i really want to get this boat back on th water, its an old "cajun" mach III.

    thanks guys
     
  13. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    Thats your decision to make.
    I'll throw something else in the mix now.
    For that bass boat I would seriously think about Nidacore.:big_smile:
     
  14. kkyyoottee

    kkyyoottee New Member

    Messages:
    754
    State:
    Iowa
    I saw my grandfather put a plywood boat together when I was 8 he sealed it with what he called pine pitch. That baby was still water tight 20 years later!! I am sure the plywood was just that plywood.
     
  15. Ketch

    Ketch New Member

    Messages:
    469
    State:
    Minnesota
    You could also use an impregnated wood (resin impregnated). It is different from treated lumber and lasts a long, long time. I believe most of the impregnated lumber has something like 40 year warranties. It is often used as flooring in marine applications and also used as a decking material. 5/4 decking lumber was around $2 a linear foot last I looked.
     
  16. Nomdic1

    Nomdic1 New Member

    Messages:
    77
    State:
    virginia
    Pound for pound, go with aluminum. Never a question of rot, lighter weight, sounds like you have experience in working in metal. I've heard that the new pressure treated can eat away aluminum, so be careful.
     
  17. fishingbuddy4

    fishingbuddy4 New Member

    Messages:
    1,564
    State:
    Warner Rob ga
    I used exterior glued plywood ,we will see how that works i am priming the sides and top, and then rolling on cabelas tough coat on the top and side hopefully it will be ok,
     
  18. txthumper1691

    txthumper1691 New Member

    Messages:
    399
    State:
    Temple, Tx.
    Mark, whats Nidacore? where would I find it, how expensive or in-expensive is it? I am not doing th whole floor, just th part right in front of th seats, about 1/3 of th floor.