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  1. #1
    Petty Officer 1st Class frozenokie's Avatar
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    Default Using Antifreeze to kill wood rot

    I remember someone telling me (in this forum) about using antifreeze to kill the wood rot on the ends of my stringers before rejoining the new stringers. I assume that it'll have to dry back out after doing so. How long will this take? Usually, the humidity is high here so would I be better off assisting the drying process somehow? And if "yes" then what should I use to help with drying - a fan?

    After completing this step, should I use an epoxy of some sort to join the two stringer ends together since the two ends would not be very accessible? What I mean by that is the ends of the old stringers are about 12" up underneath the bench seat area or cap of the boat and that's why I'm trying to figure out the best bond I can get between the old and new stringers.
    Last edited by frozenokie; March 6th, 2008 at 12:35 PM. Reason: Incorrect link
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  2. #2
    Petty Officer 1st Class seven up's Avatar
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    Default Re: Using Antifreeze to kill wood rot

    Warm Dark and Damp...all the requirements for the dreaded fungus. When the area gets wet again the antifreeze will leech out and require more treatment. It's not a done deal(just splash it on and your through).

    From my understanding of your post you want to treat the rotted wood and pour on some epoxy. If this is a structural or stressed stringer then you should consider about a gut n rehab, replacing with new.

    Yes, though, dry it out all you can. The antifreeze is more hydroscopic than water so it will seep in beyond where the water has penetrated. That stringer in your photo, is it soaked with water ?

    Let us know more about the area.

  3. #3
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    Default Re: Using Antifreeze to kill wood rot

    I have heard that A-F kille rot. However, the rotted areas still have no strength, and the rot can come back. I think it best to cut out all the rot, join new dry solid dimentional pressure treated to the old stringers and cot the whole thing with polyester resin. Now reseal the floor....

  4. #4
    Chief Petty Officer thurps's Avatar
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    Default Re: Using Antifreeze to kill wood rot

    Bite the bullit and do it right otherwise, how far can you and your family/friends swim?
    The fishin' is always good. Sometimes the catchin' is better.

  5. #5
    Supreme Mariner oops!'s Avatar
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    Default Re: Using Antifreeze to kill wood rot

    thanks for the pick...it really helps....

    looks like the rot got in there pretty good
    youve gotta dig out alll the affected areas.....

    the other guys are right.....id suggest doin it all once ....then boat happy...

    the short cut...is to dig out all the rot and marry the strings with a new set beside them.......

    my boat was done that way.......it held for a few years....

    but its all comin out now......a pic is in the hull ext thread....when i was pulling up the floor...you can see the married strings.....

    and yes a fan will help drying.....

    im gonna think some more...ill get back later after work....can you dig out some more?

  6. #6
    Petty Officer 1st Class frozenokie's Avatar
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    Default Re: Using Antifreeze to kill wood rot

    I'm right in there with all of you on replacing the whole thing. However, it's way out of my budget to do it, basically since I don't have the room, the means, or the money to have a boat shop do it. I can feel solid stringer about 8 inches behind the face of the old foam that you see in the photo. And YES, I can dig out more and plan to do so when the nasty weather goes away, along with more of the foam. I already have the new stringer (1x8x12' select pine) waiting to go back in. My main concern was doing the best adhering job to the old stringer with the space I have to work with. Then wrap the entire stringer with roven and glass. The depth is about 8 inches in that space. I already know it'll be tricky, but I'm determined to beef it the best I can.

    It's quite dry right now since I have let it air out for about three weeks now. I do plan on letting it dry for about another 6 weeks though. But, at that time, I want to be able to start reconstructing.

    I don't believe that I'll have anybody swimming to shore since I will be using the pour-in expanded boat foam to keep her afloat if something happens, but as anal as I am, I feel confident that when I get'er finished, she'll be good and stout for a long while.

    Thanks to all for your opinions and advice.
    Last edited by frozenokie; February 23rd, 2008 at 04:53 PM. Reason: Forgot some stuff
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  7. #7
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    Default Re: Using Antifreeze to kill wood rot

    gotta go with what these guys said. you'd ideally want to cut past the wet area, way past the rotted section. even if the end of that stringer looks dry, the rest of it is still wet. wood and water are a natural combination, the wood will absorb it. good luck getting anything to stick to wet wood worth a darn.

  8. #8
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    Default Re: Using Antifreeze to kill wood rot

    OK, I had almost the same scenario as you. I researched it a lot and concluded that yes, antifreeze can help kill rot in wood. So I cut out what I could then brushed antifreeze (the real stuff, not biodegratable) all over the exposed areas that were mostly just a small amount of rot. Let it dry, then drizzle epoxy resin into the exposed wood - diluted with whatever makes it absorb better (forget what it was, there is a web site "rot doctor" I think who sells penetrating epoxy resin, which i was told is mostly just cut resin.) let that set for a few days.

