Marine wood filler

Discussion in 'Jims Woodworking' started by justwannano, Mar 17, 2009.

  1. justwannano

    justwannano Active Member

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    So what should I use to fill a few dings & dents & incidental cracks in wood used on a boat.
    Its in a non flex area. Its above water level.It will be painted.
    thanks
    have a good one
    just
     
  2. Mark J

    Mark J New Member

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    Epoxy with wood flour mixed in to thicken it.
    Sands down easily with an orbital sander.
     

  3. catman-j

    catman-j New Member

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    A prime exaple of epoxy would be bondo. It hardens in 10 minutes and if you're gonna paint it nobody will know it's there.
     
  4. Mark J

    Mark J New Member

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    Bondo aint epoxy. It's a polyester or vinylester.
    Bondo maybe above the waterline if you like bondo. I never have cared for it myself.
    It definately won't hold up below the waterline.
    I can carry you to a boat right now with bondo in it. It aint pretty.
    Boats don'e have suspensions nor do they run on tires.

    I don't have my books right now but there are some products by Petite and other paint companies that are for marine use.
    Good place to look is Jamestown distributors.
    They have a website and also a great customer support over the phone.
     
    Last edited: Nov 29, 2009
  5. Jeremy Sheffey

    Jeremy Sheffey New Member

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    And Mark strikes down yet another wrong opinion:smile2::wink::eek:oooh:
     
  6. Mark J

    Mark J New Member

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    Bondo brand has a marine "bondo" that is one to one and is epoxy. 65 bucks a quart.
    What most of us call bondo isn't for boat hulls. Fairing out a pilot house in some small spots, yea bondo would probally be cool.

    Anything rated for below the waterline is costly when it comes to fillers.
    Real expensive.
    As much as 40 bucks for 12 ozs. to 80 bucks a quart.

    And material being repaired is definately a consideration.
    Tin boat
    Glass boat
    Wood boat.

    Cost will deter most people on this site.
     
  7. catman-j

    catman-j New Member

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    I'm assuming from his post that he is refering to wood that isn't part of the boat itself. I was told by a body shop guy that bondo is a 2 part epoxy. I wouldn't use it to fill a dent in aluminum hulls but I've been using it for 20+ years as a wood filler that will be hidden behind paint and it works great. The problem with trying to fill flaws in wood that will be exposed to weather is that it shrinks and expands constantly. Fill in a crack now and chances are you'll be doing it again later.
     
  8. catman-j

    catman-j New Member

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    He's a lot better at arguing with danzig:0a19:
     
  9. Mark J

    Mark J New Member

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    Epoxy is an exact ratio.
    Bondo isn't exact. If you get too much hardner in it it just kicks off quicker and harder. Same thing with polyester fiberglass resins.

    With epoxy if you get too much hardner or too little hardner you got a mess. It will never cure. You can't make it cure. You have to get the mess off and start over.
    Epoxy is chemically engineered to bond MECHANICALLY, not chemically with wood. It seeps into the fibers of the wood.
    Meaning once you fill that ding you arent going to dig it or pry it out. You'll have to chisel it out along with the wood that it is mechanically bonded to.
    With bondo you can remove it with a pocket knife. There is very little if any mechanical bond. Bondo sits on top of the wood.
    Epoxy isn't going to expand and contract in the weather causing cracking. Epoxy will flex with the wood. In a boat you'll never see a busted epoxy seam. The wood will bust first.

    Epoxy is not for everything. Not even for all woods. It's bond qualities with oily woods aren't as great.
    It doesn't achieve that mechanical bond with metals or plastics.
    That is why we use plastic sheeting in vacuum bagging or peel ply methods.
    The epoxy can fully cure and the plastic sheeting comes right off.

    When you put epoxy on wood it's there. You can't take a 5 in 1 tool and work it up under an edge and peel it off. You can sand it off down to the fiber of the wood but to remove it totally you'll have to remove some wood.
    To test this all you have to do is try to wood stain where you sanded the epoxy off. It won't stain. The epoxy saturated into the wood encapsulating the grain.
    When I mix up a batch of epoxy with wood flour mixed in to make a glue to fill a seam it appears to shrink as it starts to harden. This appearance isn't shrinkage at all.
    It's the epoxy saturating the wood. That is why seams almost always have to be done twice especially if you didn't precoat the seam with straight epoxy prior to glueing the seam.

    If you order a 15 dollar trial epoxy kit you'll see what I'm talking about.
    Bondo and epoxy are two entirely different animals. Not even remotely close in make up or what each can do.
    When applied to wood epoxy becomes part of the wood, bondo doesn't.