    Next I added PT stringers to replace the wood i removed, anchored to the bottom of the hull and the remaining stringer sections. I don't have any worries for many years. My boat was a 1985 19' BR worth maybe $3k. I figured I had to be reasonable in the restoration or i should have just bought a better, much more costly boat. My boat is solid as a rock.

    You'll know when you do the job if it's mechanically a sound fix-up design. Don't let the scare mongers worry you, if it's solid under there you'll be fine! Remember, MOST older small boats have rot hidden under there....they don't sink, they just maybe get a soft spot and/or run sluggish from the water weight. Yours is FIXED, so why would it sink?

  9. #9
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    Default Re: Using Antifreeze to kill wood rot

    Quote Originally Posted by seven up View Post

    Yes, though, dry it out all you can. The antifreeze is more hydroscopic than water so it will seep in beyond where the water has penetrated.


    uh.... hydrosopic = water-loving... anti-freeze / ethylene glycol loves water mote than water???? ...not sure I buy that. EG also has a higher viscosity than water. I suspect that either will seep completely through any dry or especially rotten wood if given time to do so.

    The other question is whether over time, the ethylene glycol will seep into and weaken the surrounding resin... ethylene glycol is actually one of the building blocks used to make polyester resin. My impression is that it will pretty much go right through polyester resin... Consider that over time, this could degrade the resin or perhaps lead to delamination of the new resin from old, etc... Might take a few years... might take so long that it doesn't matter. Would suck to find out the hard way.

    Will it work? probably, at least for a while, but the real question is...

    For the additional effort required to do it right are you willing to take a chance that it won't.


    If you decide to go the "quick and dirty" route, tmh is right on point with the thinned epoxy. ethylene glycol doesn't penetrate polyurethane or epoxy resin like it does polyester and should help protect the surrounding resin. Also if you've going to do it you might consider adding borax to the antifreeze... additional protection against fungus.

    IMHO It's probably worth the effort to replace rather than take the short cut route.

  10. #10
    Commander redfury's Avatar
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    Default Re: Using Antifreeze to kill wood rot

    Well, we all know the "Right way" to fix the boat, but a guys gotta do what a guys gotta do.

    I think warding him off of his plans would be warranted if he were selling the boat to a 3rd party instead of for personal use. He's going to know how far he can push the boat once he's finished it, and he'll also know that if something does go wrong, what it is most likely due to.

    Personally, I hate temporary fixes, because they are permanent fixes until it breaks again.

  11. #11
    Supreme Mariner oops!'s Avatar
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    Default Re: Using Antifreeze to kill wood rot

    in any case ...your gonna need to get in there......

    you said six weeks?...thats a lotta time @ 2 hrs a day.....

    remove what you can....make sure you have acess to what you need.....

    the more you can reach ....the better your repair will be.

  12. #12
    Petty Officer 1st Class frozenokie's Avatar
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    Default Re: Using Antifreeze to kill wood rot

    Well again, thanks to all (Salty87, TMH, wca_tim, RedFury, Oops!).

    I will be refering to all these posts throughout this process and applying as much effort forth using all the techniques. I really don't believe that this will be my last boat. I do want to give it the best fix I can granted I can't pull the cap. All I can do is get my knees and elbows all scraped up and git'er done. This is my fifth boat, and my father has always had a boat and I have acquired a wealth of knowledge just from those two facts. I was raised to do it right the first time. But, in this case, if I start taking the boat shop route, I'll be pouring more money into it than the boat is actually worth and probably be broke AND divorced afterwards . I'm fully with the action of pulling the cap, but I just can't do it this time. I can only hope that things go the way I want, and Murphy's Law doesn't get in the way.

    I'll keep ya'll posted as I go forward. Right now, just need to get some of that penetrating epoxy...
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  13. #13
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    Default Re: Using Antifreeze to kill wood rot

    hey, gotta work with what you have

    at least dig out the foam and try to get some air flow as soon as you can. thru bolt your add-ons for extra hold and maybe you'll never have to go back under there again.

  14. #14
    Petty Officer 1st Class frozenokie's Avatar
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    Default Re: Using Antifreeze to kill wood rot

    Hmmm... I don't know why I didn't think of that, being in the Engineering field and all for over twenty years . That's a heck of an idea!! So do you mean butting the ends together and sandwiching those ends with a piece on either side and thru-bolting the each butted end?
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  15. #15
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    Default Re: Using Antifreeze to kill wood rot

    Quote Originally Posted by frozenokie View Post
    Hmmm... I don't know why I didn't think of that, being in the Engineering field and all for over twenty years . That's a heck of an idea!! So do you mean butting the ends together and sandwiching those ends with a piece on either side and thru-bolting the each butted end?
    yep, if you can get in there

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