    The reasons painters don't use epoxy on wood trim is cost and time.
    On a good warm day with a fast kicking hardner and maybe a medium hardner I can put epoxy on a boat in the morning. 12 hours later I can sand. Maybe 10 if it's warm enough.
    if it's 50 degrees outside I may not be able to sand it for 2 or 3 days.
    Sometimes it may be 4 or 5 days if I use a slow hardner.

    Yes, with epoxy we have hardner speeds which can be mixed to custom make a hardner speed.
     
    Last edited: Nov 30, 2009
  10. catman-j

    catman-j New Member

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    I've never had ANY problem with bondo sticking and bonding to wood. It bonds to wood better than metal since metals are non porous. Oily woods that it wouldn't stick to aren't something you'd want to use bondo on anyway.
     
  11. catman-j

    catman-j New Member

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  12. Mark J

    Mark J New Member

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    You are under the impression that because you mix 2 parts it's an epoxy.
    It's not. I use a 2 part primer that isn't epoxy.
    Vinylester and polyester compounds are not epoxies. That is the family bondo comes from.

    I been working with boat building epoxy for years. Been through a helluva lot of gallons of it. I know what it will do and what it won't do. I know that bondo aint even remotely close to epoxy on wood and won't come close to doing what epoxy will on a piece of wood strength wise or repair wise.
    I know that if you repair wood with marine epoxy on a door frame and paint it, you'll never be bothered with repair again no matter the weather condition.
    That repair will outlast the rest of the door frame.
    We're talking about a product manufactured explicitly to bond with wood vs a product that manufactured to fill door dings on cars.
    Two vastly different products and chemical compounds.
    Epoxy is waterproof. Try using bondo below the waterline.

    Like I said, the best thing for you to do is to buy the products and fill some dings in wood since you don't believe what I'm saying.
    Epoxy becomes part of the wood.
    Bondo sits on top of wood.

    Key thing here is to buy some marine epoxy.
    No, don't take my word for it. That would be much to easy based on my experience.
    Go buy an 80 dollar jug of epoxy and educate yourself and the guy that told you bondo was epoxy.
     
    Last edited: Nov 30, 2009
  13. catman-j

    catman-j New Member

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    if you continue to insist on having the last word well nevermind.
     
  14. catwhisper

    catwhisper New Member

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    bondo makes a filler that has fiberglass hairs in it and it adheres great to wood and is waterproof. you mix it just like body filler and after it hardings it sands easy and takes any kind of paint and will do fine above or below waterlines. cost about the same as body filler. i have used it on wood boats with no problems.
     
  15. Mark J

    Mark J New Member

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    The fiberglass strands aren't a wood bonding agent. They just hopefully hold the patch in piece instead of cracking into multiple pieces.
    Polyester or vinylester resin based systems aren't a substitute for epoxy based systems.

    In fact what do the yacht yards use to correct the problems associated with vinylester and polyester? Epoxy.

    Buy a 15 dollar trial kit and the argument will be over.
    You can't remove epoxy from wood without removing wood.
    That isn't the case with bondo.

    People are continually trying to substitute epoxy because of the cost.
    You can't. It's tried over and over even with all of the available information on the internet.

    You aren't going to buy a gallon of anything epoxy based for 15 bucks a gallon.

    If bondo worked like epoxy, companies like Jarrettbay would be using it instead of the expensive epoxy based fairing compounds they are using. They would literally save a 1/2 million or more a year. If they used bondo they would lose millions in warranty claims.

    It's a matter of permanent vs. temporary.
    Again, epoxy is formulated to soak into the wood and cure to be part of the wood. Works the same way on glass.
    Bondo can't accomplish this feat nor will it.
    Repair the keel on a wood or glass boat with thickened epoxy and whack it with a hammer. It aint coming off. It won't even crack.
    Try that with bondo. That hunk of bondo will wind up on the floor.
    I've got a hull right now where someone thought bondo with glass strands was a fix. That bondo is hanging on by threads.
    I have to remove and clean up someone else's patch and fix it permanent with epoxy.


    But the 15 dollar epoxy trial kit will straighten the misconceptions of bondo right out.
    You doubt what I'm saying a measley 15 bucks will tell the truth .
    Do your own testing.

    The only reason I bother saying anything on these threads is to save someone the expense and trouble. That wheel has already been invented and greatly improved upon. Once epoxy is there it isn't going anywhere in your lifetime.
    I wouldn't steer you wrong.
     
    Last edited: Dec 4, 2009
  16. catman-j

    catman-j New Member

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    .